Making silicone rubber products is a careful balance between making something of quality or making something efficiently. For many in the industry, the processes of choice are either injection moulding or transfer moulding.
We’ve made a simple guide on these two processes, comparing their key features and benefits, and highlighting which is better for your product.
How does transfer moulding work?
Transfer moulding pushes material into a mould through a sprue, but uses a plunger instead of a screw injector. This process makes it the leading way for coating electronic components in plastic or rubber, and makes it important for several different industries. It is mostly used by the electrical industry, to make wires, or the hydraulic industry to make sharp lip seals.
This process has a few unique advantages over rubber injection moulding. It’s fast and cheap to set up, has lower maintenance costs, and allows for greater definition in moulding. However, it does generate much more waste and is much slower. It can lead to defects, such as warping and ejector marks.
Wondering how does rubber injection moulding work?
Injection moulding is the more common process for plastic and rubber parts. First patented way back in 1872, in this process, material is fed into a heated barrel and forced through a sprue into the mould cavity using a reciprocating screw. This process produces thin-walled plastic parts, most commonly in 3D shapes, and is often used to make household products, power tools, and plastic toys.
This process is very fast and creates minimal waste, and rubber injection moulding machines have a higher capacity, meaning they can create more goods per production cycle. However, it creates thin uniform walls, only creates units with rounded corners, and the machines cost far more to set up. It can lead to defects such as bubbles and warping.
Which is better?
The injection moulding machine is significantly more expensive than a transfer mould machine, but both will require a machinist to build the initial moulds. A transfer mould machine takes more time to set up, and an injection moulding machine involves high long-term maintenance costs. They can create similar defects and similar running costs.
Ultimately, injection moulding is better suited to higher quantities of larger, thin-walled parts, while transfer moulding is preferable for encasements and simpler moulds.