From surgical instrument handles and catheters, to drug-eluting implants and stents, medical manufacturing companies employ a variety of techniques to produce medical devices and components used in the healthcare sector. The following provides an overview of the transfer molding process as well as the materials medical manufacturing companies typically utilize with this method.

What is Transfer Molding?

Transfer molding is a proven processing method that has been used by medical manufacturing companies for a long time. This technique produces high quality silicone molded products including parts with complex geometries and intricate features. This method is similar to injection molding and employs many of the same elements: a heated mold cavity, sprue channels, and an external actuator that pushes the molten material into the mold. In transfer molding, an open chamber called the pot is filled with the material to be molded. Then, a plunger pushes on this material and squeezes it into the mold, which is connected to the pot via channels. As the name implies, this method of manufacturing “transfers” material from the exterior of a mold through the sprue and runner system into the cavities of the mold.

While transfer molding and injection molding have some similarities, there are some key differences. Transfer molding typically uses higher pressures than injection molding to ensure the mold is adequately filled. Additionally, the material used in transfer molding may begin the process as a solid or liquid, in contrast to injection molding that utilizes only liquids.

Transfer molding may also be combined with overmolding or insert molding to manufacture the desired final part. These techniques can be used together to create a composite product which has a plastic or silicone layer molded over some or all of a different material. Both overmolding and insert molding are great for joining parts to moldable materials without using adhesives or mechanical fasteners.

Looking for a medical manufacturing partner that offers a wide range of silicone molding solutions?

Contact the team at ProMed to learn more about our capabilities and the various silicone molding techniques we employ.

What Materials are the Best Fit for Transfer Molding?

Medical manufacturing companies have long relied on silicone for molding processes. Silicone elastomers are a good fit for medical manufacturing due to their durability, ease of molding by many methods, wide temperature range, chemical inertness, high tensile strength, vast range of available durometers, low toxicity, and compatibility with many sterilization methods. Silicone has unique material characteristics that enable parts to be molded with intricate features, undercuts, finishes, and tight tolerances. At ProMed, we specialize in silicones for medical manufacturing and offer custom compounding to meet the performance requirements of your design. From concept to existing production, whether your part is simple or complex, our highly qualified technology staff guide you through the project.

Silicone raw materials for medical manufacturing are available in two main forms: Liquid Silicone Rubber (LSR) and High Consistency Rubber (HCR). When it comes to silicone injection molding, LSR is typically the silicone of choice. Due to its higher viscosity and more challenging handling properties, HCR is typically processed using transfer or compression molding methods. Additionally, transfer molding can be used for any volume of production but is often most cost-effective for low to medium size runs.

About ProMed

ProMed was founded in 1989 to address an industry need for cleanroom manufacturing of silicone components, specifically those having a medical application. We have garnered a reputation as the world benchmark of implantable silicone components and assemblies – and are one of few companies in the world to provide contract manufacturing of drug-eluting products.

ProMed has expertise in working with the full spectrum of silicones covering a wide range of properties and characteristics. We will assist in your material selection to help ensure all design requirements are met. Our manufacturing facilities and equipment are designed for a single purpose—to mold medical and implantable silicone, combination components, and bio-material grade plastics with uncompromising quality and service. We currently have four divisions that are located within two manufacturing sites. All are certified class 10,000 / ISO Class 7 cleanrooms.

We can identify the right manufacturing solution for any project. We have extensive experience in a wide range of injection molding techniques including:

  • Automated Injection Molding
  • Multi-cavity tooling
  • Micro molds and micro molding
  • Servo-controlled de-molding capabilities
  • Insert molds, overmolds, and automation integration
  • Transfer molding
  • Compression molding

Contact ProMed today at 763-331-3800 to discuss how we can help with your next project!

Transfer Molding 101
Article Name
Transfer Molding 101
Transfer molding is a versatile silicone molding technique that is typically used with high consistency rubber, HCR, to deliver high quality products.
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ProMed Molding
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