阅读说明：本技术 用于增材制造中的层厚度控制的方法和设备 (Method and apparatus for layer thickness control in additive manufacturing ) 是由 梅雷迪思·埃莉萨·杜伯曼 玛丽·凯瑟琳·汤普森 克里斯多佛·巴恩希尔 杨熙 于 2020-02-18 设计创作，主要内容包括：一种增材制造设备(10)包括：构建表面(24),其至少一部分是透明的；第一材料沉积器(106、306、406、506、606、706、806),其可操作以沉积可固化树脂,从而在构建表面(24)上形成沉积树脂层(110、210、310、410、510、710、810、910)；第一感测装置(224、225、325、725),其被构造为测量沉积树脂层(110、210、310、410、510、710、810、910)的厚度。至少一个感测装置(224、225、325、725)被构造为产生指示沉积树脂层(110、210、310、410、510、710、810、910)的厚度的信号。(An additive manufacturing apparatus (10) comprising: a build surface (24) at least a portion of which is transparent; a first material depositor (106, 306, 406, 506, 606, 706, 806) operable to deposit a curable resin to form a deposited resin layer (110, 210, 310, 410, 510, 710, 810, 910) on a build surface (24); a first sensing device (224, 225, 325, 725) configured to measure a thickness of a deposited resin layer (110, 210, 310, 410, 510, 710, 810, 910). At least one sensing device (224, 225, 325, 725) is configured to generate a signal indicative of a thickness of the deposited resin layer (110, 210, 310, 410, 510, 710, 810, 910).)

1. An additive manufacturing apparatus (10), comprising:

a build surface (24), at least a portion of which is transparent;

a first material depositor (106, 306, 406, 506, 606, 706, 806) operable to deposit a curable resin to form a deposited resin layer (110, 210, 310, 410, 510, 710, 810, 910) on the build surface (24);

a table (14) positioned facing the build surface (24) and configured to hold a stacked arrangement of one or more cured layers (79) of the resin;

one or more actuators (32) operable to change the relative positions of the build surface (24) and the table (14);

a radiant energy device (18) positioned adjacent to a build plate (190), opposite the table (14), and operable to generate and project radiant energy through the build plate (190) in a predetermined pattern on the resin; and

a first sensing device (224, 225, 325, 725) configured to measure a thickness of the deposited resin layer (110, 210, 310, 410, 510, 710, 810, 910), wherein at least one first sensing device (224, 225, 325, 725) is configured to generate a signal indicative of the thickness of the deposited resin layer (110, 210, 310, 410, 510, 710, 810, 910).

2. The additive manufacturing apparatus (10) according to claim 1, comprising:

a first thickness adjustment mechanism (106) configured to adjust the thickness of the deposited resin layer (110, 210, 310, 410, 510, 710, 810, 910) in response to the signal.

3. The additive manufacturing apparatus (10) of claim 2, wherein the first thickness adjustment mechanism (106) is one of: suction means and a scraper (210, 211).

4. The additive manufacturing apparatus (10) according to claim 2, comprising a second thickness adjustment mechanism (106).

5. The additive manufacturing apparatus (10) of claim 4, wherein the second thickness adjustment mechanism (106) is positioned downstream of the first thickness adjustment mechanism (106) and in series with the first thickness adjustment mechanism (106).

6. The additive manufacturing apparatus (10) of claim 2, wherein the first sensing device (224, 225, 325, 725) is located downstream of the first thickness adjustment mechanism (106).

7. The additive manufacturing apparatus (10) of claim 6, wherein the first sensing device (224, 225, 325, 725) is located upstream of the second thickness adjustment mechanism (106).

8. A method of producing a three-dimensional part comprising a void using an apparatus (10) for additive manufacturing, characterized in that the method comprises the steps of:

depositing an uncured resin layer (110, 210, 310, 410, 510, 710, 810, 910) defining a resin surface and a resin base spaced apart by a thickness, and wherein the uncured resin layer (110, 210, 310, 410, 510, 710, 810, 910) comprises a plurality of thicknesses, thereby defining a first uncured layer (110, 210, 310, 410, 510, 710, 810, 910) profile;

curing the resin layer (110, 210, 310, 410, 510, 710, 810, 910) to create a build layer (110, 210, 310, 410, 510, 710, 810, 910) that is an integral part of the part; and is

Wherein the build layer (110, 210, 310, 410, 510, 710, 810, 910) has a build layer (110, 210, 310, 410, 510, 710, 810, 910) profile that defines at least a portion of the void.

9. The method according to claim 8, wherein the first uncured layer (110, 210, 310, 410, 510, 710, 810, 910) profile is substantially the same as the build layer (110, 210, 310, 410, 510, 710, 810, 910) profile.

10. The method of claim 8, wherein the size of the build layer (110, 210, 310, 410, 510, 710, 810, 910) is defined by the size of the uncured resin layer (110, 210, 310, 410, 510, 710, 810, 910) produced by the depositing step.

11. The method of claim 8, further comprising the step of repeating the depositing and curing steps to produce a part comprising a plurality of build layers (110, 210, 310, 410, 510, 710, 810, 910) and comprising the void and the void having a predetermined geometry.

12. The method of claim 11, wherein the predetermined geometry can include at least a portion of one of: an overhang, an internal void including a structure positioned therein, and combinations thereof.

13. The method of claim 8, wherein the uncured resin layer (110, 210, 310, 410, 510, 710, 810, 910) is positioned such that it has an x-axis, a y-axis, and a z-axis, and the first profile is oriented generally perpendicular to the x-axis.

14. The method of claim 8, wherein the uncured resin layer (110, 210, 310, 410, 510, 710, 810, 910) is positioned such that it has an x-axis, a y-axis, and a z-axis, and the first profile is oriented generally perpendicular to the y-axis.

15. The method of claim 8, further comprising the step of depositing the uncured resin layer (110, 210, 310, 410, 510, 710, 810, 910) such that a plurality of streets are defined within the uncured resin layer (110, 210, 310, 410, 510, 710, 810, 910).

Technical Field

The present invention relates generally to additive manufacturing and more particularly to an apparatus and method for determining layer thicknesses in additive manufacturing.

Background

Additive manufacturing is a process in which materials are built up layer by layer to form a part. One prior art method is the tape casting (tape casting) process. In this process, the resin is deposited as a layer having the desired thickness onto a flexible, radiation transparent tape fed from a supply reel. The upper plate is lowered onto the resin, compressing it between the belt and the upper plate and defining the layer thickness. The radiant energy is used to cure the resin through the radiant transparent tape. Once the curing of the first uncured layer is complete, the upper plate is retracted upwardly while carrying away the cured material. The belt is then advanced to expose a new clean section in preparation for depositing additional resin in a subsequent new cycle.

Another prior art method employs a vat (vat) of liquid radiant energy curable photopolymer "resin" and a source of curing energy (e.g., a laser). Also, DLP 3D printing uses a two-dimensional image projector to build up parts one layer at a time. For each layer, the projector will flash a radiation image of a cross-section of the component on the surface of the liquid or through a transparent object defining the constrained surface of the resin. Exposure to radiation cures and consolidates the pattern in the resin and bonds it to the previously cured layer. Other types of additive manufacturing processes utilize other types of radiant energy sources to consolidate a pattern in a resin.

