Silicone Transfer Molding
Silicone Transfer Molding, also called Rubber Transfer Mold is one kind of rubber molded way, which belongs to rubber compression molding. Silicone Transfer Mold can be described as a simplified rubber injection mould, or a advanced compression mold. The production equipment is silicone rubber press (compression) machine, but not real injection machine.
Silicone Transfer Molding Design Guide is similar to rubber compression moulding, but there is a pot on the top plate and a ram above the pot. This mold pot is used to contain pre-measured rubber raw material and transfer it to the cavities throug pot runner and sprues.
Silicone Transfer Molding Main Advantage VS. Silicone Rubber Compression Molding
Silicone Transfer Molding is designed:
To manufacture relatively high precision silicone rubber molded parts & sealing gasket etc.
To overmolded with metal, plastic & glass parts etc.
To produce small-inner-diameter shaped silicone rubber products, like tubing, nozzles, valves, bellows, bushing & needle etc.
Silicone Transfer Molding Manufacturing Process
Raw material silicone rubber are measured and put into the pot. Then mold close. High pressure and temperature is applied to the mold and raw material will tranfer to cavities. After specific cycle time, trnasfer molding open and we remove the flash pad. Finally, take out the transfer molded rubber parts from cavities.
Silicone Transfer Molding for Rubber Diaphragm Advantages
Silicone Transfer Injection mold is adaptable to overmolding rubber parts production, composite rubber seal with metal, plastic inserts.
Why silicone transfer molding is good for rubber diaphragm with metal insert production?
In silicone diaphragm curing, metal pieces will not move easily because they are fixed in transfer mold cavities, and silicone raw material is in the pot. Due to the seperate material pot and cavities, material transfering start after mold close. Besides, rubber transfering will not affect the location of metal piece, but wrap the metal piece perfectly, as rubber is from runner and sprue flowing to molding cavity.
Different from compression molding, the raw material is placed in the compression mold cavities directly. When mold close, material flow to each cavity under high mold pressure. Flowing of silicone may cause mismatch of silicone diaphragm and metal insert.
Silicone Transfer Molding is a better choice for small rubber pipe production.
Small and slim mold cores are required for small pipe holes. These fragile mold cores damage easily, especially when raw material is put on these cores.
Silicone Transfer Molding cores mechanical life will be longer than compression mold cores as the raw material is not directly on the cores, but in the transfer mold pot.
Rubber Transfer Molding parts are more precise.
Silicone transfer injection molding allows for precise rubber seals production. Tolerance can be less than 0.05mm. Moreover, parting line is small.
Runers and sprues on rubber transfer mold pot can help transfer raw material evenly. Since transfer molding pot is seperated from cavities, and rubber can evenly run evenly from pot to every cavity, it reduces the variations of tolerance largely. So rubber transfer molded parts can stay consistent.
For rubber bellow or silicone sleeve with tight tolerance for wall thickness, transfer injection mold can be considered.
Silicone Transfer Inejction Molding contains more cavities compared with plastic / LSR injection molding.
Due to liquid silicone injection molding machine limit and mold design limit, liquid silicone injection mold plate is smaller than transfer molding plate. More cavities are available in transfer molding, which can increase production efficiency and reduce unit cost.
Silicone Tansfer Injection Molding generate less flash on finished rubber part.
In rubber injection molding curing, raw material feeding area is separted from tool cavity area. And feeding is after mold close. So it is not easy to generate flash around the part chambers.
Silicone Rubber Transfer Injection Molding Defects
Large amount of flash will occur in the pot after curing, which add more material cost to unit price.
Higher silicone transfer injection mold development cost.
Silicone Transfer Injection Molding is more complex than compression molding, so the mold investment is higher. But it is not more expensive than plastic or LSR injection molding.