A workpiece support

Abstract

A workpiece support (18) for supporting a workpiece (14), the workpiece support (18) comprising a workpiece support body (54) and a workpiece support element (20) associated with the workpiece support body (54) for engaging the workpiece (14) and a piezo electric actuator (32) being associated with the workpiece support body (54) for moving the workpiece support element (20) for supporting the workpiece (14). The workpiece support body (54) comprising one or more flexures (44) that enable a movable portion (42) of the workpiece support body (54) to move when acted on by the piezo electric actuator (32) and to move the workpiece support element (20). The workpiece support (18) can comprise two or more workpiece support bodies (54) and a piezo electric actuator (32) being associated with each workpiece support body (54) for moving the respective workpiece support elements (20).

Description

A WORKPIECE SUPPORTPriority Cross-Reference

[0001] The present application claims priority from Australian Provisional Patent Application No. 2024902656 filed 26 August 2024 the contents of which is to be considered to be incorporated into this specification by this reference.Technical Field

[0001] The present invention relates to a workpiece support, such as a steady (or "steady rest"), top clamp or tailstock, for supporting a workpiece that is clamped for machining, such as by a multi-axis CNC machine tool. A multi-axis CNC machine tool may be a grinding machine, tool and cutter grinder or milling machine. Workpieces relevant to the present invention include longitudinal workpieces, for example those that are ground to form cutting tools, or machined parts such as cutting tips, known as inserts, such as carbide inserts. Many other workpieces and machined parts can be relevant to the present invention.Background of the Invention

[0002] The discussion of the background to the invention that follows is intended to facilitate an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any aspect of the discussion was part of the common general knowledge as at the priority date of the application.

[0003] CNC machine tools relevant to some aspects of the present invention are those that grip or clamp a longitudinal workpiece for rotation, so that the workpiece can be ground into the required profile. The workpiece would typically be held by a workholder, such as a collet and supported by a top clamp, steady or a tailstock. The workholder will establish the clamping axis of the workpiece, while a tailstock may support the free or opposite end of the workpiece. In some arrangements, a collet is used to clamp and rotate the workpiece so that the collet establishes the clamping axis of the workpiece. In other arrangements, that employ a top clamp and a collet, the top clamp clamps the workpiece and the collet rotates the workpiece, but in these arrangements, it is the top clamp that establishes the clampingaxis of the workpiece, not the collet. Once clamped and where appropriate, after a tailstock is introduced, the workpiece can be rotated by the collet and ground.

[0004] In many arrangements, a workpiece is clamped at one end by a collet and projects outwardly from the collet. Where the workpiece is longitudinal, it is usually subject to grinding loads that are transverse, usually normal or tangential to the longitudinal axis of the workpiece. Particularly with longitudinal workpieces of small diameter, and where the length to diameter ratio is large, the workpieces are prone to bending or deflection under the grinding loads, thus affecting the workpiece geometry and accuracy of the grinding and of the finished product. If the bending is sufficient, that can lead to the complete failure of the workpiece by snapping.

[0005] Accordingly, workpiece supports are often employed to support the workpiece at a position spaced from the workholder, for example at the opposite end of the workpiece by a tailstock support, or at a point along the length of the workpiece by a "steady", or by both of a tailstock support and a steady. The requirement for these supports is often related to the length and diameter of the longitudinal workpiece, where shorter or greater diameter workpieces require less support than longer, smaller diameter workpieces, due to higher stiffness. Often a workpiece is supported by a steady at the position where the workpiece is being ground, which is often referred to as the 'grind point'.

[0006] Workpiece supports are brought into a support position relative to a workpiece after the workpiece is initially clamped by the workholder. Clamping of the workpiece establishes the longitudinal axis of the workpiece and the workpiece support can then be shifted into engagement with the workpiece to support the workpiece against deviation from that axis during grinding. Ideally, the axis of the workpiece aligns with the axis of the workholder, but often this is not the case. Where the axis of the workpiece is not aligned with the axis of the workholder, the workpiece will experience axial misalignment known as "run out" when it rotates. This can affect the accuracy of workpiece machining to the detriment of the tools that are produced from the workpiece. The use of workpiece supports can correct this run out misalignment and thus improve the accuracy of workpiece machining.

[0007] Often with small diameter longitudinal workpieces, very fine movement of the workpiece support is required to properly position the workpiece support to engage the workpiece. For high precision workpieces movement or adjustment of the workpiece support at the micron level can be required. In these applications, the adjustment mechanisms need to be fine and precise.

[0008] The workpieces discussed above are longitudinal, however it is to be appreciated that workpieces of different geometry are also applicable to the present invention. Some types of cutting tools, such as endmills and drills for example, can accept cutting tips, known as inserts. These cutting tips can be replaceable as a cost-effective alternative to resharpening or replacing complete cutting tools. The inserts for these types of tools can be clamped by various types of workholders when they are ground into shape to form a cutting edge. In some arrangements, the insert is clamped by clamping jaws, or is held on a pin or an anvil, either of which is clamped by a collet.

[0009] Workpiece supports are used already. European application EP1712331A1 in the name of Rollomatic SA discloses a support that has lengthwise movement and rotation in two different reference planes. The support is adjustable by screw controlled levers.

[0010] European application EP4094888A1 also in the name of Rollomatic SA discloses a set of customized supports for supporting workpiece blanks of different diameters and teaches that the supports can be manually or automatically interchanged in a grinding facility to suit the particular workpiece being machined.

[0011] US 5,237,780 in the name of Arobotech Systems Inc discloses a steady rest in which one or more support arms for supporting a workpiece can be shifted to accommodate a shift in the axis or centerline of the workpiece during grinding of the workpiece. The support arms incorporate cam followers that interact with cam contours in guide plates in order to shift the support arms in the manner required. The guide plates can be shifted manually by adjustment screws for adjustment of the support arms within very fine tolerances.

[0012] US6699113 also in the name of Arobotech Systems Inc discloses a steady rest in which a camming arrangement is employed to adjust the vertical position of wear pads thatare attached to gripping arms. The arrangement employs a manual adjusting screw to move a pair of guides that engage a cam follower on each of the gripper arms. The manual adjusting screw moves one or both of the guides to an adjusted position.

[0013] Other patents in the name of Arobotech Systems Inc disclose adjustable fixture mechanisms which incorporate manual, screw adjustable gripping arm arrangements. For example, US 9,114,490 discloses a pair of gripping arms and an adjustment member that can be manually rotated for adjusting the spatial position of the wear pads of the gripping arms, while US 9,174,317 also discloses gripping arms that can be manually adjusted vertically and horizontally by the use of separate adjustment rods.

[0014] US20210016402 in the name of Fanuc Corp discloses an adjustment device for adjusting the height of an object to be supported. The device includes a fixed portion and a movable portion whereby the movable portion is provided to support an object and is movable in the height direction relative to the fixed portion. The movable portion is moved up and down in the height direction by a ball screw that drives a wedge shaped slide member that acts between the fixed and movable portions.

[0015] A consistent feature of the arrangements of the prior art discussed above is the manual nature of the adjustment mechanisms. While the manual adjustment is still able to provide for very fine adjustment (US 5,237,780 describes "controlled displacement of the support arms of as little as 0.00008 inches or less"), manual adjustment requires access to the workpiece support and relies on operator skills, such as sight and feel, to adjust the support arms to the extent required. Even though these prior art arrangements offer very fine adjustment, the accuracy of the adjustment is often affected by the skills of the operator making the manual adjustments, so that the accuracy required is not always achieved. Prior art arrangements also cannot perform adjustments in-process, ie during the process of workpiece grinding and batch grinding.

[0016] Adjustment mechanisms that are not manual also exist. For example, CH656564A5 in the name of Robert Bosch Gmbh discloses a tailstock for a lathe or a grinding machine in which a piezo electric drive is employed for opening and closing slots formed in the body of the tailstock. The slots are open through the surface of the tailstock and allowthe parts of the tailstock on either side of the slots to move relative to each other under the piezo electric drive.

[0017] US 2018 / 0095223 Al in the name of 3SAE Technologies Inc also discloses a multiaxis relative positioning stage that utilises piezo electric drive with multiple drives acting directly on plates that support a longitudinal component, such as an optical fibre. Multiple drives are employed to provide multiple degrees of freedom.

[0018] The present invention aims to provide an alternative workpiece support that is adjustable for positioning the support relative to workpieces of different diameter and / or shape and that offers an adjustment mechanism that provides fine and precise adjustment that may be used in-process.Summary of the Invention

[0019] According to the present invention there is provided a workpiece support for supporting a workpiece, the workpiece support comprising a workpiece support element for engaging a workpiece and a piezo electric actuator being associated with the workpiece support element for moving the workpiece support element for supporting the workpiece.

[0020] In a more specific form of the invention, there is provided workpiece support for supporting a workpiece, the workpiece support comprising a workpiece support body and a workpiece support element associated with the workpiece support body for engaging a workpiece and a piezo electric actuator being associated with the workpiece support body for moving the workpiece support element for supporting the workpiece, the workpiece support body comprising one or more flexures that enable a movable portion of the workpiece support body to move when acted on by the piezo electric actuator and to move the workpiece support element.

