A laser beam scanner and a laser processing apparatus comprising a laser beam scanner

Abstract

A laser beam scanner (106a, 106b) configured to be mounted in a mounting position on a laser processing apparatus. The laser beam scanner (106a, 106b) comprises a laser beam input (136a, 136b) for receiving a laser beam (118a, 118b) generated by a laser (105a, 105b); steering optics (140a, 140b) for steering the laser beam (118a, 118b) received by the laser beam input (136a, 136b) across a working surface of the laser processing apparatus; and a mounting detection system configured to change state when the laser beam scanner (106a, 106b) is separated and / or unlocked from the mounting position. The mounting detection system is connectable to the laser such that the laser is deactivated when the mounting detection system changes to a state indicating that the laser beam scanner (106a, 106b) is separated and / or unlocked from the mounting position.

Description

[0001] A LASER BEAM SCANNER AND A LASER PROCESSING APPARATUS COMPRISING A LASER BEAM SCANNER

[0002] Field of Invention

[0003] This invention concerns a laser beam scanner and a laser processing apparatus comprising a laser beam scanner. The invention has particular, but not exclusive, application to a laser beam scanner for a powder bed fusion apparatus and a powder bed fusion apparatus on which the laser beam scanner is mounted.

[0004] Background

[0005] Laser powder bed fusion apparatus produce objects through layer-by-layer solidification of a material, such as a metal powder material, using a laser beam. A powder layer is formed in a build plane across a powder bed contained in a build sleeve by lowering a build platform in the build sleeve to lower the powder bed, dosing a heap of powder adjacent to the lowered powder bed and spreading the heap of powder with a recoater across (from one side to another side of) the powder bed to form the layer. Portions of the powder layer corresponding to a cross-section of the workpiece to be formed are then solidified through irradiating these areas with the laser beam steered by a laser beam scanner. The laser beam melts or sinters the powder to form a solidified layer. After selective solidification of a layer, the powder bed is lowered and a further layer of powder is spread over the surface and solidified, as required.

[0006] The laser beam scanner is usually located outside of a build chamber housing the powder bed and directs the laser beam into the build chamber through a window. This protects the laser beam scanner from the powder and particles generated by the melting or sintering of the powder. Typically, the laser beam scanner is mounted on a build chamber housing the powder bed. An example of such a powder bed fusion apparatus is disclosed in W02010 / 026397. During the additive build,the build chamber heats up and this change in temperature results in thermal expansion of the build chamber, which can alter a position of the laser beam scanner relative to the powder bed. Furthermore, conduction of the heat to the laser beam scanner through the mounting formations can result in thermal distortion of the laser beam scanner, which can also result in inaccuracy in the positioning of the laser beam on the powder bed. This inaccuracy in the positioning of the laser beam on the powder bed can reduce a quality of the build or even result in failure of the build.

[0007] WO2019 / 096421 attempts to solve this problem by providing a support frame outside the build chamber for supporting the laser beam scanner, the support structure arranged to not be influenced by process heat generated in the build chamber. However, such a solution adds additional complexity and cost as it requires the addition of the support frame.

[0008] It is also desirable, when mounting the laser beam scanner on the powder bed fusion apparatus, to mount the laser beam scanner as close as possible to the intended mounting position to minimise subsequent adjustments that need to be made through calibration of the laser beam scanner.

[0009] WO2014 / 199149 Al discloses optical assemblies mounted on a flow device so as to move therewith. Each optical assembly comprises a sealed housing containing a lens for focusing the laser beam and a mirror for steering the laser beam on the powder bed. Accurate positioning of the optical assembly on the flow device is achieved through the provision of cooperating formations on the housing and the flow device, respectively. The cooperating formations are a series of kinematic mounts that provide for repeatable positioning of the optical assembly on the flow device. Thermal changes in a carriage on which the flow device is mounted will result in changes in position of the optical assemblies.

[0010] Summary of InventionAccording to a first aspect of the invention there is provided a laser processing apparatus comprising a build chamber for containing a working surface to be processed with a laser beam, the build chamber comprising a window through which the laser beam enters into the build chamber, a laser beam scanner mounted on the build chamber to direct the laser beam through the window into the build chamber, and a kinematic mount for mounting the laser beam scanner on the build chamber.

