Coating soluble tooling inserts

Patent metadata

Field	Value
Publication number	US-10538019-B2
Application number	US-201514720071-A
Country	US
Kind code	B2
Filing date	May 22, 2015
Priority date	May 22, 2015
Publication date	Jan 21, 2020
Grant date	Jan 21, 2020

Abstract

The surface of a tooling insert is coated with a polymer layer having a low surface energy in order to cover surface irregularities and thereby provide a smooth surface against which a composite part may be compression molded.

First claim

What is claimed is:

1. A method of forming a thermoplastic composite aerospace part having a smooth surface on a tooling insert having surface irregularities, comprising:
forming a polyamic acid solution;
applying the polyamic acid solution to a surface of the tooling insert;
forming a polyimide coating on a surface of the tooling insert by heating the tooling insert;
forming the thermoplastic composite aerospace part around the tooling insert;
removing the tooling insert from the aerospace part by dissolving the tooling insert; and
removing the polyimide coating from the aerospace part, after the tooling insert has fully dissolved.

2. The method of claim 1 , wherein the polyimide has low surface energy relative to the thermoplastic composite part.

3. The method of claim 1 , wherein forming the polyamic acid solution includes introducing at least two monomers into a solvent in predetermined proportions.

4. The method of claim 3 , wherein coating the surface of the tooling insert further includes removing the solvent from the coating by drying.

5. The method of claim 1 , wherein forming the polyamic acid solution includes combining at least two monomers in a predetermined order to achieve a desired concentration of the polymer in the solution.

6. The method of claim 5 , wherein combining the at least two monomers include combining at least dianhydride and diamine.

7. The method of claim 1 , wherein applying the polyamic acid solution is performed by one of:
dipping the tooling insert in the solution,
spraying the solution onto the surface of the tooling insert;
brushing the solution onto the surface of the tooling insert; and
rolling the solution onto the surface of the tooling insert.

8. The method of claim 1 , wherein forming the polyamic acid solution is performed using monomers.

9. The method of claim 1 , wherein applying the polyamic acid solution to the surface of the tooling insert is repeated until the coating has a desired thickness.

10. A method of compression molding a fiber reinforced plastic aerospace part, comprising:
coating a surface of at least one soluble tooling insert with a polyamic acid solution;
placing the at least one soluble tooling insert inside a mold tool;
introducing plastic into the mold tool;
applying heat and pressure to the plastic within the mold tool;
removing the soluble tooling insert from the mold tool by dissolving the soluble tooling insert;
removing a polyimide coating formed from the polyamic acid solution after the soluble tooling insert has completely dissolved; and
removing a molded aerospace part from the mold tool.

11. The method of claim 10 , wherein the soluble tooling insert is formed of an inorganic material, and coating the surface of the tooling insert includes:
preparing a solution of polyamic acid in a solvent; and
applying the solution to the surface of the soluble tooling insert.

12. The method of claim 11 , wherein applying the solution to the surface of the soluble tooling insert is performed by one of:
dipping the soluble tooling insert in the solution;
spraying the solution onto the surface of the soluble tooling insert;
brushing the solution onto the surface of the soluble tooling insert; and
rolling the solution onto the surface of the soluble tooling insert.

13. The method of claim 11 , further comprising:
forming the coating by removing the solvent from the solution, including drying the solution after applying the solution to the surface of the soluble tooling insert; and
adhering the coating to the surface of the soluble tooling insert.

14. The method of claim 13 , wherein adhering the coating includes heating the soluble tooling insert.

15. The method of claim 14 , wherein heating the soluble tooling insert is performed before placing the soluble tooling insert into the mold tool.

16. The method of claim 14 , wherein heating the soluble tooling insert is performed after the tooling insert is inserted into the mold tool, and includes heating the mold tool.

17. The method of claim 13 , wherein the soluble tooling insert is water soluble, and the method further comprises:
wherein removing the soluble tooling insert from the mold tool includes dissolving the soluble tooling insert with water.

18. A method of making a thermoplastic composite aerospace part having an aerodynamic finish, comprising:
forming a water-soluble inorganic tooling insert having surface irregularities;
coating the tooling insert with a polyamic acid solution that covers the surface irregularities;
forming a smooth outer finish on the tooling insert by evaporating a solvent from the polyamic acid solution;
molding the aerospace part on the tooling insert, including heating a thermoplastic mold charge to a melt temperature of the thermoplastic mold charge;
removing the tooling insert from the aerospace part by dissolving the tooling insert; and
removing a polyimide coating formed from the polyamic acid solution from the aerospace part, after the tooling insert has fully dissolved.

19. The method of claim 18 , wherein heating the thermoplastic mold charge includes heating the thermoplastic mold charge to a temperature of approximately 725° F.

20. The method of claim 18 , further comprising forming the polyamic acid solution, including introducing at least two monomers into a solvent in predetermined proportions.

21. The method of claim 20 , wherein forming the polyamic acid solution includes combining at least two monomers in a predetermined order to achieve a desired concentration of the polymer in the solution.

22. The method of claim 21 , wherein combining the at least two monomers include combining at least dianhydride and diamine.

23. The method of claim 18 , wherein coating the tooling insert with the polyamic acid solution is performed by one of:
dipping the tooling insert in the solution,
spraying the solution onto the surface of the tooling insert;
brushing the solution onto the surface of the tooling insert; and
rolling the solution onto the surface of the tooling insert.

24. The method of claim 18 , wherein applying the polyamic acid solution to the surface of the tooling insert is repeated until the coating has a desired thickness.

Assignees

• Boeing Co

Inventors

• Gaw Kevin O'Brien
• Larson Michael Harris

Classifications

• B29C2043/3668

  destructible or fusible · CPC title

• B29K2879/08

  PI, i.e. polyimides or derivatives thereof · CPC title

• B29C43/02

  of articles of definite length, i.e. discrete articles {(B29C35/0227 takes precedence)} · CPC title

• C09D179/08

  Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors · CPC title

• B29L2023/22

  Tubes or pipes, i.e. rigid (bent tubes not for use as pipe couplings B29L2023/004) · CPC title