[0021] A workpiece support according to the present invention assigns piezo electric actuation to at least some of the movement of the workpiece support element. The workpiece support element can be moved entirely by piezo electric actuation, or piezo electric actuation can be used for a portion of the movement, for example for fine control. In some forms of the present invention, a pair of workpiece support elements is provided. In other forms of the invention, multiple (such as two or more) workpiece support elements areprovided. The workpiece support elements can initially undergo coarse movement manually, or by manual means, such as a screw drive in order to position the workpiece support elements close to the final engagement position with the final, fine adjustment being driven by the piezo electric actuators. This arrangement can equally be adopted in workpiece supports that employ a single workpiece support element, such as a "half-moon" bush, or more than two workpiece support elements. This arrangement that uses a manual screw drive followed by piezo electric actuation, allows the workpiece support elements to approach the workpiece quickly through relatively coarse adjustment (using the manual screw drive), but only to a position very close to the workpiece, to be within the range of the workpiece supports displacement, while the piezo electric actuators can finalise this movement through relatively fine adjustment. The coarse adjustment may bring one or both of the workpiece support elements into engagement with the workpiece, with the fine adjustment of the piezo electric actuation shifting the workpiece to the final position prior to the commencement of grinding. This is relevant to a workpiece steady, in which the steady can be adjusted upwardly manually to a position approaching engagement of the workpiece, or into engagement with the workpiece, whereafter micro adjustment is undertaken via piezo electric actuation. In a workpiece support according to the present invention which is formed as a steady, the piezo electric actuators can be digitally controlled to adjust the positions of the workpiece centreline relative to the centreline of the work holder / clamp / collet to ensure alignment or to remove runout by offsetting the workpiece centreline.

[0022] It is to be noted that more than one workpiece support element and an associated piezo electric actuator can be provided to support a workpiece. In relation to a workpiece support element formed as a steady, more than a single piezo actuated steady might be provided and each steady might include one or more piezo electric actuators.

[0023] Where the workpiece is a longitudinal workpiece, the present invention provides a workpiece support for supporting a longitudinal workpiece, the workpiece support comprising a workpiece support element which is movable laterally to the longitudinal axis of the workpiece to engage and / or shift the workpiece. A piezo electric actuator is associated with the workpiece support element for moving the workpiece support element. The workpiece support can also comprise a workpiece support body and the workpiece supportelement can be associated with the workpiece support body and the piezo electric actuator can be associated with the workpiece support body for moving the workpiece support element.

[0024] According to another embodiment of the present invention there is provided a workpiece support for supporting a longitudinal workpiece, the workpiece support comprising a pair of workpiece support bodies and a pair of workpiece support elements which are operable in combination to support a workpiece, the workpiece support elements being movable for engaging and / or shifting and supporting a workpiece and a piezo electric actuator being associated with each of the workpiece support bodies for moving the workpiece support elements.

[0025] The following discussion relates mainly to workpieces that are longitudinal workpieces such as end mills, drills, taps but it can also relate to workpieces that are other than longitudinal, such as workpieces that are inserts as discussed above.

[0026] According to the present invention, a pair of workpiece support elements can engage and support a longitudinal workpiece generally on opposite sides of the workpiece. It is not a requirement that the engagement be precisely on diametrically opposite sides of the workpiece, but rather, that the engagement be positioned to allow the centerline or axis of the workpiece to be shifted as required. The piezo electric actuation can be operable to independently shift each of the workpiece support elements, so that the workpiece can be shifted to move the centerline or axis in any direction perpendicular to the longitudinal axis of the workpiece. The required movement of the workpiece support elements may include movement of the workpiece support elements towards each other to initially engage the workpiece and following this, the movement may comprise one of the workpiece support elements moving towards the workpiece and the other moving away from the workpiece, to shift the workpiece in the desired direction.

[0027] A workpiece support according to the present invention does not rely on manual manipulation of adjustment mechanisms to adjust the position of workpiece support elements, or support arms or gripping arms of the prior art. Rather, the unique use of piezo electric actuators enables adjustment to be both fine and precise, and digitally controlled through an interface. The unique use of piezo electric actuators also enables adjustmentwithout requiring manual access to the machinery. This is a particular advantage in machine tools where the grinding operation is performed within a guarded enclosure so that access to the workpiece is more restricted. Of course, the fine adjustment of the piezo electric actuation can be combined with coarse adjustment as described above, however, the coarse adjustment can be an initial adjustment in the machine set up, while the fine adjustment might be an ongoing adjustment that occurs automatically prior to grinding and in some forms of the present invention, during grinding and between workpiece loading for cycles of batch grinding.

[0028] The use of piezo electric actuation advantageously also facilitates the potential for greater accuracy and control of the positioning of the workpiece support elements relative to a workpiece. In some of the prior art discussed above, manual setting of the workpiece support elements takes place by the operator using precision measurement instruments such as dial indicators to guide incremental manual adjustments. Other means such as touch probing, camera vision or detection by laser can be employed to assist positioning of the workpiece support elements but still the operator is required to judge when the workpiece support elements have engaged the workpiece and whether the centerline or axis of the workpiece is properly positioned. Clearly this can introduce errors in positioning, depending on operator experience and skill, noting that the movement the workpiece support elements are undergoing can be in the region of microns, which movements are not visible to the naked eye and which are difficult to view even with camera magnification. Computer imaging and probing can be used to analyse position, but still the accuracy and control of the positioning of the workpiece support elements can be improved.

[0029] The applicant has established that the use of piezo electric actuation can improve the accuracy and control of the positioning of the workpiece. To extend further, an optional feature allows for establishing electrical contact between each workpiece support element, driven by a piezoelectric actuator, and the workpiece itself as soon as the support element engages with the workpiece. Accordingly, as the piezo electric actuators approach the workpiece, there will be no flow of voltage between the workpiece support element and the workpiece, but as soon as contact occurs, voltage flow will occur and can be detected, functioning as a form of probe. As soon as voltage flow is detected, confirmation of contact between one or both of the workpiece support elements and the workpiece is established.This occurs without any requirement for operator skill or judgement and the control system can immediately terminate further movement of the piezo electric actuators as soon as contact is established. This process can also function in the reverse direction from a contact / preload state between the workpiece and the workpiece support element, to a state just to the point of losing voltage flow, so that there is no force exerted on the workpiece, but there is still contact.

[0030] Moreover, once contact between one or both of the workpiece support elements and the workpiece is detected, further or continued movement of the piezo electric actuators can occur, if the centerline or axis of the workpiece is out of alignment with the workholder so that realignment is required, or is a selected centreline offset is desired. Advantageously, this further or continued movement of the piezo electric actuators can be controlled without any requirement for operator skill or judgement, again based on the electrical contact between the workpiece support elements and the workpiece. Once the workpiece support elements have engaged the workpiece, voltage flow will occur and can be detected. However, if the piezo electric actuators continue to shift the workpiece, the resistance to workpiece movement will increase and that increase in resistance can be detected by strain gauges fitted to piezo electric actuator based on the load imparted on the piezo electric actuators. The position of the workpiece can thus be accurately identified based on the electrical feedback provided by the piezo electric actuators or workpiece support elements acting as contact probes. The use of strain gauges with a closed loop control system, ensures that the true strain / displacement of the piezo electric actuators, which is effectively the position of the workpiece support elements, remains consistent with variable force applied on them, especially seen during workpiece grinding. The positioning consistency is maintained without requiring manual access to the workpiece and without manually manipulating the adjustment facility to account for varying load conditions.

[0031] The applicant has also established that the use of piezo electric actuation can facilitate dynamic adjustment during a machining process. This distinguishes the present invention over prior art manual adjustment arrangements that make an initial operator adjustment prior to machining and that initial operator adjustment is retained throughout the machining process. Accordingly, in the prior art arrangements, if the workpiece would benefit from realignment during the machining process, realignment is not available. Incontrast, in the present invention, the position of the workpiece can be automatically digitised and adjusted during the machining process, by piezo electric actuation.

[0032] The possibility of dynamic adjustment provides the present invention with a significant advantage over manual adjustment arrangements. The dynamic adjustment can be automated based on determining the desired position of the centerline or axis of the workpiece so that the predetermined position of the workpiece is obtainable and maintained throughout the machining process. This might require the piezo electric actuators to preload the workpiece during machining, removing the run-out of the workpiece and shifting the workpiece centreline to a predetermined offset centerline or axis of the workpiece. An open or closed loop control system can be automated to constantly monitor the position of the workpiece by utilising a position feedback system such as a strain gauge system to correct the position where it is determined that the workpiece has shifted away from the preferred position due to grinding loads.

[0033] The use of electrical contact between individual workpiece support elements and the workpiece to provide electrical feedback for initial and dynamic adjustment requires the workpiece support elements and the workpiece to be electrically conductive, which in most applications of the present invention will be the case.

[0034] The discussion above has been made in respect of a workpiece support that has two workpiece support elements. However, it is within the scope of the present invention to provide a workpiece support that has a single workpiece support element, and such a workpiece support could be a clamp, such as a top clamp. Accordingly, the present invention also provides a workpiece support for supporting a workpiece, the workpiece support comprising a workpiece support element which is operable to clamp a workpiece, the workpiece support element being movable to engage and clamp a workpiece and a piezo electric actuator being associated with the workpiece support element for moving the workpiece support element.

[0035] It is also within the scope of the present invention to provide a workpiece support that has more than two workpiece support elements. For example, a workpiece support can be provided for supporting a workpiece in which the workpiece support comprises at least three workpiece support elements which are operable in combination to support aworkpiece, the workpiece support elements being movable relative to each other for engaging and supporting a workpiece and a piezo electric actuator being associated with each of the workpiece support elements for moving the workpiece support elements. This could also be considered a form of clamping. The workpiece support can comprise a workpiece support body associated with each workpiece support element and a piezo electric actuator associated with each workpiece support body.

[0036] In the above form of the invention, as an example, the workpiece support elements may be positioned to engage a longitudinal workpiece generally at 120° to each other, or alternatively, two of the workpiece support elements can be positioned to engage a workpiece at positions closer to each other and the third workpiece support element can be positioned to engage the workpiece spaced apart further from the first and second workpiece support elements.