[0011] The laser scanner, as a three-dimensional body, has six independent degrees of freedom: the translational (X, Y, Z) and the rotational (Rx, Ry, Rz). A mount is considered a kinematic mount if the mount is configured to define a repeatable position in all degrees of freedom. Accordingly, the kinematic mount may form six points of contact. H. J. J. Braddick, "Mechanical Design of Laboratory Apparatus", Chapman & Hall, London, 1960, pages 11 to 30, describes kinematic designs constraining the degrees of freedom of motion of a body or feature using the minimum number of constraints and in particular involves avoiding over constraining. The use of a kinematic coupling ensures highly repeatable positioning of the laser beam scanner with the laser processing apparatus and means that the laser beam scanner and laser processing apparatus will be coupled in a predictable and known manner. It is to be understood that, to avoid any degree of over constraint whatsoever, a kinematic coupling would in theory require point contacts between the coupled parts. However, the generally accepted meaning of a kinematic coupling is one that conforms generally with kinematic design principles, even if small area contacts are used instead of point contacts.

[0012] Due to the point contacts of the kinematic mount, the kinematic mount forms a poor thermal conductor for conducting heat between the build chamber and the laser beam scanner (which is mounted outside of the build chamber). Accordingly, the build chamber is used both to protect the laser beam scanner from powder and particles generated by the melting or sintering of the powder and as a structural element for supporting the laser beam scanner whilst thermal distortion of the laserbeam scanner from heat conducted from the build chamber is mitigated through the poor thermal conductivity of the kinematic mount. Y et further, the kinematic mount provides for accurate mounting of the laser beam scanner on the build chamber.

[0013] The kinematic mount may be configured such that the contact points are in a common plane. The common plane may be parallel to a plane of the working surface.

[0014] The kinematic mount may comprise kinematic mounting formations on the laser beam scanner. The kinematic mount may comprise complementary kinematic mounting formations on the build chamber. The kinematic mounting formations on the laser beam scanner may engage with the complementary kinematic mounting formations on the build chamber at six contact points.

[0015] The arrangement of complementary kinematic mounting formations on the build chamber may have rotational symmetry, preferably three-fold rotational symmetry. Symmetry of the kinematic mounting formations may aid small or no changes in a position of the laser beam scanner defined by the kinematic mount for larger changes in the relative position of the kinematic mounting formations.

[0016] The kinematic mount may comprise three pairs of cooperating kinematic mounting formations, each pair comprising one of the kinematic mounting formations on the laser beam scanner and one of the complementary kinematic mounting formations on the build chamber. Each pair of cooperating kinematic mounting formations may provide two contact points (a 2-2-2 formation). Each pair of kinematic mounting formations may comprise a kinematic mounting formation providing two opposed walls on one of the laser beam scanner and the build chamber, and a contact element on the other of the laser beam scanner and the build chamber, the contact element comprising a circular contour configured to contact each opposed wall at a contact point. The two opposed walls may be provided by two discrete contact elements, such as two balls, two cylinders or the like, or a single continuous elementsuch as a V-groove.

[0017] The two opposed walls may be provided by two spherical surfaces, such as two balls.

[0018] The two opposed walls may be parallel. The pair of parallel walls may be provided by opposed walls of a V-groove or opposed surfaces of a pair of parallel cylinders. The contact element may be a ball, a hemisphere, a cone or frustum of a cone.

[0019] A line midway between the opposed walls of a one of the pair of cooperating kinematic mounting formations may meet the corresponding lines of the other pairs of cooperating kinematic mounting formations at a midpoint between the three pairs of cooperating kinematic mounting formations. Preferably, the lines are at an angle of 120° to each other. In this way, if the kinematic mount expands or contracts due to temperature changes substantially equally for all pairs of cooperating kinematic mounting formations, translation or rotations about this midpoint will be minimised as the contact points will all move radially from the midpoint along the lines.

