WO2017055853A1 - Dispositif et procédé de génération de données de balayage pour un processus de fabrication additive - Google Patents

Dispositif et procédé de génération de données de balayage pour un processus de fabrication additive Download PDF

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Publication number
WO2017055853A1
WO2017055853A1 PCT/GB2016/053035 GB2016053035W WO2017055853A1 WO 2017055853 A1 WO2017055853 A1 WO 2017055853A1 GB 2016053035 W GB2016053035 W GB 2016053035W WO 2017055853 A1 WO2017055853 A1 WO 2017055853A1
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WO
WIPO (PCT)
Prior art keywords
workpiece
feature
data object
voids
data
Prior art date
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PCT/GB2016/053035
Other languages
English (en)
Inventor
Ramkumar REVANUR
Original Assignee
Renishaw Plc
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Publication date
Application filed by Renishaw Plc filed Critical Renishaw Plc
Publication of WO2017055853A1 publication Critical patent/WO2017055853A1/fr

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Classifications

    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
    • G05B19/4097—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by using design data to control NC machines, e.g. CAD/CAM
    • G05B19/4099—Surface or curve machining, making 3D objects, e.g. desktop manufacturing
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/49—Nc machine tool, till multiple
    • G05B2219/49014—Calculate number and form of 2-D slices automatically from volume on screen
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/49—Nc machine tool, till multiple
    • G05B2219/49018—Laser sintering of powder in layers, selective laser sintering SLS
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/49—Nc machine tool, till multiple
    • G05B2219/49038—Support help, grid between support and prototype, separate easily
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/49—Nc machine tool, till multiple
    • G05B2219/49039—Build layer of different, weaker material between support and prototype
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
    • Y02P90/02—Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Definitions

  • This invention concerns a device and method for generating scan data for an additive manufacturing process.
  • the invention has particular application to devices and methods for incorporating features into a workpiece in computer aided design for manufacture (CAM) for additive manufacturing.
  • CAM computer aided design for manufacture
  • Additive manufacturing or rapid prototyping methods for producing parts comprise layer-by-layer solidification of a flowable material.
  • additive manufacturing methods including powder bed systems, such as selective laser melting (SLM), selective laser sintering (SLS), electron beam melting (eBeam) and stereolithography, and non-powder bed systems, such as fused deposition modelling.
  • SLM selective laser melting
  • SLS selective laser sintering
  • eBeam electron beam melting
  • stereolithography stereolithography
  • non-powder bed systems such as fused deposition modelling.
  • selective laser melting a powder layer is deposited on a powder bed in a build chamber and a laser beam is scanned across portions of the powder layer that correspond to a cross-section (slice) of the workpiece being constructed. The laser beam melts or sinters the powder to form a solidified layer.
  • the powder bed is lowered by a thickness of the newly solidified layer and a further layer of powder is spread over the surface and solidified, as required.
  • a single build more than one workpiece can be built, the parts spaced apart in the powder bed.
  • Computer programs are used to convert geometric data, such as CAD or STL file formats, defining a workpiece into scan data defining how the additive manufacturing apparatus operates to build the part.
  • Generation of the scan data may comprise determining cross-sections (slices) of the workpiece corresponding to areas to be melted or sintered in each layer and how the energy beam is to be scanned across the areas to solidify the material to form the slices.
  • Software such as Magics of Materialise NV, include operations for slicing a workpiece defined in a StereoLithography /Standard Tessellation language (STL) file format to identify slices of the workpiece to be built and for defining scan paths and scan parameters for a laser or electron beam.
  • the planning software may include operations for orientating parts and for generating supports for supporting the workpiece during the build.
  • WO2014/207454 Al discloses apparatus in which slicing and/or scan path operations can be carried out on at least one of the objects located in a common build volume independently from another one of the objects located in the common build volume. This allows the user to make changes to one object that may require a repeat of the slicing or scan path operations without repeating these operations for all the objects located in the common build volume.
  • the application also discloses different data structures for defining the objects and the supports. In the support data structure, an instance of data defining a standard support cross-section is used to define cross-sections of multiple supports and/or multiple cross-sections of a single support.
  • WO2013/0167904 discloses an article built using additive manufacturing comprising a plurality of dental abutments each of which is attached to a common location hub via a connecting bar.
  • the hub comprises two gross -orientation bores used to ensure the correct orientation of the article in a clamp during subsequent processing.
  • EP1683593 discloses additive manufacture of a hip component comprising a femoral attachment and a body.