[0037] In any of the workpiece supports according to the present invention, the workpiece support elements can be formed to engage a workpiece in any suitable manner. In some forms of the present invention, the engagement surfaces of the workpiece support elements are shaped or configured for sliding engagement with the workpiece, so that the workpiece can shift relative to the engagement surfaces as the workpiece support elements are shifted by the piezo electric actuators. The workpiece support elements can have a flat or planar engagement surface, or the engagement surface can be curved, concave for example, or it can be configured for point engagement. The shape or form of the workpiece can influence the shape or form of the engagement surface. Also, in workpiece supports that employ more than one workpiece support element, the workpiece support elements can have different engagement surface shapes or configurations.

[0038] The piezo electric actuators act on the workpiece support elements or the workpiece support bodies in any suitable manner. In some forms of the invention, the workpiece support bodies can comprise lever arms which have a workpiece engagement section and a piezo electric actuator engagement section which are offset. This arrangement can be used to provide mechanical advantage.

[0039] In other forms of the invention, the workpiece support bodies can comprise columns so that the piezo electric actuator engages the column at one end to push thecolumn along its lengthwise axis and the opposite end of the column comprises the workpiece support element for engaging the workpiece and the shift in the workpiece is equal to the shift in the column. This can be considered to be direct drive. In other forms of the invention, the workpiece support bodies can instead be a block or plate, or any suitable intervening member positioned between the end of the piezo electric actuator and the workpiece support element that transfers piezo electric actuator movement to the associated workpiece.

[0040] The workpiece support body can be formed as, by or in plate form, most likely metal plate form, with the plate including one or more slots or flexures that enable a portion of the plate to shift when acted on by a piezo electric actuator. For example, in some forms of the present invention a workpiece support for supporting a workpiece can comprise a workpiece support body and a workpiece support element for engaging a workpiece and a piezo electric actuator being associated with the workpiece support body for moving the workpiece support element for supporting the workpiece, the workpiece support comprising one or more flexures that enable a movable portion of the workpiece support body to move when acted on by one or more piezo electric actuators.

[0041] The portion of the plate that shifts can also comprise the workpiece support element. The plate can include a pocket, slot or opening to accommodate the piezo electric actuator. In these forms of the invention, each workpiece support element can remain attached to or part of the plate, but also can be shiftable relative to other parts of the plate, for example a workpiece support body or a workpiece support plate body of the plate. Advantageously, the resilience or memory of the plate (in the form of repeatable elastic rotation of flexures) can be used in order to return the workpiece support elements from an actuated position. That is, the portion of the plate that can shift under piezo electric actuation, shifts by elastic flexing of the slots or flexures and thus that portion of the plate returns to the original position once the actuation load is relieved or removed. Accordingly, a workpiece can be gripped or supported by movement of the workpiece support element or elements under piezo electric actuation and once the grip or support is no longer needed, the actuation load can be removed and the workpiece support element or elements will return to the original or initial position by plate material resistance to finite rotation and displacement.

[0042] The plate can include multiple slots or flexures. Depending on the configuration, multiple slots or flexures can be provided to reduce the load required to be applied to the workpiece support element by the piezo electric actuator, whereby as the number of slots or flexures increases, the plate resistance to rotation and displacement decreases. To increase plate rotation and deformation resistance various design elements of the flexure and plate configuration may be implemented, including but not limited to; decreasing the number of flexures or shortening the flexures, or thickening the plates or changing the geometry of the flexures. There are many types of flexure designs, some rotation based, some displacement based, but for suitable flexures for the present invention, the overall elastic characteristic is common across them all.

[0043] In some forms of the invention, the workpiece support body is formed from a plate and two or more slots or flexures are formed in two columns in the plate that are spaced apart and generally parallel, with a column being formed between the spaced apart slot or flexure columns. The column can be a solid column, or it could be other than solid, for example if the plate were a perforated plate where the column would be a perforated column. An actuation column will be referred to hereinafter, to cover solid and non-solid plate columns. A piezo electric actuator can act against the base or one end of the actuation column to shift the actuation column in the direction of actuation by the slot or flexure columns flexing in the direction of the load applied to the actuation column. The opposite end of the actuation column can include the engagement surface of the workpiece support element, or it can extend to a main body or a plate body that includes the engagement surface of the workpiece support element, or it could be a mount for a replaceable workpiece support element. Piezo electric actuation thus translates the actuation column, or the actuation column and the main body or plate body.

[0044] A workpiece support according to the present invention can comprise two or more actuation columns formed between spaced apart columns of slots or flexures. The actuation columns can be formed or extend parallel to each other, or they can be formed or extend laterally to each other.

[0045] In some forms of the invention, an actuation column comprises a pocket, cavity or opening, or is hollow or partially hollowed out (hereinafter a pocket), and a piezo electricactuator is accommodated within the pocket. The piezo electric actuator acts against an inner surface of the actuation column. The actuation column is connected by flexures on opposite sides to an adjacent part of the workpiece support body and the flexures allow the actuation column to shift or move in the direction of actuation relative to the adjacent part of the body. The piezo electric actuator can have an actuation end and a fixed end, whereby the fixed end is fixed relative to the workpiece support body and the actuation end acts against the inner surface of the actuation column.

[0046] In the above form of the invention, the actuation column can be elongate and the flexures can be positioned at opposite ends of the actuation column. There can be four flexures in which a pair of top flexures extend in opposite direction to the body and a pair of bottom flexures extend in opposite direction to the body. Intermediate flexures can be provided if required in between the top and bottom flexures.

[0047] In the above form of the invention, an actuation column can comprise a single workpiece support element. In this form of the invention, the workpiece support can comprise a pair of actuation columns that each comprise a single workpiece support element and that can each be independently driven by a piezo electric actuator. The pair of actuation columns can be parallel and adjacent each other. The body associated with each actuation column can be connected together to form a unitary assembly while maintaining independent control of each actuation column. The respective bodies can be connected together by bolting for example.

[0048] In other forms of the invention, a lever arm can be formed in a workpiece support body by one or more slots or flexures separating the arm from parts of the workpiece support body, but with the lever arm remaining attached to the workpiece support body. A piezo electric actuator can engage the arm to shift the arm, magnifying translation. The arm can be shifted to tilt by the piezo electric actuator engaging the arm spaced from the connection of the arm to the adjacent part of the workpiece support body. The connection of the arm to the adjacent part of the workpiece support body forms a hinge or fulcrum about which the lever arm can shift, or rotate, however the lever arm will return to a starting or home position once the piezo electric actuation is withdrawn or removed, using the same rotational elasticity as discussed previously. In this form of the invention, use of the leverarm provides a mechanical advantage by amplification of the piezo actuator displacement on the one hand with a trade-off of applied force on the other hand. Amplification can be of varying orders of magnitude of the initial piezo actuator displacement and is appropriate depending on the displacement and force requirements of the particular application.

[0049] Engagement and disengagement of a workpiece support element with / from a workpiece can be arranged with either of piezo electric actuation or deactivation, which can be full or partial actuation or deactivation. That is, a piezo electric actuator can be activated by any amount to move the workpiece support element into engagement with a workpiece, or it can be activated by any amount to disengage from a workpiece. The starting or home position discussed above can be a retracted position of the workpiece support elements, or an expanded position, or anywhere inbetween. Workpiece supports according to the present invention can also employ a mixture of piezo electric actuators in which the starting or home positions between the piezo electric actuators is a retracted position or an expanded position or any position in between.

[0050] In some forms of the invention, a workpiece holder or clamp can be formed with three workpiece support bodies, in which two of the workpiece support bodies are formed with lever arms that are tilted or rotated by piezo electric actuation to move the workpiece support elements into and out of engagement with a workpiece. The third workpiece support body can be formed with a column that is shifted by piezo electric actuation along its longitudinal axis to move the workpiece support element into and out of engagement with a workpiece.

[0051] The workpiece support bodies and elements can have any suitable shape. They can be elongate in the form of a lever, or they can be a block or plate as discussed above. They can also be formed to have an irregular shape that includes a piezo electric actuator engagement surface and workpiece engagement shoes (otherwise known as wear pads or wear shoes) and a body portion that extends between the actuator engagement surface and the workpiece engagement shoes. The body portion can be shaped to position the workpiece engagement shoes for workpiece engagement and for example, the where the workpiece support provides for three point engagement of a workpiece, the body portion of one of the workpiece support elements can be shaped differently to one or both of the otherworkpiece support elements for positioning the workpiece engagement shoe of that workpiece support element at a different position to the workpiece engagement shoes of the other two workpiece support elements. That is, in three point engagement, two of the workpiece engagement shoes could engage an upper surface of the workpiece, while the remaining workpiece engagement shoe could engage a lower surface of the workpiece, so that the body portions of the respective workpiece support elements will be shaped and positioned differently in order to position the workpiece engagement shoes appropriately about the workpiece- depending on the workpiece geometry and application.

[0052] In a specific form of the present invention, there is provided a workpiece support for supporting a longitudinal workpiece, the workpiece support comprising: a plate assembly comprising two, spaced apart plate sections, the plate sections comprising an actuation surface for actuation by a piezo electric actuator, the actuation surfaces being at an angle to each other, the plate sections comprising a pair of spaced apart slots inboard of each actuation surface, and a flex or column section between the slots, a pair of piezo electric actuators, arranged for respective engagement of the actuation surfaces of the plate sections in alignment with the column sections, each plate having a workpiece support element, the workpiece support elements being operable in combination to support a workpiece, whereby actuation of the piezo electric actuators against the actuation surfaces in alignment with the column sections facilitates elastic planar flexing of the plate sections to translate the plate sections and to shift the workpiece support elements linearly to a workpiece support position.