[0020] Each pair of cooperating kinematic mounting formations may comprise a pair of balls on one of the laser beam scanner and the build chamber and a contact element on the other of the laser beam scanner and the build chamber, the contact element having a circular contour configured to be received between the pair of balls and contact each ball of the pair of balls at a contact point. In such an embodiment, the pair of balls provide the opposed walls contacted by the contact element. A midline between the pair of balls may be arranged at 120° to the corresponding midline of the pair of balls of each other pair of kinematic mounting formations.

[0021] Each pair of cooperating kinematic mounting formations may comprise a pair of parallel cylinders on one of the laser beam scanner and the build chamber and a contact element on the other of the laser beam scanner and the build chamber, the contact element having a circular contour configured to be received between thepair of parallel cylinders and contact each cylinder of the pair of parallel cylinders at a contact point. In such an embodiment, the pair of parallel cylinders provide the opposed walls contacted by the contact element. Parallel longitudinal axes of the parallel cylinders of each pair of cooperating kinematic mounting formations may be arranged at 120° to the longitudinal axes of the parallel cylinders of each other pair of kinematic mounting formations.

[0022] Alternatively, each pair of kinematic mounting formations may comprise a pair of discrete contact elements on one of the laser beam scanner and the build chamber, each discrete contact element having a circular contour and a cylinder on the other of the laser beam scanner and the build chamber configured to be received between the pair of discrete contact elements and contact the circular contour of each discrete contact element at a contact point. In such an embodiment, the circular contours of the pair of discrete contact elements provide the opposed walls. The longitudinal axis of the cylinder of each pair of cooperating kinematic mounting formations may be arranged at 120° to the longitudinal axis of the cylinder of each other pair of kinematic mounting formations.

[0023] Each pair of cooperating kinematic mounting formations may comprise a V-groove on one of the laser beam scanner and the build chamber and a contact element having a circular contour on the other of the laser beam scanner and the build chamber, the contact element configured to be received in the V-groove such that the circular contour contacts each opposed wall of the V-groove at a contact point. In such an embodiment, the V-groove provides the opposed walls contacted by the contact element. A longitudinal axis of the V-groove of each pair of cooperating kinematic mounting formations may be arranged at 120° to the longitudinal axis of the V-grooves of each other pair of kinematic mounting formations.

[0024] With such a kinematic mount, thermal expansion of the build chamber may cause movement of the cooperating kinematic mounting formations on the build chamber but a position of the laser beam scanner may not move at all or less than themovement of the cooperating kinematic mounting formations because the movement of contact points on the opposed walls is in a radial direction from the midpoint. Accordingly, even though the contact points change with temperature changes, the location of the midpoint, and therefore, the position defined by the kinematic mount, remains substantially the same.

[0025] The laser beam scanner may comprise at least one movable optic for steering a laser beam and a housing containing the at least one movable optic. The kinematic mounting formations may be located on the housing.

[0026] The laser processing apparatus may be a powder bed fusion apparatus. The working surface may be a surface of a powder bed.

[0027] According to a second aspect of the invention there is provided a laser beam scanner configured to be mounted in a mounting position on a laser processing apparatus, the laser beam scanner comprising a laser beam input for receiving a laser beam generated by a laser; steering optics for steering a laser beam received by the laser beam input across a working surface of the laser processing apparatus; and a mounting detection system configured to change state when the laser beam scanner is separated and / or unlocked from the mounting position and connectable to the laser such that the laser is deactivated when the mounting detection system changes to a state indicating that the laser beam scanner is separated and / or unlocked from the mounting position.

[0028] The mounting detection system may comprise at least one pair of electrical contacts arranged such that separating the laser beam scanner from the mounting position electrically connects or disconnects the at least one pair of electrical contacts.

[0029] The laser beam scanner may comprise a locking mechanism for locking the laser beam scanner in the mounting position. The mounting detection system may comprise a locking detection device for detecting whether the locking mechanismis in a locked position or an unlocked position. The locking detection device may comprise at least one pair of electrical contacts arranged such that unlocking the laser beam scanner electrically connects or disconnects the at least one pair of electrical contacts.

[0030] The state (connected or disconnected) of the electrical contacts indicates that the laser beam scanner is separated and / or unlocked from the mounting position.

