Precision optical assembly for three dimensional printing

A three dimensional printer includes a projector, an adaptive support apparatus, a resin support apparatus, and a plurality of vertical struts. The projector includes a projection lens module which includes an optical housing that contains a series of lenses for projecting an image from the projector onto a build plane. The projection lens module includes a laterally extending flange having an upwardly facing flange surface. The adaptive support apparatus includes a downward facing surface in facing relation with the upward facing flange surface. The resin support apparatus is configured to contain resin and includes a transparent sheet and a downward facing surface. The transparent sheet defines a lower bound for the resin proximate to a build plane. The plurality of vertical struts couple an upward-facing surface of the adaptive support apparatus to the downward-facing surface of the resin support apparatus.

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. More particularly, the present invention improves the fabrication accuracy of a three dimensional (3D) article of manufacture by reducing an optical path variation.

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 surface, and a controllable light engine. The stereolithography system forms a three dimensional (3D) article of manufacture by selectively curing layers of the photocurable resin. Each selectively cured layer is formed at a “build plane” within the resin.

One challenge with stereolithography systems is a mechanical variability in an optical path from the light engine to the build plane. This variability leads to errors including “keystone distortion” and scaling. Keystone distortion is a result of a difficulty in maintaining an accurate trajectory of the optical path. Scaling errors result from variability in the light engine itself and in controlling a distance from the light engine optics to the build plane.

SUMMARY

In a first aspect of the disclosure, a three dimensional printer includes a projector, an adaptive support apparatus, a resin support apparatus, and a plurality of vertical struts. The projector includes a projection lens module which includes an optical housing that contains a series of lenses for projecting an image from the projector onto a build plane. The projection lens module includes a laterally extending flange having an upwardly facing flange surface. The adaptive support apparatus includes a downward facing surface in facing relation with the upward facing flange surface. The resin support apparatus is configured to contain resin and includes a transparent sheet and a downward facing surface. The transparent sheet defines a lower bound for the resin proximate to a build plane. The build plane is where resin is cured during a layer-by-layer formation of a three-dimensional article. The plurality of vertical struts couple an upward-facing surface of the adaptive support apparatus to the downward-facing surface of the resin support apparatus.

In one implementation the projector includes an upper housing having an opening that receives a lower portion of the projection lens module. The adaptive support apparatus is coupled to the upper housing.

In another implementation the adaptive support apparatus includes an interface plate and a lateral adapter. The interface plate defines the downward-facing surface of the adaptive support apparatus. The lateral adapter has an upward-facing surface that is coupled to the downward-facing surface of the interface plate.

In yet another implementation the printer includes a spacer ring clamped between the upward-facing flange surface and the downward-facing surface of the adaptive apparatus. In this way, the adaptive support apparatus is mechanically referenced to the projection lens module. The spacer ring can include one or more spacer rings of the same or varied thicknesses.

In a further implementation, the resin support apparatus includes a resin vessel and a support plate. The resin vessel is for containing the resin and includes the transparent sheet. The support plate supports the resin vessel and defines the downward-facing surface of the resin-supporting apparatus. The transparent sheet can be rigid or a flexible sheet or a flexible polymer sheet. The support plate can include a ridge extending upwardly that impinges upon and tensions the transparent sheet thereby determining a vertical location of the build plane. In some alternative implementations, the ridge can be integrated into the resin vessel.

In a yet further implementation the printer includes a main vertical support. The resin support apparatus is directly coupled to the main vertical support.

In a second aspect of the disclosure, a three-dimensional printer includes a vertical support, a support plate, a plurality of struts, a light engine, a motorized support, and a controller. The support plate is coupled to the vertical support. The support plate is for supporting a resin vessel having a transparent sheet on a lower side. The plurality of struts extend downwardly from the support plate. The adaptive support apparatus is coupled to lower ends of the struts. The light engine includes an upper housing and a projection lens module. The adaptive support apparatus is coupled to the upper housing and mechanically referenced to the projection lens module. The motorized support is for supporting a support tray above the resin vessel. The motorized support is configured to move vertically along the vertical support. The controller is configured to operate the light engine and the motorized support to manufacture a three-dimensional article by selectively curing a sequence of layers of resin onto a lower surface of the support tray.

In one implementation the projection lens module has a laterally extending flange. The adaptive assembly has a downwardly-facing surface in facing relation with the flange. The projection lens module has upper portion that extends upwardly from the flange and a lower portion that extends downwardly from the flange. The upper housing defines an opening. The lower portion of the projection lens module extends into the opening. The flange is above the opening.

In another implementation the adaptive support apparatus includes an interface plate defining the downwardly-facing surface of the adaptive assembly. The interface plate is coupled to the upper housing. The adaptive support includes a lateral adapter that defines an upward-facing surface. The upward-facing surface is coupled to the struts and to the interface plate.