[0053] In the above form of the present invention, the plate sections can be equivalent to the workpiece support bodies previously described. The slots in the plate sections allow the plate sections to flex in the plane of the plate sections by the flex or column section between the slots being able to elastically translate forward and back, to shift the workpiecesupport elements linearly so that the workpiece support elements can move toward a workpiece and subsequently away from the workpiece. This is what is intended by the expression "planar flexing" which is that the plate sections flex within their plane to cause the workpiece support elements to move linearly only. The flexing movement does not provide or promote other movement of the workpiece support elements such as rotational movement or axial movement relative to the longitudinal axis of a workpiece being supported. The plate sections will typically be metal sections of a thickness that allows the movement that is required to be generated upon actuation of the actuators. Prototypes of the present invention have successfully used electrical discharge machining (EDM) aluminium at the required thickness (for example 8-10mm) for effective flexure operation.

[0054] The plate sections can comprise multiple pairs of spaced apart slots on either side of the flex sections. This increases the length of the flex sections so that the flex sections form column sections. For example, two pairs of spaced apart slots can be provided in one or each of the plate sections. Alternatively, three pairs of spaced apart slots can be provided in one or each of the plate sections. Alternatively, one of the plate sections can include a different number of pairs of plate sections than the other plate section. Where multiple pairs of spaced apart slots are provided in one or both of the plate sections, the slots can be parallel to each other. The multiple pairs of spaced apart slots can have the same length and width dimensions. Where more than two pairs of spaced apart slots are provided, the spacing between slots on either side of the column can be the same.

[0055] The slots can form flexures between the actuation surfaces and the adjacent slot, and between adjacent slots, where multiple pairs of slots are provided. The piezo electric actuators push on the actuation surfaces and the flexures pivot or rotate about the ends of the slots (referred to as right circular flexure hinge rotation points) distal to the piezo electric actuators.

[0056] In some forms of the invention, one or more of the slots extends through opposite edges of the plate sections. In these forms of the invention, the plate sections can have an actuation surface, a slotted section and an adjustment section, whereby the adjustment section is operable to elastically translate on actuation of the actuation surface by the piezo electric actuator. The slotted section can also elastically shift, although not all ofthe section needs to shift. The flex or column section will shift as will the plate sections between opposite ends of the slots, whereas the plate sections beyond the ends of the slots distal to the piezo electric actuators might not shift.

[0057] The actuation surfaces can be at any suitable angle to each other. In some forms of the invention, the actuation surfaces have a V orientation between them. The V orientation can form about a 90 degree angle to each other. The actuation surfaces can be part of an edge of the plate sections, which can be a straight edge.

[0058] In some forms of the invention, the workpiece support elements are attached to the plate sections so that the workpiece support elements can be formed of different thickness to the plate sections and of different material. In some forms of the invention, the workpiece support elements can be replaceable so that different workpiece support elements can be attached to the plate sections to suit different workpieces and applications.

[0059] The present invention has mainly been discussed above in relation to the engagement and support of a longitudinal workpiece. However, the present invention can also relate to a tailstock device which is a well known device to engage and support the end of a longitudinal workpiece opposite where the workpiece is engaged by the workholder (a collet for example). A tailstock includes a longitudinal clamping member known as a "centre" and engages the end face of the workpiece, which is usually formed with a concave cavity to accept the centre. In prior art arrangements, the centre of a tailstock is aligned with the end face of the workpiece manually and as will be apparent from earlier discussion, manual alignment can introduce errors in both alignment of the centre with the end face of the workpiece and alignment of the centre with the clamping axis of the workholder. The present invention is therefore proposed for use with tailstock devices to not only improve alignment of the centre with the end face of a workpiece, but also to be able to shift the end face of a workpiece for planar alignment of the workpiece with the clamping axis of the workholder to reduce or eliminate run out and reduce or remove misalignment between them.

[0060] Accordingly, a workpiece support can comprise a workpiece support element formed as a tailstock in which a piezo electric actuator is associated with the tailstock. In some forms of the invention, the arrangements as discussed above are employed in which atailstock is formed as part of, or is connected to a body or plate, most likely a metal plate, with the body or plate including one or more slots or flexures that enable a portion of the plate to shift when acted on by a piezo electric actuator. The tailstock is thus shifted with movement of the portion of the body or plate that is acted on by a piezo electric actuator, and multiple plates can be stacked to allow multiple axes of adjustment.

[0061] In the same manner, the present invention can also relate to devices that clamp non longitudinal workpieces such as inserts. As an example, an insert can be clamped for grinding by a pair of anvils that extend into engagement with opposite sides of the insert. In this respect, an insert will usually have planar (flat) opposite surfaces and with clamping against those surfaces, an edge or edges of the insert can be presented for grinding. A first of the anvils can be a driven anvil which can be driven to rotate for example. The first anvil can be clamped within a collet for example and the collet can be driven. The other and second anvil can also be rotatable, but passively, so that it is rotated only in response to rotation of the driven anvil. The second anvil can comprise one or more workpiece support elements and one or more piezo electric actuators can be associated with the second anvil. This allows the axis of the second anvil to be precisely aligned with the axis of the first anvil. Precise planar alignment of the axes of the first and second anvils allows precise positioning of the insert for more accurate grinding. This arrangement is similar to the use of a tailstock, except that the second anvil is a different form of clamp to a tailstock. However, the mounting of the second anvil can be in the same or similar manner as previously described for the tailstock.

[0062] The present invention can be used for mounting other workpieces and parts to be machined. For example, knee implants, and turbine blades can also be supported in this manner. Rasps for medical use, such as for bone filing can also be machined between a mandrel and a tailstock and the tailstock can comprise the workpiece support element that is associated with a piezo electric actuator.

[0063] The present invention has been described above principally in respect of shifting or movement in the Y and Z axes, with relative movement in the X axis also available either through piezo electric actuation or mechanical movement. However, some applications of the present invention can provide rotational movement of the workpiece support bodyand / or the workpiece support element. This is relevant for some uses of the present invention, for example for a workpiece support element that is formed as a bush for supporting a workpiece such as an endmill, drill or reamer. In this example, the bush has an axis and that axis should be accurately aligned with the longitudinal axis of the workpiece for accurate grinding to form the workpiece. A workpiece support according to the present invention can be arranged to provide independent piezo electric actuation acting on the bush at or towards the opposite ends in Y and Z directions. By independent actuation, opposite ends of the bush can be shifted independently of each other so that the movement applied to the ends can be equal or unequal. Equal movement can for example, lift the bush in the Z direction or shift it sideways in the Y direction. Unequal movement can rotate the bush about either of the_Y and Z axes, pitch and yaw respectively. Piezo electric actuation in both of the Y and Z directions at either or both of the ends of the bush can shift or rotate the bush in or about the Y and Z directions.

[0064] In the above example, more than a single piezo electric actuator can be associated with the workpiece support (the bush in the above example) to move and rotate the workpiece support element.

[0065] It will be evident that the workpiece support of the present invention can take any suitable form and that the workpiece support element can take different forms as required or suitable to support a particular workpiece.Brief Description of the Drawings

[0066] In order that the invention may be more fully understood, some embodiments will now be described with reference to the figures in which:

[0067] Figure 1 is a perspective view showing a workpiece support according to the present invention in use within a tool and cutter grinding machine.

[0068] Figure 1A is a side view of the workpiece support and tool and cutter grinding machine of Figure 1.

[0069] Figure 2 is a perspective view of the workpiece support of Figure 1 and showing the mounting facility to which the workpiece support is mounted.

[0070] Figure 3 is a front view of the arrangement illustrated in Figure 2.

[0071] Figure 4 is an internal plan view of a workpiece support according to the present invention.

[0072] Figures 5A and 5B are detailed views showing the arrangement and exaggerated movement of flexures in the workpiece support of Figure 4.

[0073] Figures 6, 7 and 7A are detailed views of different support elements used in workpiece supports according to the present invention. Figure 7 , and 7A support the tool on a 45° angle relative to the longitudinal workpiece axis.

[0074] Figures 8 to 10 show the present invention embodied in a workpiece support comprising a top clamp arrangement.

[0075] Figures 11 to 14 show the present invention embodied in workpiece supports comprising workpiece clamps or jaws.

[0076] Figures 15 and 16 illustrate the present invention embodied in a workpiece support comprising a tailstock device mounted on a travelling axis.

[0077] Fig 16A is an exploded view of the workpiece support of Figures 15 and 16.

[0078] Figures 16B and 16C are rear views of different intermediate plates of the workpiece support of Figure 16 that comprise piezo electric actuators.

[0079] Figures 17 (perspective view) and 18 (side view) illustrate the present invention embodied in a workpiece support for a long drill, endmill or reamer in which the workpiece support element is formed as a bush.

[0080] Figure 19 is a front view of the workpiece support arrangement of Figures 17 and 18 with the spring removed for clarity.

[0081] Figure 20 illustrates the present invention embodied in a grinding machine comprising a pair of anvils for clamping an insert.

[0082] Figure 21 is a perspective view of workpiece support according to a further embodiment of the present invention.

[0083] Figures 22 and 23 are end and side views of the workpiece support shown in Figure 21.

[0084] Figure 24 is a cross-sectional view of the workpiece support taken through A-A of Figure 23.Detailed Description

[0085] Figure 1 illustrates a portion of a grinding machine suitable for use with the present invention and shows the X, Y and Z axes that are relevant to the drawings as described herein. The grinding machine 10 includes a workholder in the form of a collet adaptor and collet 12 that clamps a longitudinal workpiece 14. It can be seen from Figure 1, that the workpiece 14 has a length to diameter ratio which is large, so that the length of the workpiece 14 is much longer than the diameter. The diameter of the workpiece 14 can be in the region of 25 pm to 20 mm in the described embodiment but the invention can be applied to larger diameter workpieces.

[0086] The grinding machine 10 includes a top clamp 16 that is positioned into contact with the upper surface of the workpiece 14. The top clamp 16 presses or clamps the workpiece 14 into a cradle 17 and establishes the axis about which the workpiece 14 rotates. The collet adaptor and collet 12 is operable to clamp and to rotate the workpiece 14 as required and a rotating grinding wheel (not shown) removes material from the surface of the workpiece, so that a suitable profile can be ground into the outer surface of the workpiece 14. In the grinding machine 10, the grinding wheel would approach the workpiece 14 from above to grind the upper surface of the workpiece 14.

