Manufacturing method and apparatus

Abstract

A method for manufacturing an article is disclosed, the method including both using a coordinate measuring machine to obtain three-dimensional point coordinate measurements of a first portion (70) of the article already in a predetermined position, and positioning a second portion (80) of the article in a predetermined spatial relationship relative to the first portion (70) depending on the measurements of the first portion (70). The predetermined spatial relationship is defined in three or more degrees of freedom. Positioning the second portion (80) relative to the first portion (70) includes controlling a machine to move the second portion (80) relative to the first portion (70) in three or more degrees of freedom. The machine is controlled to hold the first and second portions (70, 80) in the predetermined spatial relationship while performing operations that fix the first and second portions in the predetermined spatial relationship. When the first and second portions (70, 80) are in the predetermined spatial relationship, the second portion (80) does not directly contact other portions of the article, or at least does not contact them in a manner that interferes with, affects, or influences the predetermined spatial relationship.

Description

[Technical field]

[0001] The present invention relates to a manufacturing method and a manufacturing apparatus. [Background technology]

[0002] Apparatus for the automated assembly of components is known. For example, US Pat. No. 5,399,433 describes an apparatus and associated method for assembling various components of a computer hard disk drive. In particular, US Pat. No. 5,399,433 describes an assembly apparatus or robot comprising an arm that can be moved along three orthogonal axes (X, Y, and Z). The movable arm carries a vacuum collet for picking up the components, an adhesive dispensing nozzle, and an ultraviolet light source for curing the applied adhesive. A tray arranged on the flat bed of the apparatus carries a number of components to be assembled. In use, adhesive is first dispensed onto a selected area of ​​a first component using the adhesive nozzle. A second component is then picked up by the vacuum collet and placed on the first component. The components are imaged by a local imaging system to establish their position relative to one another. The adhesive is then cured using UV radiation from a UV light source. In this way, various subassemblies of the hard drive can be automatically assembled. Although automated assembly apparatus of the type described in US Pat. No. 5,399,433 allows for the automated assembly of certain components, the ability of such apparatus to assemble complex structures with high precision is limited. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 6,266,869 [Patent Document 2] German Patent No. 10055185 [Patent Document 3] International Publication No. 2017 / 174966 [Patent Document 4] International Publication No. 2007 / 144573 [Patent Document 5] International Publication No. 2019 / 073246 [Patent Document 6] International Publication No. 2005 / 059471 [Patent Document 7] International Publication No. 2004 / 005849 [Non-patent literature]

[0004] [Non-Patent Document 1] H. J. J. Braddick, The Mechanical Design of Experimental Apparatus, Chapman & Hall, London, 1960, pp. 11-30 [Non-Patent Document 2] JG Skakoon, "Precise Constraints: Knowing How Much is Enough and How Much is Too Much is the Key to Successful Design," Mechanical Engineering, September 2009, pp. 32-36 [Non-Patent Document 3] M. Orsag, C. Korpela, P. Oh, S. Bogdan, "Coordinate Systems and Transformations", chapter "Air Manipulation", part of the series "Advances in Industrial Control", 2018 (print ISBN 978-3-319-61020-7, online ISBN 978-3-319-61022-1; download from https: / / www.springer.eom / cda / content / document / cda_downloaddocument / 9783319610207-c2.pdf) Summary of the Invention [Problem to be solved by the invention]

[0005] It has also been previously proposed to use a Stewart platform or hexapod to perform component placement. For example, US Pat. No. 5,399,633 describes a technique for using a hexapod to place components on a substrate mounted on a rotatable table. However, as with US Pat. No. 5,399,633, the ability to perform high-precision automated manufacturing of complex articles using such equipment is limited. [Means for solving the problem]

[0006] According to a first aspect of the present invention, there is provided a method of manufacturing an article, the method comprising using a coordinate measuring machine both to obtain (coordinate) measurements of a first (already assembled) part of the article, and to position a second part of the article in a predetermined spatial relationship relative to the first part in dependence on the (coordinate) measurements of the first part.

[0007] A coordinate measuring machine is specifically adapted to measure point coordinates of an object and should be distinguished from a positioning machine, which is provided for placing components (e.g. supported on a movable platform of the machine) in the working volume of the machine. Such positioning machines are specifically adapted for the task of positioning or placing objects and are not specifically adapted to perform a measuring function, at least not to measure point coordinates of the surface of an article. A common example of a positioning machine is a pick-and-place machine, e.g. used in the PCB manufacturing industry, which blindly picks up parts from a tray and places them on a PCB board. Although some alignment process is required, e.g. using reference features or fiducials, to ensure that the machine is picking up from the right place and that the PCBs are where the machine expects them to be, the pick-and-place machine does not perform any measurements of parts already on the PCB and does not rely on such measurements, in particular when placing subsequent components.

[0008] One embodiment of the present invention may be considered to be a measurement-aided manufacturing method, in which a coordinate measuring machine (or measuring machine) is used for its primary purpose to measure parts with high precision, but is also given the added functionality of placing or positioning other parts relative to the measured part based on measurements made. With such a technique, the accuracy of the manufacturing method is limited only by the accuracy of the coordinate measuring machine itself, and is not dependent on, for example, complex and / or expensive fixture systems. Furthermore, in a preferred embodiment, where parts to be placed or assembled on an article are held away from the surface of the article and fixed in place, for example by applying and curing a curable adhesive in the gap, the substrate on which the parts are placed does not need to be particularly precisely formed or held, as the relative positions of the parts to be assembled on the substrate are entirely determined by the accuracy of measurements from the coordinate measuring machine, and are entirely independent of the substrate or fixture, and the parts effectively "float" above the substrate in the correct relative positions based on the accuracy of the coordinate measuring machine. This novel use of a coordinate measuring machine provides important manufacturing advantages.

[0009] The first portion of the article may be or may include a feature (e.g., an integral feature) of the article, and the second portion is disposed relative to that feature. In other words, the first portion does not necessarily have to be a separable (or previously assembled or disposed) part of the article, but instead may simply be an integral part of the article, such as a hole, recess, protrusion, or other such geometric shape or feature formed on or in the surface of the article.

[0010] The method may include obtaining (coordinate) measurements of the second part using a coordinate measuring machine, the second part being positioned in a predetermined spatial relationship relative to the first part based on the (coordinate) measurements of the first and second parts.

[0011] The measurement of the first part is reference system and the measurements of the second portion can be used to establish reference system can be used to establish a relationship between the first, second reference systemA relationship may be established between the first and second parts, and the established relationship may be established between the first and second parts, reference system can be used to move the object in a predetermined spatial relationship within the object.

[0012] No. 1 Reference frame and the second Reference frame Establishing a relationship between both reference system The method may include determining location information associated with at least one point or feature that is common to or coincident with the above-mentioned points or features.

[0013] Common reference system is the first part reference system It could be.

[0014] 1st and 2nd reference system may be a first and a second coordinate system, respectively. The established relationship may be a coordinate transformation between the first and second coordinate systems.

[0015] The predetermined spatial relationship may be defined (or specified) in three or more degrees of freedom, and measurements (of the first and / or second parts) may be obtained and may be of a type to enable this to be achieved.

[0016] Positioning the second part relative to the first part may include moving (or controlling a machine to move) the second part relative to the first part in three or more degrees of freedom, e.g., four or five or six degrees of freedom. Positioning the second part relative to the first part may include actuating several axes of the machine, the number of which corresponds to the degrees of freedom. For example, positioning the second part relative to the first part may include actuating four axes of the machine (moving the second part relative to the first part in four degrees of freedom), or actuating five axes of the machine (moving the second part relative to the first part in five degrees of freedom), or actuating six axes of the machine (moving the second part relative to the first part in six degrees of freedom). Thus, positioning the second part relative to the first part may be referred to as four-axis positioning, five-axis positioning, or six-axis positioning, depending on the number of degrees of freedom required. Positioning may even be in six or more degrees of freedom, for example by supporting one or both of the first and second parts on a rotary table, or via an articulating head such as a Renishaw REVO® probe head.

[0017] The measurement (of the first and / or second part) may be a three-dimensional measurement, ie a measurement in three dimensions.

[0018] The measurements (of the first and / or second part) may be in three or more degrees of freedom.

[0019] Measurements may be obtained by moving (or controlling a machine to move) in three or more degrees of freedom, preferably four, more preferably five, more preferably six degrees of freedom.

[0020] The measurements may be obtained by moving (or controlling a machine to move) the measuring device in three or more degrees of freedom, preferably four, more preferably five, more preferably six. The metrology (or measurement) instrument may be of the following types (e.g. probe, contact probe, touch probe, touch trigger probe, analogue probe, scanning probe or camera based measuring device).

[0021] Obtaining the measurements (of the first and / or second parts) may involve actuating more than two axes (or degrees of freedom) of the machine, for example, 4 or 5 or 6. For example, if the machine is a hexapod coordinate measuring machine, which includes six extendable legs (corresponding to the six axes), the measurements may be obtained by actuating all six extendable legs (all six axes).

[0022] The measurements (of the first and / or second part) may be coordinate measurements.

[0023] The measurements (of the first and / or second part) may be point coordinate measurements.

[0024] The measurements (of the first and / or second part) may be (or may include) machine coordinates (or coordinates derived therefrom), which may be defined within a machine coordinate system (e.g., as opposed to a part coordinate system or a global coordinate system).

[0025] Positioning the second part relative to the first part may involve controlling the machine to adopt a series of different machine coordinates (within a machine coordinate system).

[0026] The measurement (of the first and / or second part) and the positioning of the second part may be based on (or may be performed within) the same machine coordinate system.

[0027] The coordinate measuring machine may include a plurality (or a set of) measuring transducers (e.g., linear and / or rotary encoders, or length and / or angular measuring transducers), where the same plurality (or set of) measuring transducers are used to obtain (or derive) measurements of the (first and / or second parts) and to position the second part based on those measurements.

[0028] The measurements may be based on or derived from the entire measurement loop of the coordinate measuring machine. This should be distinguished from systems where measurements are made by, for example, a camera-based or laser-based vision system attached to the end effector of a positioning machine, such as a robot, which does not take into account measurements from rotary encoders of the revolute joints that also make up an articulated robot arm, but simply places the vision system within range of interest and guides the end effector (and the components held by the end effector) towards a target based on real-time feedback from the vision system. In one embodiment of the present invention, it becomes possible to determine a complete set of machine coordinates that, when executed by the machine, results in the second part being positioned in a predetermined spatial relationship relative to the first part.

[0029] Positioning the second part in a predetermined spatial relationship relative to the first part may include calculating a set of machine coordinates dependent on the measurements (of the first and / or second parts), which will position the first and second parts in the predetermined spatial relationship and control a machine to adopt the calculated machine coordinates. The machine may be controlled to adopt the calculated machine coordinates directly or substantially directly, i.e., substantially in one movement. This is to be compared with a series of repetitive or incremental small movements that could be performed based on visual feedback from, for example, a separate camera or imaging system.