One problem with conventional methods of additive manufacturing is that the actual thickness of the deposited layer may vary within a given layer for a given cycle and from cycle to cycle with respect to the actual thickness. Such variations in the thickness of the deposited layer of additive manufacturing material or resin can lead to various problems and drawbacks.

Another problem with conventional methods of additive manufacturing is that the photopolymer cures in response to light or radiation, and the penetration depth of the light or radiation into the resin is typically greater than the desired layer thickness. In some cases, the penetration depth (Dp) may be 5 to 10 times greater than the desired layer thickness. The cured or partially cured resin transmits more light or radiation than the uncured resin. This often results in a phenomenon known as "show through" in which light penetrates existing features and inadvertently and undesirably cures the resin. Show-through makes it difficult to create thin internal structures. These internal structures define at least part of the void and may be overhangs, channel walls, ribs and other geometric features.

Typically, the print-through problem is solved by a technique called "Z compensation". Z compensation involves careful control of layer thickness, curing energy (and hence curing depth), and intentional omission of printing a particular layer. These steps are done in anticipation of print-through from a later layer, creating the desired cured geometry. However, Z compensation does not provide precise control of individual layers and may result in manufacturing inefficiencies.

Disclosure of Invention

At least one of these problems is addressed by an additive manufacturing apparatus configured to deposit a resin for additive manufacturing to form a deposited layer, wherein a thickness of the deposited layer is monitored. Methods for closed-loop control of the thickness of a deposited layer across the width and along the length of the layer are also provided.

According to one aspect of the technology described herein, an additive manufacturing apparatus includes a build surface, at least a portion of which is transparent. The apparatus includes a first material depositor operable to deposit a curable resin to form a layer of deposited resin on the build surface. The first sensing device is configured to measure a thickness of the deposited resin layer; and wherein the at least one sensing device is configured to generate a signal indicative of the thickness of the deposited resin layer. The first sensing device may be connected to a computer such that the additive manufacturing apparatus is configured to control a thickness of the deposited resin layer. The thickness of the deposited resin layer may be controlled to vary from side to side, i.e. in a lateral direction along the x-axis across the width of the deposited resin layer. The thickness can also be controlled so that it varies over time. In other words, the thickness can be controlled to vary in the machine direction along the y-axis.

According to another aspect of the technology described herein, a method of producing a component layer by layer using an additive manufacturing apparatus includes a step of maintaining a thickness of a resin layer for additive manufacturing at a predetermined thickness by: depositing a curable resin using a first material depositor to form a deposited resin layer on a build surface, at least a portion of the build surface being transparent; sensing the thickness of the deposited resin layer; adjusting the thickness of the deposited resin layer to define an area of the deposited layer having a predetermined thickness; and positioning an area of the deposition layer having a predetermined thickness in the build area. The method then comprises a step of performing a build cycle, and the step comprises the steps of: positioning a stage relative to the build surface to define a layer increment in a deposited resin layer having a predetermined thickness; selectively curing the resin using the application of radiant energy in a particular pattern, thereby defining the geometry of the cross-sectional layer of the part; moving the build surface and the table relatively apart to separate the part from the build surface; introducing new resin into the build area; and repeating the steps of maintaining the thickness and performing the build cycle for the plurality of layers until the part is completed.

According to yet another aspect of the technology disclosed herein, a method of producing a three-dimensional part including a void using an apparatus for additive manufacturing includes the steps of: A) depositing an uncured resin layer defining a resin surface and a resin base spaced apart by a thickness, wherein the uncured resin layer comprises a plurality of thicknesses, thereby defining a first uncured layer profile; and B) curing the resin layer to produce a build layer that is an integral part of the part. The build layer has a build layer profile that defines at least a portion of the void.

Drawings

The invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic side view of an exemplary cast additive manufacturing apparatus including a material depositor;

FIG. 2 is a schematic view of one embodiment of the material depositor shown in FIG. 1;

FIG. 3 shows a stylized representation of initial relative positions of a stage and a platform in an additive manufacturing apparatus;

FIG. 4 illustrates a further relative position of the table and platform of FIG. 3;

FIG. 5 illustrates a further relative position of the table and platform of FIG. 3;

FIG. 6 shows a stylized representation of a failure mode;

FIG. 7 shows a stylized representation of a failure mode;

FIG. 8 shows a stylized representation of a failure mode;

FIG. 9 is a schematic view of the material depositor of FIG. 1 including an additional sensor;

FIG. 10 is a schematic view of the material depositor of FIG. 1 including two sensors and two control mechanisms;

FIG. 11 is a schematic diagram of a material depositor configured for side-to-side thickness control of a deposited layer according to another embodiment;

FIG. 12 is a schematic view of the material depositor of FIG. 1 configured for side-to-side thickness control of a deposited layer using one sensor;

FIG. 13 is a schematic view of a material depositor;

fig. 14 is a schematic side view of an exemplary barrel type additive manufacturing apparatus including a material depositor showing material being deposited in a barrel;

FIG. 15 is a view of the apparatus of FIG. 14 showing the suction device positioned to remove material after the drum is overfilled;

FIG. 16 shows the resin layer further defined by contact with the table;

FIG. 17 is a view of the apparatus of FIG. 15 showing an alternative curing mechanism;

FIG. 18 shows a configuration of the apparatus of FIG. 1 in which three material depositors are positioned side-by-side to define three spaced-apart lanes;

FIG. 19 shows a cross-section of three spaced apart resin deposition layers provided by the configuration of the apparatus shown in FIG. 18 taken along line 19-19;

FIG. 20 illustrates an alternative embodiment configured to define three consecutive lanes of deposited resin;

FIG. 21 illustrates another alternative embodiment configured to define three consecutive lanes of deposited resin;

FIG. 22 shows a cross-section of a deposited resin layer, showing one possible profile;

FIG. 23 shows a cross-section of a deposited resin layer, showing another possible profile;

FIG. 24 shows a cross-section of a deposited resin layer showing another possible profile;

FIG. 25 shows a cross-section of a deposited resin layer showing another possible profile;

FIG. 26 shows a cross-section of a deposited resin layer, showing another possible profile;

FIG. 27 shows the deposited resin layer shown in FIG. 26 in contact with a work process part prior to curing the deposited layer according to one disclosed method;

FIG. 28 illustrates a perspective view of a machined part made according to the methods disclosed herein, showing a single cured layer; and

fig. 29 illustrates a perspective view of a finished part manufactured according to the methods disclosed herein.

Detailed Description

Referring to the drawings, wherein like reference numbers refer to like elements throughout the several views, fig. 1 schematically illustrates an example of one type of suitable apparatus 10 for additive manufacturing, with improved layer control. The apparatus 10 uses a resin processing assembly 11, which is a casting device 20 according to the illustrated embodiment. The resin processing assembly 11 is adapted and benefits from the use of a device for measuring the thickness of a deposited resin layer. It should be understood that the resin treatment assembly 11 is an apparatus configured for monolayer treatment. As described herein, casting is a monolayer process. As described herein, the use of a plate as the resin substrate in place of a tape (i.e., "plate casting") is also a monolayer treatment. For barrel processing, the monolayer processing may be performed when the barrel is filled only to a depth that provides a monolayer of resin, or when the part is positioned relative to the barrel and uncured resin to define a monolayer of resin.