[0087] The large length to diameter ratio of the workpiece 14 means that the workpiece 14 is prone to bending or flexing during grinding and this can lead to inaccuracies in the workpiece geometry and the workpiece even snapping along its length. Accordingly, the grinding machine 10 includes a workpiece support or steady 18 that supports the workpiece 14 under the grind point, remote from the collet adaptor and collet 12. The workpiece support 18 could alternatively support the workpiece 14 closer to the collet adaptor andcollet 12, particularly if the workpiece 14 is longer than shown in Figure 1 or if grinding is taking place elsewhere along the workpiece.

[0088] The workpiece support 18 supports the workpiece 14 in opposite directions to the loads applied to the workpiece 14 by the grinding wheel (not shown in Fig 1, but shown as 19 in Fig 1A). Thus, in Figure 1, the grinding wheel applies a generally vertical downward grinding load on the workpiece 14, while the workpiece support 18 applies a generally vertical upward supporting load on the workpiece 14. Lateral loads are also generally supported by the workpiece support 18.

[0089] The workpiece support 18 shown in Figure 1 will be described in more detail in relation to later figures, but it includes a pair of workpiece support elements 20 that can be moved towards and away from the workpiece 14. The support elements 20 form a cradle in which the workpiece 14 is supported against lateral and vertical movement and vibration. Importantly, given the potential micro sizes that the workpiece 14 might take, very fine and precise movement of the support elements 20 is required to ensure that the support elements 20 properly engage and support the workpiece 14. Of significant importance is that the workpiece support 18 should not impose loads on the workpiece 14 that causes the workpiece 14 to bend or flex in the direction to the grinding loads being applied to it. The workpiece support 18 needs to be able to bring the support elements 20 into a supporting position in which the end of the workpiece 14 is supported against bending or flexing due to loads applied by the grinding wheell9, but not to cause the workpiece 14 to bend or flex other than within acceptable tolerance levels.

[0090] The workpiece support 18 employs a unique construction combined with piezo electric actuators to achieve precise and fine adjustment of the support elements 20 to properly support the workpiece 14.

[0091] Figures 2 and 3 show perspective and side views, respectively, of the workpiece support 18 fitted to a mounting facility 22 that could be part of the grinding machine 10. It is not necessary to go into detail in relation to the construction of the mounting facility 22 other than to say, the mounting facility 22 is mounted for movement so that the workpiece support 18 can be shifted to a position where it is in close proximity to the workpiece 14 that is to be supported. Once the workpiece support 18 has been shifted to that position by themounting facility 20, the workpiece support 18 can be activated to bring the support elements 20 into supporting engagement with the workpiece 14.

[0092] Figure 4 shows the workpiece support 18 in isolation. The workpiece support 18 comprises a plate assembly 24 that includes first and second workpiece support body or plate sections 26 and 28. The plate sections 26 and 28 each include a pocket, cavity or opening 30 within which is disposed a piezo electric actuator 32. The actuators 32 have leading actuation ends 34 that bear against an actuation surface 36. In Figure 4, the respective actuation surfaces 36 are disposed at 90° to each other.

[0093] The plate sections 26 and 28 also include pairs of spaced apart slot groups 38 and 40, the ends of which are terminated in circular openings 41 to prevent stress cracking. The circular openings also facilitate repeatable elastic rotation about the centre of the right circular flexure in between the circular openings. The respective slot groups 38 and 40 respectively form outer slot groups and inner slot groups, and the respective slot groups are parallel to each other and of the same dimensions. Inner ends of the slot groups 38 and 40 define a column section 42.

[0094] Between the respective slots 38 and 40, flexures 44 are formed. These flexures 44 will be described in more detail later herein, however it is the flexures 44 that flex to allow shifting movement of the workpiece support elements 20. For context, the space between the circular openings at the ends of the slots 38 and 40 is in the order of 1mm. The thickness of the plate is in the order of 10mm.

[0095] The end of the column 42 that extends to the actuation surface 36 is separated from adjacent parts of the plate sections 26 and 28 by slots 46, although in Figure 4, the slots 46 comprise a short slot section that opens at one end into the actuation surface 36 and that terminates at the other end in circular openings (which is what is most clearly shown in Figure 4). Accordingly, the column section 48 is shiftable relative to adjacent parts of the plate sections 26 and 28 upon actuation of the piezo electric actuators 32.

[0096] The plate sections 26 and 28 are spaced apart via a central spacing 50. In some forms of the present invention, the spacing 50 is in the order of 1mm. The spacing 50 between the plate sections 26 and 28 extends into connection with the innermost slots 40,while the outermost slots 38 connect with slots 52 that extend through the edge of the plate sections 26 and 28. With this arrangement, actuation of the actuators 32 causes the column section 42 to shift forward, with the flexures 44 pivoting about the ends of the slots 38 and 40. This allows the main body 54 of the plate sections 26 and 28 to shift in the direction of the actuation force which means that the spacing 50 between the plate sections 26 and 28 reduces and with that movement, the support elements 20 will have two components of movement one being towards each other and the other being upward movement (in the orientation of the workpiece support 18 shown in Figure 4). Figures 5A and 5B show the column section 42 moving from the position shown in Figure 4 (the same position as Figure 5A) to a forward position (Figure 5B) and clearly shows the flexures 44 pivoting as discussed above. Figures 5A and 5B also show how the workpiece 14 is shifted in the direction shown by the arrow in Figure 5B, by actuation of only one of the actuators 32 of Figure 4, if the other actuator 32 is not actuated. It will be appreciated that the workpiece 14 can be shifted in various directions by selective actuation of the actuators 32. The actuators 32 can both be actuated the same amount, or different amounts, or one can be actuated while the other is not actuated.

[0097] It is to be noted that the flexure path can vary to suit the support requirements, so that for example, flexures can be arranged at an angle to each other such as at 90° to each other. Other configurations can be adopted.

[0098] Figure 6 is a close-up view of the support elements 20 of Figure 4 (shown as support elements 20a and 20b) to show the movement of the support elements 20a and 20b by the arrows A under actuation of the actuators 32. That movement comprises both a horizontal and vertical component in the orientation of the workpiece support elements 20a and 20b shown in Figure 6. The support elements 20a and 20b shown in Figure 6 form a V- shape cradle 56 for supporting the outer surface of a workpiece. The depth of the cradle 56 will change as the support elements 20a and 20b move in the direction of the arrows A and so the supporting ends of the support elements 20a and 20b are shaped so that workpiece support is provided at the point at which there is no further available movement of the support elements 20a and 20b towards each other, at which point the depth of the cradle 56 will be at a minimum.

[0099] The ends of the support elements 20a and 20b can be shaped differently if different workpiece support is required. Figure 7 illustrates differently shaped support elements 58, in which the cradle 60 is formed between adjacent surfaces 61 and 62. This configuration advantageously allows the workpiece support 18 to be rotated about a workpiece centreline through a wide angle from the position or orientation shown in Figure 4 and still support the workpiece from underneath and to provide grinding clearance. For example, the workpiece support 18 is shown in Figure 2 rotated through 45° clockwise from the position or orientation shown in Figure 4 and in that rotated position or orientation, the surfaces 61 and 62 of the support elements 58 will still provide upward support for the workpiece. Figure 7A illustrates differently shaped support elements 58A, in which the cradle 60A is formed between adjacent surfaces 61A and 62A. The support elements 58A are shown as being bolted to the plate sections 26 and 28 of the Figure 4 arrangement, but the plate sections 26 and 28 are obscured in Figure 7A by a housing 64 which is visible in Figures 2 and 3 and comprises cover plate applied to each side of the support 18.

[0100] The workpiece support 18 as illustrated in Figure 4 is shown without the housing within which it is encased in use. Also, it can be seen in Figure 2, that the support elements 20 are three dimensional, although they can alternatively be two-dimensional plate elements such as 58A shown in Figure 7A.

[0101] Returning to Figure 4, the movement in the plate sections 26 and 28 under the influence of the actuators 32 has been described earlier herein as planar flexing of the plate sections 26 and 28. The expression planar flexing is intended to indicate that the plate sections 26 and 28 flex within the plane of the plate sections 26 and 28 and cause the support elements 20 to move linearly only. That is, it is not intended that the workpiece support 18 promote other movement of the support elements 20 such as rotational movement or axial movement relative to the longitudinal axis of a workpiece being supported. Of course, the mounting facility 22 to which the workpiece support 18 is mounted can be arranged for rotational or axial movement, but that movement is not intended to be provided by the workpiece support 18 itself and once the position or orientation of the workpiece support 18 is set by the mounting facility, it remains in that position and orientation and is not changed.

[0102] It has been explained above that the invention has been developed to provide very fine and precise movement of the support elements 20. Movement in the order of 40pm is provided in the workpiece support 18 illustrated in the figures, but of course, the construction of the workpiece support 18 could be modified to provide greater or lesser movement of the support elements 20. Also, while the present invention has been developed for micro movement, the present invention could easily be constructed for larger or macro movement.

[0103] The piezo electric actuators 32 can be controlled to apply the same actuation load against the actuation surface 36, or they can be controlled so that different loads are applied. This electronic control can be useful to apply loads in different directions to a workpiece to maintain accurate longitudinal alignment of the workpiece. For example, in Figure 6, the support element 20a could be shifted further in the direction of the arrow A then the support element 20b, if there is a need to shift the workpiece slightly to the right (as illustrated in Figure 6) for correct axial alignment of the workpiece. The present invention thus allows dynamic positioning of the support elements 20 to constantly maintain the correct position of the workpiece. Thus, the longitudinal axis of the workpiece can be monitored as the workpiece is machined and where the axis deviates from the desired position, the actuators 32 can apply a greater or lesser load as required to return the workpiece axis to the desired position. This response happens can be made to happen so fast, that no displacement change is visible.