[0030] The method may include controlling a machine to hold the first and second portions in a predetermined spatial relationship while performing an operation to fix the first and second portions in the predetermined spatial relationship, which may allow the second portion to be released from the second platform, such that the first and second portions remain in the predetermined spatial relationship without support from the second platform.

[0031] Controlling the machine to hold the first and second parts in a predetermined spatial relationship may include controlling the machine to maintain calculated machine coordinates.

[0032] The fixation operation may include applying a fixation medium to contact the second portion when in a predetermined spatial relationship with the first portion, and activating the fixation medium to fix the first and second portions in the predetermined spatial relationship.

[0033] The method may include applying a fixation medium prior to moving the first and second portions into the predetermined spatial relationship, and then activating the fixation medium when the first and second portions are in the predetermined spatial relationship.

[0034] The fixing medium may be a curable adhesive and activation of the fixing medium may involve curing of the adhesive.

[0035] The fixing operation may include a welding process, and the fixing medium and its activation are the result of carrying out the welding process. For example, the fixing material may be a deposited (e.g., molten) material resulting from the welding process, and the activation of the fixing material is the hardening or cooling of the deposited material.

[0036] The welding process can be a laser welding process, but also a bonding process, a friction welding process, an electron beam welding process, a hot air bonding process, or an electrochemical process.

[0037] Advantageously, when the first and second portions are in the predetermined spatial relationship, the second portion does not directly contact (e.g., touch) any other portion of the article, or at least does not contact in a way that interferes with, affects, or would affect the predetermined spatial relationship.

[0038] The method may include leaving a gap between the second portion and any other portion of the article when in the predetermined spatial relationship.

[0039] The voids may be at least partially filled by a fixing medium applied in the fixing operation.

[0040] The gap is preferably at least 25 μm, more preferably at least 50 μm, more preferably at least 100 μm, eg, determined as an average over the overlap area between the parts concerned.

[0041] The method may include using the established relationship to determine where to apply the fixation medium.

[0042] The machine may include first and second platforms movable relative to one another, and the method may include supporting the first portion on the second platform and supporting the second portion on the first platform. Positioning the second portion relative to the first portion may include controlling the machine to move the first and second platforms relative to one another.

[0043] Supporting the second portion on the first platform may include picking up the second portion using a pick-up device supported on the first platform.

[0044] The pick-up device may include a gripper.

[0045] The second part, when supported by the first platform, may be kinematically (or at least pseudo-kinematically) coupled to the pick-up device. The pick-up device may comprise a set of kinematic (or at least pseudo-kinematic) features that engage with the second part when supported by the first platform. The second part may comprise a set of corresponding kinematic (or at least pseudo-kinematic) features that engage with the kinematic (or at least pseudo-kinematic) features of the pick-up device. If relative constraint between the pick-up device and the second part is required in less than six degrees of freedom, then the surfaces of the second part that engage with the kinematic (or at least pseudo-kinematic) features of the pick-up device may be designed accordingly to achieve the required degree of constraint. For example, if the second part is a ball and constraint to the pick-up device is only required in three translational degrees of freedom (rotation in three degrees of freedom about the center of the ball is allowed), then sufficient kinematic coupling is achieved by having kinematic features on the pick-up device (e.g. three point-like contacts located on the spherical surface corresponding to the contacts of the ball).

[0046] The method may include obtaining measurements of the second part using a model of the second part and knowledge of a position of the second part relative to the first platform through a kinematic coupling, rather than using a coordinate measuring machine to obtain measurements of the second part.

[0047] The first platform may be a mobile platform and the second platform may be a fixed platform.

[0048] The method may include measuring a first portion using a first probe supported on a first platform.

[0049] Measuring the first portion with the first probe may include moving the first and second platforms relative to one another to bring the first probe into sensing relationship with the first portion.

[0050] The first probe may be a movable probe.

[0051] The first probe may be a contact probe. The first probe may be a touch probe. The first probe may be a touch trigger probe. The first probe may be an analogue probe. The first probe may be a scanning probe.

[0052] The method may include measuring a second portion using a second probe supported on a second platform.

[0053] Measuring the second portion with the second probe may include moving the first and second platforms relative to one another to bring the second probe into sensing relationship with the second portion.

[0054] The second probe can be an immobilized probe.

[0055] The second probe may be a contact probe. The second probe may be a touch probe. The second probe may be a touch trigger probe. The second probe may be an analog probe. The second probe may be a scanning probe.

[0056] The method may include measuring a first probe with a second probe, and / or vice versa, and the first and second reference system Establish relationships between.

[0057] Measuring a first probe with a second probe, and / or vice versa, may involve moving the first and second platforms relative to one another to bring the first and second probes into sensing relationship to one another.

[0058] The first and second probes may each include (a stylus having) a stylus tip. The common or coincident point may be the centre of the stylus tips of the first and second probes when the first and second platforms are in positions relative to one another that would place (their respective centres) of the first and second stylus tips in the same position.

[0059] Where one of the first and second probes is a touch trigger probe and the other of the first and second probes is a scanning or analogue probe, the method may include measuring or characterising a surface of a stylus tip of the touch trigger probe using an extrapolation to zero technique and then determining a centre point of the stylus tip.

[0060] The second portion can be supported on a rotatable stage. The rotatable stage can be supported on the first platform. Positioning the first portion relative to the second portion can include controlling a machine to rotate the rotatable stage relative to the first platform.

[0061] The article (and with it the first portion) may be supported on a rotatable stage. The rotatable stage may be supported on a second platform. Positioning the first portion relative to the second portion includes controlling a machine to rotate the stage relative to the second platform.

[0062] The first and second platforms may be moved relative to one another in three or more degrees of freedom to position the second portion relative to the first portion.

[0063] The first part may be the support or substrate part of the article.

[0064] The first and second portions may be operative parts of the article that have a function in the use of the article, and are not merely reference features, fiducials, or the like, that have a function only during the manufacture of the article.

[0065] The portions may be functionally and / or mechanically and / or optically interrelated parts of the final product.

[0066] The second portion may be supported by the first portion in the resulting article. When multiple portions are supported in this manner, a stack or serial arrangement is produced. A fixing medium used in the fixing operation may be provided between the first and second portions. A fixing medium used in the fixing operation may be provided in contact with the first and second portions.

[0067] The first and second parts may be supported in the resulting article on a base part of the article. The first and second parts may not be supported directly one on the other. When multiple parts are supported in this manner, a juxtaposed or parallel arrangement is produced. A fixing medium used in the fixing operation may be provided between the second part and the base part. A fixing medium used in the fixing operation may be provided in contact with the second part and the base part.

[0068] A combination of parallel and series arrangements of sections is also possible.

[0069] The first part may be or may include a base part or substrate of the article.

[0070] The method includes using a measurement device other than a probe to obtain the measurements. A measurement device such as a camera may be used. Such a camera-based measurement device may include at least two, preferably three, imaging sensors positioned at different respective angles or orientations relative to the target (i.e. the part being measured). A non-contact measurement device may be used. An optical measurement device may be used.

[0071] Obtaining measurements of the portion may include obtaining measurements of one or more characteristics of the portion.

[0072] Obtaining the measurements of the part may include obtaining measurements of one or more discrete points on a surface of the part.

[0073] A coordinate measuring machine may be a machine adapted to measure the geometry or geometric properties of a physical object in three dimensions by sensing discrete points on the surface of the object with a probe.

[0074] A coordinate measuring machine may be a machine that has a coordinate measuring device, such as a probe, for measuring the coordinates of points on the surface of an object.

[0075] The coordinate measuring machine may be a non-Cartesian coordinate measuring machine.

[0076] The coordinate measuring machine may be a parallel kinematic coordinate measuring machine. Such a machine may have multiple measuring and / or drive axes arranged in parallel rather than in series, so that the positioning errors associated with each axis are not accumulated as they are with a serial kinematic coordinate measuring machine, which typically results in improved measurement accuracy and better measurement results.

[0077] The coordinate measuring machine may include a number of extendable legs.

[0078] The coordinate measuring machine may be a hexapod coordinate measuring machine, with six extendable legs, or the machine may be a pentapod, with five extendable legs, or the machine may be a quadrapod, with four extendable legs.

[0079] A coordinate measuring machine may be in the form of an articulated arm, having multiple rotary joints arranged in series, which may be considered similar to machines commonly referred to as robotic arms.

[0080] The coordinate measuring machine may have a measurement accuracy (or error) of less than 50 μm, more preferably less than 25 μm, more preferably less than 10 μm, more preferably less than 5 μm, more preferably less than 1 μm.

[0081] The machine coordinates of the coordinate measuring machine may each include values ​​related to and / or derived from the lengths of the multiple extendable legs.

[0082] A plurality of measurement transducers may be associated with a plurality of extendable legs, respectively.

[0083] The second part and a measuring device (e.g., a probe) for taking measurements of the first part may be supported simultaneously on a common platform of the machine that is moved when measuring the first part and when positioning the second part.

[0084] The method may include repeating the method for one or more additional second portions of the article. The first portion in each iterative execution of the method may be any portion or portions of the article resulting from a previous execution of the method.

[0085] The first portion in at least one of the iterative executions of the method may include at least one second portion from a previous execution of the method.

[0086] In a subsequent run of the method, the second part from the previous run of the method (which is now considered the first part because it has already been placed on the article once the new second part has been placed) may be one of the parts measured by the coordinate measuring machine and used to place the new second part. It is also possible that the second part from the previous run of the method (which is now the first part because it has already been placed on the article) is not measured in the subsequent run of the method, and instead measurements of other parts of the article (new or previous) are relied upon when placing the new second part.

[0087] In at least one of the iterative executions of the method, using the machine to obtain measurements of the first part may extend to using measurements of that first part obtained in a previous execution of the method, in other words, if the first part has already been measured in a previous execution of the method, it does not have to be measured again, it simply needs to retrieve (using the coordinate measuring machine, e.g. its machine controller for that purpose) the measurements already obtained for the first part.

[0088] The or each second part may be part of, or form part of, a bearing assembly for an extendable leg of a coordinate positioning machine, or may be the ball or tip of a stylus for a measurement probe. The first part may be part of, or form part of, a readhead or readhead holder for an extendable leg of a coordinate positioning machine, or may be the stem of a stylus for a measurement probe.

[0089] The invention is therefore applicable to a method of manufacturing an extendable leg for a coordinate positioning machine and / or a stylus for a measurement probe.

[0090] According to a second aspect of the present invention there is provided a method of manufacturing an article having a plurality of parts, the method comprising performing, for a first selected part of the plurality of parts, at least the measuring and positioning steps of the method according to the first aspect of the invention to position the first selected part on the article, and performing, for each subsequent selected part of the plurality of parts, at least the positioning step, optionally also performing the measuring step of the method according to the first aspect of the invention to position the subsequent selected part on the article, the positioning step comprising using measurements obtained when performing the method on the current and / or previously selected parts.