  • a Boolean operation is performed in Magics to subtract a reduced femoral attachment from the original. This creates a jacket to be used as an interconnecting porous construct.
  • the jacket is processed by a bespoke application that populates STL shapes with repeating open cellular lattice structures (OCLS).
  • OCLS is sliced using a bespoke program.
  • the main body of the construct is loaded into Fusco, a user interface for the MCP Realizer.
  • the file is then prepared for manufacture by slicing and applying the hatching necessary for building solid constructs.
  • the component and OCLS femoral coating are then merged.
  • apparatus for generating scan data for use in an additive manufacturing process in which a workpiece is built layer-by-layer by consolidating material with a laser or electron beam, the apparatus comprising a processing unit, the processing unit arranged to: i) receive a first data object, the first data object defining surface geometry of the workpiece in three-dimensions;
  • iii) define a location of a feature in the build volume such that, during the additive manufacturing process, the feature is integrated into the workpiece, wherein a second data object, separate from the first data object, defines surface geometry of the feature in three-dimensions; and iv) determine scan paths for the laser or electron beam to follow when consolidating material based upon the first and second data objects without merging data of the first and second data objects to form a single data object defining surface geometry of a combination of the workpiece and feature in three-dimensions, characterised in that the feature is a void to be formed within the workpiece; a landmark feature for use as a datum in a measurement process; an identification tag; an allowance of material beyond nominal dimensions of the workpiece, the allowance to be removed by a subsequent subtractive process; and/or a mounting formation for mounting the workpiece for subsequent processing.
  • the invention allows a user to add the feature to be built in the additive manufacturing process without changing the surface geometry of the workpiece defined in the first data object. In this way, if the geometry of the workpiece has been "locked down" to prevent changes to the three-dimensional model, additional features, for example required for subsequent manufacturing processes, can be added using the apparatus.
  • the apparatus may be used as part of a computer aided design for manufacture (CAM) process for additive manufacturing.
  • CAM computer aided design for manufacture
  • a unique identification tag may be used with each of the workpieces or different landmark features, voids, allowances and/or mounting formations may be provided depending upon the type of machines that are to be used for subsequent processing of each workpiece.
  • different ones of the workpiece may be subsequently processed by different machine tools having different setups/capabilities.
  • the voids, landmark features, allowances and/or mounting features may be selected/designed based on knowledge about the different attributes of the machines to be used for subsequent processing. Accordingly, a customer may send out a workpiece design for manufacture to multiple manufacturing sites and the apparatus can be used to plan the additive manufacturing process based upon the capabilities at the manufacturing site.
  • the CAM process can be adapted for changes in the capabilities at a manufacturing site rather than requiring a workpiece redesign.
  • data object as used herein means an instance of a defined data structure that is sufficient to define the surface geometry of the workpiece or feature and on which operations, such as operations to determine slices and/or scan paths, can be carried out independently from other instances of the data structure.
  • the instance may be, but is not limited to, an instance of a class in an object-oriented program.
  • the first data object and the second data object may be different instances of the same data structure type, such as different instances of an STL file format. Alternatively, the first data object and the second data object may use different data structures.
  • the first data object may define surface geometry using a surface mesh model, such as a triangular mesh as provided by the STL file format, or a solid model.
  • the second data object may define surface geometry using by a solid model, such as defined by a mathematical function. This may be particularly advantageous when the feature is/comprises a lattice structure as defining complex lattice structures as a surface mesh model can result is very large file sizes because of the large surface area of the lattice.
  • a definition of the lattice structure using a mathematical function or vector format can provide a more memory efficient data structure for defining the lattice structure.
  • the apparatus allows the definitions of the surface geometry of the workpiece and the feature to be defined in different data structures as appropriate but the workpiece and feature to be integrated together when built in the additive manufacturing process.
  • the processor may be arranged to generate the surface geometry of the feature as defined in the second data object. For example, the processor may be arranged to generate the feature based on a user request. The processor may generate the feature from a predetermined profile modified based on the requirements for the workpiece. The processor may be arranged to generate the feature based on the surface geometry defined by the first data object. For example, the processor may be arranged to generate the feature such that a three-dimensional shape of the feature conforms to the surface geometry defined by the first data object. The processor may be arranged to locate the feature in the build volume based on a user input. The processor may constrain where the user can place the feature in the build volume to locations in which the feature is adjacent the surface of the workpiece. Alternatively, the processor may be arranged to generate bridging elements if the user selects a location for the feature in the build volume that is spaced from the workpiece and/or within a volume of the workpiece.
