Precision mechanism for positioning lower face of article at build plane

A three-dimensional printing system includes a vertical support beam, a resin vessel assembly coupled to the vertical support beam and including a resin vessel, and a support tray positioning system. The support tray positioning system includes a support tray elevator, a lead screw nut, a motorized lead screw, an intermediate nut, and a linear bearing. The motorized lead screw engages the lead screw nut to raise and lower the support tray elevator. The linear bearing constrains motion of the support tray elevator to vertical motion. The support tray elevator, the intermediate nut, and the lead screw nut interlock to constrain rotational motion of the lead screw nut with respect to the support tray elevator while allowing for two dimensional lateral motion of the lead screw nut with respect to the support tray elevator to accommodate mechanical tolerances of the lead screw with respect to the linear bearing.

FIELD OF THE INVENTION

The present disclosure concerns an apparatus and method for fabrication of solid three dimensional (3D) articles of manufacture from radiation curable (photocurable) resins or other materials. More particularly, the present disclosure improves speed and accuracy of a precision vertical movement.

BACKGROUND

Three dimensional (3D) printers are in rapidly increasing use. One class of 3D printers includes stereolithography printers having a general principle of operation including the selective curing and hardening of radiation curable (photocurable) liquid resins. A typical stereolithography system includes a resin vessel holding the photocurable resin, a movement mechanism coupled to a support tray, and a controllable light engine. The stereolithography system forms a three dimensional (3D) article of manufacture by selectively curing layers of the photocurable resin onto the support tray. Each selectively cured layer is formed at a “build plane” within the resin. As layers are formed onto the support tray, the movement mechanism moves the support tray vertically to compensate for an added material thickness. One challenge with such systems is to provide precision vertical movements with the movement mechanism.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG.1is a block diagram schematic of an embodiment of a three-dimensional printing system2. In describing system2, mutually perpendicular axes X, Y, and Z will be utilized in various views. Axes X and Y are lateral axes that are generally horizontal. Axis Z is a vertical axis that is generally aligned with a gravitational reference. Upwardly is in the +Z direction and downwardly is in the −Z direction. An upper surface generally faces upwardly and a lower surface generally faces downwardly. Forward or forwardly generally means in the +X direction. Backward generally means −X. Side to side directions are along the Y-axis. “Generally” means by design and to within manufacturing and design tolerances but not exact.

A vertical support beam4is coupled to a resin vessel assembly6. Vertical support beam4has a front side3and a rear side5with respect to the X-axis. Resin vessel assembly6includes a support plate8that is coupled to the vertical support beam4. The support plate8supports a resin vessel10containing a photocurable resin12. Resin vessel10includes a transparent sheet14on a lower side that defines a lower bound for resin12contained in the resin vessel10.

Extending downwardly from a downward-facing surface16of the support plate8are a plurality of struts18. The struts18support a light engine20at a fixed distance from the support plate8. The light engine20projects light up through the transparent sheet14to define a build plane32that is proximate to a lower face34of the three-dimensional article28.

A support tray22is coupled to a support tray positioning system24. Support tray22has a lower surface26supporting a three-dimensional article28that is being manufactured by system2. A controller30is controllably coupled to the light engine20and the support tray positioning system24.

The controller30includes a processor and an information storage device. The information storage device includes a non-transient or non-volatile storage device storing software instructions. When executed by the processor, the software instructions operate the light engine20and the support tray positioning system24to fabricate the three-dimensional article28in a layer-by-layer manner. The controller can be embodied at one location or multiple locations within and/or outside of the three-dimensional printing system2.

In one embodiment, the controller30is configured to manufacture a three-dimensional article28using the following steps: (1) Operate the support tray positioning system24to position the lower surface26of support tray22at the build plane32. (2) Operate the light engine30to selectively cure resin12at the build plane32which accretes onto the lower surface26of the support tray22. (3) Operate the support tray positioning system24to position a lower face34of cured resin at the build plane32. (4) Repeat step (2). Then, repeat steps (3) and (4) to selectively accrete remaining layers of resin onto the lower face34to complete fabrication of the three-dimensional article28.

FIG.2is an isometric view of an embodiment of a portion of the three-dimensional printing system2with emphasis on the support tray positioning system24. Additional details of the support tray positioning system24are shown inFIGS.3,4,5A, and5B. The support tray positioning system24includes a support tray elevator40, a motor42, a lead screw44, a linear bearing46, a lead screw nut48, and an intermediate nut50.