[0091] At least one of the plurality of parts may be a module created in the course of performing a method from the plurality of other parts.

[0092] According to a third aspect of the invention there is provided a manufacturing system or apparatus including a coordinate measuring machine configured to carry out a method according to the first or second aspect of the invention.

[0093] According to a fourth aspect of the present invention there is provided a computer program which, when executed by a controller for a coordinate measuring machine, causes the controller to operate the coordinate measuring machine to perform a method according to the first or second aspect of the present invention.

[0094] According to a fifth aspect of the present invention there is provided a computer readable medium having stored thereon computer program instructions for controlling a coordinate measuring machine to carry out a method according to the first or second aspects of the present invention.

[0095] A "position" of a part should be understood to be the location and / or orientation of the part relative to the appropriate number of degrees of freedom. In particular, the terms "position" and "positioning" should not be understood to be limited to describing only translational motion (e.g., motion in X, Y, Z), but are intended to describe both translational and rotational motion, or a combination thereof, relative to the relevant number of degrees of freedom. For example, if position is defined in six degrees of freedom, then both position and orientation are relevant. However, if position is defined in only three degrees of freedom, then this may or may not include orientation. The terms "position" and "positioning" as used herein should be interpreted accordingly.

[0096] Reference is now made, by way of example, to the accompanying drawings in which: [Brief description of the drawings]

[0097] [Figure 1A] FIG. 1 is a schematic diagram of a hexapod coordinate measuring machine having six extendable legs. [Figure 1B] FIG. 1B is a schematic diagram of a bottom-up configuration as shown in FIG. 1A. [Figure 1C]FIG. 1C is a schematic diagram of a top-down arrangement, which is an alternative to the bottom-up arrangement of FIG. [Diagram 2] 1 is a schematic diagram illustrating various stages of a manufacturing method embodying the invention; [Diagram 3] 1 is a schematic diagram illustrating various stages of a manufacturing method embodying the invention; [Figure 4] 1 is a schematic diagram illustrating various stages of a manufacturing method embodying the invention; [Diagram 5] 1 is a schematic diagram illustrating various stages of a manufacturing method embodying the invention; [Figure 6] 1 is a schematic diagram illustrating various stages of a manufacturing method embodying the invention; [Figure 7] 1 is a schematic diagram illustrating various stages of a manufacturing method embodying the invention; [Figure 8] 1 is a schematic diagram illustrating various stages of a manufacturing method embodying the invention; [Figure 9] 1 is a schematic diagram illustrating various stages of a manufacturing method embodying the invention; [Figure 10] 1 is a schematic diagram illustrating various stages of a manufacturing method embodying the invention; [Figure 11] 1 is a schematic diagram illustrating various stages of a manufacturing method embodying the invention; [Figure 12] 1 is a schematic diagram illustrating various stages of a manufacturing method embodying the invention; [Figure 13] FIG. 2 is a schematic diagram showing an article resulting from the method. [Figure 14] 1 is a flow chart summarizing a manufacturing method according to one embodiment of the present invention. [Figure 15] FIG. 2 is a schematic diagram illustrating the concept of a reference system in an embodiment of the present invention. [Figure 16] FIG. 2 is a schematic diagram illustrating the concept of a reference system in an embodiment of the present invention. [Figure 17] FIG. 2 is a schematic diagram illustrating the concept of a reference system in an embodiment of the present invention. [Figure 18] FIG. 2 is a schematic diagram illustrating the concept of a reference system in an embodiment of the present invention. [Figure 19]FIG. 2 is a schematic diagram illustrating the concept of a reference system in an embodiment of the present invention. [Figure 20] FIG. 2 is a schematic diagram illustrating the concept of a reference system in an embodiment of the present invention. [Figure 21] FIG. 2 is a schematic diagram illustrating the concept of a reference system in an embodiment of the present invention. [Figure 22] FIG. 2 is a schematic diagram illustrating the concept of a reference system in an embodiment of the present invention. [Figure 23] FIG. 2 shows a more realistic arrangement of parts of an article produced by a method embodying the invention. [Figure 24] 1A-1C provide a more realistic and practical implementation of an article produced by a method embodying the present invention. [Diagram 25] 1A-1C provide a more realistic and practical implementation of an article produced by a method embodying the present invention. [Figure 26] 13A-13C illustrate determining an offset between a probe coincidence point and a specific point on a portion of an article supported on a moving platform for use in changing the center of rotation of the moving platform. [Figure 27] 13 illustrates the manufacturing method being repeated to place an additional second portion of the article alongside the base portion. [Figure 28] The first part shows an alternative to FIG. 27, including only the base part of the previous embodiment. [Figure 29] FIG. 28 illustrates an alternative stacking arrangement to the parallel arrangement of FIG. 27. [Diagram 30] FIG. 29 illustrates an alternative stacking arrangement to the parallel arrangement of FIG. 28. [Diagram 31] FIG. 1 illustrates using this concept to assemble one or more modules and then apply the same concept to assemble the one or more modules into a larger whole (or complex product). [Diagram 32] 1 illustrates the application of a method embodying the invention to the manufacture of a measurement stylus; [Diagram 33]13A-13C show alternative arrangements of the second portion on the base portion, where at least one point of the second portion is in contact with the base portion. [Diagram 34] FIG. 13 shows in more detail how the V-grooves of the bearing assembly kinematically engage with the balls of the gripper. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0098] A non-Cartesian coordinate measuring machine 10 is shown diagrammatically in Figure 1A. The coordinate measuring machine 10 generally comprises a movable platform 12 and a fixed platform 14 that are supported and moved relative to one another by a plurality of telescoping or extendable legs 16 provided between the movable platform 12 and the fixed platform 14. The movable and fixed platforms 12, 14 may also be referred to as stages (or structures or parts), and the extendable legs 16 may also be referred to as columns (or actuators). When there are six such extendable legs 16 (as shown in Figure 1A), the machine is generally referred to as a hexapod.

[0099] The extendable legs 16 are typically attached to the platforms 12, 14 via ball joints 18, with each leg 16 either having its own ball joint 18 at one or both ends (as shown in FIG. 1A) or sharing a ball joint 18 with an adjacent leg 16 at one or both ends. Each extendable leg 16 is typically formed as a pair of tubes, one tube being telescopically moved within the other by a drive mechanism (e.g., a linear motor) to provide extension and retraction of the extendable leg 16, as indicated by the arrows in each extendable leg 16, as described in more detail in, for example, U.S. Pat. No. 5,399,633. A degree of separation between the drive and measurement portions of each strut may also be provided, as described in U.S. Pat. No. 5,399,633.

[0100] Various relative positions between the movable platform 12 and the fixed platform 14 can be achieved by extending the legs 16 by different amounts. The relative position at any instant is monitored by a number of length measuring transducers 17, one such transducer for each extendable leg 16. Each length measuring transducer 17 may comprise an encoder scale paired with a read head, the encoder scale being suitably mounted on one of a pair of telescopic tubes and the read head being suitably mounted on the other. Thus, extension of the leg 16 causes the encoder scale to move past the read head, thereby allowing the length of the extendable leg 16 to be measured. The computer controller 15 operates to set the length of each extendable leg 16, providing the necessary relative motion between the platforms 12, 14. By having six such length measuring transducers 17, the relative position can be measured in six corresponding respective degrees of freedom (three translational degrees of freedom and three rotational degrees of freedom).

[0101] The workpiece 19 is attached to the lower (fixed) platform 14 and the measurement probe 13 is attached to the upper (movable) platform 12. A working volume (or operational volume) 11 is defined between the upper (movable) platform 12 and the lower (fixed) platform 14, and the measurement probe 13 is positioned within the working volume 11 (i.e., moved to a desired position) by operation of the extendable legs 16. The arrangement of Fig. 1A may be referred to as a bottom-up arrangement, since the extendable legs 16 extend upward from the fixed platform 14 to the movable platform 12. This arrangement is shown diagrammatically in Fig. 1B. Alternatively, in a top-down arrangement, as shown diagrammatically in Fig. 1C, the extendable legs 16 extend downward from the fixed platform 14 to the movable platform 12, the measurement probe 13 is attached to the underside of the movable platform 12, and the workpiece is attached to another part of the fixed platform (or structure) 14 below. These types of arrangements are described in more detail in US Pat. No. 5,399,323, which also describes the use of a non-hexapod drive arrangement in combination with a hexapod measurement arrangement.

[0102] A manufacturing method according to one embodiment of the present invention will now be described with reference to Figures 2 to 12. The method may be described as a measurement-aided manufacturing or assembly method, utilising a coordinate positioning machine 10 of the type described with reference to Figure 1A. Figures 2 to 12 show the machine 10 at different stages of the method, as will become apparent below.

[0103] The machine 10 of this embodiment includes a set of extendable legs 16, a first platform 12, and a second platform 14, where the first platform 12 is movable relative to the second platform 14 by movement of the extendable legs 16, just as described above with reference to FIG. 1A. Thus, in this embodiment, the first platform 12 is a movable platform and the second platform 14 is a fixed platform. The machine 10 of this embodiment differs from that shown in FIG. 1A primarily in what is attached to the movable platform 12, what is placed on the fixed platform 14, and, of course, how the machine is operated.

[0104] The support 22 is attached to the first (movable) platform 12 via the quill 20, and the first (movable) measurement probe 30, the gripper 50 and the adhesive applicator 90 are attached to the support 22. The second (fixed) platform 14 is provided with the second (fixed) measurement probe 40, as well as the various parts 60, 70 and 80 of the article to be manufactured (or assembled) in the method. Due to the limitations of representing a three-dimensional machine diagrammatically in only two dimensions, the adhesive applicator 90 is only shown in FIG. 8 (which is the stage of the method at which the adhesive applicator 90 operates), but all three tools 40, 50, 90 are supported simultaneously on the support 22 (and therefore also on the movable platform 12 via the quill 20). The quill 20 is of a length suitable to position the support 22 (and in particular the tools 40, 50 and 90) in the appropriate positions within the working volume 11 of the machine.

[0105] In the above arrangement, it can be seen in particular that there are two probes: a first (movable) probe 30 is mounted on the first (movable) platform 12 and a second (fixed) probe 40 is mounted on the second (fixed) platform 14. The reasons for this arrangement will become apparent below. The first probe 30 has a stylus tip (or probe tip) 32 and the second probe 40 has a stylus tip (or probe tip) 42.

[0106] Also, as shown in Fig. 2, the article to be assembled has a base part 60, a first part 70 already fixed to the base part 60, and a second part 80 that is placed (as part of the method) on the base part 60 in a predetermined spatial relationship with the first part 70. The first part 70 has a representative feature 72 and the second part 80 has a representative feature 82, and it is important that, particularly in the final article, these representative features 72, 82 are accurately positioned relative to each other. The base part 60 (and with it the first part 70) is supported on the fixed platform 14 via a first support 21, and the second part 80 is supported on the fixed platform 14 via a second support 23, which are intended to raise the supported parts to a more convenient height for measurement and / or manipulation, but may also provide a fixation function for holding the supported parts in place.