  • the processor may be arranged to automatically locate the feature in the build volume such that the feature is integrated into the workpiece when built in the additive manufacturing process.
  • the processor may automatically locate the feature based on an intended function of the feature and/or requirements of the workpiece.
  • the function of the feature may be to provide voids in the workpiece for cooling fluid, the cooling channels conforming to surfaces of the workpiece to be cooled.
  • the processor may be arranged to locate the feature in the build volume based upon tolerance data and/or critical surfaces, such as bearing surfaces, associated with the workpiece, which dictate locations where the feature can/cannot be placed.
  • the processor may be arranged to determine a first set of slices based on the surface geometry defined in the first data object and a second set of slices from the surface geometry defined in the second data object and merge the slices of each of the first and second set of slices that are in the same plane such that scan paths for forming the workpiece and feature are based upon the merged slices.
  • the merging of the slices may comprise a Boolean operation, such as adding of the slices together or subtracting the slice of the feature from the slice of the workpiece. Merging at the 2-dimensional level of the slices rather than at the three-dimensional level of the first and second geometric data allows one to retain the advantages of model separation at the three-dimensional level.
  • the void to be formed within the workpiece may be cooling channels, mounting recesses for subsequent processing, channels for the removal of powder from internal chambers within the workpiece after the additive manufacturing process and/or channels for subsequent polishing of the workpiece, for example chemical or electrochemical polishing.
  • the processor may be arranged to define locations of a plurality of voids in the build volume such that, during the additive manufacturing process, the plurality of voids are integrated into the workpiece and intersect to define a lattice, wherein one or more second data objects, separate from the first data object, define surface geometry of each void in three-dimensions; and determine scan paths for the laser or electron beam to follow when consolidating material based upon the first data object and the one or each second data object without merging the first and the or each second data object to form a single data object defining surface geometry of a combination of the workpiece and plurality of voids in three-dimensions.
  • the plurality of voids may comprise at least two voids having an identical three- dimensional shape defined by a common second data object.
  • the shape of the at least two voids may be defined in a master data object in a hierarchical data structure, as described in WO2014/207454 Al .
  • a large lattice structure may be defined in a data efficient manner.
  • the locations of the plurality of voids may be determined pseudo-randomly or may be provided in a regular pattern.
  • the processor may be arranged to define locations of a first plurality of intersecting voids at a surface of the workpiece (referred to hereinafter as "surface voids") and a second plurality of intersecting voids within a core of the workpiece (referred to hereinafter as "core voids") and a transition between the core voids and the surface voids such that the core voids join with the surface voids to define an open lattice.
  • Locations of the surface voids may be defined to conform to a contour of a surface of the workpiece.
  • Locations of the core voids may be independent from the contours of the workpiece.
  • the void may be act as an identifier.
  • the void may be an identifier that acts to identify an origin of the workpiece.
  • a void may be entirely enclosed within the workpiece such that the nature of the void can only be seen by destructive testing (e.g. cutting through the workpiece) or a scanning technique, such as CT scanning, that allows one to obtain images indicative of internal cavities within the workpiece.
  • the landmark feature may comprise multiple datums arranged to allow a measurement process to determine a position of the workpiece in multiple degrees of freedom.
  • the measurement process may be carried out as part of a subsequent subtractive process and/or a validation process.
  • the processor may be arranged to store a relative location of a feature to be measured/machined on the workpiece in a subsequent process to the datum(s).
  • the landmark feature may comprise one or more circular profiles, for example the landmark feature may be comprise one or more spheres and/or two or more orthogonal planes.
  • the processor may be arranged to automatically generate the landmark features based upon a feature identified by the user as to be measured/machined in a subsequent process.
  • the identification tag may comprise a planar three-dimensional object bearing a unique identifier, such as a unique alphanumeric code or a barcode.
  • the processor may generate the identification tag, for example by applying a Boolean operation to a predetermined three-dimensional shape to subtract or add the unique identifier to the predetermined three-dimensional shape.
  • the processor may be arranged to shape the identification tag to confirm to the surface geometry defined by the first geometric data.
  • the processor may be arranged to generate the allowance of material.
  • the processor may generate the allowance of material based on known tolerances achievable in the additive manufacturing process. For example, if the geometric data defines a shape unachievable using the additive manufacturing process, the processor may add an allowance to the workpiece that is to be removed by a subsequent subtractive process that can form such shapes.
  • the processor may be arranged to receive the second geometric data defining the mounting formation.
  • the processor may be arranged to receive a user input for locating the workpiece on the mounting formation.
  • the processor may be arranged to constrain the locations on the mounting formation where the workpiece can be mounted.
