FEEDBACK CONTROL SYSTEM FOR PRINTING 3D PARTS
An electrophotography-based additive manufacturing system is used to print a three-dimensional part. An electrophotography engine is used to print a part layer of the three-dimensional part is using a part material compositionally including part material particles. The developed part layer is transferred from the electrophotography engine to a transfer medium, and the transferred part layer is transfused together to previously-printed layers using a layer transfusion assembly. A surface height profile of the transfused part layers is measured using a surface profilometer, and a thickness profile of a subsequently-printed part layer is controlled responsive to the measured surface height profile.
1 . A method for printing a three-dimensional part and with an electrophotography-based additive manufacturing system, the method comprising:
providing a part material compositionally including part material particles;
developing a part layer of the three-dimensional part from the part material with a first electrophotography engine;
transferring the developed part layer from the first electrophotography engine to a transfer medium;
transfusing the transferred part layer together to previously-printed layers using a layer transfusion assembly;
measuring a surface height profile of the transfused part layers using a surface profilometer; and
controlling a thickness profile of a subsequently-printed part layer responsive to the measured surface height profile.
2 . The method of claim 1 , further including analyzing the surface height profile to determine an overall height error by comparing an overall height of the transfused part layers relative to a nominal height, and wherein controlling the thickness profile of the subsequently-printed part layer includes controlling an overall layer thickness.
3 . The method of claim 1 , further including analyzing the surface height profile to determine a localized height error in a localized surface region, and wherein controlling the thickness profile of the subsequently-printed part layer includes adjusting a layer thickness in a portion of the three-dimensional part corresponding to the localized surface region responsive to the determined localized height error.
4 . The method of claim 1 , further including analyzing the surface height profile to detect localized height errors associated with the presence of a printing artifact, and wherein controlling the thickness profile of the subsequently-printed part layer includes adjusting a layer thickness in a portion of the three-dimensional part corresponding to the printing artifact responsive to the determined localized height error.
5 . The method of claim 4 , wherein the printing artifact is a streak artifact, a banding artifact or a spot artifact.
6 . The method of claim 4 , wherein the printing artifact is a registration artifact, and further including adjusting the registration of the subsequently-printed part layer.
7 . The method of claim 1 , wherein the surface profilometer is a non-contact device.
8 . The method of claim 7 , wherein the non-contact device is an optical device.
9 . The method of claim 8 , wherein the optical device includes a radiation-emitting element that directs a beam of radiation onto a surface of the transfused part layer and a detector which senses a surface height based on detecting radiation reflected from the surface of the transfused part layer.
10 . The method of claim 7 , wherein the non-contact device is an ultrasonic sensing device that includes an ultrasonic source that directs ultrasonic waves onto the surface of the transfused part layer and a detector which senses a surface height based on detecting ultrasonic waves reflected from the surface of the transfused part layer.
11 . The method of claim 7 , wherein the surface profilometer is a contact device including a mechanical probe that contacts the surface of the transfused part layer.
12 . The method of claim 11 , wherein the surface profilometer determines a position of the mechanical probe using a linear variable differential transformer.
13 . The method of claim 1 , wherein a position of the surface profilometer is adjusted in accordance with data specifying the shape of the three-dimensional part.
14 . The method of claim 1 , further including building a support structure together with the three-dimensional part by:
providing a removable support material compositionally including support material particles;
developing a support layer of the support structure from the support material with a second electrophotography engine; and
transferring the developed support layer from the second electrophotography engine to the transfer medium;
wherein the transfusing step includes transfusing the transferred support layer together to the previously-printed layers using the layer transfusion assembly, and wherein the measuring the surface height profile step includes measuring a surface height profile of the transfused support layers.
15 . The method of claim 14 , further including controlling a thickness profile of a subsequently-printed support layer responsive to the measured surface height profile.
16 . The method of claim 15 , wherein the thickness profile of the subsequently-printed support layer is controlled to reduce differences between the surface heights of the transfused part layers and the surface heights of the transfused support layer.
17 . A method for printing a three-dimensional part and with an additive manufacturing system, the method comprising:
providing a part material compositionally including part material particles;
printing a part layer of the three-dimensional part onto a transfer medium by applying the part material with a first printing engine;
transfusing the printed part layer together to previously-printed layers using a layer transfusion assembly;
measuring a surface height profile of the transfused part layers using a surface profilometer; and
controlling a thickness profile of a subsequently-printed part layer responsive to the measured surface height profile.