[0107] With brief reference now to other known manufacturing techniques to place embodiments of the present invention in context, when assembling components on a printed circuit board, it is usually not important that the components be very precisely positioned on the circuit board, either absolutely or relative to other components. Rather, it is merely required that the contacts of the components be positioned on the correct corresponding solder pads on the circuit board, so that the components will make electrical contact with their solder pads via solder, allowing for a reasonable degree of manufacturing tolerance. In this regard, most manufacturing of printed circuit board assemblies (PCBA) is carried out using surface mount techniques that include a reflow soldering step. In such techniques, the solder pads of the board are covered with solder paste prior to placement of the components. An automated "pick and place" machine is then used to place the components on the appropriate pads of the board in turn, and release each component so that it is very loosely held by the uncured solder paste, i.e., the component is not fixed or firmly held in place prior to being released by the pick and place machine. The board is then placed in a reflow soldering oven, which typically involves multiple stages to gradually heat the entire board (e.g., using heated gas or infrared radiation) until it reaches a temperature where the solder paste melts or reflows. The board is then slowly cooled, whereupon the molten solder solidifies and securely fastens the components in place.

[0108] In the manufacture of the PCBAs described above, the placement of components on the circuit board does not need to be highly accurate due to the relatively large size of the solder pads. In the image-based system method of US Pat. No. 6,299,433 (further described above), where the components to be assembled together are imaged by an imaging (e.g., video) system to establish their position relative to each other, the method is not only computationally intensive (and therefore relatively slow), but also relatively inaccurate for an image-based method. Furthermore, the components may slightly shift position after being released by the machine and before being processed in a reflow soldering oven, but this is not important in the context of PCBA manufacture, where precise spatial positioning is not required, only reliable electrical connections are required.

[0109] In one embodiment of the present invention, it is envisaged that greater positional accuracy is required than is possible with these known methods, in particular that the first and second parts 70, 80 must be precisely fixed relative to one another in a predetermined spatial relationship.

[0110] With this in mind, in FIG. 2 it can be seen that the first portion 70 (and in particular the representative feature 72) sits at a slight angle relative to the base portion 60 due to a small imperfection (e.g., bump) 62 on the surface of the base portion 60. It is important that the second portion 80 (and in particular the representative feature 82) is accurately aligned with the first portion 70 (and in particular the representative feature 72), regardless of any positional inaccuracies or imperfections associated with the already placed portions. For example, if a simple pick-and-place machine were employed to place the second portion 80 on the base portion 60, as in the PCBA example above, then the presence of the imperfection 62 on the base portion 60 would not be taken into account, and as a result the second portion 80 (and in particular the representative feature 82) would not end up being accurately aligned with the first portion 70 (and in particular the representative feature 72). Also, image-based methods would not be able to detect such small imperfections or misalignments and / or would not be able to detect them at a high enough refresh rate. For PCBA manufacturing, it is sufficient to assume that the substrate is perfectly planar, however, embodiments of the present invention are applicable to precise positioning of portions 70, 80 onto imperfect and / or non-planar substrates or base portions 60.

[0111] 3, the first and second platforms 12, 14 are moved relative to one another to bring the first probe 30 into a sensing relationship with the first portion 70. This relative movement of the first and second platforms 12, 14 is accomplished by varying the length of the extendable legs 16 under the control of the controller 15, as described above (see FIG. 1A). This is equivalent to measuring the first portion 70 with the first probe 30 at one or more points to provide a series of measurements. For example, if the first portion 70 is known to be generally cubic, measurements can be taken at each side of the first portion 70 to establish which are the sides and how the plane of each side is oriented. Furthermore, if necessary, measurements can be taken at one or more corners, etc., to better characterize the first portion 70, or it is also possible that fewer measurements are taken only if necessary, for example, to determine information regarding the plane of the top surface. These measurements of the first portion 70 are then used to determine the shape of the first portion 70. reference system The measurements of first portion 70 are three-dimensional point coordinate measurements. Because they define both the position (three translational degrees of freedom) and orientation (at least one rotational degree of freedom, preferably three rotational degrees of freedom) of first portion 70, they may be considered, collectively, to be measurements in more than two degrees of freedom.

[0112] As shown in FIG. 4, in this embodiment, the base portion 60 also has a reference system , is measured with the first probe 30 to establish. This may be necessary if it is desired to place one or more features on the base portion 60 that are used to determine exactly where on the base portion 60 the second portion 80 should be placed. For example, there may be one or more placement features (e.g., markings or indentations) on the base portion 60 into or on which the second portion 80 should be placed, such that the positioning of the second portion 80 relative to the first portion 70 is determined in part by the features of the first portion 70 and in part by the features of the base portion 60.

[0113] First portion 70 may conveniently be thought of as including base portion 60, and therefore FIGS. 3 and 4 are schematic views of first portion 70 (including base portion 60). reference system 3 shows a single step of measuring the first portion 70 (including the base portion 60) with the probe 30 to establish the . In other words, the first portion 70 may itself have multiple portions, any one or more of which may be the . reference system , and may be relevant to determining how second portion 80 is positioned relative to first portion 70.

[0114] In this embodiment, the first probe 30 is a contact or touch probe, as is the second probe 40. Touch probes are well known. For example, to make a measurement with the first probe 30, the machine is controlled to bring the stylus tip 32 into contact with the object to be measured. When a touch is sensed, the machine coordinates (e.g., the length of the extendable leg 16) are recorded, and from these machine coordinates the X, Y, Z coordinates of the touch point can be calculated. This assumes that the machine has been calibrated to provide some sort of mapping between the machine coordinates (such as the output from the length measurement transducer 17 shown in FIG. 1A) and the coordinates of the stylus tip, or at least the coordinates of the support to which the stylus is attached. Machine calibration techniques typically have in common the goal of identifying a parametric model of the relevant machine, in which a number of parameters are used to characterize the machine's geometry. Uncalibrated values ​​are initially assigned to these parameters as a starting point for the machine geometry. During calibration the machine is moved to a variety of different poses (based on current estimates of the machine parameters). For each pose, a calibrated measuring device is used to measure the actual pose and a measure of the error between the expected and the actual machine pose can be determined. The task of calibrating the machine then amounts to determining a set of values ​​for the various parameters of the machine that minimizes the error, using known numerical optimization or error minimization methods (such as the Levenberg-Marquardt algorithm).

[0115] Next, in the step shown in FIG. 5, the first probe 30 is used to measure the second probe 40 (or vice versa), and these measurements are taken based on the above-determined luminance of the first portion 70. reference system and the second part 80 to be determined (see below). reference system This is used to establish a relationship between the first probe 30 and the second probe 40. This is equivalent to measuring the probe coincidence position, which is the position of the machine (i.e. the relative position of the first and second platforms 12, 14) that will place the stylus tip 32 of the first probe 30 in exactly the same position as the stylus tip 42 of the second probe 40. As it is not possible to do this in practice, instead this is done by touch measurements with the first stylus tip 32 around the second stylus tip 42 and a sphere is fitted to these measurements to determine where the coincidence point is (i.e. the position of the centre of the second stylus tip 42). The two probes 30, 40 may be arranged to be of different stiffness to ensure that the second probe 40 triggers in preference to the first probe 30 or that the first probe 30 triggers in preference to the second probe 40 when the two stylus tips 32, 42 touch each other.

[0116] As mentioned above, coincident probe calibration using two touch-trigger probes can potentially suffer from different stiffness in X and Y relative to Z of the probe stems and kinematic springs. To overcome this, instead of using two touch-trigger probes, it is also possible to use an analog or scanning probe to measure the touch-trigger probe. Analog probes usually have a more uniform stiffness or response in X, Y and Z than touch-trigger probes. Furthermore, if an analog probe is used to measure the touch-trigger probe, the "extrapolate to zero" technique described, for example, in US Pat. No. 5,399,433 or US Pat. No. 5,499,433, can be employed to provide a very accurate measurement of the tip surface of the mating probe, from which a sphere fit can be performed as described above to determine the coincident position of the probes. The extrapolation can be performed within the range of deflection experienced by the analog probe before the touch-trigger probe misses and triggers. The analog probe could be moved relative to the touch-trigger probe, or vice versa.

[0117] As mentioned above, in this example, the first part 70 of the article has already been provided to the second (fixed) platform 14, while the second part 80 is still waiting to be used on the support 23. The next step is to support the second part 80 of the article on the first platform 12 so that it can be moved and placed in the desired position of the article. This is achieved in this embodiment by picking up the second part 80 from the support 23 using a gripper 50 supported on the first platform 12 via the support 22, as shown in FIG. 6. The machine is controlled (by appropriate modifications to the lengths of the various extendable legs 16) to bring the gripper 50 close to the second part 80. The gripper 50 includes a suction pad 52 that is activated when the gripper 50 is close to the second part 80, which holds the second part 80 to the gripper 50 with sufficient force that the second part 80 can be lifted from the support 23 against the action of gravity.

[0118] On the surface of the gripper 50 facing the second part 80, the gripper 50 is provided with a set of three balls 54 that kinematically engage with a corresponding set of three V-grooves 84 on the surface of the second part 80 facing the gripper 50. This ensures a predictable and consistent position of the second part 80 relative to the gripper 50, which aids in the subsequent measurement steps. It also ensures that if the second part 80 shifts slightly from the gripper 50, for example due to a slight loss of suction of the suction pads 52 or because the second part 80 is pushed slightly, the second part 80 will re-couple in exactly the same relative position when properly coupled again.

[0119] The concept of kinematic design requires restricting the degrees of freedom of movement of the body using a minimum number of constraints, and in particular avoiding excessive constraints. This means that it ensures a very repeatable positioning of the body relative to the holding device, and that the body will seat on the holding device in a predictable, repeatable and known manner. This is explained in [1] and [2]. It will be understood that the theoretical kinematic coupling requires a pure point contact, which is not possible in practice. Rather, in practice the contact will extend over a small area, which may be considered beneficial to distribute the load, and therefore the term kinematic coupling should be understood as covering a pseudo or quasi-kinematic coupling with a small contact area rather than a point contact area. Kinematic design considerations may still be considered to be met even with a small area contact, the actual contact area depending on the application concerned.

[0120] As shown in FIG. 7, after picking up the second portion 80 to move with the first platform 12, the second portion 80 is measured with the second probe 40 to determine the reference systemThis is entirely equivalent to that described above with reference to FIG. 3, although this time the measurements relate to the second portion 80 and are provided by triggers from a second probe 40, which is supported on a second (fixed) platform 14. The measurements of the second portion 80 are three-dimensional point coordinate measurements. Taken together, they can be considered as measurements in more than two degrees of freedom, since they define both the position (three translational degrees of freedom) and the orientation (at least one rotational degree of freedom, preferably three rotational degrees of freedom) of the second portion 80.