  • the processor may be arranged to receive data on a post-processing orientation in which the workpiece is to be mounted in a machine subsequent to the additive manufacturing process and locate the workpiece relative to the mounting formation in the build volume based upon the post-processing orientation.
  • the post-processing orientation may be user defined or the processor may be arranged to determine the post-processing orientation based upon knowledge of subsequent processes to be carried out.
  • the processor may determine a post-processing orientation based upon a required orientation in a machine tool to enable removal of the allowance.
  • the processor may be arranged to determine a location of landmark features based upon a postprocessing orientation as defined by the mounting formation.
  • iii) locate a feature in the build volume such that, during an additive manufacturing process, the feature is integrated into the workpiece, wherein a second data object, separate from the first data object, defines surface geometry of the feature in three-dimensions;
  • iv) determine scan paths for the laser or electron beam to follow when consolidating material based upon the first and second data objects without merging the data of the first and second data objects into a single data object defining surface geometry of a combination of the workpiece and feature in three-dimensions, characterised in that the feature is a void to be formed within the workpiece; a landmark feature for use as a datum in a measurement process; an identification tag; an allowance of material beyond nominal dimensions of the workpiece, the allowance to be removed by a subsequent subtractive process; and/or a mounting formation for mounting the workpiece for subsequent processing.
  • apparatus for generating scan data for use in an additive manufacturing process in which a workpiece is built layer-by-layer by consolidating material with a laser or electron beam, the apparatus comprising a processing unit, the processing unit arranged to: i) receive a first data object, the first data object defining surface geometry of the workpiece in three-dimensions;
  • iii) define a location of a feature in the build volume such that, during the additive manufacturing process, the feature is integrated into the workpiece, wherein a second data object, separate from the first data object, defines surface geometry of the feature in three-dimensions;
  • a data carrier having instructions stored thereon, which, when executed by a processor, cause the processor to:
  • iii) define a location of a feature in the build volume such that, during the additive manufacturing process, the feature is integrated into the workpiece, wherein a second data object, separate from the first data object, defines surface geometry of the feature in three-dimensions;
  • the feature is a void to be formed within the workpiece; a landmark feature for use as a datum in a measurement process; an identification tag; an allowance of material beyond nominal dimensions of the workpiece, the allowance to be removed by a subsequent subtractive process; and/or a mounting formation for mounting the workpiece for subsequent processing.
  • apparatus for generating scan data for use in an additive manufacturing process in which a workpiece is built layer-by-layer by consolidating material with a laser or electron beam, the apparatus comprising a processing unit, the processing unit arranged to: i) receive a first data object, the first data object defining surface geometry of the workpiece in three-dimensions;
  • iii) define locations of a plurality of intersecting voids within the build volume, the plurality voids located within a solid volume of the workpiece, wherein one or more second data objects, separate from the first data object, define surface geometry of the voids in three-dimensions;
  • iv) determine scan paths for the laser or electron beam to follow when consolidating material based upon regions of the workpiece that do not coincide with the plurality of voids.
  • a data carrier having instructions stored thereon, which, when executed by a processor, cause the processor to:
  • iii) define locations of a plurality of intersecting voids within the build volume, the plurality voids located within a solid volume of the workpiece, wherein one or more second data objects, separate from the first data object, define surface geometry of the voids in three-dimensions;
  • iv) determine scan paths for the laser or electron beam to follow when consolidating material based upon regions of the workpiece that do not coincide with the plurality of voids.
  • the data carrier may be a suitable medium for providing a machine with instructions such as non-transient data carrier, for example a floppy disk, a CD ROM, a DVD ROM / RAM (including - R/-RW and +R/ + RW), an HD DVD, a Blu Ray(TM) disc, a memory (such as a Memory Stick(TM), an SD card, a compact flash card, or the like), a disc drive (such as a hard disc drive), a tape, any magneto/optical storage, or a transient data carrier, such as a signal on a wire or fibre optic or a wireless signal, for example a signals sent over a wired or wireless network (such as an Internet download, an FTP transfer, or the like).
  • non-transient data carrier for example a floppy disk, a CD ROM, a DVD ROM / RAM (including - R/-RW and +R/ + RW), an HD DVD, a Blu Ray(TM) disc, a memory (such as
  • Figure 1 is a schematic of an additive manufacturing apparatus according to an embodiment of the invention.
  • Figure 2 is the additive manufacturing apparatus of Figure 1 shown from another side;
  • Figure 3 is an example of a user interface of CAM software in accordance with an embodiment of the invention.