Referring to fig. 3-8, the disclosed techniques are suitable for reducing the number and magnitude of erroneous and imprecise layer developments that occur using conventional additive manufacturing equipment and methods. As will be described in more detail below, but described here to detail errors addressed by the disclosed techniques, the additive manufacturing apparatus includes a station 14. Referring now to FIG. 3, the table 14 defines a surface 30 on which a part 74 is formed. When referring to the casting apparatus 20, the machine direction, i.e., the direction in which the film 12 travels, is denoted by Y; the transverse direction is denoted by X; the vertical direction is denoted by Z.

The feature 74 defines a surface 75 on which a new layer of the feature (described in more detail below) is added by transferring a cured portion of the resin layer 110 that is located adjacent to the surface 75 and supported by the membrane 12. Layer 110 defines surface 77. As shown in FIG. 4, error-free operation involves a predetermined amount of contact between surface 75 and surface 77. The predetermined amount of contact causes the solidified portion of layer 110 to transfer to form a new layer of part 74 and define a new surface 75. A new portion of layer 110 moves under part 74 to define a new surface 77. This configuration is shown in fig. 5.

When considering the formation of a single layer, at least two types of errors are typical. As shown in FIG. 6, layer 110 is not thick enough to allow surface 77 to contact surface 75 when table 14 and part 74 are moved to a build position that fits the existing geometry of part 74. In this case, the cured portion of layer 110 is not transferred to part 74. As shown in FIG. 7, in a second error condition, layer 110 is too thick such that when table 14 and part 74 are moved to a build position that is appropriate for the existing geometry of part 74, surface 75 actually penetrates surface 77, causing the part to deform and possibly also damage the part.

There are at least three typical types of errors in considering layer-based errors that affect the formation of the entire part. In a third error case, also shown in FIG. 6, an error in the thickness of the previous layer 110 results in a series of layers of the part 74, some or all of which are too thin. Thus, the part 74 is not as high as expected. Thus, when stage 14 is moved to a build position suitable for the desired geometry, surface 75 does not contact material layer 110 if the thickness of material layer 110 is as thick or thinner as desired. In a fourth error case, also shown in FIG. 7, an error in the thickness of the previous layer 100 results in a series of layers, some or all of which are too thick. Thus, part 74 is taller than desired, such that when table 14 is moved to a build position suitable for the desired geometry, surface 75 penetrates surface 77, causing the part to deform or fail. In a fifth error case, as shown in FIG. 8, an error in the thickness of the previous layer 100 causes the part 74 to be much higher than expected. Thus, when the table 14 is moved to the build position, the table 14 is lowered so far that it "bumps" into the layer 110, thereby damaging the part. It may also push the part 74 through the material layer 110 to contact the membrane 12 or even push through the membrane 12 to damage the machine. As shown in fig. 8, the membrane 12 contacts the feature 74 with such force that the membrane 12 separates at several locations, resulting in web damage or breakage. The disclosed technique addresses these errors by providing an apparatus and method for accurately defining the thickness of layer 110 to enable part 74 to be properly constructed.

It is to be understood that the configuration of equipment other than tape casting may be used for the apparatus 10 and the method described below may be performed. Those other configurations include different types of resin treatment equipment, such as buckets and/or plates. The method is applicable to lower viscosity resins, slurries and pastes, and higher viscosity resins and/or powders. It should be understood that other configurations of equipment may be used to implement the method. The basic components of the exemplary apparatus 10 include a material deposition device 106 and a resin processing assembly 11, which in fig. 1 is a casting apparatus 20. The casting apparatus 20 includes a support film or belt 12, and a radiant energy apparatus 18.

The casting apparatus 20 includes spaced apart rollers 15 between which the flexible polymeric strip or foil 12 extends. A portion of the foil 12 is supported from below by a support plate 190. Suitable mechanical supports (frames, brackets, etc. -not shown) will be provided for the rollers 15 and the support plate 190. The foil 12 is an example of a "resin support".

Both the support plate 190 and the foil 12 are transparent or comprise one or more portions that are transparent. As used herein, the term "transparent" refers to a material that allows radiant energy of a selected wavelength to pass through. For example, as described below, the radiant energy used for curing may be ultraviolet light or laser light in the visible spectrum. Non-limiting examples of transparent materials include polymers, glasses, and crystalline minerals such as sapphire or quartz.

Suitable means, such as motors, actuators, feedback sensors and/or controllers of known type (not shown) will be provided to drive the rollers 15 to keep the foil 12 taut between the rollers 15 and to wind the foil 12 from one roller 15 onto the other roller 15.

The foil 12 extending between the rollers 15 defines a first "build surface" 24, which is shown as being planar, but may also be arcuate (depending on the shape of the support plate). For ease of description, the first build surface 24 may be considered to be oriented parallel to the XY plane of the apparatus 10. The direction perpendicular to the XY plane is denoted as the Z direction (X, Y and Z are three mutually perpendicular directions).

The first build surface 24 may be configured to be "non-stick," i.e., resistant to adhesion of the cured resin. The non-stick property may be manifested by a combination of variables such as the chemistry of the foil 12, its surface finish, and/or the applied coating. In one example, a permanent or semi-permanent non-stick coating may be applied. One non-limiting example of a suitable coating is polytetrafluoroethylene ("PTFE"). In one example, all or a portion of first build surface 26 may incorporate a controlled roughness or surface texture (e.g., protrusions, dimples, grooves, ridges, etc.) having non-stick properties. In one example, the foil 22 may be made in whole or in part of an oxygen permeable material.

Means are provided for applying or depositing the resin R to the first build surface 24 in a generally uniform layer. Fig. 1 schematically illustrates a material depositor 106 configured for this purpose. As shown in fig. 2, the material depositor 106 includes a reservoir 182. The reservoir 182 includes upstream and downstream walls 194, 196 and a side wall 192. The upstream wall 194 has a slot 200 defined therein to receive the foil 12. The downstream wall 196 defines an aperture or slot 202 that serves as an outlet for the foil 12 and the layer 110 of resin R.

With continued reference to fig. 2, the material depositor 106 includes a first doctor blade 210 and a second doctor blade 211, the first doctor blade 210 and the second doctor blade 211 being used to control the thickness of the resin R applied to the foil 12 as the foil 12 passes under the material depositor 106. According to the illustrated embodiment, the thickness of layer 110 is determined by the doctor blade. By way of example and not limitation, other material deposition devices may be used alone or in combination with the first and second blades 210 and 211, such as: gravure rolls, metering rolls, weir-based cascades, direct die casting, and combinations thereof. The first doctor blade 210 is configured to act as an overall control of the thickness 213 of the initially deposited layer 215. An adjustment device 212 is provided that is configured to adjust an angle 216 defined by a surface of the blade 210 and a top edge of the wall 192. The larger the angle 216, the smaller the thickness 213, i.e. the thinner the initially deposited layer 215. The adjustment device 212 may be a threaded screw assembly configured to extend and retract to affect a change in the angle 216. The adjustment device 212 is mechanically coupled to the first scraper 210.