[0121] Currently, the first reference system (i.e., the first portion 70 reference system ) and the second reference system (i.e., the second portion 80 reference system 5. Since no relationship has been established between the first and second probes 30, 40, the measurements of the first portion 70 taken by the first probe 30 are essentially independent of the measurements of the second portion 70 taken by the second probe 40. In other words, no link has yet been established between the respective measurements associated with the two different probes 30, 40. This is when the information obtained from the step shown in FIG. 5 comes to be used, because the match positions of the probes determined in that step are sufficient to determine the relationship between the first and second probes 30, 40. reference system Establish a link or relationship between or in common reference system As shown in Figures 8 to 12, two reference system The relationship established between the first and second portions 70, 80 is used in a subsequent step to form a common reference system and fix the first and second portions 70, 80 in the predetermined spatial relationship relative to one another. reference system This idea of ​​establishing relationships between will be explained further below with reference to Figures 15 to 22.

[0122] As shown in Figure 8, two reference systemOnce the relationship between them is established, some hardenable adhesive 64 is applied by an adhesive applicator 90 to the base portion 60 on which the second portion 80 is to be placed. Next, as shown in FIG. 9, the machine is controlled (by appropriate changes to the lengths of the various extendable legs 16) to rotate the first (movable) platform 12 relative to the second (fixed) platform 14 so that the second portion 80 is mounted to the common reference system 7, in order to be properly aligned with the first portion 70. Conveniently, the relative rotation of the platforms 12, 14 is arranged to provide a fixed point of rotation, for example coinciding with a point 86 located at the bottom of the second portion 80, although this is not required.

[0123] Next, the common reference system Once the established relationship has been used to achieve the correct alignment (orientation) of the second portion 80 relative to the first portion 70 in the common position, as shown in FIG. 10, the machine is brought to a common position, although not yet in the correct position. reference system The first (movable) platform 12 is controlled to move (by appropriate change in the length of the various extendable legs 16) relative to the second (fixed) platform 14 to place the second part 80 relative to the first part 70 in the correct spatial relationship (both in position and orientation) within the machine, with a gap intentionally left between the first and second parts 70, 80. With the uncured adhesive 64 applied in the correct location, the second part 80 is still held and supported by the machine relative to the first part 70, and the uncured adhesive 64 fills the gap between them. As shown in FIG. 11, a UV source on the gripper 50 applies ultraviolet light 56 ​​to the adhesive 64 to cure it. The second part 80 could be at least partially transparent to ultraviolet light (e.g., formed of a plastic material) or the ultraviolet light could be applied around the second part 80, or a separate UV source could be provided on the support 22 or even elsewhere on the machine.

[0124] As shown in Figure 12, once the adhesive has cured, the first platform 12 is moved away from the second platform 14, leaving the assembled article on the support 21, with the first and second portions 70, 80 now precisely secured to one another on the base portion 60. The final article 100 is shown in close-up in Figure 13, which shows how the described method has resulted in the desired alignment between the representative features 72, 82 of the first and second portions 70, 80, despite the presence of imperfections 62 in the surface of the base portion 60.

[0125] The above method is summarized in the flow chart of FIG.

[0126] The concept of using a fixed probe and a moving probe, and the two probes measuring separately reference system The idea of ​​establishing a relationship between is summarized diagrammatically in Figures 15-22. Similar to the representation used in Figures 2 to 12, Figure 15 shows a movable platform and a fixed platform which are movable relative to one another. Of course, both platforms could be movable, and in practice it is simply convenient to have one fixed and the other which moves, since it is the relative movement between the two platforms that is important, rather than the absolute position of either one. The fixed platform is reference system A supports or carries a plurality of objects and a probe in a fixed relationship to one another within A, while the moving platform reference system Within B, a plurality of objects and probes are supported or carried in fixed relationship to one another. Initially, reference system It is unclear how A and B are related to each other.

[0127] In FIG. 16, the movable platform is moved to bring the movable probe into sensing relationship with a point (feature or corner) of one of the articles on the fixed platform. The coordinates of this point are expressed by the vector a1The coordinates are recorded as a set of machine coordinates that define the relative position of the platform at that particular pose (i.e., the pose that places the tip of the movable probe in contact with a particular point on the article), for example the lengths of each of the extendable legs of the hexapod machine, and the raw readings from transducer 17 that are used to derive those lengths. a1 are assumed to be derived (transformed) from machine coordinates based on the known geometry of the machine, and then recorded as Cartesian X, Y, Z coordinates, into which normal vector arithmetic fits.

[0128] Next, in FIG. 17, another point (feature or corner) on the article is sensed using the moving probe, and the point coordinates are calculated using the vector a2 A point (feature or corner) on another item on the fixed platform is then sensed with the moving probe and the point coordinates are recorded. a3 19-21, the movable platform is moved to bring the points or features of the movable article into sensing relationship with the fixed probe, respectively, and the point coordinates are recorded as b1 , b2 , and b3 This results in:

[0129] What is being controlled for all such measurements is the same set of extendable legs, and each point coordinate is therefore expressed in a common set of machine coordinates (e.g., a set of leg lengths), so that these point coordinates a1 from a3 , and b1 from b3 are all measured in the same machine coordinate system, but reference system A (or an equivalent coordinate system A) has coordinates in another reference system B (or equivalent coordinate system B) and the coordinates of the Earth reference system (or coordinate system), how they relate to each other is still unclear. For example, reference system Although it is known how the points in are spatially related (e.g., a2 - a1 teeth, reference system A is a vector from point 1 to point 2 in A), different reference system It is unclear how the points in are spatially related (e.g., b2 - a1 is not a valid consideration at this time). reference system The relationship between them is established in the steps shown in FIG.

[0130] Conceptually, the relationship is established by moving the platform to bring the detection points of both probe tips (i.e., their respective centers) to the same point, i.e., the same location in the Earth's coordinate space (coincidence point). Once this is determined to have occurred, the two reference system A link is established between A and B, and various items on both platforms can be shared reference system C(Earth reference system , or two reference system A and B).

[0131] When this point is in the coincident position shown in FIG. reference system A a4 As, reference system B b4 However, this is also recorded as reference system And the point c0 The match score can be recorded as c0 There are two reference system It effectively connects A and B. Now the points measured in Figure 20 b2 is a common reference system In C, c0 +( b2 - b4 ), and the points measured in FIG. a2 is a common reference frame. c0 +( a2 - a4 )

[0132] Returning now to the schematic diagrams of Figures 2 to 13, in which the first and second portions 70, 80 are shown positioned side-by-side on the final article (see particularly Figure 13). The first portion 70 is described as having a representative feature 72, and the second portion 80 is described as having a representative feature 82, and it is noted that it is important that in the final article, these representative features 72, 82 are positioned with high precision relative to one another. A practical application of the schematic example will now be described with reference to Figures 23 to 25.

[0133] FIG. 23 shows a simple rearrangement of the parts 60, 70, 80 that make up the article 100. In the depiction of FIG. 23, the base part 60 is an elongated tube (in this example, with a square cross section) with a longitudinal axis 90, and the first and second parts 70, 80 are arranged in line along the longitudinal axis 90 of the base part (tube) 60. Although the first and second parts 70, 80 are still shown diagrammatically, it is now clear that the representative features 72, 82 are aligned transversely to the longitudinal axis 90. The base part (tube) 60 constitutes the first tube 60, and the article 100 also comprises a second tube 66 (in this example, with a square cross section) that slides telescopically inside the first tube 60. The first part 70 represents a read head of a measurement encoder of the type described above with reference to FIG. 1A, and a corresponding encoder scale 68 is provided on the second tube 66.

[0134] Thus, the article 100 produced by the method embodying the invention (as described above) corresponds to one of the extendable legs 16 described above, such that the coordinate measuring machine 10 is used to make an extendable leg 16 for use in another such coordinate measuring machine. The second portion 80 represents a bearing, allowing the second tube 66 to slide within the first tube 60, and the representative feature 82 is the axle of the bearing. The representative feature 72 is the sensing portion of the readhead, which must in fact be precisely aligned with the encoder scale 68 for the most accurate measurement results, and the alignment of the second tube 66 within the first tube 60 is defined by the alignment of the second portion (bearing) 80. Because the method ensured that the second portion (bearing) 80 is precisely aligned with the first portion (readhead), the result is a precisely formed article (extendable leg) 100, in which the encoder scale 68 operates in precise alignment with the readhead sensor 72.

[0135] A more realistic depiction of a bearing assembly 800 for use in such an article 100 is shown in FIG. 24. The bearing assembly 800 corresponds to the second part 80. The bearing assembly 800 comprises a wheel 860 supported on an axle 820, which corresponds to the representative feature 82 described above. A kinematic positioning feature 840, which corresponds to the V-groove 84 described above, is provided on one side of the bearing assembly 800, with the wheel 860 protruding most prominently from the other side of the bearing assembly 800. The kinematic positioning feature 840 includes two sets of three V-grooves (i.e., six in total), allowing the bearing assembly 800 to be picked up by the gripper 50 (with three balls 54) in two different orientations (or in any one of six different orientations, since with only three rotationally symmetric V-grooves it is already possible to pick up in any one of three different orientations). FIG. 34 shows in more detail how the V-groove 840 of the bearing assembly 800 kinematically engages the ball 54 of the gripper 50.

[0136] 25 shows how four such bearing assemblies 800 (corresponding to the four second portions 80) are assembled onto the outer tube 600 (corresponding to the base portion 60), with the bearing assemblies 800 seated partially through a corresponding number of openings (or pockets) formed in the outer tube 600. The flanges 830 of the bearing assemblies 800 are wider than the openings 610 and cannot pass through the openings 610, but instead seat on and are supported by the outer tube 600 via adhesive 64, which fills the gaps purposefully left between the bearing assemblies 800 and the outer tube 600, as described above. The wheels 860 protrude through the openings 610 when assembled, so that the wheels 860 run along the inner tube 660 (corresponding to the inner tube 660 of FIG. 23).

[0137] The inner tube 660 has a square cross section and there are two bearing assemblies 800 for each of the two adjacent sides of the inner tube 660. The inner tube 660 is held in contact with the bearing assemblies 800 by magnetic means, a magnet (not shown) is provided for each bearing assembly 800 and the inner tube is at least partially formed of a magnetic material. A third side of the inner tube 660 (just hidden in the view of FIG. 25) is provided with an encoder scale 680. A readhead mounting block (or bracket) 700 is provided in an opening 630 formed in the outer tube 600 and a readhead 710 is mounted to the mounting block 700. The mounting block 700 corresponds to the first portion 70 described above and the sensor portion 720 of the readhead corresponds to the representative feature 72. An electrical cable 730 provides power to the readhead 710 and carries the sensor signal from the readhead 710.

[0138] A method of manufacture will now be described based on the particular embodiment and features shown in Figures 24 and 25. This method is generally consistent with that described above, for example with reference to Figures 2 through 12, although it involves some additional features that are relevant in the particular context of this embodiment, however these additional features will also apply to the more general teachings above.