[0104] The present invention can take various other forms each of which employs piezo electric actuation. Figures 8 to 10 show a top clamp arrangement that embodies the present invention whereby a collet 12 (the collet 12 is shown suspended in mid-air, but in fact the collet 12 is part of a collet adapter, which in turn is part of a grinding machine, all of which is absent from Figures 8 to 10 in order for those figures to concentrate just on the components relevant to the present invention) clamps a work piece 14 and a top clamp 70 bears downwardly on the upper surface of the workpiece 14. The workpiece 14 is supported from underneath in a groove 72 of a workpiece support element in the form of a cradle 74 and the cradle 74 forms part of a workpiece support body comprising tool support 78 that attaches to a plate assembly 82 that includes a piezo electric actuator 76. The tool support 78 and thus the cradle 74 is displaceable in the Y and Z directions as will be explained in hereinafter.

[0105] The plate assembly 82 includes a number of flexures 80 that allow the portion of the plate assembly 82 to which the tool support 78 is attached to shift upwardly or downwardly under the influence of the piezo electric actuator 76 to lift and lower the cradle 74. It will be apparent by a comparison of the flexures 44 of Figure 4 and the flexures 80, that the respective flexures 44 and 80 are formed differently. The flexures 44 are defined or are spaced apart by the respective slot groups 38 and 40 and the slots of each of the slot groups 38 and 40 have circular openings at either end. In Figure 10, the flexures 80 are defined or spaced apart by openings 81 which are generally rectangular openings of different dimensions to the slots of the slot groups 38 and 40. The respective dimensions of the flexures 44 and 80 show how the configuration of the flexures can change to suit different forms of workpiece supports.

[0106] Actuation of the piezo electric actuator 76 facilitates flexing of the flexures 80 so that the cradle 72 can be shifted upwardly to engage the underneath of the workpiece 14. The workpiece 14 is then clamped between the top clamp 70 and the cradle 72.

[0107] The arrangement of Figures 8 to 10 further illustrates a piezo electric actuator 84 that acts on the plate assembly 82 at 90° to the actuator 76. The plate assembly 82 includes two sets of four flexures 86 (some of which in the upper set are obscured in Figures 8 to 10 by the tool support 78) that are separated by openings and that facilitate sideways movement of the section of the plate assembly 82 to which the tool support 78 is attached, so that the tool support 78 can be shifted sideways. The mechanism of this sideways movement is effectively the same as the upwards movement that is driven by the piezo electric actuator 76, so that the flexures 86 pivot upon actuation of the actuator 84 and so that the section of the plate assembly 82 to which the tool support 78 is attached, and the tool support 78, can be shifted sideways to the left in the orientation shown in Figure 10 and backwards to the right as required. The cradle 74 can thus be shifted both upwardly and downwardly and side to side by actuation of either or both of the piezo electric actuators 76 and 84 for two-dimensional movement of the cradle 74 in the Y-Z plane.

[0108] The movement of the cradle 74 by the piezo electric actuators 76 and 84 provides micro movement in the order of micrometres. Figure 8 also illustrates the capacity for macro movement by the connection of the plate assembly 82 to a carriage 88 that is movableforward and back along a track 89. That movement can be driven by screw drive for example and can be electrically or manually driven for example. Macro sideways movement can also be provided although the mechanism to provide that movement is not shown in Figures 8 to 10.

[0109] In operation, in no particular order, the workpiece 14 is clamped in the collet 12, the plate section assembly 82 is shifted by macro movement to position the groove 72 of the cradle 74 into close but approximate underneath alignment with the workpiece 14, the plate section assembly 82 is shifted by micro movement to engage the workpiece 14 in the groove 72 of the cradle 74, and the top clamp 70 is lowered into engagement with the upper surface of the workpiece 14. The workpiece 14 is thus clamped by the collet 12 for rotation, and is also clamped between the top clamp 70 and the cradle 74. The top clamp 70 and the cradle 74 set the working or grinding axis of the workpiece 14, while the collet 12 rotates the workpiece 14.

[0110] Figures 11 to 14 also illustrate different embodiments of the present invention. Each of the embodiments of Figures 11 to 13 is a workpiece clamp or jaw.

[0111] With reference to Figures 11 and 12, a workpiece support 90 is shown which has a workpiece support body formed from plate metal. The plate assembly 92 accommodates three piezo electric actuators 94, 95 and 96 within pockets, openings or slots 97, 98 and 99 formed in the plate assembly 92.

[0112] The plate assembly 92 is separated at separations 100 and 101 to form two workpiece support elements as lever arms 102 and 104. Flexures 106 and 108 are formed between openings 107 and 109 to form hinges about which the lever arms 102 and 104 can rotate. The lever arms 102 and 104 extend to workpiece support elements 110 which are shown in contact with a workpiece 112.

[0113] The workpiece support elements 110 connect to struts 114 at one end and the struts 114 connect at the other end to the plate assembly 92, specifically to posts 111. These connections are formed as hinges so that the struts 114 can shift with the lever arms 102 and 104 as shown in Figure 12. In Figure 12, actuation of the piezo electric actuators 94 and 96 tilts the lever arms 102 and 104 inwardly and towards each other about the connection ofthe lever arms 102 and 104 with the flexures 106 and 108. Likewise, the struts 114 also tilt inwardly and towards each other about the connection of the struts 114 with the posts 111. If required, the actuators 94 and 96 can be actuated independently of each other so that for example, only one of the actuators 94 and 96 is actuated, or the actuators 94 and 96 are actuated to different extents.

[0114] Figures 11 and 12 also show a further workpiece support element 116 which is acted on by the piezo electric actuator 95. The support element 116 is connected to the plate assembly 92 by the struts 118 which connect to the posts 111 and which allow the support element 116 to shift upwardly and downwardly. The support element 116 is shown in Figure 11 in contact with the underneath surface of the workpiece 112. Any movement of the lever arms 102 and 104 by the actuators 94 and 96 is independent of any movement of the workpiece support element 116 driven by the actuator 95. This independent actuation of the actuators 94, 95 and 96 and the resulting independent movement of the lever arms 102 and 104 and the support element 116 allows for precise positioning of the workpiece 112.

[0115] It will be evident from Figures 11 and 12, that the support elements 110 and 116 can be brought into engagement with the workpiece 112 by actuation of the piezo electric actuators 94, 95 and 96. Not all of these actuators need to be actuated to engage the workpiece at 112, and if the workplace 112 needs to be realigned, the extend of the actuation of the piezo electric actuators 94, 95 and 96 can be modified depending on the distance and direction that the workpiece 112 needs to shift in the X and Y axes.

[0116] Figure 13 illustrates a further example of a workpiece support 120 in the form of a clamp according to the present invention. The workpiece support 120 comprises a plate assembly 122 and utilises flexures and columns of a similar construction to the flexures 44 and the column sections 42 of the workpiece support 18 shown in Figure 4. Thus, the workpiece support 120 includes flexures 124 and column sections 126 between the flexures 124 to shift the main bodies 127 and the workplace support elements 128 that are connected to the main bodies 127 under actuation of the piezo electric actuators 130 on the column sections 126.

[0117] The workpiece support 120 includes a further piezo electric actuator 132 that acts at the base of a workpiece support element formed as a block 134 which can shift upwardlyand downwardly (in the orientation of Figure 13) against the underside of the workpiece 136. While the block 134 could have taken a similar form to the workpiece support element 116 of Figures 11 and 12, it is shown in Figure 13 to be connected to the plate assembly 122 by flexures 138. The flexures 138 can pivot about their connection with the plate assembly 122 under actuation of the actuator 132. It will be appreciated that the workpiece support elements 128 and 134 can be shifted into and out of engagement with the workpiece 136. Similar to the three piezo electric actuators actuators 94, 95 and 96 of the workpiece support 90 of Figures 11 and 12, in Figure 13, the piezo electric actuators 130 and 132 can each be actuated independently of each other for precisely positioning the workpiece 136.

[0118] Figure 14 illustrates yet a further example of a workpiece support 140 in the form of clamp according to the present invention. Again, the clamp employs flexures 142 to define three column sections 144 which are actuated by piezo electric actuators 146, 148 and 150. Actuation by the piezo electric actuators 146 and 150 shifts the main bodies 152, while actuation by the piezo electric actuator 148 shifts the main body 154. The workpiece 156 is thus engaged by the respective workpiece support elements 158 and 160.

[0119] It is evident from Figure 14 that actuation of the piezo electric actuators 146 and 150 disengages the workpiece support elements 158 from the workpiece 156, whereas actuation of the piezo electric actuator 148 engages the workpiece 156. This illustrates that actuation of the piezo electric actuators is not always engagement actuation, and in this case, it is instead the resistance of the plate to flexing that provides engagement actuation.Without actuating the actuators 146 and 150, the workpiece support elements 158 are in a home or starting position. To bring the workpiece support elements 158 into engagement with the workpiece 156, the actuator 148 can be actuated to shift the workpiece support element 160 upwardly so as to also shift the workpiece 156 upwardly and into engagement with the workpiece support elements 158. If the workpiece 156 needs to be shifted further upwardly, the actuators 146 and 150 can be actuated to lift the the workpiece support elements 158 away from the upper surfaces of the workpiece 156 and to actuate the actuator 148 further to push the workpiece 156 upwardly and back into engagement with the workpiece support elements 158. Of course, the workpiece support elements 158 may never lose contact with the workpiece 156 as the actuators 146, 148 and 150 can all be actuated to lift the workpiece 156.

