Liquid Injection Molding (LIM) is a method in which liquid silicone rubber (LSR) is injected under pressures into a heated mould, filling the cavity entirely before hardening into a solid object that is then expelled from the mould. Compression mold silicon products Apart from the feature that LSR is a thermoset polymer, this procedure is nearly comparable to injection molding of polyester.
This implies that the mould must be heated (rather than chilled, as with thermoplastic polymers) so that the silicone is permanently cured in a process known as vulcanization. The component will not dissolve back into a liquid state once it has been cured. This temperature zone reversal also implies that LIM uses “cold decking” rather than “hot tracks” to save material and minimise development cycles.
Shaping by transfer
Transfer molding is a procedure that is similar to injection molding in many ways, including the use of a heated mould cavity, sprue passages, and an external actuator that forces the melted metal into a mold. In transference molding, the material to be moulded is placed in an open container (called the pot) (which can start as either a solid or liquid). The substance is then pushed and squeezed into the mould, which is attached to the pot through channels.
To fill the mould, transfer molding often employs higher pressures than injection molding. Another distinction is that, unlike LIM and plastic injection molding, the mould casting materials may start the process as a solidified.
Casting by compression
Compression molding would ensue if the pot in the transfer molding process was removed and the upper half of the heated mould replaced the plunger. In contrast to injection molding and transfer molding, which both force the moulded material into the cavity, compression molding presses the heated cavity onto the material.
The molding material in transfer molding and LIM is thermoset elastomers such as silicone. The mould provides heat for synthetic rubber, and the material is frequently preheated as well. When compared to other processes, compression molding excels in manufacturing big components at a cheap cost and with less waste in high-volume production
Parts produced by the three molding procedures discussed above do not have to be constructed entirely of a single material. A composite object with a plastic or silicone covering moulded over part or all of a different material is typically highly desired. One example of such over molding is silicone grasping regions on steel surgical tools.
Over molded items are often made in two (or more) steps, with each layer requiring a distinct molding process. Given that not all combinations of rubber compounds, thermosetting, and metals are conceivable, OEMs must carefully evaluate the material compatibility of the materials they seek to mix. Overall, there are minimal impediments, with the ingenuity of the OEM’s design team serving as the limiting constraint.
RTV casting, a low-cost method of producing tiny volumes of components, replicates characteristic properties and other fine characteristics. Additionally, because silicones have excellent heat and chemical stability, RTV moulds may be used to cast low melting point metals, epoxy resins, beeswax, and limestone without the use of a mould release agent.