Rapid prototype injection molding

• US 7,125,512 B2
• Filed: 04/17/2003
• Issued: 10/24/2006
• Est. Priority Date: 04/17/2002
• Status: Active Grant

• Current Assignee: Stratasys Incorporated
• Original Assignee: Stratasys Incorporated
• Inventors: Priedeman, William R. Jr., Crump, Steven Scott, Hanson, Jeffery J.
• Primary Examiner(s): Johnson, Christina
• Assistant Examiner(s): HUSON, MONICA ANNE
• Application Number:
  US10/511,787
• Publication Number:
  US 20050173839A1
• Time in Patent Office: 1,286 Days
• Field of Search: None
• US Class Current: 264/328.1
• CPC Class Codes: B29C 2045/465 using pumps for injecting the material into the mould
• CPC Class Codes: B29C 33/3842 Manufacturing moulds, e.g. shaping the mould surface by machining
• CPC Class Codes: B29C 45/00 Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor injection blow-moulding B29C49/06
• CPC Class Codes: B29C 71/0009 using liquids, e.g. solvents, swelling agents spectacle cases, e.g. for cleaning contact lenses A45C11/04; disinfecting or sterilising contact lenses A61L12/00, using liquid substances A61L2/20; cleaning involving the use of liquid in general B08B3/00; for hydrating contact lenses B29D11/00067
• CPC Class Codes: B33Y 30/00 Apparatus for additive manufacturing; Details thereof or accessories therefor
• CPC Class Codes: B33Y 80/00 Products made by additive manufacturing

Abstract

Disclosed is a method and apparatus for making a prototype injection molded part. An extruder of the type used for fused deposition modeling injects production thermoplastic material into a heated nonconductive plastic mold tool slowly at low pressure in an isothermic process. The mold tool may be built from a CAD drawing by fused deposition modeling or another rapid prototyping technique. Using the present invention, an injection molded prototype part can be made from a digital representation of the part within 24 hours by an engineer in an office environment.

Claims

1. A method for making a prototype plastic injection molded part, comprising the steps of:

providing a plastic mold tool defining a mold cavity;

injecting a liquified ribbon of plastic material into the mold cavity using an extrusion head at a pressure of less than 20 psi, until the material fills the cavity;

curing the plastic material in the mold cavity to form the prototype part.

2. The method of claim 1, wherein the plastic mold tool is formed from an alkali-soluble modeling material.

3. The method of claim 1 and further comprising:

heating the mold tool to approximately the extrusion temperature, prior to the injecting step.

4. The method of claim 1, further comprising building the plastic mold tool using a rapid prototyping technique based at least in part on computer data.

5. The method of claim 4, wherein the plastic mold tool is built in a fused deposition modeling machine.

6. The method of claim 5, wherein the building step and the injecting step are performed in the same fused deposition modeling machine.

7. The method of claim 1, and further comprising the step of:

clamping the mold tool to a fixture with a clamping force of less than or equal to 10 tons, prior to the injecting step.

8. The method of claim 1, wherein the injection step is an adiabatic process.

9. A method for making a prototype plastic injection molded part, comprising the steps of:

providing a plastic mold tool defining a mold cavity;

injecting a thermoplastic material into the mold cavity as a liquified ribbon of material using an extrusion head, at a pressure of less than 20 psi, so that the thermoplastic material fills the mold cavity; and

cooling the thermoplastic material in the mold cavity to form the prototype part.

10. The method of claim 9 and further comprising the step of:

building the mold tool using a rapid prototyping technique, based on computer file data representing a desired prototype part.

11. The method of claim 10, wherein the mold tool is built in a fused deposition modeling machine.

12. The method of claim 11, wherein the building step and the injecting step are performed in the same fused deposition modeling machine.

13. The method of claim 9, wherein the injecting step is done in a fused deposition modeling machine.

14. The method of claim 9, wherein the mold material is injected into the mold cavity using a melt extruder.

15. The method of claim 14, wherein the melt extruder comprises a filament pump.

16. The method of claim 14, wherein the melt extruder comprises a piston pump.

17. The method of claim 14, and further comprising the steps of:

positioning a sprue in the mold tool such that a dispensing end of the sprue is directed into the mold cavity; and

attaching an inlet end of the sprue to a dispensing tip of the melt extruder;

wherein the thermoplastic material is injected from the melt extruder into the mold cavity via the sprue.

