Silicone Injection Molding Tooling and Processing ???

[plasticsguru]

I know that there are IM grades of Silicone. As I understand the process it uses no heat in the barrel and all the heat is in the mold. Is this correct?

The part will need to withstand a upper use temp of 400F is this the temp of the mold to use?

The part is 5 grams If I use a 4 cavity tool what would the expected cycle time be?

Are Silicone IM tools more expensive to produce than a Thermoplastic tool lets say for Polyethylene? Same shape and size of part.

Thanks

 

[rk12]

liquid silicone for injection molding is a thermoset material. material crosslinks(cures) by addition of heat to mold. the injection press barrel and nozzle are water cooled to reduce material crosslinking due to material shear heating. mold heating is typically 250F to 400F depending on part design and mold layout.

depending on part design and demolding cure times for this would typically be 20 to 40 seconds w/ a mold clamp to clamp cycle time of 35 to 90 seconds dependant on automation.

LSR injection tooling is slightely more costly than simple thermoplastic tooling because the LSR is an extreme shear thinning material, mold must be tight and flat, vents typically .0002 inch deep, gates .002 deep.