[0139] First, a "quill offset" is determined. This involves measuring the center of a fixed ball using the moving probe 30 with the moving platform 12 set in multiple orientations. The center of the ball is used to calculate the center of rotation of the moving platform 12. The "quill offset" value in the controller 15 is adjusted so that when the moving platform 12 is commanded to rotate, the center of rotation is approximately at the moving probe tip 32.

[0140] Next, a "probe coincident position" is determined, which is the position at which the moving probe 30 is calibrated relative to the stationary probe 40. The relationship between the moving probe 30 and stationary probe 40 is established by measuring one probe tip 32, 42 with the other 42, 32. This is done using contact and sphere fitting to find the center point. The two probes 30, 40 are chosen to be of different stiffness so that a known one of the two probes will trigger. The deflection of the stylus(s) is assumed to be symmetric with respect to Z, so the XY positions are well known and the Z positions are less well known (but well enough known).

[0141] The tube 600 is then measured using the moving probe 30 to determine the coordinate system (or "Csys" for short) of the tube 600, which is denoted as TubeCsys. The coordinate system TubeCsys is the same as that described in the first part above. reference system and in this context the first part includes the tube 600 and the readhead bracket 700. The coordinate system TubeCsys is determined as follows:

[0142] (a) Touching around the tube 600 with the moving probe 30 is used to find the axis of the cylinder of the tube 600.

[0143] (b) Touching one or more of the pockets 610 at the front and rear with the moving probe 30 is used to determine the Z-axis position of the tube 600 .

[0144] (c) A touch on the side of the readhead bracket 700 with the moving probe 30 is used to fit a plane and the axis of the plane which is used to give the orientation of the tube 600.

[0145] (d) The measurements from (a), (b), and (c) are used to create a coordinate system, TubeCsys, of the tube 600 and the readhead bracket 700.

[0146] Subsequently, the bearing assembly 800 is picked up. A kinematic pick-up structure consisting of three balls and a suction cup is used to pick up the bearing assembly 800 from the tray-like support 23. The bearing assembly 800 has six positions, forming two sets of three V-grooves as described above.

[0147] The bearing assembly 800 is then measured using the fixed probe 40 to obtain a coordinate system for the bearing assembly 800, denoted as BearingCsys. The coordinate system BearingCsys is the same as that described in the second part above. reference system The coordinate system BearingCsys is determined as follows:

[0148] (a) The bearing axis 820 is measured using a touch with a fixed probe 40 and a cylinder fitted to these measurements to determine the vector direction of the axis 820.

[0149] (b) The ends of axis 820 are measured using a touch with fixed probe 40 to find the Z center of axis 820.

[0150] (c) The plane is measured using a touch with a fixed probe 30 to give the orientation of the bearing assembly 800.

[0151] (d) The measurements from (a), (b), and (c) are used to create a coordinate system, BearingCsys, for the bearing assembly 800.

[0152] The center of rotation of the moving platform 12 is then moved (from the moving probe tip 32) to the bottom of the bearing assembly 800. To achieve this, an offset is calculated from the "coincident probe position" to the origin of BearingCsys, and then offset a known distance (in this particular example, this is minus 5mm in Z) to arrive at the bottom of the bearing assembly 800 (i.e., at the bottom of the wheel 860), which is shown diagrammatically in FIG. 26. This offset is then added to the "quill offset" in the controller 15 to move the rotation point of the machine to the center of the bottom of the bearing assembly 800. Now the moving platform 12 can be rotated in the A, B, or C axis (the machine is non-Cartesian, so the moving platform 12 has A, B, C axes rather than X, Y, Z axes) and the bottom of the bearing will stay in a fixed position.

[0153] A bead of UV adhesive is then precisely applied to the tube 600 around the associated pocket 610 in the TubeCsys.

[0154] A coordinate transformation is required to move the bearing assembly 800 accurately to the desired location (this is the first and second steps described above). reference system (which is equivalent to the relationship between , and T is the 4x4 coordinate transformation matrix.

[0155] T = BearingCsys -1 ×TubeCsys The concept of coordinate systems, and transformations between coordinate systems, are well understood by those skilled in the art, but further explanation can be found in Non-Patent Document 3. As examples, some transformation matrices and operations are shown below.

[0156]

number

[0157] To illustrate some of the above steps that may be performed in the controller 15, some pseudo code is provided below.

[0158] Memorize the probe's matching position point ProbeOffset = (point)CommonData[“ProbeCoincidentPosition”] Stores the bearing assembly coordinate system CSYS BearingCsys = (CSYS)CommonData[“FrontBearingCsys”] Calculate the offset between the center of the bearing point and the tip of the moving platform probe and move it to the bottom of the bearing BearingPos = [BearingCsys.M.m30, BearingCsys.M.m31, BearingCsys.M.m32] offset = ProbeOffset - BearingPos + [0, 0, -5] Here, [0,0,-5] in the above description is an offset of minus 5mm in Z (as above).

[0159] Remember Tube Coordinate System CSYS TubeCsys = (CSYS)CommonData[“TubeCsys”] Calculate the transformation T = BearingCsys^-l * TubeCsys Calculate angle x, angle y, and angle z from T Move the rotation point of the moving platform 12 to "offset" SetTipOffset(offset) Rotating moving platform 12 MoveToAngle(Angles.x, Angles.y, Angles.z, 100, 100) Set local coordinates to TubeCsys, this allows the machine to be located in the TubeCsys coordinate system, and moving the quill offset to the bottom of the bearing will position the bottom of the bearing.

[0160] mc.SetCsys(TubeCsys) mc.UseLocalCsys( ) Here, the bearing assembly 800 can be positioned relative to the tube coordinate system TubeCsys, which is positioned such that there is a gap between the tube 600 and the bearing assembly 800, typically a gap of about 100 pm is appropriate.

[0161] The bearing assembly 800 is then cured in place. A UV light source is attached to the motion platform 12. It is used to cure the adhesive and thus stop the movement of the bearing assembly 800 in place.

[0162] In the above embodiment, the second portion 80 is measured with the second probe 40. In alternative embodiments, these measurements of the second portion may instead be assumed or inferred from its known position and orientation relative to the first platform 12, due to the repeatability and precision of the kinematic coupling used to support the second portion 80 on the first platform, and from knowledge of the shape of the second portion 80 (e.g., from a CAD model of the second portion 80). Thus, in another embodiment of the invention, there is no need for a second probe 40.

[0163] In an alternative embodiment, instead of using a fixed and moving touch probe, a fixed and moving imaging camera may be used instead. Equivalent to the coincidence point measurement in the previous embodiment, a key feature of one camera (such as a sensor) could be imaged with one camera to link measurements from the other camera. To measure in three dimensions, the imaging camera could include three imaging sensors positioned at different respective angles or orientations relative to the object, or three separate imaging cameras could be employed at different respective angles. Similarly, optical measurement devices such as fringe-based systems could be used in another embodiment, where fringes are projected onto the surface of the object or part, and these fringes would be imaged and analyzed to obtain measurements of the object or part.

[0164] As an extension to the above embodiment, the article 100 may be supported on a rotatable stage, itself supported on the second platform 14. Positioning the first part 70 relative to the second part 80 may then include controlling the machine to rotate the stage relative to the second platform 14. This allows parts to be assembled to the article 100 on different sides or surfaces that would otherwise be inaccessible, effectively providing a system with more than six axes (or degrees of freedom) to operate on, i.e., in addition to the six axes (or degrees of freedom) from the coordinate measuring machine itself, another axis of rotation is provided by the rotation stage. Or there may be six degrees of freedom overall, for example five provided by the coordinate measuring machine and the sixth by the rotation stage. In fact there could be any suitable number and combination of axes provided by these respective parts. One or both of the object and part to be positioned could be supported via an articulating head, such as a Renishaw REVO® probe head, to provide an additional degree of freedom (axis).

[0165] Similarly, the second portion 80 may itself be supported on a rotatable stage, with the rotatable stage for the second portion 80 supported on the first platform 12, so that positioning the first portion 70 relative to the second portion 80 could then include controlling a machine to rotate the rotatable stage for the second portion 80 relative to the first platform 12. This may be provided as well as, or instead of, a rotatable stage for the first portion 70, providing even greater manufacturing flexibility for the system.

[0166] The measurements of the first and second portions 70, 80 are described above as being measurements in three or more degrees of freedom because they define both the position (in three translational degrees of freedom) and the orientation (in one, two or three rotational degrees of freedom) of the portions (or at least their major features). Also, even if the measurements are three degrees of freedom, an advantage is provided over known systems, such that the measurements define the position (in three translational degrees of freedom) of the portions, but not the orientation (rotational degree of freedom) of the portions. In a typical PCBA manufacturing system, the board is assumed to be planar, and because the mass of solder paste is relatively large, the absolute height of the components is of little importance, so that the placement of the components is only controlled to any precision in two degrees of freedom, namely in X and Y relative to the board; i.e., it is sufficient to simply ensure that the components are close enough to touch the solder paste.

[0167] FIG. 27 shows that the above process is repeated for three second portions 80-1, 80-2, and 80-3 disposed on the base portion 60.

[0168] Because it is explained above that the first portion 70 may conveniently be considered to include the base portion 60, Figures 3 and 4 show a single step of measuring the first portion 70 (including the base portion 60) with the first probe 30. Indeed, in another configuration, as shown in Figure 28, there is no "first portion" per se, only the base portion 60, so that the "first portion" in that example is simply the base portion 60. A "first portion of an object" could be referred to herein as an "existing or already assembled or already placed portion of an article," and a "second portion of an object" could be referred to herein instead as a "new or to be assembled or placed portion of an object." Furthermore, once the second portion 80-0 is assembled on the article 100 based on the measurements of the base portion 60, the resulting arrangement (i.e., the base portion 60 and the second portion 80-0) may then be considered the "first portion" (or "already assembled portion") for the subsequent step of adding another second portion 80-1 based on the measurements of the "first portion" (i.e., the base portion 60 and the second portion 80-0). When placing the second portion 80-1, the measurements used could simply be the previously obtained measurements of the base portion 60, or new measurements could be obtained for the now placed second portion 80-0, or a combination of these measurements could be used. Furthermore, similar considerations apply when placing the second portions 80-2 and 80-3.

[0169] Thus, for the example shown in FIG. 28, all of the portions 80-0 to 80-3 are "floating" above the base portion 60, allowing these portions 80-0 to 80-3 to be positioned very precisely (up to coordinate measuring machine accuracy) relative to one another and unaffected by any imperfections or irregularities in the base portion 60. Additionally, unlike the embodiment shown in FIG. 27, the portions 80-0 to 80-3 are not aligned with or positioned relative to the portion 70 which is directly attached to the base portion 60, but rather, all of the portions 80-0 to 80-3 are effectively positioned "freeform" in their desired relative orientations and fixed / held in their relative orientations via the base portion 60 and the fixing or support material 64 (e.g., a curable adhesive or welding). This allows for a very precise and flexible manufacturing or assembly method.

