Rubber Molding FAQ

Can you inject molded rubber?

Yes, you can injection mold rubber in many ways. See custom molding types.

What is the difference between injection molding and compression molding?

Injection molding is the process where rubber material is heated. Once heated, it is injected into a mold cavity and is useful for complex shapes. The compression molding process utilizes rubber preforms that are inserted into a mold cavity. After that, it is molded under hydraulic pressure.

How is rubber molded?

Rubber is molded by forcing a block of rubber into a metal cavity. The rubber is exposed to heat, activating a chemical reaction.

What is injection molding process?

This very automated process is commonly used for simple designs that have a high quantity required for production. The rubber compound is heated to such a degree that it can flow with ease through a number of runners into the mold, after being injected under pressure from its heating chamber. This process can be ideal, but for just the right compound and the right application.

What is compression molding used for?

Compression molding is a process used for thermoset shaped materials. So virtually any item that uses these materials can be manufactured. This includes grommets, plugs, mounts, bumpers and much more.

What is mold shrinkage?

Mold shrinkage is the where the volume of the molten rubber filled inside the cavity of the mold is being shrunk at the time it isas being cooled/solidified. The reason for this shrinkage is thermal contraction which is measured by the thermal expansion coefficient of the material.

What are the different types of molding process? How many types of molding are there?

Typicaly, 4 main ones: compression, injection, liquid and transfer.

What is compression molding process?

This process is typically used when an application calls for high quantities in production runs, medium shore in durometer or hardness, or if the material call-out is one that requires less common, but more expensive materials. An excess of your chosen material is placed into the cavity of the mold to guarantee total cavity fill. Heat and pressure are applied, which causes the rubber compound to flow and fill the cavity, with any overflow going through the overflow grooves. This overflow, or flash, can be a concern when the parts are of critical dimension, larger diameter or of a more expensive variety of a rubber compound. Compression molding reduces the amount of flash created in the molding process. Further reduction of this flash on your custom molded part is done in the deflashing process for any type of molding you may choose. Depending on your parts specifications, this deflashing is done either by tear trimming, tumbling, grinding or cryogenic deflashing.

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