- 01: Introduction
- 02: History
- 03: Propellants, Firearms, and Ammunition Development
- 04: Modern Firearms Manufacture
- 05: Small Arms Ammunition
- 06: Evidence Handling Procedures
- 07: Equipment and Instrumentation
- 08: Examination of Firearms
- 09: Cartridge and Shotshell Examination
- 10: Characterization and Evaluation of Fired Projectiles
- 11: Bullet Comparison and Identification
- 12: Gunshot Residue and Distance Determination
- 13: Toolmark Identification
- 14: Communicating Results
- Resources
Investment Casting
Home > Modern Firearms Manufacture > Gross Metal Forming Operations > Investment Casting
A modern version of lost wax casting has allowed the use of stronger steel alloys as well as any cast-capable metal alloy. Investment casting (IC) has been a significant influence in firearms manufacturing for nearly fifty years. Like the lost wax process, IC relies on sacrificial wax forms from a master mold. Unlike its predecessor, IC can produce precision parts of high-strength alloys. This level of precision allows a significant reduction in postprocess machining needed to produce a finished part. Investment casting starts with precision wax forms that are more detailed than those used in sand casting.
Steps in the IC method are described below:
- Using a precision wax form, parts are attached to runners by applying a small amount of extra hot wax to the part and attaching it to a runner.
- After the proper number of parts are combined on a runner, the assembly is repeatedly dipped in a slurry of fine ceramic material. This progressively builds up a shell around the wax.
- As the layer thickens, fine sand may be included in the buildup to strengthen the shell. The ceramic is much finer than the sand and can reproduce delicate features on the master, such as lettering. The goal is to produce a ceramic and sand mold whose interior surface is very fine, supported by a more durable layer of sand.
- After the shell reaches the proper thickness, the assembly is heated just enough to melt the wax, which flows out.
- The ceramic mold is then heated in a furnace to burn off any residual wax and fuse the shell. The mold is now ready to receive a charge of molten metal.
- The mold is preheated to slow the cooling time and permit better dimensional control. Metal poured into a cold mold may chill too quickly and not properly fill out the details in the mold.
- After preheating and pouring, the filled mold is allowed to cool.
- The cooled mold is struck, vibrated, or water-blasted to break away the brittle shell.
- Metal parts joined by runners are cut away. The cast parts are now ready for postcasting processing.
Today, some of the world’s strongest and most durable firearms have critical components that are products of investment casting.
Click here to view an animation on investment casting
