From Metal to Plastic, Silicone to TPE: Cut Cost, Enhance Performance

Learn how Enplas’s engineering and manufacturing expertise helped a major pharmaceutical OEM convert a test instrument component from metal and silicone to rigid plastic and TPE, enhancing the component’s functionality and usability, and reducing overall manufacturing cost.


Enplas was approached by a global pharmaceutical OEM to manufacture a four-channel pipette air displacement device it used in biotech test instruments. The device consisted of a brass body, four stainless steel tubes, and four silicone molded seals. The goal was to redesign this whole assembly into a single plastic part.

The final single plastic part consisted of overmolded TPE seals and a plastic substrate. This redesign enhanced the device’s functionality and usability while significantly reducing its overall manufacturing cost. The project combined two of Enplas’s strengths: expertise in manufacturing thermoplastic fluid seals and a long history of helping customers convert metal parts to plastic.

Metal to Plastics Conversion



The goals of the redesign were:

  • To reduce the cost of the device’s materials
  • To eliminate the need for assembly and reduce the number of fixtures used in the assembly
  • To eliminate the risk of damage from sub-assembly (i.e., components damaging each other during assembly)
  • To eliminate recurring maintenance issues in normal operation (e.g., sub-assembled components loosening slightly)


The redesigned device needed to maintain the same precise dimensions of the original. In addition, the device’s elastomer seals need to be consistently air-tight against its inlet ports and maintain a product life of at least 1,000 cycles of pressurization.


Enplas began this project by understanding the original device’s performance requirements and assembly consideration with surrounding components. This enabled Enplas to recommend the best materials to use (both elastomer and rigid plastics) to meet the client’s goals. To ensure reliable sealing, material considerations included hardness, compression set, and chemical bonding characteristics.

Enplas also analyzed the physical design of the elastomer fluid seal to ensure secure contact with the consumable. The size and shape of the device’s contact surfaces is critical to ensure its air-tight sealing performance when pressurized against inlet ports.

The practice of Design-for-Manufacturability (DFM) was adhered to throughout the project to ensure the consistent and efficient production of quality parts for both injection molding and assembly with other components.

Finally, Enplas provided quality manufacturing services for the redesigned device, which included injection molding the rigid plastics and overmolding the TPE seals. All manufacturing at Enplas Life Tech undergoes our rigorous process validation practice to ensure quality and consistency.


Enplas successfully manufactured the redesigned component and exceeded the original device’s performance in several critical areas:

  • The device’s separate metal parts were replaced with a single component made of injection-molded plastic substrate. The device’s silicone seals were replaced with overmolded thermoplastic elastomer (TPE) seals. This resulted in over 70% cost savings due to lower material cost and elimination of manual assembly.
  • The device was required to perform up to at least 1,000 cycles. The redesigned device achieved over 7,000 cycles during endurance and functional tests without leaking.
  • Sub-assembly damage has been eliminated.
  • The new device exhibits no quality or maintenance issues during manufacture or operation. Recurring maintenance issues in normal operation have been eliminated.

For product conversions or enhancement projects, it is important to engage an expert manufacturer with a reliable engineering team that can recommend the best materials and manufacturable designs to achieve your performance goals, ensure reliable quality, and maximize manufacturing efficiency to reduce costs. Contact Enplas early in your design process to allow necessary modification to achieve best results like the above. Contact us now for your next project!

To learn more about whether silicone or thermoplastic elastomers (TPE) might work better for your project, download our comparison sheet.