Female die facilitates the removal of a sheet metal structure from a die used for explosive forming of the metal. The female die consists of a smooth conical frustum made of fiber glass with a cured epoxy-resin surface on which a molded grid pattern made of a polyurethane resin is overlaid

Ruppe, E. P.

English

NASA Technical Reports Server

July 1966	 Brief 66-10334 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space 
program and to encourage their commercial application. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Strippable Grid Facilitates Removal of Grid-Surfaced Conical Workpiece from Die 
SHEET METAL WITH RAISED DIAMOND PATTERN 
The problem: 
To facilitate removal of a sheet metal structure from 
a die used for explosive forming of the structure. The 
completed structure is to be a one-piece, open-ended 
conical frustum with a raised diamond or square grid 
pattern on its exterior surface. An expensive die with 
at least five removable segments has been previously 
required to enable release of the explosive-formed 
structure from the die.
The solution: 
Use a female die consisting of a smooth conical 
frustum made of fiberglass with a cured epoxy resin 
surface on which a molded grid pattern made of a 
polyurethane resin is overlaid. 
How it's done: 
A smooth male plaster mold conforming to the di-
mensions of the desired conical frustum is prepared. 
Fiberglass cloth is then laid up on the mold and an 
(continued overleafl 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19660000333 2020-03-11T17:40:09+00:00Z
epoxy resin is cast over the fiberglass surface. After 
curing the epoxy resin, the plaster mold is slipped 
out, leaving a smooth surfaced female die which has 
the shape of the frustum. 
A grid mold is machined from flat metal plate with 
end mills to provide the grid design. Polyurethane 
resin is poured into the grid mold cavities and peeled 
out after curing. The cured grid lacings are then laid 
up on the smooth surfaced female die and the pre-
formed conical sheet metal workpiece is inserted over 
the grid lacings. The assembly is then subjected to 
explosive forming. After forming, the completed grid-
surfaced sheet metal structure with the adhering poly-
urethane grid lacings is easily removed from the 
smooth epoxy resin coated fiberglass die. The grid 
lacings can readily be peeled from the completed struc-
ture and used for additional explosive forming opera-
tions.
Note: 
Inquiries concerning this innovation may be di-
rected to:
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B66-10334 
Patent status: 
No patent action is contemplated by NASA. 
Source: Emil P. Ruppe 
of North American Aviation, Inc. 
under contract to 
Marshall Space Flight Center 
(M-FS-7l6) 
Brief 66-10334	 Category 05


Strippable grid facilitates removal of grid-surfaced conical workpiece from die

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