Automated metrology and model correction for three dimensional (3D) printability

• US 10,061,870 B2
• Filed: 03/18/2014
• Issued: 08/28/2018
• Est. Priority Date: 03/18/2014
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Inventors: Nelaturi, Saigopal, Kim, Walter, Rangarajan, Arvind, Kurtoglu, Tolga
• Primary Examiner(s): Fernandez Rivas, Omar F
• Assistant Examiner(s): Mikowski, Justin C
• Application Number:
  US14/217,854
• Publication Number:
  US 20150269282A1
• Time in Patent Office: 1,624 Days
• CPC Class Codes: B33Y 50/00 Data acquisition or data processing for additive manufacturing
• CPC Class Codes: B33Y 50/02 for controlling or regulating additive manufacturing processes
• CPC Class Codes: G06F 2113/10 Additive manufacturing, e.g. 3D printing
• CPC Class Codes: G06F 2119/18 Manufacturability analysis or optimisation for manufacturability
• CPC Class Codes: G06F 30/00 Computer-aided design [CAD]
• CPC Class Codes: G06F 30/17 Mechanical parametric or variational design
• CPC Class Codes: G06T 19/00 Manipulating 3D models or images for computer graphics
• CPC Class Codes: G06T 2219/008 Cut plane or projection plane definition
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

A system and a method automate metrology, measurement, and model correction of a three dimensional (3D) model for 3D printability. Slices of the 3D model are received or generated. The slices represent 2D solids of the 3D model to be printed in corresponding print layers. Medial axis transforms of the slices are calculated. The medial axis transforms represent the slices in terms of corresponding medial axes. A local feature size at any point along a boundary of the slices is determined as the shortest distance from the point to a corresponding medial axis.

Claims

1. A system to improve output operation of a 3D printer including a system for automated metrology, measurement, and model correction of a three dimensional (3D) model to ensure 3D printability and manufacturability of the 3D model as a physical object, said system comprising:

at least one processor configured to;

simulate an actual 3D printing process of the 3D model to generate a layered simulated 3D model describing the 3D model as it is to be printed, wherein operations to simulate the actual 3D printing process of the 3D model includes global model correction and local model correction being available;

receive or generate slices of the 3D model, the slices representing two dimensional (2D) solids of the 3D model to be printed in corresponding print layers;

calculate medial axis transforms of the slices, the medial axis transforms representing the slices in terms of corresponding medial axes, wherein a medial axis transform is a representation of a shape in terms of a lower dimensional medial axis that represents a focus of centers of maximal inscribed discs that are completely contained inside the shape, a medial axis topologically equivalent to the shape, and a local feature size at a point “

x”

on a boundary of the shape is thus the radius of the disc that is tangent to the shape at “

x”

;

determine the local feature size at any point along the boundary of the slices as the shortest distance from the point to a corresponding medial axis, wherein the local feature size defined in terms of the medial axis transform is used to automatically identify regions that require a differential addition of material to ensure manufacturability at regions including at least one of walls, bridges, protrusions, and holes, and wherein topological consistency between parts of the 3D model before and after manufacture is maintained;

generate a visual rendering of the layered simulated 3D model;

display the visual rendering of the layered 3D model on a display device; and

control a 3D printer to physically print the 3D model according to the layered simulated 3D model.

2. The system according to claim 1, wherein the at least one processor is further configured to:

generate each of the slices by intersecting a 2D plane parallel to a build orientation of the 3D model at a height of the corresponding print layer, subsequent to or concurrent therewith, the slices are regularized, wherein a regularized slice is a topological closure of an interior of the slice, and the regularization of the slices are performed through application of Boolean operations to automatically merge disjoint but overlapping components in the slices, the merging giving a set of regularized planar solids for the slices, wherein each solid is bounded by a polygon and a defined interior.

3. The system according to claim 1, wherein the at least one processor is further configured to:

compare the local feature size to a threshold feature size to determine a deviation; and

display the deviation to a user by a display device.

4. The system according to claim 3, wherein the threshold feature size is one of a minimum printable feature size, a minimum recommended feature size for a print material selected by a user, and a feature size specified by the user.