[0031] The laser beam input may be for connecting to a beam delivery optic of a laser beam delivery fibre.

[0032] The mounting detection system may comprise a continuity circuit configured to extend a fibre continuity monitoring circuit of the laser beam delivery fibre to the at least one pair of electrical contacts, the at least one pair of electrical contacts arranged such that mounting and / or locking of the laser beam scanner in the mounting position electrically connects the at least one pair of electrical contacts to close the fibre continuity monitoring circuit and movement to separate the laser beam scanner from the mounting position or unlocking the laser beam scanner from the mounting position electrically disconnects the at least one pair of electrical contacts to open the fibre continuity monitoring circuit.

[0033] A laser control system, such as a laser integrator unit, monitors the fibre continuity monitoring circuit allowing the laser to operate when the fibre continuity monitoring circuit is closed and preventing the laser from operating when the fibre continuity monitoring circuit is open. Extending the fibre continuity monitoring circuit to the laser beam scanner ensures that the laser will only be operated if the laser beam scanner is correctly mounted on the laser processing apparatus.

[0034] The at least one pair of electrical contacts may comprise a plurality of pairs of electrical contacts. Each pair of electrical contacts may be arranged such that mounting of the laser beam scanner on the laser processing apparatus electricallyconnects the pair of electrical contacts. The plurality of pairs of electrical contacts may be arranged such that electrically connecting every one of the pairs of electrical contacts indicates that the laser beam scanner is mounted and / or locked in the mounting position (for example, closes the fibre continuity monitoring circuit) and electrically disconnecting any one of the pairs of electrical contacts indicates that the laser beam scanner is separated and / or unlocked from the mounting position (for example, opens the fibre continuity monitoring circuit).

[0035] The or each pair of electrical contacts may comprise a pair of mounting formations configured to engage a complementary electrically conductive mounting formation on the laser processing apparatus. The complementary electrically conductive mounting formation electrically connects the mounting formations of the pair.

[0036] The laser beam scanner may comprise three pairs of mounting formations, each pair of mounting formations configured to engage a complementary electrically conductive mounting formation on the laser processing apparatus.

[0037] The three pairs of mounting formations may form a kinematic mount, for example as described with reference to the first aspect of the invention. Use of the contact points of the kinematic mount for making and breaking the electrical contacts provides a system sensitive to any movement of the laser beam scanner that would urge the laser beam scanner away from its mounted position on the laser beam processing apparatus.

[0038] The or each pair of electrical contacts may comprise a switch that is closed on mounting of the laser beam scanner in the mounting position. The or each switch may comprise a movable element comprising one of the electrical contacts, the movable element configured to be engaged by a surface of the processing apparatus when the laser beam scanner is in the mounting position to move the movable element to close the electrical contacts and to open the electrical contacts when the laser beam scanner is separated from the mounting position.The electrical contacts, for example a pair of electrically conductive pins, may be biased, for example by a spring, to protrude from the laser beam scanner so as to engage an electrically conductive element on the laser processing apparatus when the laser beam scanner is in the mounting position.

[0039] The mounting detection system may comprise at least one photogate that is configured to be obscured by a geometric element on the laser processing apparatus when the laser beam scanner is mounted and / or locked in the mounting position.

[0040] The mounting detection system may comprise a capacitance sensor for detecting a change in capacitance resulting from mounting the laser beam scanner in the mounting position.

[0041] According to a third aspect of the invention there is provided a laser processing apparatus comprising a laser beam scanner according to the second aspect of invention.

[0042] Description of the Drawings

[0043] Figure 1 is a schematic illustration of a powder bed fusion apparatus according to an embodiment of the invention;

[0044] Figure 2a is a schematic illustration of a face of the laser bean scanner showing the kinematic mounting formations and Figure 2b is a schematic illustration of a face of the build chamber showing the complementary kinematic mounting formations;

[0045] Figure 3 is a cross-sectional view of engagement between a kinematic mounting formation on the laser beam scanner and a complementary kinematic mounting formation on the build chamber;Figure 4 is a schematic illustration of the geometric arrangement of the kinematic mount;

[0046] Figures 5a, 5b; 6a, 6b; 7a, 7b and 8a, 8b show kinematic mounting formations according to other embodiments of the invention;

[0047] Figure 9 is a schematic illustration of the geometric arrangement of the kinematic mounting formations shown in Figures 6a and 6b.