  • Figure 4 illustrates the merging of two-dimensional slices of a workpiece and features added using the user interface
  • Figure 5a is a cross-section of a workpiece and a plurality of voids along a line A- A;
  • Figure 5b is a cross-section of the workpiece and the plurality of voids along a line B-B;
  • Figure 5c is a cross-section of the workpiece and the plurality of voids along a line C-C;
  • Figure 5d is a plan view of the workpiece and the plurality of voids.
  • Figure 6 is a cross-section of a workpiece and a plurality of voids that are different instances of a common void object.
  • an additive manufacturing apparatus comprises a main chamber 101 having therein partitions 115, 116 that define a build chamber 117 and a surface onto which powder can be deposited.
  • a build platform 102 is provided for supporting a workpiece 103 built by selective laser melting powder 104. The platform 102 can be lowered within the build chamber 117 as successive layers of the workpiece 103 are formed.
  • a build volume available is defined by the extent to which the build platform 102 can be lowered into the build chamber 117.
  • Layers of powder 104 are formed as the workpiece 103 is built by dispensing apparatus 108 and a wiper 109.
  • the dispensing apparatus 109 may be apparatus as described in WO2010/007396.
  • a laser module 105 generates a laser for melting the powder 104, the laser directed as required by optical module 106 under the control of a computer 130.
  • the laser enters the chamber 101 via a window 107.
  • Computer 130 comprises a processor unit 131, memory 132, display 133, user input device 134, such as a keyboard, touch screen, etc, a data connection to modules of the laser melting unit, such as optical module 106 and laser module 105, and an external data connection 135.
  • Stored on memory 132 is a computer program that instructs the processing unit to carry out the method as now described.
  • a workpiece to be built will be designed in appropriate software, such as CAD.
  • the workpiece is usually defined in a way that is unsuitable for use in determining sections and scan parameters, such as a scan path, for the laser in building the workpiece using selective laser melting.
  • scan parameters such as a scan path
  • the CAD data may be converted into an STL format.
  • a suitable conversion program may be provided on computer 130 or such a conversion may be carried out remote from the system.
  • Conversion of the CAD file into an STL file may require fixing of the data to ensure that is meets certain requirements for use in determining sections and a scan path. For example, ill-defined regions in the surfaces may have to be fixed.
  • the fixing of the data can be done using conventional software.
  • the workpiece defined in the STL file is imported into the computer program stored on computer 130.
  • a single build in an additive manufacturing machine it is common to build a plurality of workpieces together.
  • a plurality of workpieces may be imported, such as in the form of STL files, into an application program running on computer 130 or a single workpiece may be imported and copies of the workpiece made in the application program. In either case, data is provided defining a surface geometry of a plurality of workpieces.
  • a user interface of an application program is shown in Figure 3. Such a user interface may be displayed on display 133.
  • the user interface comprises a graphical depiction of the build platform 204 and the available build volume 217.
  • Geometric data on a workpiece 218 has been imported into the application program.
  • the user interacts with the computer 130 through the input device 134 to orient and locate the workpiece 218 in the build volume 217.
  • the user can toggle between each stage for each workpiece by selecting the workpiece and then selecting icons/graphical buttons 222, 223, 224 and 225 with a pointing device or by touching a touch screen.
  • the buttons 222 to 225 may change colour or otherwise change appearance to indicate to the user the stage of the process that has been selected for a particular workpiece.
  • a user can locate and orient the workpiece(s) in the build volume 217. This may be achieved using a pointing device/touch to select a workpiece and appropriate combinations of button/key operations and movement of the pointer/finger to orient and locate the workpiece.
  • the user can select workpiece(s) and then the "Section" button 223, which will cause the processing unit 131 to slice the workpiece(s) and any supports into sections to be built in the layer-by-layer selective laser melting process.
  • the orientation and, possibly, also the location, of the selected workpieces may become fixed, the user having to toggle back to the "Design" stage to change the orientation and location.
  • Re-orientation of the workpiece will require the workpiece to be re-sliced and it is likely that the time it takes to slice an workpiece with a conventional desk-top computer (typically tens of seconds, although it will depend on the shape and size of the workpiece) will be too long to provide a user friendly experience if re-slicing was carried out in real-time with re-orientation of the workpiece.
  • suitably fast computers may be able to carry real-time re-slicing of the workpiece within an acceptable time period such that re- slicing of the workpiece in "real-time" with changes in orientation may provide an acceptable user experience.
  • the user is able to alter these attributes after the slicing operation.