Second scraper 211 is movably mechanically coupled to downstream wall 196 and is movable by actuator 220 to adjust and define outlet gap 202. Conventionally known control signals are used to controllably connect the actuator 220 with the controller 120. The layer 110 has a thickness 214, which is the distance between the surface of the resin and the base of the layer 110, which is in contact with the surface of the foil 12. Thus, the thickness 214 of the material layer 110 may be adjusted by a control action, such as moving the blade 211 in response to a signal from the controller 120. By way of example and not limitation, a suitable control signal may be one of: electrical, pneumatic, acoustic, electromagnetic and combinations thereof. By way of example, and not limitation, other suitable control actions include: changing the speed of the film 12, adjusting the viscosity or other rheological properties of the resin R, changing the width of the deposited material layer 110, for example by repositioning side dams (not shown).

With continued reference to fig. 2, the first sensor 224 is located downstream of the second scraper 211. The first sensor 224 is configured to determine the thickness 214 of the deposited material layer 110. As a result, layer of deposited material 110 has a thickness 214 as it passes from material depositor 106 into and through build zone 23 (shown in FIG. 1). As shown in fig. 2, the first sensor 224 is configured to generate a monitoring signal indicative of the thickness 214 of the deposited material layer 110 and to transmit such signal to the controller 120. By way of example and not limitation, a suitable monitoring signal may be one of: electrical, pneumatic, acoustic, electromagnetic, and combinations thereof.

The controller 120 is configured to receive the monitoring signals and process such signals using a predetermined algorithm to generate the control signals discussed above, which are then communicated to the controller 220. In this manner, closed loop control of the thickness 214 of the deposited material layer 110 may be achieved according to the methods described below. It should be understood that as shown in fig. 2, sensor 224 is configured to measure the thickness of a single point in deposited material layer 110. Because the layer of deposited material 110 has a width, the sensor 224 does not detect a thickness variation across the width. The case where the thickness of the deposited material layer 110 varies across its width is addressed by embodiments described further below.

Alternatively, with respect to the following method, when the sensor indicator layer 110 is too thin, additional resin R may be added to increase the thickness of the layer 110. Additional material may be added by a second depositor (not shown) located downstream of the depositor 106. Further alternatively, the thin layer 110 may pass under the depositor 106 a second time to add additional resin R.

Referring again to the components of apparatus 10 (which are configured to cure and define a layer), stage 14 is a structure that defines a planar surface 30, planar surface 30 being capable of being oriented parallel to build surface 24 of the portion of membrane 12 that is positioned on support plate 190. Means are provided for moving stage 14 parallel to the Z direction relative to build surface 24. In fig. 1, these devices are schematically depicted as simple actuators 32 connected between the table 14 and a stationary support structure 34, it being understood that devices such as pneumatic, hydraulic, ball screw electric, linear electric, or delta drives may be used for this purpose. In addition to or instead of making the stage 14 movable, the foil 12 and/or the support plate 190 may be movable parallel to the Z-direction.

The radiant energy apparatus 18 can include any device or combination of devices operable to generate and project radiant energy on the resin R in a suitable pattern and at a suitable energy level, as well as other operating characteristics, to cure the resin R in a build process, as described in more detail below.

In one exemplary embodiment as shown in fig. 1, the radiant energy device 18 may include a "projector" 48, used generally herein to refer to any apparatus operable to generate a radiant energy patterned image having suitable energy levels and other operating characteristics to cure the resin R. As used herein, the term "patterned image" refers to the projection of radiant energy comprising an array of individual pixels. Non-limiting examples of patterned imaging devices include a DLP projector or another digital micromirror device, a 2D led array, a 2D laser array, or an optically addressed light valve. In the illustrated example, the projector 48 includes: a radiant energy source 50, such as a UV lamp; an image forming device 52 operable to receive a source beam 54 from radiant energy source 50 and generate a patterned image 59 for projection onto the surface of resin R; and optional focusing optics 48, such as one or more lenses.

The radiant energy source 50 can comprise any device operable to generate a beam having suitable energy level and frequency characteristics to cure the resin R. In the illustrated example, the radiant energy source 50 includes a UV flash lamp.

The image forming device 52 may comprise one or more mirrors, prisms and/or lenses and is provided with suitable actuators and is arranged such that the source beam 54 from the radiant energy source 50 may be converted into a pixelated image in the X-Y plane coincident with the surface of the resin R. In the illustrated example, the image forming device 52 may be a digital micromirror device. For example, projector 38 may be a commercially available digital light processing ("DLP") projector.

Alternatively, projector 48 may incorporate additional devices (e.g., actuators, mirrors, etc.) configured to selectively move image-forming device 52 or other portions of projector 48, having the effect of rasterizing or moving the position of patterned image 59 of build surface 24. In other words, the patterned image may be moved away from the nominal or starting position. This allows a single image forming device 52 to cover a larger build area, for example. Means for controlling (registering) or moving the patterned image from the image forming device 52 are commercially available. This type of image projection may be referred to herein as a "tiled image".

In another exemplary embodiment (as shown in fig. 17, in connection with a barrel-based resin delivery system discussed further below), the radiant energy apparatus 18 may include, among other types of radiant energy devices, a "scanned beam apparatus" 60, the "scanned beam apparatus" 60 as used herein generally referring to any device operable to generate a beam of radiant energy having suitable energy levels and other operating characteristics to cure the resin R and scan the beam over the surface of the resin R in a desired pattern. In the illustrated example, the scanning beam device 60 includes a radiant energy source 62 and a beam steering device 64.

The radiant energy source 62 may comprise any device operable to generate a beam of suitable power and other operating characteristics to cure the resin R. Non-limiting examples of suitable radiant energy sources include lasers or electron beam guns.

The beam steering device 64 may comprise one or more mirrors, prisms and/or lenses and may be provided with suitable actuators and arranged such that the beam 66 from the radiant energy source 62 may be focused to a desired spot size and steered to a desired position in a plane coincident with the surface of the resin R. The bundle 66 may be referred to herein as a "build bundle". Other types of scanning beam devices may be used. For example, scanning beam sources using a plurality of build beams are known, as are scanning beam sources in which the radiant energy source itself is movable by one or more actuators.

The device 10 may include a controller 68. The controller 68 in fig. 1 is a generalized representation of the hardware and software necessary to control the operation of the apparatus 10, the stage 14, the radiant energy device 18, the transport mechanism 20, the depositor 106, and the various actuators described above. For example, the controller 60 may be embodied in software running on one or more processors embodied in one or more devices, such as a programmable logic controller ("PLC") or a microcomputer. Such a processor may be coupled to the sensors and operating components, for example, by wired or wireless connections. The same processor or multiple processors may be used to retrieve and analyze sensor data, for statistical analysis, and for feedback control. It should be understood that in some embodiments, the functions and capabilities of the controller 120 are implemented in the controller 68.

Optionally, the components of the apparatus 10 may be enclosed by a housing 70, which housing 70 may be used to provide a protective or inert gas atmosphere using gas ports 72. Alternatively, the pressure within the housing 70 may be maintained at a desired level greater than or less than atmospheric air. Optionally, the housing 70 may be temperature and/or humidity controlled. Alternatively, the ventilation of the housing 70 may be controlled based on factors such as time intervals, temperature, humidity, and/or chemical concentrations.