[0170] 29 and 30 show stacked alternatives to the side-by-side arrangements of FIGS. 27 and 28, respectively, where each new second portion 80 is positioned on top of the previous second portion 80.

[0171] As shown in FIG. 31, in an extension to the above embodiment, the finished product may be considered to be a self-contained module, such as module 100-2 shown in FIG. 31, which would form part of a larger whole (or complex product). Such module 100-2 may itself be considered a "second part" that is picked up by the coordinate measuring machine and placed in a desired spatial relationship with the "first part" of the article (e.g., first part 70 and / or base part 60 and / or another such multi-part module 100-1 created in a previous series of steps) in a manner entirely similar to that described above. In this manner, a more complex product 110 may be created. FIG. 31 also illustrates a highly non-planar base part 60 and a complex arrangement of parts on the non-planar base part 60, which embodiments of the present invention are particularly suited to address because of the inherent measurement precision of the coordinate measuring machine and its ability to position parts relative to each other in three or more degrees of freedom (i.e., position and orientation).

[0172] While the above embodiment uses a hardenable adhesive as the fixing medium, it is noted that welding is also suitable as a fixing process. Welding is a process of joining materials using high heat to melt the parts together (the molten material is the fixing medium) and allow them to cool to produce a fusion (the cooling process effectively activates the fixing medium). Welding is different from low temperature joining techniques such as brazing and soldering, which do not melt the base materials, but these are also suitable techniques for the fixing process in embodiments of the present invention. In addition to melting the substrates, a filler material is usually added to the joint to form a pool of molten material (weld pool or fixing medium) that cools to form a joint that may be stronger than the substrates. Pressure can be used in combination with heat or by itself to create a weld. A variety of energy sources can be used for welding, including gas flame (chemical), electric arc (electrical), laser, electron beam, friction, and ultrasonic.

[0173] Reference has been made to a coordinate measuring machine having a number of length measuring (or distance measuring or displacement measuring) transducers, such as the length measuring transducer 17 shown in FIG. 1A. Such length measuring transducers are used to measure relative motion at linear joints, providing a measure of relative motion between two parts of the machine. The coordinate measuring machine may also include one or more rotary joints and therefore also have one or more corresponding angular measuring transducers, as would be the case, for example, if the coordinate measuring machine were in the form of an articulated arm (similar to machines commonly referred to as robotic arms) with multiple rotary joints arranged in series. If such a serial kinematic coordinate measuring machine is used, it would benefit from using a machine architecture such as that disclosed in UK Patent Application No. 1918165.0, in order to avoid the inaccuracies normally associated with a serial kinematic arrangement of axes. The various length and angle measuring transducers may collectively be referred to as measurement transducers. The outputs of these measurement transducers may be considered to be or used to obtain machine coordinates for any particular configuration or attitude of the machine (e.g., the relative positioning of platforms 12 and 14 in FIG. 1A). The outputs of the measurement transducers are used both when determining or reading the machine's configuration (attitude) (for measurement operations) and when setting or changing the machine's configuration (attitude) (for positioning operations).

[0174] One example application of a manufacturing method embodying the invention is described above in which a coordinate measuring machine is used to make an extendable leg for use on another such coordinate measuring machine. Another exemplary application of a manufacturing method embodying the invention is for the manufacture of a stylus for a measurement probe, such as probe 30 described above and shown in Figure 2.

[0175] Such an application will now be described with reference to Figure 32, which is a schematic diagram similar to that shown in Figure 26, but adapted to the manufacture of a stylus rather than an extendable leg. The stylus has a stem 310 to which is attached a stylus tip (or ball) 320, the diameter of which can be as small as 2 μm. It is desirable for the stylus tip 320 to be located as precisely (and concentrically) as possible on the stem 310.

[0176] The basic methodology is equivalent to that described above and will not be described in detail again here. Figure 32 differs from Figure 26 by having a different type of gripper, which in the embodiment of Figure 32 is in the form of a suction tube 500. The suction tube 500 has an internal channel 510 through which air can be sucked in, thereby drawing and holding the stylus tip 320 into a cup 520 at the end of the suction tube 500. The inner surface of the cup 520 may have kinematic features 530 to allow the ball 320 to seat in a predictable and reproducible position within the cup; for example, three protrusions (from a concave portion-spherical surface) would be suitable as kinematic features, as shown most clearly in the dotted outline A of Figure 32. This forms a kind of tripod arrangement, which is very stable and allows the ball 320 to seat in a predictable manner within the cup 520. The three point contacts create three constraints, no more and no less than required (thereby satisfying kinematic design considerations by avoiding over-constraints). Thus, with the three constraints, ball 320 is constrained in three translational degrees of freedom, but is free to rotate about its center in three rotational degrees of freedom, which is not a problem since ball 320 is spherically symmetric.

[0177] As in the previous embodiment, after measuring the end of the stem 310 with the moving probe 30, a mass of hardenable adhesive (or brazing paste) 640 is applied to the end of the stem 310, taking into account the measurements of the stem 310 obtained with the probe 30. The ball 320 is then precisely positioned relative to the stem 310 using the method previously described, again taking into account the measurements of the stem 310 obtained with the probe 30. Preferably, a gap is maintained between the ball 320 and the stem 310, and the machine still holds the parts relative to each other while the adhesive 640 is cured. This results in the stylus shown in the left-hand view contained within the dotted outline B of FIG. 32.

[0178] It is also possible for the adhesive 640 to be partially (rather than fully) cured while the relative position is maintained by the machine, for example by blowing hot air on the curable adhesive for a short period of time, and then this is followed by a full curing (sintering) operation, but the machine has already released the ball 320 and the partially cured adhesive 640 has sufficient strength and holding power to hold the ball 329 in a fixed position relative to the stem 310 while the part is transferred to a sintering station and sintered (fully cured). It is also possible for the adhesive 640 to have sufficient holding power to hold the parts in a fixed relative position without first being partially cured.

[0179] In this example, since the orientation of the ball 320 on the stem 310 is not important (because the ball is spherical), it is not necessary to leave a gap between the ball 320 and the stem 310; instead, the ball 320 could be positioned to contact the end of the stem 310, as shown in the right-hand illustration contained within the dotted outline B of Figure 32. What is most important in this exemplary application is that the ball 320 is positioned concentrically with the stem 310; in other words, the radial positioning of the ball 320 relative to the longitudinal axis of the stem 310 is more important than its positioning along the longitudinal axis of the stem 310.

[0180] From the above, it is clear that it is not necessary that there be a gap left all around the part to be placed on the article, or even any gap at all. For example, an embodiment of the present application also finds use in precisely assembling parts to an article very precisely, with very tight tolerances, and engaging the parts with corresponding parts or features on the article without necessarily leaving any gaps. This may be the case, for example, where a part having a cylindrical protrusion is securely placed in or on an article having a cylindrical recess or hole, with the protrusion seating snugly and securely within (and contacting) the recess. The present invention provides a new approach to this assembly process, in which a coordinate measuring machine is used both to obtain three-dimensional measurements of the feature of the article (e.g., the cylindrical recess) and, based on those measurements, to use multi-axis positioning (e.g., 4-axis, 5-axis or 6-axis positioning) to position the feature of the part (e.g., the cylindrical protrusion) in a predetermined spatial relationship (multiple degrees of freedom) with respect to the feature of the article.

[0181] It will be appreciated that there may be gaps left in some places around the portion to be placed, but not in others; for example, if the orientation of the portion relative to the surface of the article is important, and not its height above the surface of the article, the portion may be placed to contact the article at one point (or points), but will still be held and fixed in the desired orientation relative to the article. This is shown in FIG. 33, which differs from FIG. 13 only in that the second portion 80 is placed to contact the base portion 60 at the circled point, but is left protruding from the base portion 60 in other places; in other words, it is not the case that there are gaps all around the second portion 80. This means that the height of the second portion 80 above the base portion 60 will be affected by surface imperfections such as ridges 62, but its orientation relative to the base portion 60 (and other already placed portions 70, such as the first portion) could still be controlled.

[0182] It will be appreciated that operation of the coordinate measuring machine 10 may be controlled by a program running on the machine 10, in particular by a program running on a coordinate measuring machine controller such as controller 15 shown diagrammatically in Figure 1A. It will be appreciated that control of the extendable legs may be provided by a program running on the controller 15. Such an operating program may be stored on a computer readable medium or may be embodied in a signal, for example a downloadable data signal provided from an internet website. The appended claims are to be understood as covering a program operating by itself or as a record on a carrier or as a signal or in any other form.

Claims

1. A method of assembling an article, the article including a first portion already in place and a second portion to be assembled on the article, the method comprising using a coordinate measuring machine to both obtain measurements of the first and second portions and to position the second portion on the article in a predetermined spatial relationship to the first portion in dependence on the measurements of the first and second portions, the coordinate measuring machine including first and second platforms movable relative to one another, the first portion being supported on the second platform, the second portion being supported on the first platform, and the coordinate measuring machine controlling the coordinate measuring machine to move the first and second platforms relative to one another. a first probe supported on the first platform and measurements of the first portion are taken using a first probe supported on the first platform and measurements of the second portion are taken using a second probe supported on the second platform, the method further comprising using the measurements of the first portion to establish a first frame of reference for the first portion, using the measurements of the second portion to establish a second frame of reference for the second portion, establishing a relationship between the first and second frames of reference, and using the established relationship to move the first and second portions to the predetermined spatial relationship within a common frame of reference.

2. 2. The method of claim 1, wherein establishing a relationship between the first frame of reference of the first portion and the second frame of reference of the second portion comprises determining position information associated with at least one point or feature that is common or coincident in both frames of reference.

3. 3. A method according to claim 1 or 2, characterized in that said common frame of reference is said frame of reference of said first part.

4. 4. The method of claim 1, 2 or 3, wherein the first and second reference systems of the first and second parts are first and second coordinate systems, respectively, and the established relationship is a coordinate transformation between the first and second coordinate systems.

5. 5. A method according to any one of claims 1 to 4, characterized in that the predetermined spatial relationship is defined in three or more degrees of freedom.

6. 6. The method of claim 1, wherein positioning the second part relative to the first part comprises controlling the coordinate measuring machine to move the second part relative to the first part in three or more degrees of freedom.

7. 7. The method according to claim 1, wherein the measurements are three-dimensional measurements.

8. 8. A method according to any one of the preceding claims, characterized in that the measurements are obtained by controlling the coordinate measuring machine to move a measuring device in three or more degrees of freedom.

9. 9. The method according to any one of the preceding claims, characterized in that the measurements are coordinate measurements.

10. 10. The method according to any one of the preceding claims, characterized in that the measurements are point coordinate measurements.

