Composite Mould manufacturing

Project 3 sacrificial mold

Concept

• When a mold is made with a negative curvature, the lamina can not be removed.

• A lamina is shrinking when resin curing, this for small mold aspect ratio may lead to clamping of the lamina to the mold.

• The mold is removed from the lamina rather than other way around. Materials that mak such possible is wax, salts and some special metals.

Example: Winding tube

• If the mold is thicker in the center of the lamina than at the ends the lamina can not be removed from a ridig mold.

• Consider and mold for the mold such that the mold (core) is actually casted of some material. The resulting mold (core) is used in a winding process and as the lamina is cured ready removed from the lamina by melting/disolving it.

Material for sacrificial molds

• Lead, rose metal• Wax and wax on metal• Salt on metal

Semi expanding molds

• Silicon expands 8% at dT=100K. This can be used to simplify demolding

Design task

• Design a casting mold that is 30cm long, and at least 20mm in diameter at the smallest position.

• The mold contains at least ONE thicker section at the center of the mold that would make demolding imposibble

• The designed mold is to function such that a metal rod is placed inside the old and than casted out using wax or rose metal. After lamination (winding) the rod is heated such that the wax och rose metal melts and the rod can be removed from the lamina.