The resin R comprises a material that is curable by radiant energy and is capable of adhering or bonding the filler (if used) together in the cured state. As used herein, the term "radiation energy curable" refers to any material that solidifies in response to application of radiation energy of a particular frequency and energy level. For example, the resin R may comprise a photopolymer resin of a known type which contains a photoinitiator compound which acts to initiate the polymerization reaction, changing the resin from a liquid state to a solid state. Alternatively, the resin R may include a material containing a solvent that can be evaporated by applying radiant energy. The uncured resin R may be provided in solid (e.g., granular) or liquid form (including paste or slurry).

According to the casting embodiment shown, the viscosity of the resin R is at a higher viscosity, so that contact with a doctor blade or leveling device (e.g., table 14) is required. The composition of the resin R may be selected as desired to suit a particular application. Mixtures of different compositions may be used.

The resin R may be selected to have the ability to outgas or burn off during further processing, such as the sintering process described below.

The resin R may contain a filler. The filler may be premixed with the resin R. The filler comprises particles, which are generally defined as "a very small amount of material". The filler may comprise any material that is chemically and physically compatible with the selected resin R. The particles may be regular or irregular in shape, uniform or non-uniform in size, and may have a variable aspect ratio. For example, the particles may take the form of powders, globules or granules, or may be shaped like small rods or fibers.

The components of the filler, including its chemistry and microstructure, can be selected as desired to suit a particular application. For example, the filler may be metallic, ceramic, polymeric, and/or organic. Other examples of potential fillers include diamond, silicon, and graphite. Mixtures of different components may be used.

The filler may be "fusible", meaning that the filler is capable of consolidating into a mass upon application of sufficient energy. For example, fusibility is a characteristic of many available powders, including but not limited to polymers, ceramics, glass, and metals.

The ratio of filler to resin R can be selected to suit a particular application. In general, any amount of filler may be used as long as the combined material is able to flow and be leveled and there is sufficient resin R to hold the filler particles together in the cured state.

An example of the operation of the device 10 will now be described in detail with reference to fig. 1 and 2. It should be understood that component 65, as a precursor to producing the component and using device 10, is software modeled as a stack of planar layers arranged along the Z-axis. Each layer may be divided into a grid of pixels depending on the type of curing method used. The actual component 65 may be modeled and/or fabricated as a stack of tens or hundreds of layers. Suitable software modeling processes are known in the art.

The resin treatment assembly 11 is operated to provide new resin R in the build zone 23. After material deposition, the apparatus 10 is positioned to define selected layer increments. The layer increment is defined by some combination of the thickness of the deposited layer and the operation of the station 14. For casting system 20, it will be the operation of thickness 214 and table 14. For a bucket system (discussed below), it will be the depth of the bucket into which the resin is filled. For example, the table 14 may be positioned such that the upper surface 30 of the new part or the existing surface 75 of the machined part just contacts the applied resin R as shown in fig. 2, or the table 14 may be used to compress and displace the resin R to clearly define the layer increments. Layer increments affect the speed of the additive manufacturing process and the resolution of the part 74. The slice increments may be variable, with larger slice increments used to speed processing in portions of the component 74 where high accuracy is not required, and smaller slice increments used where higher accuracy is required, at the expense of processing speed.

Once the resin R has been applied and the layer increments defined, the radiant energy device 18 is used to cure a two-dimensional cross-section or layer of the part 74 built as shown in FIG. 3.

In the case of the projector 48, the projector 48 projects a patterned image 59 representing a cross section of the part 74 through the foil 12 to the resin R. This process is referred to herein as "selective" curing.

Once the curing of the first uncured layer is complete, the table 14 is separated from the foil 12, for example by raising the table 14 using the actuator 32. The techniques disclosed herein provide a method and apparatus for measuring and controlling the thickness of a deposited material (i.e., layer 110).

Referring now to fig. 2, when the casting apparatus 20 is operating, the film 12 is advanced through the material depositor 106 toward and through the build zone 23. The resin R in the material depositor 106 is dragged, flowed, or pushed through the film 12 from the reservoir 198 and then from the reservoir 182. As the resin R is drawn from the reservoir 198, it passes under the first blade 210 and defines an initial layer 215 having a thickness 213. The thickness 213 is determined by the angle 216 of the first blade 210. The dimensions of the first doctor blade 210 and its mechanical relationship with the reservoir 182 are predetermined such that the thickness 213 approaches a minimum value as the angle 216 approaches 90 °. Accordingly, as angle 216 decreases, i.e., becomes less than 90 °, thickness 213 increases and eventually approaches a maximum value. The angle 216 is set using the actuator 212. In the illustrated embodiment, this is a manual operation that is performed relatively infrequently. The thickness 213 of the layer 215 is selected such that the final thickness 214 can be achieved by adjusting the position of the second doctor blade 211 to define the size of the gap 202 and thus the thickness 214.

It should be appreciated that the actual relative position of the second doctor blade 211 and the build surface 24 of the film 12 should be related to the thickness 214. However, due to various factors, including but not limited to: the speed of the film 12; rheological and mechanical properties of resin R; the chemical nature and resulting interaction between the resin R and the material forming the film 12 and the second blade 211; and combinations thereof, the thickness 214 may be different than the height of the gap 202.

With continued reference to fig. 2, sensor 224 operates to measure thickness 214 and generate and transmit a measurement signal indicative of thickness 214 to controller 120. The controller 120 is configured to compare the thickness 214 determined by the sensor 224 to a predetermined thickness value or "set point". The controller 120 then generates a control signal that activates the actuator 220, if necessary, such that the position of the second scraper 211 changes relative to the reservoir 182; thus, the dimensions of gap 202 and thickness 214 are varied. The sampling rate of the sensor 224 and the rate of incremental action of the controller 120 are determined so that a stable and useful continuous control of the thickness 214 is maintained as the film 12 moves between the rollers 15. Thus, an area having a desired thickness is defined and the portion of the deposited material layer 110 in the build zone 23 is maintained at the desired thickness.

Referring now to fig. 9, an alternative configuration of a material depositor including a second sensor 225 is shown. The second sensor 225 is configured to determine a thickness 180 of the layer 110. The second sensor 225 is also connected to the controller 120 and is configured similarly to the first sensor 224 such that the controller 120 receives a second measurement signal from the second sensor 225 that is indicative of the thickness at a point downstream of the first sensor 224. As shown in fig. 9, the second sensor 225 is located directly downstream of the first sensor 224, in series with the first sensor 224. Thus, the second sensor provides additional data regarding the thickness of the layer 110. Such additional data may be affected by factors such as the flow or self-leveling of layer 110 and/or the drying of layer 110. It should be appreciated that the data acquired by the second sensor 225 for a given location is separated in time from the time the data is acquired by the first sensor 224 for the given location by a predetermined delay. The amount of delay is determined by the distance of the second sensor 225 from the second blade 211. For example, if the second sensor 255 is 2 meters downstream of the doctor blade 211 and the film 12 is traveling at a speed V of 1 meter per second, the delay is 2 seconds. During this time, the thickness of the particular spot may change due to settling, bleeding, evaporation or some other process. Thus, data from the second sensor 225 can be used to determine if an expected process such as sedimentation has occurred and confirm that the thickness is acceptable.

