SPIN CASTING PROCESS

The spin casting method bridges the gap between conventional die casting and sand casting methods. Like sand casting, it offers the advantages of economical prototype and low volume production, short production lead time and low cost tooling. And like die casting, spin casting produces parts with close tolerances, smooth surfaces and excellent detail at relatively low cost per piece. After preparation, the mold is placed in a ring- shaped vulcanizing frame. This frame is placed in the electrically heated vulcanizing press for curing. Hydraulic force clamps the mold frame and shut between the heated platers, forcing the silicone into all crevices and around all details of the model/pattern. The heat crosslinks the uncured silicone. After vulcanization, the mold is easily flexed to release the pattern from the cavities.

Mold Preparation

Spin Casting Process

a. Vulcanization

• Different Materials Application

• Close Dimensional Tolerance

• Smooth Surface Finish

• Capability to Produce Intricate Designs

• Design Improvement Flexibility

• Capability of Low to High Volume Requirement

• Economical Process

b. Advantages of Spin Casting

Parts or model usually machined from metals are laid out on a disc of uncured silicone rubber which is soft and hand moldable like clay. The mold parting is formed at this stage and can be built up or lowered around any section of the model/pattern. Parts of any complexity can be handled. At this time, cores and pull-out sections can also be incorporated if required. Molding parting compound is sprayed on the mold and acorntype nuts are arranged around the edge to precisely position the mold halves to each other.

c. Gating and Venting

The gates, runner system and air vents are easily cut into the rubber with a sharp knife or scalpel. If the initial spin casting tests show a need for faster flow or more airventing, the ingates can be cut thicker and air vents may also be drilled into the cavity to aid in removing entrapped air or gases. Similar gating and venting systems are used for both metals and plastics, so both materials can be cast in exactly the same mold for evaluation, if desired.

d. Spinning

The mold is placed into the centrifugal casting machine. The mold is automatically entered and closing the door actuates a pneumatic mold clamp. Spin speed, clamping pressure and cycle time are fully adjusted with the solid state controls. Speed ranges from 100-900 rpm, depending on the size of the mold and the material being cast.

e. Pouring and Set-up

After the spin cycle starts, the liquid metal or plastics melted in a suitable electric or gas fired, crucible furnace is poured into the center sprue of the mold. Pressure caused by centrifugal force pushes the liquid through the mold runner system, completely filling every section, corner, detail and surface finish in each mold cavity.

f. Fettling

After metal solidifies and/or plastic sets-up, the parts are quickly removed from the mold. With metal, 50 to 60 cycles per hour can readily be made; with plastic, 10 to 15 cycles re typical. For clean-up, the gates, runners and vents are readily broken away by hand. Many parts are ready for assembly or use, or for painting, plating or casting, with no further clean-up, because spin casting is a precision casting process.