[0048] Description of the Embodiments

[0049] Referring to Figures 1 to 4, a powder bed fusion apparatus according to an embodiment of the invention comprises a build chamber 101 having therein a processing plate 115 defining a build aperture 117, and a build sleeve 116 extending down from the build aperture 117. A build platform 102 is lowerable in the build sleeve 116 such that the build sleeve 116 and the build platform 102 together define a build volume. During a build, the build platform 102 supports a build substrate plate 102a, a powder bed 104 and workpiece (object) 103 as the workpiece is built by selective laser melting or sintering of the powder. The platform 102 is lowered within the build volume under the control of a drive mechanism (not shown) as successive layers of the workpiece / object 103 are formed.

[0050] Layers of powder 104 are formed as the workpiece / object 103 is built by dispensing apparatus (not shown) and a recoater 109. The dispensing apparatus dispenses powder 104 from hopper (not shown) onto the processing plate 115 at a dosing location such that movement of the recoater 109 spreads powder into powder layers of the powder bed 104.

[0051] A plurality of laser beam scanners (in this embodiment, four laser beam scanners, two of which 106a, 106b are shown in Figure 1) are provided for steering acorresponding laser beam 118a, 118b generated by a laser 105a, 105b across selected areas of the powder bed 104 to melt the powder. In this embodiment, the lasers 105a, 105b are fibre lasers that deliver the laser beam to the laser beam scanner 106a, 106b via a delivery optical fibre 108a, 108b and beam deliver optic (BDO) 132a. 132b. The fibre laser includes a fibre continuity monitoring circuit / system (FCMS). The FCMS comprises an electrically conductive wire, in this embodiment a copper wire, wound around the delivery fibre 108a, 108b. Two electrical contacts, illustrated in Figure 1 by reference numerals 133a and 134a; 133b and 134b, are provided in the BDO 132a, 132b, typically on a face received in or on the laser beam scanner 106s, 106b. A laser integrator unit 110a, 110b monitors the continuity of the FCMS and if the circuit is broken, the laser integrator 110a, 110b unit shuts off the laser 105a, 105b. Accordingly, for the laser 105a, 105b to operate the corresponding electrical contacts 133a, 134a of the FCMS must be shorted (to make the circuit).

[0052] Each laser beam scanner 106a, 106b comprises a housing 125 containing movable optical components 140a, 140b, such as tiltable mirrors (only one of which is shown in Figure 1), for steering the corresponding laser beam 118a, 118b across the powder bed 104 and focussing optics 141a, 141b for focussing the laser beam 118a, 118b. The laser beam enters the housing 125 via a laser beam input 136a, 136b connectable to the BDO 132a, 132b and exits the housing 125a, 125b via an aperture 122 in a housing 125 of the laser beam scanner 106a, 106b. The laser beam input 136a, 136b is sealed by material transparent to the laser beam. The aperture 122 is a windowed aperture, for example sealed by material transparent to the laser beam. The sealing of the input and output protects the optical components from dust and the like. Profiled walls 126, 127a, 127b, 127c, 127d ofthe laser beam scanner 106a, 106b and the build chamber 101 nest together when the laser beam scanner 106a, 106b is mounted on the build chamber 101 to form a labyrinth pathway 135a, 135b that prevents laser light from escaping from the gap between the laser beam scanner 106a, 106b and the build chamber 101.Each laser beam scanner 106a, 106b is identical and configured to be removably mounted to the build chamber 101 in a mounting position selected from any one of a plurality of laser beam scanner mounting positions. Figures 2a and 3 show a laser beam scanner 106 that may be used in any one of the laser beam scanner mounting positions. Each laser beam scanner mounting position is defined by a kinematic mount 120a, 120b comprising kinematic mounting features 119’, 119” and 119’” on the laser beam scanner 106 and complementary kinematic mounting formations 121a’, 121a”, 121a’”; 121b’; 121c’” on the build chamber 101. In this embodiment, the complementary kinematic mounting formations 121a’, 121a”, 121a’”; 121b’; 121c’” are in a common plane on a roof of the build chamber 101 substantially parallel to a surface of the powder bed 104. Each kinematic mount 121a, 121b is configured such that, when the laser beam scanner 106 is mounted on the build chamber 101 using the kinematic mount 121a, 121b, the laser beam scanner 106 delivers the corresponding laser beam 118a, 118b through a corresponding window 107a, 107b, 107c, 107d. However, it will be understood that, in an alternative embodiment the build chamber window is configured such that two or more of the laser beam scanners 106a, 106b may deliver its corresponding laser beam 118a, 118b through the same build chamber window.

