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EP-4737098-A1 - METHOD FOR PRINTING A THREE-DIMENSIONAL OBJECT AND A PRINTER THEREFOR

EP4737098A1EP 4737098 A1EP4737098 A1EP 4737098A1EP-4737098-A1

Abstract

A method for generating print files for a 3D object to be printed in layers on top of each other by means of a 3D printer, the method comprising the steps of a) determining the print files from data input including an intended geometry and colour information, b) simulating a print process using a thin-film equation to predict a geometry of the 3D object to be printed, c) updating the print files based on a deviation between a geometry predicted by the simulation and the intended geometry included in the data input, and d) repeating steps b) and c) until a required accuracy of the predicted geometry is achieved.

Inventors

  • MESTROM, PAULUS M.A.
  • CALLEWAERT-DORE', Tom W.J.
  • FILIPPOVYCH, Kateryna

Assignees

  • Canon Production Printing Holding B.V.

Dates

Publication Date
20260506
Application Date
20241104

Claims (12)

  1. A method for generating print files for a 3D object to be printed in layers on top of each other, the method comprising the steps of a) determining the print files from data input including an intended geometry and colour information, b) simulating a print process using a thin-film equation to predict a geometry of the 3D object to be printed, c) updating the print files based on a deviation between a geometry predicted by the simulation and the intended geometry included in the data input, and d) repeating steps b) and c) until a required accuracy of the predicted geometry is achieved.
  2. A method according to claim 1, wherein the method comprises the step of printing the 3D object according to the updated print files for which the required accuracy of the predicted geometry is achieved.
  3. A method according to claim 1 or 2, wherein the print process simulated in step b) comprises a sub-step of simulating an ink flow in the print process of the 3D object, wherein a height of a layer to be printed is small in relation to a width of the layer.
  4. A method according to any of the preceding claims, wherein the step c) comprises the sub-steps of comparing the predicted geometry to the intended geometry by calculating an average height at a pixel position on an XY plane and comparing the calculated average height at the pixel position to an intended height at the pixel position derived from the intended geometry, and adjusting an amount of ink to be deposited at the pixel position based on a difference between the average height and the intended height.
  5. A method according to claim 4, wherein the method comprises the step of comparing the required accuracy with the difference between the average height and the intended height.
  6. A method according to any of the preceding claims, wherein the method comprises the step of extending the thin-film equation to represent the effect of a shrinkage of a volume of the jetted ink (layer) due to, during and after a curing process after jetting said layer.
  7. A method according to any of the preceding claims, wherein the method comprises the step of simplifying the thin-film equation by numerical discretization.
  8. A method according to any of the preceding claims, wherein the method comprises the step of simplifying the thin-film equation by attributing same physical properties to different ink in case of printing with multiple inks.
  9. A method according to any of the preceding claims, wherein the 3D object to be printed does not exhibit large colour gradients.
  10. A method according to claim 9, wherein the 3D object is a dental element like an implant, prosthesis, a crown or a bridge.
  11. A printing system comprising a printhead assembly for jetting ink in order to form a 3D object and a print controller which is configured to perform the steps of a method according to any of the preceding claims.
  12. A non-transitory software medium comprising executable program code configured to, when executed on a printing system, enable the printing system to perform the steps of the method according to any of the claims 1 - 10.

Description

FIELD OF THE INVENTION The invention relates to a method for generating print files for a 3D object to be printed in layers on top of each other, the method comprising the step of a) determining the print files from data input including an intended geometry and colour information. A printer for printing the 3D object may hereinafter also be referred to as a printing system. An inkjet printing assembly of the printer may comprise one or more print heads. The term "perpendicular" may hereinafter also be referred to as the term "orthogonal". The term "nozzle" may be also referred to as "print element". The term "3D" is meant to be equivalent to the term "three-dimensional". A three-dimensional object may also be a 2.5D object. A 2.5D object is a 3D object wherein a height of the 3D object in the third dimension usually referred to as the z dimension or z direction is relatively small compared to the sizes of the 3D object in the other two dimensions, e.g. x and y dimensions of the 3D object or x and y directions of a surface to be printed upon. Hereinafter the term "voxel" is meant to be a three-dimensional counterpart to a pixel. It represents a value on a regular grid in a three-dimensional space. In this application a resin is a viscous substance (of e.g. synthetic origin) that is convertible into polymers. The resin is fluid during printing and solidifies under influence of radiation. BACKGROUND OF THE INVENTION When using inkjet, the geometrical accuracy of 2.5D or 3D prints is influenced by the flow of ink. The jetted drops flow out before being cured, resulting in deviations between the actual output, i.e. the print itself, and the intended output. These deviations become more critical when the edges of the to be printed object are steep, when the time before curing becomes longer or when the thickness of the printed layers is increased. Until now this problem was solved by printing wrapping material around the object to restrict ink flow. However, a disadvantage of using wrapping material is that an additional postprocessing step is required for removing said wrapping material. The disadvantage is more critical for 2.5D printing in which case postprocessing steps are generally not needed due to the absence of support material and also very undesirable considering the large size of these prints. For 3D printing more postprocessing steps, such as removing support material or polishing, are required anyway, so the additional removal of the wrapping material can be combined with the removal of the support material. Another disadvantage of wrapping the to be printed object is that the printed object has to be polished because the wrapping material and the ink mix at the interfaces between the printed object and the wrapping material. Commercially available 3D inkjet printers currently use wrapping material to completely wrap the printed object and therefore have said time-consuming post-processing steps as an intrinsic process step in print production. Alternatively a scanner can be used to scan the height of the printed object during the print job. In this way, one can correct for geometric deviations due to ink flow. A disadvantage of the approach with a scanner is that developing and applying such a scanner and the corresponding data path is very expensive. In addition, the inks may have to be adjusted to be scannable. Alternatively ink flow can be reduced by faster curing. However, it will be technically hard to cure the ink so fast that ink flow becomes negligible. Typical time scales for pin curing are hundreds of milliseconds. Alternatively ink flow can be minimized by not printing a full layer per pass. If not all droplets are able to flow together before curing, the effects of ink flow can be reduced. However, such a printing strategy slows down the print process. An objective of the invention is to provide a method and a printer for printing 3D objects with viscous materials without using any wrapping material or using substantially less wrapping material. SUMMARY OF THE INVENTION According to the present invention this object is achieved by the method according to the invention, wherein the method comprising the steps of b) simulating a print process using a thin-film equation to predict a geometry of the 3D object to be printed,c) updating the print files based on a deviation between a geometry predicted by the simulation and the intended geometry included in the data input, andd) repeating steps b) and c) until a required accuracy of the predicted geometry is achieved. The present invention ensures that the geometry of the printed object is consistent with the intended output. The thin-film equation is used to predict the output based on the input, i.e. the bitmaps. Based on the deviation between the input and the predicted output, the input is adjusted. Then the new output is again predicted. This process is repeated until the required accuracy is achieved. Finally, the real print job is start