Registration and overlay error correction of electrophotographically formed elements in an additive manufacturing system

Patent metadata

Field	Value
Publication number	US-2016339646-A1
Application number	US-201615230809-A
Country	US
Kind code	A1
Filing date	Aug 8, 2016
Priority date	Apr 1, 2014
Publication date	Nov 24, 2016
Grant date	—

Abstract

In a method for printing a three-dimensional (3D) parts with an additive manufacturing system, a developed layer of an electrically charged powder material is produced on a transfer medium using an electrophotographic (EP) engine. The transfer medium and the developed layer are fed in a feed direction. A position of the developed layer on the transfer medium is detected using a first sensor having a first output that indicates the position. A position of a moveable build platform is adjusted relative to the transfer medium to reduce one or more overlay errors between the developed layer and an intermediate build surface of a three-dimensional structure retained on the moveable build platform based on the first output. The developed layer is transferred to the intermediate build surface using a pressing element.

First claim

What is claimed is:

1 . A method for printing three-dimensional (3D) parts with an additive manufacturing system, the method comprising:
producing a first developed layer of an electrically charged powder material on a transfer medium using a first electrophotographic (EP) engine; feeding the transfer medium and the developed layer in a feed direction; detecting a position of the first developed layer on the transfer medium using a first sensor, the first sensor having an output indicating the position; adjusting a position of a moveable build platform relative to the transfer medium to reduce one or more overlay errors between the first developed layer and an intermediate build surface of a three-dimensional structure retained on the moveable build platform based on the first output, using a controller; and transferring the first developed layer to the intermediate build surface comprising pressing the first developed layer against the intermediate build surface using a pressing element.

2 . The method according to claim 1 , wherein:
the transfer medium comprises a belt; and detecting a position of the first developed layer on the transfer medium comprises:
discharging electromagnetic energy from an electromagnetic energy source of the first sensor toward the transfer medium; and
detecting a position of the first developed layer on the transfer medium using the electromagnetic energy.

3 . The method according to claim 2 , wherein discharging electromagnetic energy from the electromagnetic energy source of the first sensor comprises discharging electromagnetic energy having a wavelength selected from the group consisting of about 405 nm, about 635 nm, and about 300 nm-1000 nm.

4 . The method according to claim 1 , further comprising supporting the belt using a belt support roller at a location where the belt is exposed to the electromagnetic energy.

5 . The method according to claim 1 , wherein reducing the one or more overlay errors comprises:
predicting a position of the first developed layer at the pressing element based on the output and a speed of the transfer medium; and adjusting the position of the moveable build platform relative to the transfer medium comprises adjusting the position of the moveable build platform relative to the transfer medium based on the predicted position.

6 . The method according to claim 1 , comprising:
detecting a position of the first developed layer on the intermediate build surface using a second sensor, the second sensor including an output indicating the position of the first developed layer on the intermediate build surface; and reducing the one or more overlay errors based on the output of the second sensor, using the controller.

7 . The method according to claim 1 , wherein:
the pressing element comprises a nip roller; pressing the first developed layer against the intermediate build surface comprises pressing the first developed layer against the intermediate build surface using the nip roller; and the method comprises:
detecting a rotational velocity of the nip roller using an encoder, the encoder having an encoder output indicating the rotational velocity; and
reducing the one or more overlay errors between the first developed layer and the intermediate build surface based on the encoder output, using the controller.

8 . The method according to claim 1 , further comprising:
producing a second developed layer of an electrically charged powder material on the transfer medium using a second EP engine; detecting a position of the second developed layer on the transfer medium using the first sensor; and reducing one or more registration errors between the first and second EP engines based on the detected positions of the first and second developed layers on the transfer medium.

9 . An additive manufacturing system for printing three-dimensional (3D) parts, the additive manufacturing system comprising:
a first electrophotographic (EP) engine configured to develop layers of a first electrically charged powder material; a transfer medium configured to receive the developed layers from the first EP engine; a build platform; one or more gantry mechanisms configured to move the build platform; a pressing element configured to press the developed layers on the transfer medium into contact with intermediate build surfaces of a three-dimensional structure on the build platform in a layer-by-layer manner; a first sensor having a first output indicating a detected position of a developed layer on the transfer medium; and a controller configured to adjust the one or more gantry mechanisms to compensate for one or more overlay errors between the developed layer and the intermediate build surfaces, using the first output.

10 . The system according to claim 9 , wherein:
the pressing element comprises a nip roller; the system comprises an encoder having an encoder output that is indicative of a rotational velocity of the nip roller; and the controller adjusts the one or more gantry mechanisms to compensate for the one or more overlay errors between the developed layer and the intermediate build surfaces using the encoder output

11 . The system according to claim 9 , wherein the first sensor comprises an electromagnetic energy source, and electromagnetic energy discharged from the electromagnetic energy source is directed toward the transfer medium.

12 . The system according to claim 11 , wherein:
the transfer medium comprises a belt; and the electromagnetic energy source has a wavelength to which the transfer belt is substantially opaque or transparent.

13 . The system according to claim 12 , wherein the electromagnetic energy source is configured to discharge electromagnetic energy having a wavelength selected from the group consisting of about 405 nm, about 635 nm, and about 300 nm-1000 nm.

14 . The system according to claim 9 , wherein the first sensor is located upstream from a pressing location of the pressing element along the transfer medium relative to a feed direction of the transfer medium.

15 . The system according to claim 9 , wherein:
the transfer medium comprises a belt; and the first sensor is located along the belt greater than 4 inches from the pressing location of the pressing element.

16 . The system according to claim 15 , comprising a belt support roller positioned on an opposing side of the belt from the first sensor, wherein the belt support roller is displaced from the pressing element and is configured to support a portion of the belt that is sensed by the first sensor.

17 . The system according to claim 9 , wherein the first sensor is configured in one of brightfield illumination configuration and a darkfield illumination configuration.

18 . The system according to claim 1 , wherein:
the system includes a second sensor having a second output indicating a location of the intermediate build surfaces; and the controller is configured to detect overlay errors, and adjust the one or more gantry mechanisms to reduce overlay errors using the second output.

19 . The system according to claim 1 , wherein:
the overlay errors include a first-axis overlay error in a process direction of the moveable build platform, and a second-axis overlay error in a second direction that is perpendicular to the process direction of the moveable build platform; and the one or more gantry mechanisms comprise:
a first gantry mechanism configured to move the build platform in the process direction; and
a second gantr

Assignees

• Stratasys Inc

Inventors

• Baecker James
• Batchelder J Samuel

Classifications

• G03G15/224 Primary

  Machines for forming tactile or three dimensional images by electrographic means, e.g. braille, 3d printing · CPC title

• B29C64/147

  using sheet material, e.g. laminated object manufacturing [LOM] or laminating sheet material precut to local cross sections of the 3D object · CPC title

• B33Y30/00

  Apparatus for additive manufacturing; Details thereof or accessories therefor · CPC title

• B33Y50/02

  for controlling or regulating additive manufacturing processes · CPC title

• G03G2215/1695

  at the second or higher order transfer point · CPC title