Methods of coating stereolithographic parts

• US 5,234,636 A
• Filed: 08/13/1992
• Issued: 08/10/1993
• Est. Priority Date: 09/29/1989
• Status: Expired due to Term

• Current Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Original Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Inventors: Sekowski, Marek, Hull, Charles W., Leyden, Richard N.
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US07/929,463
• Time in Patent Office: 362 Days
• Field of Search: 264/22, 264/24, 264/129, 264/131, 264/221, 264/236, 264/250, 264/255, 264/298, 264/308, 264/317, 264/347, 264/DIG. 44, 427/180, 427/385.5, 427/386.393, 427/5.475, 427/508, 427/553, 164/34, 164/35, 164/45
• US Class Current: 264/401
• CPC Class Codes: B05D 1/045 on non-conductive substrates
• CPC Class Codes: B05D 2401/32 applied as powders
• CPC Class Codes: B05D 3/067 Curing or cross-linking the coating
• CPC Class Codes: B05D 5/061 Special surface effect
• CPC Class Codes: B05D 7/02 to macromolecular substances, e.g. rubber treatment or coating of shaped articles made of macromolecular substances C08J7/00
• CPC Class Codes: B29C 33/3842 Manufacturing moulds, e.g. shaping the mould surface by machining
• CPC Class Codes: B29C 64/135 the energy source being concentrated, e.g. scanning lasers or focused light sources
• CPC Class Codes: B29C 64/30 Auxiliary operations or equipment
• CPC Class Codes: B29C 64/35 Cleaning
• CPC Class Codes: B29K 2995/0073 smooth
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: B33Y 40/20 Post-treatment, e.g. curing, coating or polishing
• CPC Class Codes: G03F 7/0037 Production of three-dimensional images
• CPC Class Codes: H05K 3/28 Applying non-metallic protective coatings H05K3/0091 takes precedence; methods for intermediate insulating layers for build-up multilayer circuits H05K3/4673

Abstract

Methods of coating stereolithographic parts and smoothing over characteristic surface discontinuities having alternating recesses and peaks. A stereolithographic part is first substantially covered with a substance capable of becoming less viscous when heated at a temperature which does not substantially thermally degrade the part, wherein the heated substance has an appropriate surface tension. Then, the substance is heated to that temperature until the substance flows preferentially into the recesses of the surface discontinuities and away from the peaked surface discontinuities. The substance will thereafter form a short surface connection over the recesses of the discontinuities through the surface tension of the heated substance. The substance is then polymerized or hardened either by cooling, thermally setting or by UV curing.

Claims

1. In a stereolithographic method for forming a part from a material capable of selective physical transformation upon exposure to prescribed synergistic stimulation including forming successive cross-sectional patterns of the part on a selected surface of the material capable of selective physical transformation, relatively displacing the selected surface and said cross-sections as they are formed, and building up the part layer by layer in a step-wise fashion, wherein the part has surface discontinuities between at least some adjacent layers, the improvement comprising the following steps:

electrostatically coating at least a surface of the part with powder particles which melt at a temperature in the range of about 60-120 degrees Centigrade into a melted powder having an appropriate surface tension;

heating the coated part at said temperature until the particles melt into a melted powder, which flows into surface discontinuities, and thereafter forms short surface connections across the surface discontinuities through the surface tension of the melted powder; and

solidifying the melted powder to form a permanent coating which becomes a portion of the stereolithographically produced part.

2. The method of claim 1 wherein the powder is a thermoset.

3. The method of claim 1 wherein the powder is a thermoplastic.

4. The method of claim 1 wherein the powder is an epoxy.

5. The method of claim 1 wherein the powder is a polyester.

6. The method of claim 1 wherein the powder is a hybrid epoxy/polyester.

7. The method of claim 1 wherein the powder particles have a particle diameter of about at least about 50 microns.

8. The method of claim 1 wherein the powder is a UV curable powder, and the method further comprises the step of irradiating the coated part, at a time after said heating, with UV light until the melted powder cures.

9. The method of claim 1 wherein the powder is a thermoset which cross-links at a temperature below 120 degrees Centigrade, and wherein the step of solidifying the melted powder further comprises heating the coated part until the melted powder cures.

10. A method for coating a surface of a stereolithographic part having surface discontinuities between at least some adjacent layers, comprising the following steps:

applying a liquid, which is curable in response to synergistic stimulation and which is capable of becoming less viscous when heated to a temperature in the range of about 60-120 degrees Centigrade, to substantially coat a surface of the part, the less viscous liquid having an appropriate surface tension;

heating the coated part at a temperature in said range until the liquid becomes less viscous, flows into at least a portion of the surface discontinuities, and thereafter forms short surface connections across said at least portion of the surface discontinuities through the surface tension of the liquid; and

irradiating the coated part with said synergistic stimulation, at a time after said heating, until the liquid cures to form a permanent coating which becomes a portion of the stereolithographic part.

11. The method of claim 10, wherein the liquid is applied by dipping the part into the liquid.

12. The method of claim 10 wherein the liquid is applied by spraying it onto the part.

13. The method of claim 10 wherein the liquid contains a volatile solvent.

14. The method of claim 10 wherein the liquid comprises about 10-50% by volume of a photocurable resin, about 45-85% by volume of a volatile solvent, about 1-5% by volume of a photoinitiator and up to about 0.1% by volume of a flow control agent.

15. An improved stereolithographic method for forming a part from a material capable of selective physical transformation upon exposure to prescribed synergistic stimulation including forming successive cross-sectional patterns of the part on a selected surface of the material capable of selective physical transformation, reactively displacing the selected surface and said cross sections as they are formed and building up the part in a step-wise fashion, wherein the part has surface discontinuities between at least some adjacent layers, the improvement comprising the steps of:

applying a substance to at least a portion of the said at least one surface of said part which is capable of becoming less viscous when heated to a temperature which does not substantially thermally degrade the part, wherein the less viscous substance has an appropriate surface tension; and

heating the substance up to said temperature until the substance flows into at least some of the surface discontinuities and forms a short surface connection over the discontinuities through the surface tension of the less viscous substance; and

solidifying the substance after it forms the short surface connections so that it permanently becomes a portion of the stereolithography part.

16. In a stereolithographic method for forming a part from a material capable of selective physical transformation upon exposure to prescribed synergistic stimulation including forming successive cross-sectional patterns of the part on a selected surface of the material capable of selective physical transformation, relatively displacing the selected surface and said cross-sections as they are formed and building up the part layer by layer in a step-wise fashion, wherein the part has surface discontinuities between at least some adjacent layers, the improvement comprising the steps of:

substantially coating at least a portion of the part surface with a substance which is capable of becoming less viscous when heated to a temperature which does not substantially thermally damage the part, the heated substance having an appropriate surface tension;

heating the coated part to said temperature until said substance flows into the surface discontinuities and forms short surface connections across the discontinuities through the surface tension of the heated substance; and

solidifying the substance after it forms the short surface connections so that it permanently becomes a portion of the stereolithographically produced part.

17. The method of claim 16 wherein the substance is a powder.

18. The method of claim 16 wherein the substance is a liquid.

19. The method of claim 16 wherein the substance is thermally curable at a cure temperature which does not thermally degrade the part, and wherein the step of solidifying the melted powder further comprises heating the coated part at said cure temperature until the substance cures.

20. The method of claim 16 wherein the substance is UV curable, and the method further comprises the step of irradiating the coated part with UV light until the substance cures.