Further, the second measurement signal from the second sensor 225 may provide data for use in conjunction with the data from the first sensor 224, for example as an average. Alternatively, as shown in FIG. 10, the second sensor 225 may be controllably coupled to the third blade 217 by the controller 120 in a cascaded closed-loop strategy. Alternatively or additionally, data from the sensor 225 may be used to determine that an intentional change in the thickness of the material layer 110 (e.g., constructing a different portion of the part 74) has been performed properly (with the expected thickness) and that the new layer thickness will reach the build area 23 when expected.

Referring now to fig. 11, a configuration of the material depositor 106 including a plurality of first sensors 224 is shown. As shown, such a plurality of first sensors 224 may be configured to provide average thickness information across the width of the layer 110. Alternatively, each first sensor 224 may provide a separate thickness measurement signal. These independent signals may be used to determine the variation in the thickness 214 of the layer 110 across the width of the layer 110. This information may be used to control the thickness profile of layer 110. For example, as shown, a plurality of first sensors 224 are positioned one generally at a first point. In the illustrated embodiment, the first point is spaced from a first side a, also referred to as the proximal side (in the foreground of fig. 11), another at a second point, which in the illustrated embodiment is generally centered in the width of the layer 110, and another at a third point, which in the illustrated embodiment is generally spaced from a second side B, also referred to as the outer side (off side) (in the background of fig. 11) of the layer 110. The first, second and third points at which the plurality of first sensors 224 are located define a line that is substantially perpendicular to the edge of the layer 110 in the X or lateral direction. The first, second, and third points are associated with the first, second, and third thicknesses, respectively. It is often desirable in additive manufacturing that the side-center-side profile of layer 110 be flat. When the side-center-side profile is flat, the thickness 214 is uniform across the width of the layer 110, and the first, second, and third thicknesses are approximately equal. It should be understood that other profiles may be created using the material depositor 106. Examples of such profiles are shown in fig. 22-26. More specifically, fig. 22 shows a smile profile; FIG. 23 shows a sloped profile that slopes from the thicker side to the thinner side in a generally straight line; FIG. 24 shows a frown or aid profile; FIG. 25 shows a groove profile having two generally flat outer edges or lands and a generally flat central groove; fig. 26 shows a modified groove profile in which the outer edge has a high center. It should be understood that other profiles for other combinations of geometries may be produced using the depositor 106 or multiple depositors.

Referring now to fig. 11-13, a configuration of material depositor 106 is shown that includes a sensor 524 configured to scan across the width of layer 110. The sensor 524 is connected to the controller 220 in the same manner as the first sensor 224 described above. The sensor 524 may be configured to provide an average thickness or side-center-side thickness profile across the width of the layer 110, as discussed above with respect to the plurality of first sensors 224 shown in fig. 9. With continued reference to fig. 11-13, the material depositor may be configured with a second actuator 199 that is controllably connected to the controller 120 in the same manner as the actuator 220, as described above. In this configuration, the first blade 210 may be side-to-side adjustable to control the side-center-side profile described above. The first point may be controlled with respect to a first point target thickness, i.e. a set point, the center may be controlled with respect to a second target thickness, and the third point may be controlled to a third target thickness. For example, if the thickness of the layer 110 measured by the associated first sensor 224 at the first point is greater than the first target thickness, the actuator 199 may be manipulated to be thinner such that the measured thickness approaches the first side target thickness. It should be understood that all three target thicknesses may be different, the same, or other patterns, such as "tooth profiles," where each target thickness is different and results in three different generally flat tracks.

In another embodiment, the resin handling assembly 11 is a bucket system. This embodiment is described with respect to using a bucket 611, the bucket 611 having a floor and walls to define a space to receive resin. It will be appreciated that a plate may alternatively be used in the system to provide a floor rather than a wall. Generally, the resin R should be flowable when used with a barrel system and less flowable when used with a plate. According to the embodiment shown in fig. 14-17, resin R is preferably a self-leveling, relatively low viscosity liquid. The resin R may be a liquid having a high viscosity, so that contact with the stage 14 is required to level the resin R.

Conveyor 21 is used to move a new bucket 611 into build area 23. The material depositor 56 operates to deposit resin R into the barrel 611. A sensor 78 is provided to determine the thickness of the resin R in the barrel 611. If the thickness of resin R does not reach the desired thickness, controller 68 is configured to cause material depositor 56 to add additional resin R. If the thickness of the resin R in the barrel 611 is too large, the controller 68 is configured to operate the suction device 57 to remove the excess resin R. These processes are repeated until the barrel 611 is properly filled with resin at the desired height, i.e., depth. For less fluid (harder) resins, these processes are repeated until the barrel 611 is properly filled with resin at the desired height (i.e., depth) and at a level (or flat) within the desired flatness specification. In this way, a specific region, i.e., the region within the barrel 611, is measured and corrected (material R removed or added) until the thickness is correct. This is in contrast to the method noted above, where layer 110 is corrected as it is being generated. Once the appropriately filled barrel 611 is positioned in build zone 23, exposure to radiant energy selectively cures resin R as described above and bonds the new layer to the previously cured layer. This cycle of preparing the buckets 611, adding tiers, selectively curing, and unloading the buckets 611 is repeated until the entire assembly 74 is completed.

Referring now to FIG. 18, an alternative configuration of the apparatus 10 including multiple depositors is shown. In this regard, the first depositor 106; a second depositor 106'; and a third depositor 106 "are positioned adjacent to each other on the film 12. The plurality of depositors is configured to deposit three spaced-apart lanes of deposition material: a first track 110, a second track 110', and a third track 110 ". As shown in fig. 19, all three tracks 110, 110' and 110 "have the same thickness. It should be understood that the three tracks 110, 110 'and 110 "have the same material (resin R), but alternatively the tracks 110, 110' and 110" may be formed of different materials.

Referring now to fig. 20, an alternative embodiment of an additive manufacturing apparatus 310 is shown in which a first material depositor 306, a second material depositor 406 and a third material depositor 506 are provided. The first, second, and third material depositors 306, 406, and 506 are substantially similar to the material 106 described above and will be understood from the description thereof. Each material depositor 306, 406, and 506 is configured to deposit resin R onto moving belt 312 at a predetermined thickness. Alternatively, each depositor 306, 406, and 506 may include a different resin R, and thus multiple materials may be used to build part 74.

As the belt 312 moves, the depositors 306, 406 and 506 operate to discharge the resin R. In this manner, a first track 308 having a first track thickness, a second track 408 having a second track thickness, and a third track 508 having a third track thickness are created. As shown in FIG. 20, the tracks 308, 408, and 508 contact and collectively define the layer 310. Optionally, one or more of the lanes 308, 408, and 508 may be spaced apart. The spacing may be achieved by positioning the depositors 308, 408, and 508 or by controlling the width of the deposited material with the depositors. Thus, the spacing of the traces 308, 408, and 508 may be controlled over time.

In the embodiment shown in FIG. 20, each of the three tracks is generally flat from side to side, and the first track thickness, second track thickness, and third track thickness are controlled relative to the same set point such that all three thicknesses are substantially equal. It should be understood that the thicknesses of the lanes 308, 408, and 508 may be different from each other, such that all three are different or one of the three is different from the other two. It should also be appreciated that the set point may be varied such that the thickness of the tracks 308, 408, and 508 varies over time.

