Product Craft: Investment casting (Colloidal silica shell mould)

1 WAX INJECTION

Wax mold of the desired castings are produced by injection molding. These replicas are called investment patterns.

2 ASSEMBLY

The patterns are attached to a central wax stick, called a sprue, to form a casting cluster or assembly.

3 SHELL BUILDING

The shell is built by immersing the assembly in a liquid ceramic slurry and then into a bed of extermely fine sand, the binder is the colloidal silica. Up to six layers may be applied in this manner.

4 DEWAX

Once the shell is dry, the wax is melted out, creating a negative impression of the assermbly with in the shell.

5 CONVENTIONAL CASTING

In the conventional process, the shell is filled with molten metal by gravity pouring. As the metal cools, the parts and gates, sprue and pouring cup become one solid casting. (Hitchiner prefers to use its superior casting technology.)

6 KNOCKOUT

When the metal has cooled and solidified, the ceramic shell is broken off by vibration or water blasting.

7 CUT OFF AND PART CLEANING

The parts are cut a way from the central sprue using a high speed friction saw. Then the parts are going to be cleaned by Acid Pickling.

8 FINISHED CASTINGS

After minor finishing operations, first inspection, heat treatment, part blasting, dimensional inspection, final Inspection, the metal castings- identical to the original wax patterns- are ready for shipment to the customer.