  • the user can then select one or more workpieces that are at the "Section" stage and toggle to the scan path stage using button 224.
  • the processing unit 131 determines a scan path for the laser when forming each section of the selected workpiece(s) and supports.
  • WO2014/207454 describes data structures for the workpieces and supports and is incorporated herein by reference. In particular, WO2014/207454 describes data structures that allow an operation to determine slices and/or scan parameters, for example scan paths, to be carried out on one workpiece without carrying out the operation on another workpiece located within a common build volume.
  • the user interface comprises icons 227 to 231 that can be selected by the user for adding features 232 to 236, respectively, to the build.
  • Feature 232 is a void to be formed within the workpiece 218.
  • the user may define a three-dimensional geometry of the void (or "negative-object") and identify a location for this three-dimensional geometry in the workpiece 218.
  • the geometric data on the negative object 232 is stored as a separate instance of an object to the geometric data on the workpiece but identified as a void rather than a solid object.
  • the negative object may be stored as a data object separate from the data object defining the workpiece in a hierarchical data structure as described in WO2014/207454.
  • slices are determined for the workpiece 218 and negative object 232 for each layer of the build and the slices of the negative object are subtracted from the slices of the workpiece 218 to determine a final area of the layer to be scanned by the laser beam.
  • Scan paths are determined for the resulting area.
  • An example of this method is shown in Figure 4, wherein a slice 332 of the negative object is subtracted from a slice 318 of the workpiece 218 to generate resulting cross-sectional area 339. Scan paths, as represented by the lines in area 339, are determined for the resulting cross-section.
  • An algorithm may be provided for determining a geometry of the negative object 232.
  • the algorithm may generate a shape of the negative object 232 based upon a surface geometry of the workpiece 218.
  • the void may form a cooling channel/chamber for cooling fluid, such as in a hybrid mould as described in US7261550, and the algorithm may generate a channel/chamber that is spaced by a set distance from surfaces, such as moulding surfaces, of the workpiece 218.
  • the void may form a channel for the removal of powder from a central void.
  • the user may also import and/or design objects to be used as negative objects for forming voids within the workpiece 218. Selecting an object located in the build volume and selecting icon 227 results in the object being identified as a negative object, rather than solid object, such that slices of the object are subtracted from slices of a workpiece 218 with which it overlaps.
  • Negative objects may also be used to generate identification tags 239 in the form of voids that are entirely enclosed within the workpiece' s geometry such that the identification tag 239 can only be seen by imaging the internal structure of the workpiece, for example, by using a CT scan or by destructive testing. Such an identification tag 239 may be used to authenticate if the workpiece is genuine or a lookalike.
  • the mounting formations comprise three balls (only two of which are shown) connected to the workpiece by stalks, the balls arranged to be received in grooves of a mount on a machine tool.
  • each ball receiving groove may be defined by a pair of parallel rollers, the grooves oriented in different directions to define a position of the workpiece in six degrees of freedom. In this way, the balls in combination with the rollers form a kinematic mount for locating the workpiece 218 in a repeatable position on the machine tool.
  • the user may define a desired orientation Z m of the workpiece 218 in the machine tool and the processor may automatically determine a location for each mounting formation 235a, 235b on the workpiece 218, and therefore, a location in the build volume, in order that the workpiece has this orientation on the machine tool.
  • the mounting formations 235a, 235b are defined as separate objects from the workpiece. There is no 3-D Boolean operation to combine the mounting formations 235a, 235b with the workpiece 218.
  • Slices 335b are determined for the mounting formations 235a, 235b. As shown in Figure 4, the slices 335b of the mounting formations 235a, 235b are merged with slices 318 of the workpiece having a corresponding z-height in the build and scan paths determined for the merged cross- sectional shape 339.
  • Feature 233 is an identification tag for identifying the workpiece.
  • An algorithm is provided for generating identification tags with unique identifiers for each workpiece of the build and possibly, across a series of builds on the same and, possibly, multiple additive manufacturing machines.
  • the computer 130 may be connected to multiple additive manufacturing machines.
  • the identifier may be alphanumeric characters, a 1-D or 2-D barcode or the like.
  • An algorithm may generate each identification tag by generating a profile of the identifier, such as a profile of each character that makes up the identifier, which may be done using true type fonts. The identifier profile is then subtracted from a planar profile, such as a rectangular profile, of a blank/sheet of the identification tag.
  • the resulting profile is then extruded (in software) by a constant depth to extend the profile in three-dimensions. Extrusion of the outermost walls of the profile is continued to a greater depth to that of the profile of the identifier.