[0053] In this embodiment, the kinematic mount comprises three pairs 119a’ and 121a’; 119a”and 121a”; 119a’” and 121a’” of cooperating kinematic mounting formations, each pair comprising one of the kinematic mounting formations 119 on the laser beam scanner 106 and one of the complementary kinematic mounting formations 121 on the build chamber 101. Each kinematic mounting formation 119 comprises a pair of spaced apart balls 123’, 123” on the laser beam scanner 106 and the complementary kinematic mounting formation comprises a ball 121 on the build chamber 101. The ball 121 is configured to be received between and contact each ball 123’, 123” the pair of balls 123’, 123” at a contact point. Each ball 123’, 123” provides a constraining wall (opposed to the constraining wall of the other ball 123’, 123”) that is contacted by a circular contour of the ball 121. The two contact points per pair 119a’, 121a’; 119a”, 121a”; 119a’”, 121a’” of cooperatingkinematic mounting formations provides a 2-2-2 formation for the kinematic mount.

[0054] In this embodiment, the contact elements, in this embodiment balls 123’, 123”, reside in a recess 132 in the housing 125 of the laser beam scanner 106, which provides a seat for each contact element 123’, 123”. Each seat is sealed for laser safety by a seal 131’, 131” opaque to the laser beam 118a, 118b. The use of balls 123 ’, 123 ” mean that the seal can be formed about a round surface of the ball 123 ’, 123”, which is relatively easier to seal against than other surface shapes, such as a rectangular shape of a cylinder.

[0055] The contact elements 123’, 123 ’’form part of a mounting detection system, which will now be described.

[0056] Each contact element 123’, 123” is connected to an internal circuit 128 via electrically conductive elements, in this embodiment in the form of a spring 130’, 130”, which extend through the passageways from recess 132. The internal circuitry connects the contact elements 123’, 123” to the electrical contacts 133a, 134a, 133b, 134b of the FCMS circuit.

[0057] The contact elements 123’, 123”, and 121 are electrically conductive, each one mounted in an electrically insulative holder 129a’, 129a”, 129a’”, 129b’ and 129c” ’ to electrically isolate the contact element from the rest of the build chamber 101. Accordingly, contact of the contact elements 123’, 123” of each kinematic mounting formation 119a’, 119a”, 119a’” with the corresponding contact element 121a’, 121a”, 121a” completes the FCMS circuit (in a closed / shorted / connected state) allowing the laser 105a, 105b to operate. Movement of the laser beam scanner 106a. 106b causes the contact elements of at least one of the pairs of kinematic mounting formations 120a, 120b to break contact (in an open / disconnected state), breaking the circuit such that the laser 105a, 105b is switched off. This safety break protects the user from stray laser light if the nested profded walls 126a, 127a, 127b,127c, 127d around the window 107a are accidentally moved to a position which would allow the laser beam to escape if the laser beam 118a, 118b was active. As the kinematic mount 120a, 120b provides point contacts, the laser safety circuit is sensitive to even small movements of the laser beam scanner 106a, 106b.