A subsequent thickness sensor 325 is located downstream of the depositor 306 and is configured to measure the thickness of the resin R in the first lane 308 on the centerline 309 of the first lane 308. Subsequent thickness sensor 325 is configured to provide a signal indicative of the thickness along centerline 309 to controller 68. The signal generated by the sensor 325 may be used to directly control the amount of material deposited by the material depositor 306 or for confirmation. The spacing of the sensors 325 and the speed of the film 312 downstream of the depositor 306 determine the predetermined time period between the moment the material under test is deposited and the moment of measurement. It should be understood that multiple subsequent sensors may be used across layer 310 or within any one or more of tracks 308, 408, and 508. It should be understood that depositor 306, depositor 406, and depositor 506 are positioned such that they each discharge resin at about the same location across membrane 312, as shown in fig. 20.

In another alternative embodiment, shown in FIG. 21, depositors 706, 806 and 906 are provided. The depositors 706, 806 and 906 are configured to deposit the layers 708, 808 and 908, respectively, onto the film 712 and may be understood structurally and operationally from the description of depositors 306, 406 and 506. It should be appreciated that the depositor 706 is configured to deposit resin that includes a lane 708 further upstream, i.e., a lane 708 that is earlier than the lane 808. In addition, depositor 806 is configured to deposit resin further upstream, i.e., prior to lane 908, including lane 808. Such spacing of the depositors 706, 806 and 906 may allow for accommodation of mechanical structures associated with adjacent depositors. Such spacing may also allow for the mechanical and rheological properties of the resin R to be adjusted in adjacent lanes 708, 808, and 908. Likewise, it should be understood that adjacent tracks 708, 808, and 908 may be comprised of the same resin or different resins.

Referring now to fig. 26-29, an alternative embodiment is provided that is configured to produce multiple thicknesses within a build layer to precisely produce overhangs, internal voids, and other geometries. Such geometries are often difficult to create using traditional additive manufacturing methods due to the phenomenon of show-through. Thus, a manufacturing method is disclosed below for operating a 3D printer using additive manufacturing, wherein build patterns allow for the creation of multiple thicknesses within a layer.

Advantages of the disclosed methods include increased productivity, the ability to create more fragile features, the ability to create voids, and greater precision compared to prior art methods. The disclosed method should provide a layer produced at the correct thickness so that the layer is cleaner and no show-through occurs because no excess resin is deposited. Another advantage of the disclosed method over the prior art is that the prior art often fills newly created voids with uncured material. Any uncured material that is not or cannot be removed during the in-process or post-printing cleaning steps is cured into the part (thus, partially or completely filling the void) during post-processing. The disclosed method creates internal features with little or no entrapped uncured material or resin R and thus creates features that will survive post-processing.

It should be noted that one feature of the present method is that all layers are printed simultaneously and in the same plane, i.e., have their bases on the surface 24 of the membrane 12.

The part having the voids defined therein may be manufactured according to the following method. It should be understood that the void may be a passage through a part having an open end, a closed cavity, a partially closed cavity that is balanced on only one or both sides, i.e., an overhang, or other complex geometry.

Such parts may be produced by stacking one or more layers having a contoured or otherwise non-planar profile. Such a shaped layer may be interspersed with a conventional flat layer.

For example, the machined part shown in perspective view in FIG. 28 is formed from five U-shaped build layers 79, the build layers 79 being formed on an initial build layer having a generally uniform thickness. The machined part 74 defines a finished part 74 ". It should be understood that conventional cleaning and finishing steps may alternatively be applied to the machined part 74 to produce a finished part 74 ".

Preferably, machined part 74 is formed using a U-shaped layer 310, which U-shaped layer 310 is configured with square outer channels 308 and 508 as shown in FIG. 25. Such precisely deposited shaping layers allow the formation of parts without print-through. Because the layer 310 shown in fig. 25 does not have excess resin, print-through errors are not possible. In other words, the profile of layer 310 substantially matches the profile of the resulting build layer of the finished part.

However, it should be understood that similar parts having cavities therein may be formed using stacked shaping layers, wherein the contours of the deposited layers do not match the finished build layer shape. As described above, the table 14 may be used to contact the deposition layer in such a way that the surface 30 of the table 14 contacts the deposition layer 110 and defines an uppermost surface thereof. For example, fig. 26 shows a shaping layer 710 having two outer ridges 708 and 908. According to the present method, the shaping layer 710 may be utilized to fabricate the feature 74 shown in FIG. 28. As shown in fig. 27, an initial step is provided of defining the shape of the final uncured layer by moving the working surface 75 to contact and deform the deposited uncured resin layer 710. This step is used to approximate a precisely deposited U-shaped channel as shown in fig. 25.

In this regard, the uncured resin layer 710 of fig. 26 includes a generally planar central lane 808 bounded by peaked first and second outer lanes 708 and 908. The shape and size of the peaks of the outer lanes 708 and 908 are selected to conform to build style and to account for the deformation of the outer lanes 708 and 908 by contact with the surface 30 of the table 14 to define an approximation of one of the desired U-shaped layers as shown in FIG. 28. Due to the mechanical deformation process required to form the outer ridges 708, 908, it should be appreciated that some uncured resin 79' may remain within the channels 79. This uncured resin 79' may be removed by various conventional cleaning processes, such as chemical rinsing. The cleaning step may be performed on the work process part 74 or as part of a finishing process to produce the finished part 74 "shown in fig. 29. While the step of mechanically deforming the deposited layer prior to curing may produce the desired finished shape, it may also produce some waste and possible show-through artifacts.

The above-described alternative embodiments provide a method of producing a three-dimensional part including a void using an apparatus for additive manufacturing. As used herein, the term void refers to a space within a build layer defined by layers of uncured resin having various thicknesses. In this regard, the uncured resin layer defining the build layer having voids has at least one "thinner" region. The method can be better understood from the following list of steps: A) depositing an uncured resin layer defining a resin surface and a resin base spaced apart by a thickness, and wherein the uncured resin layer comprises a plurality of thicknesses such that a first uncured layer profile is defined; B) curing the resin layer to form a build layer that is an integral part of the part; C) wherein the build layer has a build layer profile defining at least a portion of the void; and D) repeating the depositing and curing steps to produce a part comprising a plurality of build layers and comprising voids and the voids having a predetermined geometry.

According to an alternative embodiment, the following steps are provided to produce a part with voids, wherein the deposited layer is shaped by contact with a mechanical shaper (e.g. table 14). The steps of the alternate embodiment method are: E) contacting at least a portion of the resin surface with a working surface; F) modifying the first uncured layer profile during the contacting step to define a second uncured layer profile; G) cleaning the part of residual uncured resin; and H) removing the unwanted cured resin to define the final part shape.

A method and apparatus for additive manufacturing has been described above. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Additional aspects of the invention are provided by the following numbered clauses:

1. an additive manufacturing apparatus comprising: a build surface, at least a portion of which is transparent; a first material depositor operable to deposit a curable resin to form a deposited resin layer on the build surface; a table positioned toward the build surface and configured to hold a stacked arrangement of one or more cured layers of resin; one or more actuators operable to change the relative positions of the build surface and the table; a radiant energy device positioned adjacent the build plate, opposite the table, and operable to generate and project radiant energy through the build plate in a predetermined pattern on the resin; and a first sensing device configured to measure a thickness of the deposited resin layer, wherein at least one of the first sensing devices is configured to generate a signal indicative of the thickness of the deposited resin layer.

