To ensure the lowest cost and high performance, rubber molded products manaufacturer Qualiform, works with it’s customers to determine the best method of rubber to metal bonding.
Utilizing injection molding and transfer molding to encapsulate and bond rubber to metal is the most effective way to adhere rubber to metal or plastic parts. Furthermore, the rubber to metal molding process provides a superior mechanical bond of rubber to metal parts, inserts or plastic parts.
Two Step Process
The process requires a two-step preparation of the metal or plastic part prior to molding the rubber. First, we degrease and clean off any contaminants, similar to preparation for industrial coatings or painting. Once we finish cleaning, we spray a special, heat-activated adhesive onto the metal parts.
Once the part is ready for rubber overmolding, the metal parts are inserted into the mold cavity. If molding a specific area, the metal part is held in place by special magnets. If the part is to be completely encapsulated with rubber, the part is held in place with chaplet pins. The mold is then closed and the rubber molding process begins. As the elevated molding temperature cures the rubber, it also activates the adhesive forming a mechanical bonding of rubber to metal or bonding rubber to plastic.
The Rubber Compression Molding Process
The rubber compression molding process uses a preformed piece of uncured rubber that is placed in an open mold cavity. The mold is preheated to an elevated temperature. As the mold closes in the press, the material is compressed and flows to fill the rubber mold cavity.
The combination of elevated temperatures and high-pressure activates the vulcanization process and curing of the rubber compound. Once an optimal cure is reached, the part hardens and cools then the mold is opened and final part removed. The next rubber preform is inserted into the mold and the cycle repeats.
The basic compression mold is usually a two-piece construction consisting of a top and bottom plate. Half of the part cavity is usually cut into each plate of the mold. A trim area is created by grooves cut around each cavity which allows the excess rubber to flow out of the cavity. Compression molds are typically secured between heated press platens. The molded parts require trimming to remove the groove overflow. An additional bake cycle may be required for partially cured parts.