[0058] Referring to Figure 4, a line midway ML’, ML”, ML’” between the contact elements 123’, 123” of each pair of kinematic mounting formations 119a’, 119a”, 119a’”on the laser beam scanner 106a, 106b may meet the corresponding lines ML’, ML”, ML’ ’ ’ of the other pairs of cooperating kinematic mounting formations 119a’, 119a”, 119a”’ at a midpoint MP between the three pairs of cooperating kinematic mounting formations. Preferably, the lines are at an angle of 120° to each other. In this way, if the kinematic mount expands or contracts due to temperature changes substantially equally for all pairs of cooperating kinematic mounting formations 119a’, 119a”, 119a’”, translation or rotations about this midpoint will be minimised as the contact points will all move radially from the midpoint along the midlines ML. The ball-on-ball kinematic mount may result in a small amount of movement of the laser beam scanner 106a, 106b in a direction (z -direction) perpendicular to the working surface if the build chamber 101 expands. However, such movement in the z-direction has less of an effect on the accuracy of the laser beam position than an equivalent movement of the laser beam scanner 106 in the x-and y- directions. Changes in a position of the laser beam scanner 106 in the z-direction are likely to be dominated by changes in dimensions in horizontal walls of the build chamber 101 as the walls change temperature.

[0059] Such z-movement can be reduced further by using a cylinder 221 rather than a ball 121 for the kinematic mount, as shown in Figures 5a and 5b. A longitudinal axis of the cylinder 221 is aligned along the midline ML. Balls 123’, 123” on the laser beam scanner 106 contact opposite sides of the cylinder 221. Movement of the cylinder 221 along the midline ML due to thermal expansion does not significantly alter a position of the balls 123’, 123” in any of x-, y- or z-directions.Figures 6a and 6b and 7a and 7b show alternative kinematic mounting formations that can be used in the invention. In these embodiments, the balls 123’ and 123” on the laser beam scanner 106 are replaced with cylinders 323’ and 323”. The contact element on the build chamber 101 may remain as a ball 121 or be replaced with a cone 421, as shown in Figures 7a and 7b. The cylinders 323’ and 323” provide the contacts to be connected to the internal circuit 128. However, it will be understood that connection of the contact elements 123’, 123”; 323’, 323” to the FCMS via the internal circuit 128 is a separable concept from the kinematic mount and each may be implemented without the other. If the kinematic mounts are used without the connection to the FCMS circuit, then the additional problems posed by sealing the cylinder contact elements to prevent laser light escaping from the laser beam scanner 106 is removed. Like the embodiment of Figures 5a and 5b, the use of cylinders 323’ and 323” helps to reduce movement of the laser beam scanner 106 in the z-direction when dimensions of the build chamber 101 change due to temperature changes.

[0060] Figure 9 illustrates how the kinematic mounting formations shown in Figures 6a, 6b and 7a, 7b may be geometrically arranged. In particular, the axes of the cylinders 323’ and 323” are aligned parallel to each other and the midline ML.

[0061] Figures 8a and 8b illustrate a further embodiment of the kinematic mount 120a / 120b, wherein a ball 523 is provided on the laser beam scanner 106 and a V-groove 521 is provided in the build chamber 101.

[0062] If two contact elements are not required on the laser beam scanner 106 to connect to the internal circuit 128, then the contact elements on the laser beam scanner 106 and build chamber 101, as described above, could be reversed.

[0063] Referring to Figure 1, each laser scanner 106a, 106b is locked in a mounting position by a locking mechanism, in this embodiment a pin 142a, 142b that is rotatable to engage with a stud 143a, 143b to urge the kinematic mountingformations 119a’, 119b’, 121a’, 121b’ together. Rotation of the pin 142a, 142b disengaging the pin 142a, 142b from the stud 143a, 143b unlocks the laser beam scanner 106a, 106b.

[0064] Modifications and alterations may be made to the above-described embodiments without departing from the invention as defined herein. For example, the mounting detection system may comprise other means for detecting separation of the laser beam scanner 106a, 106b from its mounting position. Furthermore, the mounting detection system may not be coupled to the fibre continuity monitoring circuit / system (FCMS) of the fibre laser but may comprise a separate system for deactivating the laser on separation of the laser scanner from the mounting position. Yet further, the mounting detection system may be integrated into the locking mechanism rather than the kinematic mount.