[0120] Moreover, Figure 14 illustrates that the workpiece 156 can be shifted in the Y and Z axes by selective and independent actuation of the actuators 146, 148 and 150, so that for example, if the piezo electric actuator 146 is actuated by some amount and actuator 150 is retracted by some amount, the workpiece 156 will shift to the left (in the orientation of Figure 14). While the workpiece 156 shown in Figure 14 is shown to be circular, it is to be noted that it could be otherwise shaped and could be a cutting tip insert.

[0121] The figures so far have shown support arrangements that incorporate workpiece support elements that form a cradle for supporting the outer surface of a workpiece.However, the present invention can also relate to a tailstock device which is a well known device to engage and support the end face of a long workpiece. The end face that is supported by the tailstock is opposite the end of the workpiece that is clamped in a collet and for engagement with the tailstock, the end face is usually formed with a concave cavity, usually a conical cavity, and the tailstock includes a clamping member, known as a "centre" that enters the cavity to clamp the end face of the workpiece and thereby support it. The centre typically will be formed to have the same general shape as the cavity so that usually the centre is formed as a cone, as this allows there to be a close nesting engagement between the centre and the cavity. Traditionally the centre of a tailstock is aligned with the end face of the workpiece manually and as will be apparent from earlier discussion, manual alignment can introduce errors in alignment of the centre with the end face of the workpiece. The present invention is therefore proposed for use with tailstock devices to not only improve alignment of the centre with the end face of a workpiece, but in various forms of the invention to provide for automation of the alignment process and dynamic adjustment during machining of the workpiece, and to provide improved repeatability of precise alignment when workpieces are changed.

[0122] Figures 15 and 16 show a tailstock device 170 in accordance with one embodiment of the present invention. The clamping arrangement 170 of Figures 15 and 16 includes a rotary assembly 172 for clamping one end of a workpiece 174 and a tailstock 176 for supporting the opposite end of the workpiece 174. A track arrangement 178 supports both the rotary assembly 172 and the tailstock 176 spaced apart from each other, and allows the spacing between them to be reduced or increased depending on the length of the workpiece being machined.

[0123] With reference to Figure 16, the tailstock 176 comprises front and rear housing plates 180 and 182, and a pair of intermediate plates 184 and 186. Fixed to the front of the front plate 180 is a workpiece support element in the form of a centre 188. The centre 188 is formed as a cone for nesting within a conical cavity formed in the facing end of the workpiece 174. The centre 188 is part of a centre assembly 190 that is attached to the front surface of the front plate 180.

[0124] Figure 16A is an exploded view of the tailstock 176 and the dark areas identified by reference numerals 192 and 194 indicate piezo electric actuators. Figures 16B and 16C are front views of the intermediate plates 184 and 186 respectively which form workpiece support bodies. In the orientation of the tailstock 176 in Figure 16A, the piezo electric actuators 192 act vertically as shown in Figure 16B, while the piezo electric actuators 194 act horizontally as shown in Figure 16C. Actuation of the actuators 194 shifts the plate 184 horizontally left or right, while actuation of the actuators 192 shifts the front housing plate 180 up or down. A combination of horizontal and vertical movement from intermediate plates 186 and 184 can shift the front housing plate 180 within a plane.

[0125] The tailstock 176 is a workpiece support in the form of a travelling tailstock which is movable parallel to the X-axis on a track arrangement 178. Prior art document PCT / AU97 / 00445 in the name of ANCA Pty Ltd discloses a similar arrangement relating to a travelling steady but without the use of piezo actuators. When the present invention is applied to a travelling steady or a travelling tailstock, there is relative X-axis movement between the workpiece support and the workholding. That is, in some instances the workholding is movable in the X axis and in other instances the workpiece support is movable, and in some instances, both components may be movable in the X-axis. When the present invention is applied to a travelling steady, one or more piezo actuated workpiece support elements can be arranged to form a cradle support for the workpiece. For long workpieces, one or more steady rests or tailstock may be positioned at intervals parallel to the X-axis and one or more of those steady rests may be piezo actuated.

[0126] The tailstock assembly 170 is shown in operation with a longitudinal workpiece 174 however it has been described earlier herein, that the present invention can be used for mounting other workpieces and parts to be machined such as knee implants, turbine bladesand rasps for medical use. These workpieces can be engaged or clamped at one end by the the rotary assembly 172 and at the other end by the centre 188 even though they might not be longitudinal and of uniform diameter.

[0127] Figures 17 and 18 show a workpiece support element that is formed as a bush 196 for supporting a workpiece 198 such as but not limited to an endmill, drill or reamer. In this example, the bush has an axis along the X-axis and that axis should be accurately aligned with the longitudinal axis of the workpiece 198 for accurate grinding to form the workpiece 198. A workpiece support 200 according to the present invention can be arranged to provide independent piezo electric actuation acting on the bush at or towards the opposite ends in Y and Z directions. By independent actuation, opposite ends of the bush can be shifted in plane independently of each other so that the movement applied to the ends can be equal or unequal. Equal movement can for example, lift or lower the bush in the Z direction or shift it sideways in the Y direction. Unequal movement can rotate the axis of the bush about either of the Y and Z axes to produce 'yaw' or 'pitch' as indicated in Figure 17. Piezo electric actuation in both of the Y and Z directions at either or both of the ends of the bush can shift or rotate the bush in or about both of the Y and Z directions.

[0128] The workpiece support 200 comprises a pair of spaced apart workpiece supports 202 and 204 that support opposite ends of the bush 196. The connection between the workpiece support bodies 202 and 204 and the bush 196 is shown in the end view of Figure 19, in which a pair of workpiece support elements 206 can be shifted or translated in the Y and Z axes. For this, the workpiece support bodies 202 and 204 can be connected to a plate assembly which is the same as or similar to the plate assembly 24 of Figure 4 and so further discussion on the mechanism for moving the workpiece support bodies 202 and 204 need not be provided. The spring 208 is omitted from Figure 19 for clarity.

[0129] The bush 196 is a half- moon bush which has a cross-sectional profile suitable to receive the workpiece support bodies 202 and 204, with sliding surfaces provided for movement of the workpiece supports 202 and 204 relative to the bush 196, it could also be formed as a 'Vee' cradle. The workpiece support bodies 202 and 204 can move in the direction of the arrows in Figure 19 to shift the workpiece support bodies 202 and 204 in the Y and Z axes. The springs 208 hold the bush 196 to the workpiece support bodies 202 and204. A mounting bridge 210 extends between the workpiece support bodies 202 and 204 and a post 212 connects the workpiece support 200 to a track or frame of a grinding machine (not shown).

[0130] In operation of the workpiece support 200, there may be relative travel between workpiece support and workpiece in the X direction. The piezo actuators allow alignment between the bush and the workpiece along the entire length of the bush with a corresponding length of the workpiece. That is, along a complete contact zone between the bush and the workpiece. The two sets of piezo actuators are accommodated in the workpiece support bodies 202 and 204 and as explained earlier herein, actuation of one set, say in the workpiece support 204, in the y and z axes relative to actuation of the other set in the workpiece support 202 in the y and z axes, allows rotational adjustment of the bush, providing alignment and hence the full contact zone support of the workpiece section.

[0131] The distance between the sets of workpiece support elements 206 changes the range of rotation in the Y and Z axes. By minimising the distance between the workpiece support elements 206, the rotation range can be increased, and it is possible to automatically adjust in process for the taper angle that is provided along the length of a drill or reamer. If the workpiece support elements 206 are moved the same distance, perfect planar (YZ) displacement of the bush is obtainable (rotation remains the same).

[0132] The bush may alternatively take the form of a solid bush or a split bush, a 'Vee' cradle, or a separate shoe set arrangement to maintain the centreline of the workpiece support element and the workpiece.

[0133] Figure 20 illustrates a grinding machine 220 for clamping a non-longitudinal workpieces in the form of an insert 222. The insert 222 is clamped for grinding by a pair of anvils 224 and 226 that extend into engagement with opposite sides of the insert 222. The opposite sides of the insert 222 are planar (flat) surfaces.

[0134] The anvil 224 can be driven to rotate and is clamped within a collet 228. The anvil 226 is not driven but is rotatable, so that it is rotated only in response to rotation of the anvil 224. The anvil 226 is mounted to a workpiece support 230 which can have a similar form tothe tailstock 176 of Figures 15 and 16. Thus, the workpiece support 230 includes one or more associated piezo electric actuators.

[0135] This allows the longitudinal axis of the second anvil to be precisely aligned with the longitudinal axis of the first anvil. Precise planar alignment of the axes of the first and second anvils allows precise positioning of the insert for more accurate grinding. This arrangement is similar to the use of a tailstock, except that the second anvil is a different form of clamp to a tailstock. However, the mounting of the second anvil can be in the same or similar manner as previously described for the tailstock.

[0136] Figure 21 shows another workpiece support 240, comprising a pair of plates or workpiece support bodies 242 that are bolted together. Figure 22 shows one of the bodies 242 from the inside, while Figure 23 is a side view of the workpiece support 240, and Figure 24 is a cross-sectional view of the workpiece support 240 through A-A of Figure 23.

[0137] Figures 22 and 24 show an actuation column 244. The actuation column 244 comprises a pocket 246 to accommodate a piezo electric actuator 248. The piezo electric actuator 248 is shown with a leading or actuation end 250 in engagement with or against an actuation surface 252 of the pocket 246 of the actuation column 244. The actuation column 244 extends to workpiece support elements or shoes 254 and Figures 21 and 23 show an elongate workpiece 256 supported at the leading ends of the workpiece support elements 254. The leading ends of the workpiece support elements 254 form a V-shaped cradle to receive the workpiece 256.

[0138] The actuation column 244 is connected by top and bottom flexures 258 and 260 on opposite sides to the adjacent bodies 242 of the workpiece support 240. There are four flexures in total. The actuation column 244 is otherwise spaced from the facing surfaces 262 that form an opening in which the actuation column 244 is accommodated, although the spacing is close. The actuation columns 244 are therefore free to move within the bodies 242 by virtue of the connection to the bodies 242 by the flexures 258 and 260.

