Overmolding: 2 types to know


MTD Micromolding

Some micro projects require specialty micro injection molding processes, such as overmolding. Overmolding involves two or more materials molded together to become one part. Examples include molding plastic over plastic or molding plastic over a preformed part, such as a metal insert. (See examples of common polymers and substrates below.)

MTD specializes in two types of overmolding:

  • insert molding overmolding

    Insert molding [Image from MTD Micromolding]

    Insert molding: Insert molding is injection molding a polymer around, over, under, or through a substrate material.
  • Multi-shot and multiple material molding: Injection molding multiple (two or more) materials around, over, under, or through a substrate material.

Benefits of MTD’s Overmolding Process

  • High part precision achieved by leading edge molding equipment, capable tooling, and robust validation procedures
  • Shot-to-shot consistency guaranteed by instrumented molds
  • Improved part functionality (i.e. creating a water-resistant seal)
  • Cost-effective high volume production achieved through robotics and automation
  • Ultra-precise positioning of overmolding tool inserts enabled by in-line camera systems
  • Avoidance of foreign materials such as glues and adhesives into the final medical device
  • Significant reduction or elimination of costly and cumbersome assembly operations that can lead to failure modes and high fall-out rates

The common polymers used for overmolding include: ABS, ACETAL, HDPE, LCP, PEI, PMMA, PC, PP, PPA, PPS, PS, PSU, TPE, TPU and PEEK.

multi-shot molding overmolding

Multi-shot molding [Image from MTD Micromolding]

Common substrates in micro overmolding include: Metal, plastic, tubing, fabric/mesh, delicate electronics, batteries, microfluidic chips, delicate assemblies and the biomaterials.

The opinions expressed in this blog post are the author’s only and do not necessarily reflect those of MedicalDesignandOutsourcing.com or its employees.

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