Claims

CLAIMS1. A laser beam scanner configured to be mounted in a mounting position on a laser processing apparatus, the laser beam scanner comprising a laser beam input for receiving a laser beam generated by a laser; steering optics for steering a laser beam received by the laser beam input across a working surface of the laser processing apparatus; and a mounting detection system configured to change state when the laser beam scanner is separated and / or unlocked from the mounting position and connectable to the laser such that the laser is deactivated when the mounting detection system changes to a state indicating that the laser beam scanner is separated and / or unlocked from the mounting position.

2. A laser beam scanner according to claim 1, wherein the mounting detection system comprises at least one pair of electrical contacts arranged such that separating the laser beam scanner from the mounting position electrically connects or disconnects the at least one pair of electrical contacts.

3. A laser beam scanner according to claim 1 or claim 2, comprising a locking mechanism for locking the laser beam scanner in the mounting position, the mounting detection system comprising a locking detection device for detecting whether the locking mechanism is in a locked position or an unlocked position.

4. A laser beam scanner according to claim 3, wherein the locking detection device comprises at least one pair of electrical contacts arranged such that unlocking the laser beam scanner electrically connects or disconnects the at least one pair of electrical contacts.

5. A laser beam scanner according to any one of the preceding claims, wherein the laser beam input is for connecting to a beam delivery optic of a laser beam delivery fibre and the laser beam scanner further comprises a laser beam scanner continuity circuit configured to extend a fibre continuity monitoring circuit of the laser beam delivery fibre to the at least one pair of electrical contacts, the at leastone pair of electrical contacts arranged such that mounting and / or locking of the laser beam scanner in the mounting position electrically connects the at least one pair of electrical contacts to close the fibre continuity monitoring circuit and movement to separate the laser beam scanner from the mounting position or unlocking the laser beam scanner from the mounting position electrically disconnects the at least one pair of electrical contacts to open the fibre continuity monitoring circuit.

6. A laser beam scanner according to any one of the preceding claims, wherein the at least one pair of electrical contacts comprises a plurality of pairs of electrical contacts, wherein each pair of electrical contacts is arranged such that mounting of the laser beam scanner on the laser processing apparatus electrically connects the pair of electrical contacts.

7. A laser beam scanner according to claim 6, wherein the plurality of pairs of electrical contacts is arranged such that electrically connecting every one of the pairs of electrical contacts indicates that the laser beam scanner is mounted and / or locked in the mounting position and electrically disconnecting any one of the pairs of electrical contacts indicates that the laser beam scanner is separated and / or unlocked from the mounting position.

8. A laser beam scanner according to any one of the preceding claims, wherein the or each pair of electrical contacts comprises a pair of mounting formations configured to engage a complementary electrically conductive mounting formation on the laser processing apparatus.

9. A laser beam scanner according to claim 8, wherein the laser beam scanner comprises three pairs of mounting formations, each pair of mounting formations configured to engage a complementary electrically conductive mounting formation on the laser processing apparatus.

10. A laser beam scanner according to claim 9, wherein the three pairs ofmounting formations form a kinematic mount.

11. A laser beam scanner according to any one of claims 1 to 7, wherein the or each pair of electrical contacts comprises a switch that is closed on mounting of the laser beam scanner in the mounting position.

12. A laser beam scanner according to claim 11, wherein the or each switch comprises a movable element comprising one of the electrical contacts, the movable element configured to be engaged by a surface of the processing apparatus when the laser beam scanner is in the mounting position to move the movable element to close the electrical contacts and to open the electrical contacts when the laser beam scanner is separated from the mounting position.

13. A laser beam scanner according to any one of claims 1 to 7, wherein the mounting detection system comprises at least one photogate that is configured to be obscured by a geometric element on the laser processing apparatus when the laser beam scanner is mounted and / or locked in the mounting position.

14. A laser beam scanner according to any one of claims 1 to 7, wherein the mounting detection system comprises a capacitance sensor for detecting a change in capacitance resulting from mounting the laser beam scanner in the mounting position.

15. A laser processing apparatus comprising a laser beam scanner according to any one of claims 1 to 14.

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