The motor42and lead screw44are positioned proximate to the rear side5of the vertical support beam4. The linear bearing46is mounted to the rear side5of the vertical support beam4and is configured to slide along the vertical Z-axis with low friction. The linear bearing46has a rear side52.

The support tray elevator40includes a rear portion54and a pair of arms56. The rear portion54is mounted to the rear side52of the linear bearing46. Rear portion54extends along the Y-axis beyond the extent of the vertical support beam4on both sides with respect to the Y-axis. Extending forwardly along the X-axis from two ends of the rear portion is a pair of arms56for supporting and aligning the support tray22.

The linear bearing46constrains motion of the support tray elevator40to linear motion along the Z-axis. This includes severely limiting any lateral or rotational motion to allow for precision and repeatable motion for positioning the support tray22.

FIG.3is an isometric view of portions of the support tray positioning system24including the support tray elevator40, lead screw nut48, and intermediate nut50. The support tray elevator includes a major axis along the lateral Y-axis, an intermediate axis along the lateral X-axis, and a minor axis along the vertical Z-axis. The rear portion54extends along the major axis along Y. The pair of arms56extend along the intermediate axis X. As shown, the intermediate nut50is “sandwiched” between the rear portion54and the lead screw nut48.

As will be explained later in more detail, the rear portion54, the intermediate nut50, and the lead screw nut48form an interlocking structure58which constrains rotational motion of the lead screw nut48with respect to the rear portion54along the vertical Z-axis while allowing for two dimensional lateral motion of the lead screw nut48with respect to the rear portion54along the lateral axes X and Y.

A pair of bolts60secure the lead screw nut48and the intermediate nut50to the rear portion54. The bolts60are sized in length and diameter to allow the lateral motion of the lead screw nut48with respect to the rear portion54.

FIG.4is an exploded isometric view of an embodiment of the interlocking structure58. The rear portion54of the support tray elevator40has a lower facing surface62from which two pins64extend downwardly.

The intermediate nut50has an upper side65that faces the lower facing surface62of the rear portion54. The intermediate nut50defines two elongate openings66for receiving the pins64. The intermediate nut50has a lower side68from which two pins70extend downwardly.

The lead screw nut48has an upper side72that faces the lower side68of the intermediate nut50. The lead screw nut48defines two elongate openings74for receiving the pins70.

The lead screw nut48defines a central threaded opening76that receives the lead screw44to allow rotation of the lead screw44about vertical axis Z to raise and lower the lead screw nut44and the support tray elevator40. The lead screw nut48includes a flat base75that defines openings74and a cylindrical extension77that provides a greater vertical dimension for the central threaded opening76. Cylindrical extension77extends downwardly from the flat base75and can also extend upwardly from the upper side72.

The two bolts60individually have a cylindrical section78and threads80. The cylindrical sections78pass through a pair of openings82in the lead screw nut48and through a pair of openings84in the intermediate nut50. The threads80are received into threaded openings86in the lower facing surface62to secure the lead screw nut48and the intermediate nut50to the lower facing surface62of rear portion54.

The cylindrical sections78have a diameter that is less than a diameter of the pairs of openings82and84and a length that is greater than a combined thickness of flat portions of the lead screw nut48and the intermediate nut50so that the lead screw nut48can “float” laterally in two axes.

FIG.5Ais an isometric cutaway view of the intermediate nut50mounted to the lower facing side62of the rear portion54. The pair of pins64extending downwardly from the lower facing side62are shown extending into the two elongate openings66defined by the intermediate nut50. The elongate openings66individually have a major axis that is aligned with a lateral axis88. The elongate opening geometry allows lateral motion of the intermediate nut50(and hence also the lead screw nut48) with respect to the rear portion54along the lateral axis88.

FIG.5Bis an isometric cutaway view of the intermediate nut50and the lead screw nut48mounted to the lower facing side62of the rear portion54. InFIG.5B, the cylindrical extension77has been cut away for simplicity. The pair of pins70extending downwardly from the lower side68are shown extending into the elongate openings74defined by the lead screw nut48. The elongate openings74individually have a major axis that is aligned with a lateral axis90. The elongate opening geometry allows lateral motion of the lead screw nut48with respect to the intermediate nut50and hence with respect to the rear portion54along the lateral axis90.

ConsideringFIGS.5A and5B, the lateral axes88and90are non-parallel so that the lead screw nut48can move or “float” laterally in two dimensions with respect to the rear portion54. In an illustrative embodiment, the axes88and90are generally or nearly at right angles with respect to each other to maximize the degree of two dimensional float.

The specific embodiments and applications thereof described above are for illustrative purposes only and do not preclude modifications and variations encompassed by the scope of the following claims.