5. The system according to claim 1, wherein the at least one processor is further configured to:

simulate printing of the slices to identify corresponding printability maps, each printability map partitioning a slice into at least two disjoint sets of regions, the at least two disjoint sets including a first set of regions formed of features sized smaller than a threshold feature size and a second set of regions formed of features sized larger than the threshold feature, wherein the printability maps are used for visualizing the 3D model, and for the automated metrology and the model correction of the 3D model, wherein regions in the 3D model that require modification for additive manufacturing are identified in each of the printability maps, these regions corresponding to at least one of weakly printable regions, and unprintable regions, the identified regions then being automatically modified to ensure printability.

6. The system according to claim 5, wherein the threshold feature size is one of a minimum printable feature size, a minimum recommended feature size for a print material selected by a user, and a feature size specified by the user.

7. The system according to claim 5, wherein the at least one processor is further configured to:

quantify deviations between designed and manufactured geometries by determining the difference between the threshold feature size and a local feature size at any point along a boundary of the first set that overlaps with a boundary of the slice, the local feature size being the shortest distance from the point to a corresponding medial axis of the slice.

8. The system according to claim 5, wherein the at least one processor is further configured to:

automatically or manually determine corrections to the 3D model; and

display the determined corrections to a user by a display device.

9. The system according to claim 5, wherein the at least one processor is further configured to:

identify a largest local feature size of the second set for each of the slices;

determine a padding value for each slice of the 3D model or for the entire 3D model from the largest local feature sizes of the slices; and

thicken each of the slices by the corresponding padding value.

10. The system according to claim 1, wherein the at least one processor includes a plurality of processors, and wherein the plurality of processors are configured to simultaneously calculate medial axis transforms of a plurality of the slices in parallel.

20. The system of claim 1 wherein (i) the global model correction includes a step to determine a least upper bound for each of the printability maps, the least upper bounds for the printability maps being a measure of a largest local feature size of the identified regions of the printability maps that are smaller than the minimum printable or recommended feature size, the least upper bound for the printability maps determined as a maximum local feature size of the identified regions of the printability maps, and the determined least upper bounds of the printability maps being used to determine padding values for each slice of the 3D model or the entire 3D model, (ii) the local model correction includes a step which prunes the medial axis of each slice by removing segments that contact the slice boundary, the pruned medial axes being used to locally thicken corresponding slices to the minimum printable or recommended feature size, wherein local thickening includes determining a corrected slice for each slice of the corresponding pruned medial axis and a structuring element representing the desired thickness, the structuring element suitably sized to model the minimum printable or recommended feature size.

21. The system of claim 20 wherein in the local model correction the slices are not uniformly thickened causing changes in topology and continuity at points common to the boundary of the slice before and after correction, wherein changes in topology occur by a change in connectivity or a change in the number of holes, wherein changes in continuity occur by qualitative changes in the form of the 3D model, and changes in continuity or topology after local model correction act as an indication of a need for re-design of the simulated 3D object.

11. A method to improve output operation of a 3D printer including a method for automated metrology, measurement, and model correction of a three dimensional (3D) model to ensure 3D printability and manufacturability of the 3D model as a physical object, said method comprising:

simulating an actual 3D printing process of the 3D model to generate a layered simulated 3D model describing the 3D model as it is to be printed, wherein operations to simulate the actual 3D printing process of the 3D model includes global model correction and local model correction being available;

receiving or generating by at least one processor slices of the 3D model, the slices representing two dimensional (2D) solids of the 3D model to be printed in corresponding print layers;

calculating by the at least one processor medial axis transforms of the slices, the medial axis transforms representing the slices in terms of corresponding medial axes, wherein a medial axis transform is a representation of a shape in terms of a lower dimensional medial axis that represents a focus of centers of maximal inscribed discs that are completely contained inside the shape, a medial axis topologically equivalent to the shape, and a local feature size at a point “

x”

on a boundary of the shape is thus the radius of the disc that is tangent to the shape at “

x”

;

determining by the at least one processor the local feature size at any point along the boundary of the slices as the shortest distance from the point to a corresponding medial axis, wherein the local feature size defined in terms of the medial axis transform is used to automatically identify regions that require a differential addition of material to ensure manufacturability at regions including at least one of walls, bridges, protrusions, and holes, and wherein topological consistency between parts of the 3D model before and after manufacture is maintained;

generating a visual rendering of the layered simulated 3D model;

displaying the visual rendering of the layered 3D model on a display device; and

controlling a 3D printer to physically print the 3D model according to the layered simulated 3D model.