[0139] The piezo electric actuator has a fixed end 264. The fixed end 264 is fixed using a preload screw 266. The screw 266 extends through an opening 268 in the base 270 of the body 242, and a portion of the base 270 is threaded for threaded engagement between theopening 268 and the screw 266 to fix the screw 266 in place relative to the body 242. The shank 272 of the screw 266 extends through the opening 268 in the base 270 and through the opening 274 in the bottom end of the actuation column 244 to press against the end 264 of the piezo electric actuator 248 to fix the end 264 in place. The shank 272 extends through the openings 268 and 274 without any interference with the openings (other than the threaded engagement with the opening 268) and is threaded until the leading end of the shank 272 engages the bottom or facing end of the piezo electric actuator 248. Thus, there is no contact between the shank 272 and the actuation column 244 at all. The screw 266 can be threaded into the pocket 246 until a pre-determined preload is reached with the piezo electric actuator 248. Voltage can be provided to activate the piezo electric actuator 248 to extend or expand. When the piezo electric actuator 248 extends or expands, it can only expand upwardly (in the orientation shown in Figures 21 to 24, due to its threaded connection to the body 242. Extension or expansion of the piezo electric actuator 248 drives the actuation column 244 upwardly and causes the flexures 258 and 260 to flex.

[0140] The pair of actuation columns 244 can be activated to drive the workpiece support elements 254 separately, although as shown in Figures 21 and 23, the workpiece support elements 254 have been driven to the same position to support the workpiece 256.

[0141] The bodies 242 can be connected together and may have a spacer between them, minimizing friction when the pair of actuation columns 244 move independently of each other.

[0142] The workpiece support elements 254 are shown for supporting the workpiece 256, but obviously different shaped workpiece support elements can be employed. It is also to be appreciated that the workpiece support 240 can be used in workpiece support elements that are formed as a bush, or as a steady, top clamp or tailstock.

[0143] Unless the context requires otherwise, where the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components, or group thereof.

[0144] Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all such variations and modifications which fall within the spirit and scope of the present invention.

Claims

Claims1. A workpiece support for supporting a workpiece, the workpiece support comprising a workpiece support body and a workpiece support element associated with the workpiece support body for engaging a workpiece and a piezo electric actuator being associated with the workpiece support body for moving the workpiece support element for supporting the workpiece, the workpiece support body comprising one or more flexures that enable a movable portion of the workpiece support body to move when acted on by the piezo electric actuator and to move the workpiece support element.

2. A workpiece support according to claim 1, the workpiece support comprising two or more workpiece support bodies and a piezo electric actuator being associated with each workpiece support body for moving the respective workpiece support elements.

3. A workpiece support according to claim 1 or 2, the workpiece support body comprising a pocket to accommodate the piezo electric actuator.

4. A workpiece support according to any one of claims 1 to 3, the one or more flexures are formed in two flexure columns of at least two flexures each, the flexure columns being spaced apart and the flexures being generally parallel, so that an actuation column is formed between the spaced apart flexure columns and forms the movable portion, so that upon piezo electric actuation on the actuation column, the actuation column moves in the direction of actuation.

5. A workpiece support according to claim4, the piezo electric actuator acting against an actuation surface of the actuation column.

6. A workpiece support according to claim 1 or claim 2, the movable portion being formed by an actuation column and flexures connecting the actuation column for movement in the direction of actuation.

7. A workpiece support according to claim 6, the actuation column comprising a pocket and the piezo electric actuator being accommodated within the pocket and acting against an actuation surface of the actuation column.

8. A workpiece support according to claim 7 or 8, the actuation column being connected by flexures on opposite sides to the workpiece support body and the flexures being positioned at opposite ends of the actuation column.

9. A workpiece support according to any one of claims 4 to 8, comprising two or more actuation columns.

10. A workpiece support according to claim 9, the actuation columns extending generally parallel to each other or generally laterally to each other.

11. A workpiece support according to claim 1 or claim 2, the workpiece support body comprising a lever arm connected to the workpiece support body by one or more flexures, the lever arm comprising the workpiece support element and the piezo electric actuator being associated with the lever arm to move the lever arm.

12. A workpiece support according to claim 11, the lever arm being movable by the piezo electric actuator to tilt the lever arm.

13. A workpiece support according to claim 12, the connection of the lever arm to the workpiece support body forming a hinge or fulcrum about which the lever arm can rotate, the one or more flexures using material resistance such that lever arm returns to a pre-actuated position upon removal of the piezo electric actuation.

14. A workpiece support according to claim 1, the workpiece support comprising three workpiece support bodies and a piezo electric actuator being associated with each workpiece support body for moving the respective workpiece support elements.

15. A workpiece support according to claim 14, comprising three workpiece support bodies, two of the workpiece support bodies comprising lever arms that are tilted or rotated by piezo electric actuation to move the workpiece support elements into and out of engagement with a workpiece and the third workpiece support body being formed as an actuation column that is shifted by piezo electric actuation along its longitudinal axis to move the workpiece support element into and out of engagement with a workpiece.

16. A workpiece support according to claim 1 or claim 2, the workpiece support comprising one or more steadies.

17. A workpiece support according to claim 16, the workpiece support bodies being sandwiched between a pair of end plates, wherein one of the end plates comprises a steady or a tailstock.

18. A workpiece support according to claim 17, pair of piezo electric actuator being associated with each of the first and second workpiece support bodies, the piezo electric actuators of each of the first and second workpiece support bodies being spaced apart and generally parallel, the pair of piezo electric actuators of the second workpiece support body acting in a different direction to the pair of piezo electric actuators of the first workpiece support body .

19. A workpiece support according to claim 18, the pair of piezo electric actuators of the second workpiece support body acting perpendicular to the pair of piezo electric actuators of the first workpiece support body.

20. A workpiece support according to claim 19, the first and second workpiece support bodies being sandwiched between a pair of end plates, wherein one of the end plates comprises a steady or a tailstock.

21. A workpiece support according to claim 2 or 18, the piezo electric actuators being operable independently of each other.

22. A workpiece support according to any one of claims 1 to 21, engagement and disengagement of a workpiece support element with / from a workpiece being either by piezo electric actuation or deactivation.

23. A workpiece support for supporting a longitudinal workpiece, the workpiece support comprising: a plate assembly comprising two, spaced apart plate sections, the plate sections comprising an actuation surface for actuation by a piezo electric actuator,the plate sections comprising a pair of spaced apart slots and defining column sections between the slots, a pair of piezo electric actuators, arranged for respective engagement of the actuation surfaces of the plate sections in alignment with the column sections, each plate section associated with a workpiece support element, the workpiece support elements being operable in combination to support a workpiece, whereby actuation of the piezo electric actuators against the actuation surfaces in alignment with the column sections facilitates resilient movement of the plate sections to shift the workpiece support elements linearly.

24. A workpiece support according to claim 23, whereby actuation of the piezo electric actuators against the actuation surfaces facilitates resilient movement of the plate sections to move the plate sections to shift the workpiece support elements linearly.

25. A workpiece support according to claim 23 or 24, the actuation surfaces being at an angle to each other.

26. A workpiece support according to any one of claims 23 to 25, the pair of spaced apart slots being inboard of each actuation surface. A workpiece support according to any one of claims 23 to 26, the plate sections comprising multiple pairs of spaced apart slots on either side of the column sections.

27. A workpiece support according to claim 26, the plate sections comprising at least three pairs of spaced apart slots on either side of the column sections.

28. A workpiece support according to any one of claims 1 to 27 , comprising a mounting arrangement that facilitates coarse adjustment of the position of the workpiece support, while the piezo electric actuation facilitates fine adjustment of the position of the workpiece support element.

29. A workpiece support according to any one of claims 1 to 28, comprising electrical circuitry suitable to establish contact between the workpiece support element and the workpiece when the workpiece support element first engages the workpiece.

30. A workpiece support according to claim 29, the electrical circuitry comprising an open or closed loop control system which is automated to constantly monitor the position of the workpiece by utilising a position feedback system to correct the position where it is determined that the workpiece has shifted away from a preferred position due to grinding loads and also to maintain the position of the workpiece from changing during changing loading conditions.

31. A workpiece support according to claim 30, the position feedback system comprising a strain gauge system.

32. A method of controlling a workpiece support, in which the workpiece support comprises a workpiece support body and a workpiece support element which is associated with the workpiece support body, the workpiece support element being movable to engage a workpiece and a piezo electric actuator being associated with the workpiece support body for moving the workpiece support element, comprising moving the workpiece support by coarse adjustment to a position in which the workpiece support is close to or is in engagement with a workpiece, moving the workpiece support element by fine adjustment by activating the piezo electric actuator to engage the workpiece, or to move the workpiece.

33. The method of claim 32, the workpiece support comprising a pair of workpiece support bodies and an associate pair of workpiece support elements and a piezo electric actuator being associated with each workpiece support body for moving the respective workpiece support elements, the piezo electric actuators being operable to independently shift the workpiece support elements independently of each other.

34. The method of claim 32 or 33, comprising clamping a workpiece in a clamp that has a centreline, detecting the centreline of the workpiece and comparing that centreline with the centreline of the clamp and automatically adjusting the position of the workpiece support element by actuation of the piezo electric actuator to move the workpiece for alignment of the workpiece centreline with the clamp centreline.

35. The method of any one of claims 32 to 34, comprising continuously monitoring the centreline of the workpiece with the centreline of the clamp and dynamicallyadjusting the position of the workpiece support element by actuation of the piezo electric actuator during a machining process.

36. The method according to claim 35, utilising CNC closed loop control for continuous monitoring and dynamic adjusting.

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