Imaging monitoring method and apparatus for fabricating three dimensional models

A method of monitoring operation of a fabrication system for fabricating a three dimensional model by successive deposition of at least one material comprising at least one of a model material for forming the model and at least one subsequently removed sacrificial material for supporting the model material during fabrication of the model, the system including;

• a camera,
• a workpiece platform for supporting the composite model during fabrication,
• a tool platform for supporting at least one material deposition device for depositing the at least one material on layers of the model,
• the at least one material deposition device and the camera having a known orientation and planar relationship with a tool platform reference plane, and
• the workpiece platform and the tool platform being movable with respect to each other along an X axis, a Y axis and a Z axis, the method comprising:
• depositing at least one test pattern comprising the at least one material on at least one imaging surface related to one of a layer of the composite model, the workpiece platform, a test surface, or a currently topmost layer of the model,
• capturing, via the camera;
• an image of the at least one test pattern,
• examining, via an imaging monitoring system the image of the at least one test pattern to determine at least one characteristic of the test pattern representing operation of the fabrication system,
• illuminating the imaging surface with an illumination source having an axis of emission that is oblique to an imaging axis of the camera and to the imaging surface at a known angle of illumination,
• capturing, via the camera, the image of the at least one test pattern and an adjacent area of the imaging surface including a shadow cast on the imaging surface by the material of the test pattern as illuminated by the illumination source,
• determining a width of the shadow cast on the imaging surface,
• and determining a thickness of the material of the test pattern from a width of the shadow cast on the imaging surface and the known angle of illumination.

A method of monitoring operation of a fabrication system for fabricating a three dimensional model by successive deposition of at least one material comprising at least one of a model material for forming the model and at least one subsequently removed sacrificial material for supporting the model material during fabrication of the model, the system including:

• a camera,
• a workpiece platform for supporting the composite model during fabrication,
• a tool platform for supporting at least one material deposition device for depositing the at least one material on layers of the model,
• the at least one material deposition device and the camera having a known orientation and planar relationship with a tool platform reference plane,
• the workpiece platform and the tool platform being movable with respect to each other along an X axis, a Y axis and a Z axis, and
• a test surface, separate from the workpiece platform, comprising a surface of a test tape stored on a test tape supply spool and configured to be advanced by a test tape take-up mechanism through a test region in which test patterns may be created on the surface of the test tape, the method comprising:
• depositing at least one test pattern comprising the at least one material on at least one imaging surface related to one of a layer of the composite model, the workpiece platform, a test surface, or a currently topmost layer of the model,
• capturing, via the camera, an image of the at least one test pattern,
• examining, via an imaging monitoring system, the image of the at least one test pattern to determine at least one characteristic of the test pattern representing operation of the fabrication system,
• incrementing the imaging surface toward the tool platform reference plane so that a cutting edge of one of a milling tool and a planing tool at a known displacement from the tool platform reference plane intersects the at least one test pattern along a milling plane parallel with the tool platform reference plane and at a height between an upper surface of the at least one test pattern and the imaging surface,
• planing an area of the at least one test pattern,
• capturing, via the camera, an image of the planed at least one test pattern, and
• examining, via the imaging monitoring system, the captured image of the planed at least one test pattern to determine an offset between the image plane and the tool platform reference plane and a parallelism of the image plane with the tool platform reference plane.