2. An additive manufacturing apparatus according to any one of the preceding claims, comprising: a first thickness adjustment mechanism configured to adjust a thickness of the deposited resin layer in response to the signal.

3. An additive manufacturing apparatus according to any one of the preceding claims, wherein the first thickness adjustment mechanism is one of: a suction device and a scraper.

4. An additive manufacturing apparatus according to any one of the preceding claims, comprising a second thickness adjustment mechanism.

5. An additive manufacturing apparatus according to any one of the preceding claims, wherein a second thickness adjustment mechanism is positioned downstream of and in series with the first thickness adjustment mechanism.

6. The additive manufacturing apparatus of claim 2, wherein the first sensing device is located downstream of the first thickness adjustment mechanism.

7. An additive manufacturing apparatus according to any one of the preceding claims, wherein the first sensing device is located upstream of the second thickness adjustment mechanism.

8. An additive manufacturing apparatus according to any one of the preceding claims, wherein the second thickness adjustment mechanism is located upstream of a second sensing device configured to measure the thickness of the deposited resin layer.

9. An additive manufacturing apparatus according to any one of the preceding claims, wherein there is a first sensing device and a second thickness adjustment mechanism located downstream of the second sensing device.

10. An additive manufacturing apparatus according to any one of the preceding claims, wherein the thickness adjustment mechanism is configured to adjust the thickness of the deposition layer across the width of the deposition layer such that the thickness remains approximately equal to the thickness target.

11. An additive manufacturing apparatus according to any one of the preceding claims, wherein the deposited layer has a first thickness target and a second thickness target, and the first thickness target is different from the second thickness target.

12. An additive manufacturing apparatus according to any one of the preceding claims, wherein the thickness adjustment mechanism is configured to be actuated based on at least one signal indicative of the thickness of the deposited layer at a plurality of points across the width of the deposited layer.

13. Additive manufacturing apparatus according to any one of the preceding claims, wherein the plurality of points define a line oriented substantially perpendicular to a side of the deposited layer.

14. A method of producing a component layer by layer using an additive manufacturing apparatus, comprising the step of maintaining a thickness of a layer of radiation energy curable resin at a predetermined thickness by: depositing resin using a first material depositor to form a layer of deposited resin on a build surface, at least a portion of the build surface being transparent; sensing the thickness of the deposited resin layer; adjusting the thickness of the deposited resin layer to define an area of the deposited layer having a predetermined thickness; positioning an area of a deposition layer having a predetermined thickness in a build zone; executing a build cycle comprising the steps of: positioning a stage relative to the build surface to define layer increments in the deposited resin layer; selectively curing the resin using the application of radiant energy in a particular pattern, thereby defining the geometry of the cross-sectional layer of the part; moving the build surface and the table relatively apart to separate the part from the build surface; and repeating the steps of maintaining the thickness and performing the build cycle for the plurality of layers until the part is completed.

15. The method according to any of the preceding claims, wherein the step of locating an area of the deposited layer comprises the step of passing a further area of the deposited layer having a thickness less than a predetermined thickness through the build zone.

16. The method of any of the preceding clauses, further comprising the steps of: using a first thickness adjustment mechanism configured to adjust the thickness of the deposited resin layer in response to the thickness sensed in the adjusting the thickness step.

17. The method of any of the preceding claims, wherein the additive manufacturing apparatus comprises a second thickness adjustment mechanism.

18. The method of any of the preceding claims, wherein a second thickness adjustment mechanism is positioned downstream of and in series with the first thickness adjustment mechanism.

19. The method of any of the preceding claims, further comprising the step of measuring the thickness with a first sensing device located downstream of the first thickness adjustment mechanism.

20. The method of any one of the preceding claims, further comprising the step of measuring the thickness of the deposited layer with a second device, wherein a second thickness adjustment mechanism is located upstream of the second sensing device.

21. The method according to any of the preceding claims, further comprising the step of monitoring the thickness of the resin R for a predetermined time after the resin R is deposited.

22. The method of any preceding claim, further comprising the step of determining the thickness of the deposited resin layer using a second sensing device for a predetermined time after the resin layer is deposited.

23. The method according to any one of the preceding claims, wherein the thickness adjustment device is configured to adjust the thickness of the deposited layer across the width of the deposited layer.

24. The method of any preceding claim, wherein the thickness adjustment device is actuated based on at least one signal indicative of the thickness of the deposited layer at a plurality of points located across the width of the deposited layer.

25. A method of producing a three-dimensional part comprising a void using an apparatus for additive manufacturing, the method comprising the steps of: depositing an uncured resin layer, the uncured resin layer defining a resin surface and a resin base spaced apart by a thickness, and wherein the uncured resin layer comprises a plurality of thicknesses, thereby defining a first uncured layer profile; curing the resin layer to create a build layer, the build layer being an integral part of the part; and wherein the build layer has a build layer profile that defines at least a portion of the void.

26. The method of any one of the preceding clauses wherein the first uncured layer profile is substantially the same as the build layer profile.

27. The method of any of the preceding claims, wherein the dimensions of the build layer are defined by the dimensions of the uncured resin layer produced by the depositing step.

28. The method according to any one of the preceding claims, further comprising the step of repeating the depositing and curing steps to produce a part comprising a plurality of build layers and comprising voids and the voids having a predetermined geometry.

29. The method of any of the preceding clauses, wherein the predetermined geometry may include at least a portion of one of: an overhang, an internal void including a structure positioned therein, and combinations thereof.

30. The method of any of the preceding claims, wherein the uncured resin layer is positioned such that it has an x-axis, a y-axis, and a z-axis, and the first profile is oriented generally perpendicular to the x-axis.

31. The method of any of the preceding claims, wherein the uncured resin layer is positioned such that it has an x-axis, a y-axis, and a z-axis, and the first profile is oriented generally perpendicular to the y-axis.

32. The method of any of the preceding clauses, further comprising the step of depositing an uncured resin layer such that a plurality of lanes are defined within the uncured resin layer.

33. The method of any of the preceding claims, further comprising the step of depositing a plurality of lanes such that at least two lanes have different thicknesses.

34. The method of any of the preceding claims, further comprising the step of depositing a plurality of lanes such that at least two lanes have substantially similar thicknesses.

35. The method of any of the preceding clauses, further comprising the steps of: an additional track is deposited between two tracks having substantially similar thicknesses, such that the thickness of the additional track is different from the thickness within the thickness of the two lines having substantially similar thicknesses.

36. The method of any of the preceding claims, wherein the additional lanes are thinner than at least a portion of the two lanes having substantially similar thicknesses.

37. The method of any of the preceding clauses, further comprising the steps of: contacting at least a portion of the resin surface with a working surface; and

the first uncured layer profile is altered during the contacting step to define a second uncured layer profile.

38. The method of any one of the preceding clauses wherein the second uncured layer profile is substantially the same as the build layer profile.

39. The method of any of the preceding claims, further comprising the step of cleaning residual uncured resin from the part.

40. The method of any of the preceding claims, further comprising the step of removing unwanted cured resin to define a final part shape.

41. The method of any of the preceding claims, further comprising the step of curing by exposing different portions of the resin layer to different amounts of radiation.

42. The method of any of the preceding claims, further comprising the step of repeating the depositing and curing steps to form at least one additional build layer further defining the void.