In yet another implementation the projection lens module has a laterally extending flange. The adaptive assembly has a downwardly-facing surface in facing relation with the flange. The printer further includes one or more spacer rings between the flange and the adaptive assembly.

In a further implementation the projection lens module has a laterally extending flange. The adaptive assembly has a downwardly-facing surface in facing relation with and directly pressed against the flange.

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. “Generally” faces upwardly or downwardly means that the surface may have undulations or recesses that don't exactly face in a particular direction but the overall surface is a top or bottom surface respectively.

A vertical support4is coupled to a resin support apparatus6. Resin support apparatus6includes a support plate8that is coupled to the vertical support4. 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 motorized support24. Support tray22has a lower surface26supporting a three-dimensional article28that is being manufactured by system2. A controller30is controllably coupled to the light engine20and the motorized support24.

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 motorized support24to 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 article using the following steps: (1) Operate the motorized support24to position the lower surface26of support tray22at the build plane32. (2) Operate the light engine30to selectively cure resin12at the build plane which accretes onto the lower surface26of the support tray22. (3) Operate the motorized support24to 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 drawing illustrating additional mechanical details of an embodiment of system1. The support plate8includes a ridge36. When the resin vessel10is installed upon the support plate8the ridge36impinges upon a lower surface of the transparent sheet14. This is further illustrated inFIGS. 3 and 4.

FIG. 3is a top view of an embodiment of the resin vessel10. Resin vessel10has a sloped frame38that supports the transparent sheet14. In the illustrated embodiment, the transparent sheet14is formed from a flexible polymeric material.FIG. 4is a diagram representing a cross-section taken through a portion of the frame38, transparent film14, and the support plate8. A downward force F of the frame (weight and external force) is counteracted by an upward force of the ridge36upon the transparent film14. This has the effect of tensioning the transparent film14. The ridge36controls a height of the transparent film14. This is an important factor in controlling a vertical distance between the light engine20and the build plane32.

In the illustrated embodiment, the ridge36is a portion of the support plate8. In other embodiments, the ridge36can be an integral portion of the resin vessel10. With such an arrangement, the ridge36still controls a height of the tensioned transparent film14and the build plane32.

Referring back toFIG. 2, additional details are illustrated. The illustrated light engine20is a DMD (digital mirror device) light engine20. The light engine includes a projection lens module40that includes a set of lenses for focusing imaging light upon the build plane32. An adaptive support apparatus42couples and references the struts18to the light engine20. This will be discussed in more detail infra.

As will be discussed infra, the adaptive support apparatus42is mechanically referenced to the projection lens module40. The adaptive support apparatus42has a downward facing surface that mechanically references to an upward-facing flange surface of the projection lens module40.

FIG. 5is a side view of a portion of the system2fromFIG. 2. The resin support apparatus6is shown without the resin vessel10. Apparatus6includes a latching cover9that is configured to align and secure the resin vessel10onto the support plate8. In the illustrative embodiment, the support plate8is directly connected to the vertical support4.

Also coupled to the vertical support4is a motor23that controllably rotates a lead screw25. Lead screw25is threaded into the motorized support24. Controller30controls motor23for vertical motion and positioning of the motorized support24.

Underneath the support plate8is a removable resin spill vessel11. Resin spill vessel11captures any spilled resin12in an event for which the resin vessel10is damaged or overfilled. Resin spill vessel11has a transparent lower portion (not shown) to allow light from light engine20to reach the transparent sheet14.

FIG. 6is an isometric drawing depicting added details fromFIG. 2. The support plate8has an upper side44. The upper side44includes a recess46for receiving a lower portion of the frame38of the resin vessel10. The ridge36surrounds an opening48in the support plate8. In operation, the light engine20projects radiation up through opening48to the transparent sheet14which is being tensioned by the ridge36.

The struts18individually have upper18U and lower18L ends. The upper end of strut18is coupled to the downward facing surface16(FIG. 1) of support plate8. The lower end of strut18is coupled to an upward-facing surface50of adaptive support42. Adaptive support42includes two parts including an interface plate52and a lateral adapter54. The interface plate52couples the lateral adapter54to the light engine20. The lateral adapter54defines the upward facing surface50that is coupled to the lower ends18L of the struts18.

FIGS. 7-9depict assemblage details of the light engine20, adaptive support42, and the struts18.FIG. 7is an exploded isometric view depicting assembly at a top portion of light engine20. Light engine20includes the projection lens module40, which contains a series of optical components (e.g., lenses) that project a light signal to the build plane32. The projection lens module40includes a laterally and radially extending flange56having an upward facing flange surface58.

Light engine20also includes an upper housing60defining an opening62. The projection lens module40includes a tubular lower portion64that is received into the opening62such that flange56rests upon or above the upper housing60. The projection lens module40also has a tubular upper portion66that extends above the flange56.

