Transfer molding

A ram or plunger forces material from the pot into the heated mold cavity.

If feed-stock is initially solid, the forcing pressure and mold temperature melt it.

Standard mold features such as sprue channels, a flow gate and ejector pins may be used.

The process is versatile and can fabricate products with embedded objects such as foam cores or other components in addition to the fiber preform.

VARTM uses lower plunger forces which allows molding to be carried out with cheaper equipment.

[4] This temperature independence allows thicker fiber preforms and larger product geometries to be economical.

VARTM can produce parts with less porosity than regular transfer molding with a proportional increase in casting strength.

For example, voids in a transfer molded parts significantly reduce strength and modulus.

[8] Pressure distribution There are several contributing factors to voids in the final product of transfer molding.

This type of polymer is easy to mold and manipulate, but upon curing, hardens into a permanent form.

This is because a high viscosity plastic flowing through a thin mold may miss entire vacated areas, leaving air pockets.

Figure 1: Transfer Molding basic process
Figure 2: Resin Transfer Molding
  1. Cope
  2. Drag
  3. Clamp
  4. Mixing chamber
  5. Fiber preform
  6. Heated mold
  7. Resin
  8. Curative
Figure 3: Sharp corner generates voids in transfer molding