11. 11. A method according to any one of claims 1 to 10, characterized in that the measurements are or include machine coordinates or coordinates derived therefrom.

12. 12. A method according to any one of claims 1 to 11, characterized in that positioning the second part relative to the first part comprises controlling a machine to adopt a series of different machine coordinates.

13. 13. The method according to claim 1, wherein the measurements and the positioning of the second part are based on the same machine coordinate system.

14. 14. The method according to any one of claims 1 to 13, characterized in that the coordinate measuring machine comprises a plurality of measurement transducers, the same plurality of measurement transducers being used for obtaining the measurements and for positioning the second part based on those measurements.

15. 15. A method according to any one of claims 1 to 14, wherein positioning the second part in a predetermined spatial relationship relative to the first part comprises calculating a set of machine coordinates that will position the first and second parts in the predetermined spatial relationship in response to the measurements, and controlling a machine to adopt the calculated machine coordinates.

16. 16. A method according to any one of claims 1 to 15, comprising controlling a machine to hold the first and second parts in the predetermined spatial relationship while performing an action to fix the first and second parts in the predetermined spatial relationship.

17. A method as described in claim 16 dependent on claim 15, characterized in that controlling a machine to maintain the first and second parts in the predetermined spatial relationship includes controlling the machine to maintain calculated machine coordinates.

18. 18. The method of claim 16 or 17, wherein the fixing operation includes applying a fixing medium to contact the second portion when in the predetermined spatial relationship with the first portion, and activating the fixing medium to fix the first and second portions in the predetermined spatial relationship.

19. 20. The method of claim 18, comprising applying the fixation medium prior to moving the first and second portions into the predetermined spatial relationship, and then activating the fixation medium when the first and second portions are in the predetermined spatial relationship.

20. 20. The method of claim 18 or 19, wherein the fixing medium is a curable adhesive, and activating the fixing medium comprises curing the curable adhesive.

21. 21. The method according to claim 18, 19 or 20, characterized in that the fixing operation comprises a welding process, and the fixing medium and its activation are the result of carrying out the welding process.

22. 22. The method of claim 21, wherein the welding process is a laser welding process.

23. 23. A method according to any one of claims 18 to 22, comprising using the established relationship to determine where to apply a fixation medium.

24. 24. The method of any one of claims 1 to 23, wherein when the first and second portions are in the predetermined spatial relationship, the second portion does not directly contact the first portion of the article, the article includes one or more portions in addition to the first and second portions, and the second portion does not directly contact any of the one or more portions.

25. 25. The method of any one of claims 1 to 24, comprising leaving a gap between the second portion and the first portion of the article when in the predetermined spatial relationship, the article including one or more portions in addition to the first and second portions, and leaving a gap between the second portion and any of the one or more portions.

26. A method according to claim 25 dependent on claim 18, characterized in that the voids are at least partially filled by the fixing medium applied in the fixing operation.

27. 27. The method of any one of claims 1 to 26, wherein supporting the second part on the first platform comprises picking up the second part using a pick-up device supported on the first platform.

28. 28. The method of claim 27, wherein the pick-up device comprises a gripper.

29. 29. The method according to any one of claims 1 to 28, wherein the first platform is a movable platform and the second platform is a fixed platform.

30. 30. The method of any one of claims 1 to 29, wherein measuring the first portion with the first probe comprises moving first and second platforms relative to one another to bring the first probe into a sensing relationship with the first portion.

31. 31. The method of any one of claims 1 to 30, wherein measuring the first portion with the first probe comprises moving first and second platforms relative to each other in three or more degrees of freedom.

32. A method according to claim 29, claim 30 depending on claim 29 or claim 31 depending on claim 29, wherein the first probe is a movable probe.

33. 33. A method according to any one of the preceding claims, wherein the first probe is a contact probe, such as a touch probe or a tactile probe.

34. 34. The method of claim 33, wherein the first probe is a touch trigger probe.

35. 34. The method of claim 33, wherein the first probe is an analog or scanning probe.

36. 33. The method of any one of claims 1 to 32, wherein the first probe is a camera-based probe having at least one imaging sensor arranged at different respective orientations relative to each other.

37. 37. The method of any one of claims 1 to 36, wherein measuring the second portion with the second probe comprises moving first and second platforms relative to one another to bring the second probe into a sensing relationship with the second portion.

38. 38. The method of any one of claims 1 to 37, wherein measuring the second portion with the second probe comprises moving first and second platforms relative to each other in three or more degrees of freedom.

39. 39. A method according to claim 29 or any one of claims 30 to 38, respectively dependent on claim 29, wherein the second probe is an immobilized probe.

40. 40. A method according to any one of claims 1 to 39, wherein the second probe is a contact probe, such as a touch probe or a tactile probe.

41. 41. The method of claim 40, wherein the second probe is a touch-trigger probe.

42. 41. The method of claim 40, wherein the second probe is an analog or scanning probe.

43. 40. The method of any one of claims 1 to 39, wherein the second probe is a camera-based probe having at least one imaging sensor arranged at different respective orientations relative to each other.

44. 44. A method according to any one of claims 1 to 43, comprising measuring a first probe with a second probe and / or vice versa to establish a relationship between the first and second reference systems.

45. 45. The method of claim 44, wherein measuring the first probe with the second probe and / or vice versa comprises moving first and second platforms relative to one another to bring the first and second probes into sensing relationship to one another.

46. A method according to claim 2 or any one of claims 3 to 45 each dependent on claim 2, wherein the first and second probes each include a stylus tip, and wherein at least one point or feature which is common or coincident in both reference systems is the centre point of the stylus tips of the first and second probes when the first and second platforms are in positions relative to one another which would place the stylus tips of the first and second probes in the same position.

47. 47. A method according to claim 46, wherein one of the first and second probes is a touch trigger probe and the other of the first and second probes is a scanning or analogue probe, comprising using a zero extrapolation technique to measure or characterise a surface of the stylus tip of the touch trigger probe and determining therefrom the centre point of the stylus tip.

48. 48. A method according to any one of claims 1 to 47, comprising supporting the second part on a rotatable stage, the rotatable stage being supported on a first platform, and wherein positioning the first part relative to the second part comprises controlling the coordinate measuring machine to rotate the rotatable stage relative to the first platform.

49. 49. A method according to any one of claims 1 to 48, comprising supporting the article on a rotatable stage, the rotatable stage being supported on a second platform, and wherein positioning the first part relative to the second part comprises controlling the coordinate measuring machine to rotate the stage relative to the second platform.

50. 50. The method of any one of claims 1 to 49, wherein the first and second platforms are moved relative to one another in three or more degrees of freedom to position the second portion relative to the first portion.

51. 51. The method of any one of claims 1 to 50, wherein the first portion is a support or substrate portion of the article.

52. 52. The method of any one of claims 1 to 51, wherein the first and second portions are operative parts of the article that have a function in the use of the article and are not merely reference features, datums or the like that have a function only during manufacture of the article.

53. 53. The method of any one of claims 1 to 52, wherein the first and second parts of the article are functionally and / or mechanically and / or optically related parts of a final article.

54. 54. The method of any one of claims 1 to 53, wherein the second portion is supported on the first portion in the resulting article.

55. A method according to claim 54 dependent on claim 18, characterized in that the fixing medium used in the fixing operation is provided between the first and second parts.

56. 56. The method of any one of claims 1 to 55, wherein the first and second portions are supported in a resulting article on a base portion of the article.

57. A method according to claim 56 dependent on claim 18, characterized in that the fixing medium used in the fixing operation is provided between the second part and a base part.

58. 58. The method of any one of claims 1 to 57, wherein the first portion is or includes a base portion or substrate of the article.

59. 59. The method of any one of claims 1 to 58, wherein the first portion is or includes a feature of the article, e.g. an integral feature, such as a geometric feature formed on a surface of the article.

60. 60. A method according to any one of the preceding claims, comprising using a measurement device other than a probe to obtain the measurements.

61. 61. The method of any one of claims 1 to 60, wherein obtaining the measurements of a first portion of the article comprises obtaining measurements of one or more characteristics of the first portion.

62. 62. The method of any one of claims 1 to 61, wherein obtaining the measurements of a first portion of the article comprises obtaining measurements of one or more discrete points on a surface of the first portion.

63. 63. A method according to any one of claims 1 to 62, characterised in that the coordinate measuring machine is a machine adapted to measure in three dimensions the geometry or geometric properties of a physical object by sensing discrete points on a surface of the object using a sensing device such as a probe.

64. 64. A method according to any one of claims 1 to 63, wherein the coordinate measuring machine is a machine having a coordinate measuring device, such as a probe, for measuring the coordinates of points on a surface of the article.

65. 65. A method according to any one of the preceding claims, wherein the coordinate measuring machine is a non-Cartesian coordinate measuring machine.

66. 66. A method according to any one of claims 1 to 65, wherein the coordinate measuring machine includes a plurality of extendable legs.

67. 67. The method of any one of claims 1 to 66, wherein the coordinate measuring machine is a hexapod coordinate measuring machine, comprising six extendable legs.

68. 68. A method according to claim 66 or 67, wherein the machine coordinates of the coordinate measuring machine include values ​​respectively associated with lengths of a plurality of extendable legs.

69. A method as described in claim 66, 67, or 68, each dependent on claim 14, characterized in that the plurality of measurement transducers are associated with the plurality of extendable legs, respectively.

70. 70. A method according to any one of the preceding claims, wherein the second part and a measuring device, such as a probe, for obtaining the measurements of the first part are supported simultaneously on a common platform of the coordinate measuring machine that is moved when measuring the first part and when positioning the second part.

71. 71. The method of any one of claims 1 to 70, comprising repeating the method with one or more additional second portions of the article, the first portion in each iterative execution of the method being any portion or portions of the article resulting from any previous execution of the method.

72. 72. The method of claim 71, wherein the first portion in at least one of the iterative executions of the method includes at least one second portion from any previous execution of the method.

73. 73. A method according to claim 71 or 72, wherein using the coordinate measuring machine to obtain measurements of the first part in at least one of the iterative executions of the method comprises using measurements of the first part obtained in a previous execution of the method.

74. 74. A method according to any one of the preceding claims, wherein the, or each, second part is, or forms part of, either: (a) a bearing assembly for an extendable leg for a coordinate positioning machine; or (b) a ball or tip of a stylus for a measurement probe.

75. 75. A method according to any one of claims 1 to 74, wherein the first part is, or forms part of, either (a) a readhead or readhead holder for an extendable leg for a coordinate positioning machine, or (b) the stem of a stylus for a measurement probe.

76. 76. A manufacturing system or apparatus including a coordinate measuring machine configured to carry out the method of any one of claims 1 to 75.

77. 76. A computer program product which, when executed by a controller of a coordinate measuring machine, causes the controller to operate the coordinate measuring machine and performs the method of any one of claims 1 to 75.

78. A computer readable medium having stored therein computer program instructions for controlling a coordinate measuring machine to carry out a method according to any one of claims 1 to 75.

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