  • the end profiles (that of the identifier and that of the outermost walls) are then closed by planar triangulation to form a closed three-dimensional object.
  • the software may automatically adjust the 3-dimensional profile of the identification tag 233 to wrap the identification tag 233 around a non-planar profile of the workpiece 218, as shown in Figure 4.
  • the identification tag 233 is defined as a separate object from the workpiece. There is no 3-D Boolean operation to combine the identification tag 233 with the workpiece 218. Slices are determined for the identification tag 233. The slices of the identification tag 233 may be merged with the slices of the workpiece to avoid lines of weakness between the identification tag 233 and the workpiece. If later removal of the identification tag 233 is desirable, the slices may not be merged to ease removal of the identification tag 233 from the workpiece 218.
  • an identification tag 233 is generated with a raised identifier.
  • Feature 234 is an allowance of material beyond nominal dimensions of an element 237 of the workpiece 218 that is to be removed by a subsequent subtractive manufacturing process.
  • the allowance 234 may be added because the element 237 of the workpiece is deemed too small/fragile to manufacture using the additive manufacturing process. Accordingly, the process may add the allowance 234 based upon knowledge of the capabilities of the additive manufacturing process.
  • the allowance is defined as a separate object from the workpiece. There is no 3-D Boolean operation to combine the allowance 234 with the workpiece 218. Merging is carried out at the 2-dimensional level of the slices as described above with reference to the identification tag 233 and mounting formations 235.
  • Features 236a, 236b, 236c are landmark features for use as a datum in a measurement process.
  • the landmark features 236a, 236b, 236c are spheres that can be measured with a contact or optical probe to determine centres of the spheres. The measured position of the sphere centres can be used to determine a position of the workpiece in 6 degrees of freedom.
  • a subsequent subtractive manufacturing process may comprise measuring the landmark features to determine a position of the workpiece before or during the subtractive process.
  • a location of elements of the workpiece to be machined or other features, such as an allowance, to be removed relative to the landmark features may be deduced from the geometric data used to drive the additive manufacturing process, i.e. as both the landmark features and the element/features to be machined have been built using the additive manufacturing process, their relative positions are known within the tolerances achievable with the additive manufacturing process.
  • a method of generating instructions for producing a lattice structure using additive manufacturing will now be described with reference to Figures 5a to 5d.
  • the solid geometry of a workpiece 418 is defined in a first data object and negative data objects defining voids 401, 402 are defined in one or more second data objects.
  • voids 401 which do not directly open to a surface of the workpiece 218, are "core voids” having a first geometry and voids 402, which do directly open to a surface 218a of the workpiece 218, are "surface voids” having a second geometry that conforms with a geometry of a surface of the workpiece 418 (in this embodiment, a planar surface 402a to match to a planar shape of surface 418a of the workpiece 418).
  • the lattice is defined by defined locations for the surface and core voids 401, 402 and the data objects defining the surface geometry of the voids 401, 402. The locations are defined such that the voids intersect to form an open lattice structure. If a shape of a void 401, 402 is repeated within the lattice, then each one of these repeated void shapes may be defined by reference to a common instance of a master object in a hierarchical data structure, as is described in WO2014/207454 Al. A location, orientation about a Z-axis and size of the void relative to the master object within the lattice is defined by a position vector V (a reference point and a vector) within the build volume.
  • V a reference point and a vector
  • a master vector of the master object and the position vector of an instance of the master object together can be used to generate a quaternion that gives a rotation matrix for transforming the master object into that instance.
  • a direction vector generated by the reference point on the master and the reference point on the instance gives the translation.
  • the ratio of the magnitude of the master vector to the position vector of the instance gives the scaling factor of the void.
  • the core voids 401 are all of the same size with some oriented at 90 degrees about the Z-axis to others. Similarly, the surface voids 402 are also the same size relative to each other.
  • a shape of each core void 401 is defined by a corresponding vector V and reference to a common master object. Surface voids 402 are defined in a similar manner but with reference to a common master object different to that of the core voids 401.
  • An algorithm is provided for joining the core voids 401 to the surface voids 402.
  • the pattern of core voids is generated such that no core void 401 is located within a pre-set distance from the workpiece surface.
  • Surface voids 402 are then located, oriented and scaled such that the surface void 402 opens the core voids 401 to the surface 418a of the workpiece 418 designated as having surface voids 402.
  • a pattern of surface voids 402 may be based on the pattern of core voids and/or a contour of the workpiece surface 418a.
  • a size of the core voids 401 and surface voids 402 may be partly determined by the ease in extracting powder from the resultant lattice after the additive build.