12. The method according to claim 11, further including:

generating one of the slices by intersecting a 2D plane parallel to a build orientation of the 3D model at a height of the corresponding print layer, subsequent to or concurrent therewith, the slices are regularized, wherein a regularized slice is a topological closure of an interior of the slice, and the regularization of the slices are performed through application of Boolean operations to automatically merge disjoint but overlapping components in the slices, the merging giving a set of regularized planar solids for the slices, wherein each solid is bounded by a polygon and a defined interior.

13. The method according to claim 11, further including:

comparing the local feature size to a threshold feature size to determine a deviation, the threshold feature size being one of a minimum printable feature size, a minimum recommended feature size for a print material selected by a user, and a feature size specified by the user; and

displaying the deviation to a user by a display device.

14. The method according to claim 11, further including:

simulating printing of the slices to identify corresponding printability maps, each printability map partitioning a slice into at least two disjoint sets of regions, the at least two disjoint sets including a first set of regions formed of features sized smaller than a threshold feature size and a second set of regions formed of features sized larger than the threshold feature, wherein the printability maps are used for visualizing the 3D model, and for the automated metrology and model correction of the 3D model, wherein regions in the 3D model that require modification for additive manufacturing are identified in each of the printability maps, these regions corresponding to at least one of weakly printable regions, and unprintable regions, the identified regions then being automatically modified to ensure printability.

15. The method according to claim 14, wherein the threshold feature size is one of a minimum printable feature size, a minimum recommended feature size for a print material selected by a user, and a feature size specified by the user.

16. The method according to claim 14, further including:

quantifying deviations between designed and manufactured geometries by determining the difference between the threshold feature size and a local feature size at any point along a boundary of the first set that overlaps with a boundary of the slice, the local feature size being the shortest distance from the point to a corresponding medial axis of the slice.

17. The method according to claim 14, further including:

automatically or manually determine corrections to the 3D model; and

display the determined correction to a user by a display device.

18. The method according to claim 14, further including:

identifying a largest local feature size of the second set for each of the slices;

determining a padding value for each slice of the 3D model or for the entire 3D model from the largest local feature sizes of the slices; and

thickening each of the slices by a corresponding padding value.

19. A system to improve output operation of a 3D printer including a system for automated metrology, measurement, and model correction of a three dimensional (3D) model to ensure 3D printability and manufacturability of the 3D model as a physical object, said system comprising:

at least one processor configured to;

simulate an actual 3D printing process of the 3D model to generate a layered simulated 3D model describing the 3D model as it is to be printed, wherein operations to simulate the actual 3D printing process of the 3D model includes global model correction and local model correction being available;

receive or generate slices of the 3D model, the slices representing two dimensional (2D) solids of the 3D model to be printed in corresponding print layers;

calculate medial axis transforms of the slices, the medial axis transforms representing the slices in terms of corresponding medial axes, wherein a medial axis transform is a representation of a shape in terms of a lower dimensional medial axis that represents a focus of centers of maximal inscribed discs that are completely contained inside the shape, a medial axis topologically equivalent to the shape, and local feature size at a point “

x”

on a boundary of the shape is thus the radius of the disc that is tangent to the shape at “

x”

;

identify segments of the medial axes where thickening the slices does not change topology and continuity of the slices;

thicken the slices up to a threshold feature size along the identified segments,

user selection of a print material to be used to represent the received or generated slices of the 3D model and parameters of a 3D printing process to be used for a simulation of printing of the 3D model, the parameters including a process type, and one of a printing nozzle and laser beam diameter,

generate a visual rendering of the layered simulated 3D model;

display the visual rendering of the layered 3D model on a display device;

a 3D printer configured to receive data from the at least one processor and to print a 3D physical object in accordance with the data received from the at least one processor; and

control a 3D printer to physically print the 3D model according to the layered simulated 3D model.