18. The method of claim 14, wherein ultrasonic energy is induced in the extruder during the injecting step creating a thixotropic flow of thermoplastic.

19. The method of claim 9 and further comprising:

heating the mold tool to approximately the extrusion temperature, prior to the injecting step.

20. The method of claim 9 and further comprising:

coating surfaces of the mold cavity with a release agent, prior to the injecting step.

21. The method of claim 9, and further comprising the step of:

monitoring pressure in the mold cavity during the injecting step and responsively adjusting the injection pressure.

22. The method of claim 9, wherein the plastic mold tool is formed from an alkali-soluble modeling material.

23. The method of claim 9, wherein the thermoplastic material comprises a curable material.

24. The method of claim 9, wherein the curable material is selected from the group consisting of a photopolymer and a thermosetting material.

25. The method of claim 9, and further comprising the step of:

clamping the mold tool to a fixture with a clamping force of less than or equal to 10 tons, prior to the injecting step.

26. The method of claim 9, and further comprising the step of:

maintaining constant pressure on the mold tool during the cooling step to compensate for shrinkage of the prototype part and the mold tool.

27. The method of claim 9, wherein the prototype part is cooled in the mold cavity to a temperature approximating room temperature.

28. The method of claim 9, and further comprising the step of:

vapor smoothing surfaces of the mold tool prior to the injecting step.

29. The method of claim 9, wherein the thermoplastic material is selected from a group consisting of ABS, polycarbonate, polystyrene, acrylics, amorphous polyamides, polyesters, polyphenylsulfone, polyphenylene ether, nylon, PEEK, PEAK, and blends thereof.

30. The method of claim 9, wherein the plastic mold tool is formed from a thermoplastic material comprising at least 50 weight percent of a thermoplastic selected from the group consisting of polycarbonate, polystyrene, acrylics, amorphous polyamides, polyesters, polyphenylsulfone, polysulfone, polyphenylene ether, nylon, PEEK, PEAK, poly(2-ethyl-2-oxazoline), and blends thereof.

31. The method of claim 30, wherein the thermoplastic forming the mold tool comprises a polyphenylsulfone-based resin.

32. The method of claim 30, wherein the thermoplastic forming the mold tool comprises a polyphenylsulfone-based resin and the injected thermoplastic is ABS.

33. The method of claim 9, wherein the injecting step is performed using a vacuum assist.

34. The method of claim 9, wherein the injection step is an adiabatic process.

35. A method for making a prototype plastic injection molded part, comprising the steps of:

providing a plastic mold tool defining a mold cavity, the plastic mold tool being built with an additive process rapid prototyping machine;

injecting a polymer into the mold cavity using the additive process rapid prototyping machine at a pressure of less than 20 psi, until the material fills the cavity; and

solidifying the polymer in the mold cavity, thereby forming the molded prototype part.

36. The method of claim 35, wherein the polymer comprises a photopolymer, and wherein solidifying the polymer comprises exposing the polymer to light.

37. The method of claim 35, wherein the rapid prototyping machine comprises a fused deposition modeling machine.

38. The method of claim 35, and further comprising vapor smoothing the plastic mold tool prior to the injecting step.

39. The method of claim 35, and further comprising monitoring pressure in the mold cavity during the injecting step and responsively adjusting the injection pressure.

40. The method of claim 35, wherein the injection step is an adiabatic process.

41. A method for making a prototype plastic injection molded part, comprising the steps of:

providing a plastic mold tool defining a mold cavity;

providing a supply of two or more reactant materials which form a thermoset resin when reacted together;

mixing the reactant materials together;

injecting the reactant materials from an extruder into the mold cavity as a liquified ribbon of material, at a controlled pressure of less than 20 psi, so that the reactant materials fill the cavity;

heating the reactant materials in the mold cavity to form the molded prototype part; and

cooling the molded prototype part in the mold cavity.

42. The method of claim 41, further comprising building the plastic mold tool using a rapid prototyping technique based at least in part on computer data.

43. The method of claim 42, wherein the plastic mold tool is built in a fused deposition modeling machine.

44. The method of claim 41, wherein the injection step is an adiabatic process.