  • Defining a lattice in this way lends itself to optimisation techniques, for example finite element analysis and computational fluid dynamics, as changes can easily be made, for example in an iteration of an optimisation routine.
  • shape of the master object can be generated outside of CAD to allow the geometry to be easily changed.
  • locations, sizes and/or orientations of the voids can be easily changed without having to generate a new definition of the void geometry.
  • the optimisation routine may comprise building of workpieces comprising lattices and testing of the resultant workpieces.
  • an array of workpieces with integrated lattices may be built within a build volume, each workpiece having a lattice with a variation in a lattice property. These can then be tested to determine which variants produce better results for a particular requirement. Such variants can be quickly generated because of the separation of the definitions of the workpiece geometry and the lattice/void geometry.
  • Figure 6 illustrates a further embodiment in which the core voids 501 are of the same shape (so defined by a common master object 501a) but with different scaling and orientations as defined by vectors V.
  • the core voids 501 are located within the workpiece 518 volume to provide appropriate nesting of the voids.
  • the locations of the voids 501 within the workpiece volume may be determined pseudo-randomly.

Abstract

La présente invention concerne un appareil (130) permettant de générer des données de balayage destinées à être utilisées dans un processus de fabrication additive dans lequel une pièce est construite couche par couche par consolidation d'un matériau au moyen d'un faisceau laser ou électronique. L'appareil comprend une unité de traitement (131), l'unité de traitement (131) étant conçue pour recevoir un premier objet de données, le premier objet de données définissant une géométrie de surface de la pièce (218) en trois dimensions; pour recevoir un emplacement de la pièce (218) à l'intérieur d'un volume de construction (217); et pour localiser une caractéristique (233 à 236, 239) dans le volume de construction (217) de sorte qu'au cours du processus de fabrication additive, la caractéristique (233 à 236, 239) est intégrée dans la pièce (218). Un second objet de données, distinct du premier objet de données, définit une géométrie de surface en trois dimensions de la caractéristique (233 à 236, 239). L'unité de traitement (131) est en outre conçue pour déterminer des trajets de balayage pour le faisceau laser ou électronique à suivre lors de la consolidation d'un matériau sur la base des premier et second objets de données, sans fusion des données des premier et second objets de données en un seul objet de données définissant une géométrie de surface en trois dimensions d'une combinaison de la pièce (218) et de la caractéristique (233 à 236, 239). La caractéristique est un vide (232, 239) devant être formé à l'intérieur de la pièce (218); un élément de repère (236a, 236b, 236c) destiné à être utilisé en tant que donnée dans un processus de mesure; une étiquette d'identification (233, 239); une addition de matériau (234) au-delà des dimensions nominales de la pièce (218), ladite addition étant destinée à être éliminée par un processus soustractif ultérieur; et/ou une structure de montage (235a, 235b) permettant de monter la pièce (218) en prévision d'un traitement ultérieur.
PCT/GB2016/053035 2015-09-30 2016-09-29 Dispositif et procédé de génération de données de balayage pour un processus de fabrication additive WO2017055853A1 (fr)

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Cited By (1)

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Publication number Priority date Publication date Assignee Title
WO2019112805A1 (fr) * 2017-12-05 2019-06-13 Fisher Controls International Llc Procédés et appareil pour positionner de manière optimale des objets pour un usinage automatisé

Citations (3)

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Publication number Priority date Publication date Assignee Title
EP1683593A2 (fr) * 2004-12-30 2006-07-26 Howmedica Osteonics Corp. Structure poreuse produite par laser
WO2014125258A2 (fr) * 2013-02-14 2014-08-21 Renishaw Plc Procédé et appareil de solidification sélective par laser
WO2014207454A1 (fr) * 2013-06-26 2014-12-31 Renishaw Plc Procédé et appareil pour générer des données géométriques destinées à être utilisées dans l'impression 3d

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
EP1683593A2 (fr) * 2004-12-30 2006-07-26 Howmedica Osteonics Corp. Structure poreuse produite par laser
WO2014125258A2 (fr) * 2013-02-14 2014-08-21 Renishaw Plc Procédé et appareil de solidification sélective par laser
WO2014207454A1 (fr) * 2013-06-26 2014-12-31 Renishaw Plc Procédé et appareil pour générer des données géométriques destinées à être utilisées dans l'impression 3d

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019112805A1 (fr) * 2017-12-05 2019-06-13 Fisher Controls International Llc Procédés et appareil pour positionner de manière optimale des objets pour un usinage automatisé

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