We at Elastomer Technologies Inc. (ETI) know that if you can’t measure it, you can’t manage it. This certainly holds true for manufacturing and producing parts, especially with regard to the cycle time for each unit. Reducing the amount of time from the beginning to the end of the manufacturing process allows greater process efficiency which improves throughput and delivery and reduces stress for our customers.
For some projects, transfer molding and/or compression molding offers a reliable and cost-effective way to reduce your cycle times. Below, we’ve outlined some of the most effective ways to incorporate transfer molding into your production process.
The Transfer Molding Process
Transfer molding generally operates by transferring a predetermined amount of a heated polymer substance, or charge, into a heated mold designed for the desired end goal. Workers then cool the mold and subsequently release and use the molded part as needed.
To begin, workers place a piece of uncured catalyzed rubber into a portion of the mold, although not the portion carrying the needed shape for the final product. They then close the mold and force the rubber through a small hole into the mold’s cavity, which is shaped in the form of the desired end product, using hydraulic pressure. The molding press holds the mold closed while the rubber cures. This process time varies in relation to how quickly the material in the mold cures—often, only a few minutes.
After this, workers open the mold, and the plunger used to inject the material, remove the transfer pad material and release the fashioned, solidified part from the mold cavity. They often trim any flash, and other excess material from the end piece at the molding press during the next molding cycle.
Advantages of Transfer Molding
Producing parts via transfer molding comes with many advantages, including:
• Fast setup time. This is especially the case when using a large number of molds or mold cavities. Generally speaking, molded rubber products require only a few simple pre-forms for the mold cavities.
• Low maintenance cost.
• Ability to make rubber parts with metal inserts. In certain transfer molding processes, workers can alternate layers of the heated rubber with metal or other material, creating specialized inserts.
• Design flexibility. Customers can design parts for this process to incorporate many complex features.
• Custom blends of materials are available.
• Dimensional stability.
• Uniform part thickness.
• Large production rate.
Drawbacks to Transfer Molding
However, some considerations must be taken into account before embarking on a transfer molding production run:
• Material use. The transfer pad and sprues, which are channels through which uncured rubber or other charges get transferred to the mold cavity, are removed and discarded in order to complete the process. This material cannot be re-used.
• Competition with injection molding. For a higher up-front cost, injection molding can usually produce a faster cycle than transfer molding, rendering it more suitable for some applications than transfer molding.
• Movement of the material in the mold can be complicated by some part designs that create defects in the finalized product.
• Transfer molding is a labor intensive process and therefore can be costly for parts.
Transfer molding works with a wide range of viable materials, including:
• Conductive rubber material
• FKM and other fluorocarbon rubbers.
• Nitrile rubber
• Custom rubber compounds.
• Kevlar fibers
• Organic fibers
Transfer molding offers varied and manifold applications. For instance:
• Natural gas industry workers implement metal-to-rubber face seals to create gas valve interfaces
• Medical components such as syringe tips, grommets, tool holders, and parts for complex machinery used in surgery or life support.
• Transfer molding allows manufacturers to encapsulate items such as integrated circuits, plugs, connectors, pins, coils, and studs
• In addition to metal inserts, transfer molding can also create materials with electronics, ceramic or other inserts.
Transfer molding allows the manufacture of items as diverse as wind turbine blades, helmets, and bathroom fixtures. Manufacturers also use transfer molding to make radio and television cabinets as well as car body shells. Transfer molding simplifies the production of a vast number of products.
Transfer Molding at ETI
Transfer molding efficiently creates a wide variety of lightweight and durable rubber products. If you would like to learn more about our transfer and compression molding services, contact us at Elastomer Technologies, Inc. Our breadth of professional expertise will leverage transfer molding to your company’s advantage.