Copyright 2017 - HITCHINER Manufacturing Co., Inc. · 594 Elm Street · Milford, NH 03055 · USA · IMAGINATION IN METALLURGY®

Understanding Investment Casting

The investment casting process is a complex, multi-step process. The basic steps illustrated below have been highly optimized and automated at Hitchiner Manufacturing Co., Inc.

Wax injection

Wax Injection

Wax replicas of the desired castings are produced by injection molding. these replicas are called patterns.

At Hitchiner® (right), complex multi-cavity dies are often used to cast ring segment patterns with several part replicas attached to a center ring.

Wax Injection

 

Assembly

Assembly

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

Hitchiner's® ring segment waxes are simply stacked to form the assembly. The ring is notched so that the optimum spacing is automatically achieved.

Assembly

 

Shell building

Shell

The shell is built by immersing the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand. up to eight layers may be applied in this manner.

At Hitchiner®, specialized shell building robots are used to build the shell. This automation provides for a consistent build and allows for larger molds than could be built by manual methods.

Shell

 

Dewax

Dewax

Once the ceramic is dry, the wax is melted out, creating a negative impression of the assembly within the shell.

Steam autoclaves are used for this purpose. At Hitchiner®, the wax is reclaimed, purified and recycled.

Dewax

 

Casting

Gravity casting

In the conventional process, used by most foundries, 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® uses its exclusive Countergravity Casting Services to cast the mold. In these processes, molten metal is siphoned up into the mold cavity in a controlled fashion, resulting in superior castings. The vacuum is released when the parts and a portion of the gates have solidified, allowing the molten metal in the central sprue to return to the melt.

Countergravity casting

 

Knockout

Knockout

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

After countergravity casting, the molds are discharged from the casting machine into a special hopper that separates the castings from the process materials. The castings are tumbled, stripping them of all shell remnants.

Knockout

 

Cut-off

Cutoff

Traditionally, the parts are cut away from the central sprue using a high speed friction saw.

Hitchiner's® countergravity-cast parts do not have a solidified central sprue and therefore do not require this operation. Only a small gate stub remains after casting which is easily removed by a mass production grinding operation.

Cutoff

 

Finished Castings

Finished casting

After minor finishing operations, the metal castings—identical to the original wax patterns—are complete.

Hitchiner Manufacturig Co., Inc. has the capacity and experience to offer complete-to-print machining and subassembly operations, delivering a finished component ready for installation in the finished product.

Finished casting