Application Review: Spray Metal Tooling

Process:
Spray Metal Molds

Applicable Industries:
Aerospace, Computer, Toys, Consumer Products, Packaging, Sports Equipment & Automotive

Types of Masters Used:
Rapid Prototypes
Machined or Fabricated Masters
Urethane Reproductions
Wax Sculptings
Types and Quantities of Parts Made:
Polyurethane 300 to 20,000
Polyurea 300 to 20,000
Epoxy 100 to 600
Investment Wax Patterns 500 to 10,000
Low Melt Metal Alloys 100 to 1,500
Polyurethane Foam 2,000 to 20,000
Silicone Rubber 10,000+
Injection Molding 10 to 1,000
Rim Molding 1,000 to 15,000
Blow Molding 300 to 500
Vacuum Forming 5,000 to 100,000

Procedure:
Model preparation is the first and one of the most important steps in this process. Depending on the finish of the model, it should be sanded smooth because all surface imperfections become apparent in the sprayed shell. Typically, the master, (SLA, LOM etc...) must be hand finished to the desired quality before the mold is made. In most cases a silicone mold and urethane reproduction are made for the tooling master because chances are this master will be destroyed.

The parting lines are established with clay or parting boards. Slides and loose pieces can be made in a similar manner to prototype injection molds and installed prior to spraying the surface. An aluminum or steel frame is fabricated to absorb the pressures of molding and to allow the completed mold to be installed in the molding equipment. These materials will absorb most of the compression produced by the machine.

At this time the metal surface is sprayed on. After the metal surface is applied, water lines and any additional supports can be added. Next a high strength aluminum filled epoxy is poured in to back fill the mold. This epoxy is similar to the material used for the epoxy molds.

Another technique is to back fill the mold with a low melt metal alloy. This material has excellent heat transfer and can sustain more compression than the epoxy.

The same process is applied to the other side of the mold. The mold is post cured, secondarily machined and put in to service. These molds can also be plated to increase tooling strength.

The Rapid Prototype model is an ideal starting point to produce spray metal tooling. The longevity of the tool is process dependent. Low pressure operations such as casting, blow molding or rim will yield more parts than the higher pressure applications. Turnaround time for producing a sprayed tool from Rapid Prototype Pattern is between ten days to three weeks depending on complexity of the tool.