The interface plate52has a downward-facing surface68(or downward-facing adapter surface68) that is in facing relation with the upward-facing flange surface58. Between interface plate62and flange56is a spacer ring70. Spacer ring70can be a plurality of spacer rings70of varying thickness. Spacer ring70is used to precisely adjust a distance between the projection lens module40and the build plane32. This is a very precise and mechanically robust way of adjusting a scale factor for the projection from light engine20to the build plane32.

The upper housing60can include a plurality of stiffeners72that are used to rigidify the assembly of the interface plate52to the light engine20. The purpose is to maintain an extremely precise vertical positioning for the interface plate52relative to the projection lens module40even during shipping of the overall assembly. Screws74pass through openings in the interface plate52and pass into the upper housing60including into the stiffeners72. Tightening the screws74clamps the downward facing surface68of interface plate52onto the spacer ring70. The spacer ring70in turn is clamped onto the upward-facing surface58of flange56.

The downward-facing surface68is “mechanically referenced to” the upward-facing flange surface58. In other words, they are not attached by screws or bolts or other attachment features. Rather, they are pressed either directly together or with an intervening spacer ring70therebetween. On the other hand, the interface plate52is attached to the upper housing60but it does not reference to it.

FIG. 8is a side view of the interface plate52mounted to a top portion of the light engine20. Tightened bolts74pass through interface plate52and into the upper housing60. Compressed and sandwiched between interface plate52and flange56is the spacer ring70. As discussed supra, in an alternative embodiment, the interface plate52can directly press against the flange56without an intervening spacer ring70.

FIG. 9is an isometric drawing depicting the lateral adapter54about to be mounted to the interface plate52. The downward-facing surface68of interface plate52is in facing relation with the upward-facing surface50of the lateral adapter54. Screws76pass through interface plate52and into the lateral adapter54. Tightening screws76would press surfaces68and50together. Also shown are the lower ends18L of struts18mounted into the upward facing surface50of the lateral adapter54.

As depicted inFIG. 9and earlier figures, mechanical referencing of the adaptive support is between the upward-facing flange surface58and the downward-facing surface of the adaptive support apparatus42. The mechanical referencing between flange56and adaptive support apparatus42is within a radius R from the optical axis21of the light engine20. This radius R is generally within the radius R of the flange (seeFIG. 8). To provide mechanical stability for the support plate8, the mechanical referencing between struts18and the upper-facing surface50of the adaptive support apparatus42is at a distance of more than 2R from the optical axis21. In an illustrative embodiment, approximate centers of struts18can be at least about 3R or more than 3R from the optical axis21.

FIG. 10is a flowchart of an embodiment of a method for assembling a portion of system2. Certain details are left out except as pertain to the proper positioning of the projection lens module40relative to the build plane.

According to 82, the following articles are provided: (1) Projector20with upper housing60and projection lens module40; (2) adaptive support apparatus42; (3) struts18; (4) support plate8; (5) a plurality of spacer rings70. In an illustrative embodiment, the articles listed include those described with respect toFIGS. 1-9.

In one embodiment, the spacer rings70have varying thicknesses. In one particular embodiment, there are five spacer rings individually having thicknesses of 1 millimeter, 500 microns (0.5 mm), 250 microns, 100 microns, and 50 microns. In an embodiment, the 1 millimeter spacer ring is a “nominal” spacer ring.

According to 84, the projector20scale factor is measured. The scale factor correlates with a feature size of a projected image feature at the build plane32. If the feature size is too small, then the projector needs to be moved away from the build plane. The adaptive support apparatus42and struts18are sized whereby the projected image feature correct with the installation of a nominal spacer ring which defines a nominal vertical position. The measured scale factor from step84will determine whether and how far the projector needs to be moved downward from a nominal position.

In one embodiment of step84, the plurality of spacer rings70includes a spacer ring having a nominal thickness. Measuring the scale factor includes (1) partially assembling the components including disposing the nominal spacer ring between an upper portion of the light engine and the adaptive support apparatus, (2) projecting an image from the light engine to a simulated build plane, and (3) measuring a dimension of the image. In an illustrative embodiment, measuring a dimension of the image includes measuring one or more distances between features (or the centroids of features) in the image. In another illustrative embodiment, measuring a dimension of the image includes individually measuring a dimension or area of a feature in the image.

According to 86 a selection of one or more of the spacer rings70is determined. The determination is based upon the measured scale factor.

According to 88, the selected one or more spacer rings70are placed upon the upward-facing flange surface58. According to 90, remaining assembly takes place between the above-listed elements.

In one particular embodiment, steps88and90include the following steps: (1) Disposing the selected one or more spacer rings between the interface plate52and the flange56. (2) Attaching the interface plate52to housing60. (3) Attaching the lateral adapter54to the interface plate54. (4) Coupling the struts18between the support plate8and the lateral adapter54. In other embodiments the order of these steps can vary.

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.