Overmolding service

Manufacture parts with multi-shot thermoplastic injections for enhanced consistency, strength, and durability in high volume projects.

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Overmolding service

What is overmolding?

Overmolding is an injection molding process in which multiple shots of thermoplastic are injected separately to create a single part. The first thermoplastic injection into a tool or cavity forms a substrate, before an overmolding material is injected into, onto, or around it. The thermoplastic layers bond as they cool to produce a unified and highly durable final product. The bond between substrates depends on the properties of the relevant overmolding materials. Learn more about the bonding process with our material compatibility chart.

Overmolding is ideal for high-volume production runs. Kickstarting your injection molding project is simple. Upload your CAD file to the Fast Radius Cloud Manufacturing Platform™, optimize your design and choose your desired thermoplastic, and then greenlight production with the click of a button.

For more on-demand manufacturing options, browse our injection molding capabilities, including our insert molding and multi-cavity/family molding services.

Design considerations

Unlock the potential of your overmolding project with the following injection molding design considerations, including tooling details, available materials and colors, and finishing and post-processing options.

Overmolding general process information
Substrate wall thicknessThe thickness of the substrate’s wall determines how effectively the overmold material flows in, on, and
around the substrate. Due to temperature differences between substrate and overmold materials, having
an inconsistent wall thickness can lead to warping, increase flash, and render fills incomplete.
Ensure that the wall thickness of the substrate and thickness of the overmold are even and consistent
from the beginning of the process. Wall thicknesses ranging from 0.060″ to 0.120” (1.5 mm-3 mm) will
ensure good bonding in most overmolding applications.
Maximum part size​800 x 800 x 400 mm
31.5 x 31.5 x 15.7 in
Minimum part size1 x 1 x 1 mm
0.04 x 0.04 x 0.04 in
ToleranceBest achievable tolerance: ±0.001″ (0.025mm)
Standard: ±0.005″ (0.127mm)
For larger part tolerances please contact a Fast Radius engineer
Lead timeAs low as 2 weeks for T1 samples
After T1 sample approval, lead time for < 10,000 parts is as low as 1 week
Tool validationStandard process is to produce a small set of T1 samples for approval before initiating full production
Maximum press size1600T
Minimum order size100 parts and $5000
Set-up fee$500 per mold per order (applies to sample runs after initial T1 samples or engineering changes)
Overmolding tooling information
Rapid toolingMolds with steel cavity and core with a shot life of 5,000-10,000 shots
Typically machined in 2 weeks
Production toolingSteel tool with shot life up to 1M shots
Ability to integrate side-pulls or cam-actions
Typically machined in 3 weeks
Multi-cavity or family moldsMultiple identical cavities or family of parts machined into a single tool
Allows for more parts to be produced per shot, minimizing unit costs
OvermoldsPremade parts are placed into the mold and molded over
Allows for multi-material injection molding
Overmolding materials
Most common materialsOther supported materialsAdditives and fiber
Acrylonitrile Butadiene Styrene (ABS)Nylon (PA 6, PA66, PA 12)UV absorbers
Polyethylene (PE)Polycarbonate/Acrylonitrile Butadiene Styrene
Flame retardants
Polypropylene (PP)Polyurethane (PU)Plasticizers
Polycarbonate (PC)Polymethyl Methacrylate (PMMA/Acrylic)Colorants
High Density Polyethylene (HDPE)Glass fibers
Low Density Polyethylene (LDPE)
Polystyrene (PS)
Polyvinyl chloride (PVC)
POM (Acetal/Delrin)
Polyethylene Terephthalate (PET)
Thermoplastic Elastomer (TPE)
Thermoplastic Vulcanizate (TPV)
Polyetherimide (PEI)
Polysulfone (PSU)
Inquire for additional options
Overmolding colors, finishing, post-processing
ColorsFinishing and post-processing options
Pantone color matchingStandard SPI finishes (A2-D3)
RAL color matchingMold-tech textures also available
Pad printing
Inserts (e.g. heat stake inserts)
Light assembly
Protective packaging / film

Get an instant quote for your overmolding project

Use our quoting platform for quick quotes on injection molded parts.

Why choose overmolding?

Overmolding produces strong, long-lasting parts for improved component reliability.
Explore the key benefits and challenges of the process:

  • Strong, durable parts
  • High consistency and precision
  • Customization potential
  • Cosmetic finishing options
  • Create safe, comfortable parts for customer end-use
Cross icon Challenges
  • Requirement to check compatibility between thermoplastic materials
  • Precision set-up required to prevent fractures.
  • Requires 2 mold cavities to produce the substrate and the overmold
  • Upfront design and tooling costs

Overmolding applications

Overmolding is used to produce customized parts and components for a variety of applications:

Niche manufacturing

The overmolding process is useful for the manufacture of niche, durable parts, including gaskets, filters, and brackets. Overmolding is also suitable for functional prototyping.

High-volume production

Overmolding produces consistent parts quickly with low tooling costs, and is ideal for projects with high volume production requirements.

Medical devices

The overmolding process is capable of creating specialized parts with complex dimensions, making it particularly useful for manufacturing medical devices and instruments, and high-end consumer-grade products.

Ergonomic features

Overmolding offers a range of customisation and finishing options, and can be used to add grips, buttons, knobs, and other ergonomic features to pre-existing parts while minimizing additional labour.

Fast Radius manufacturing solutions

Fast Radius manufacturing solutions, including overmolding, are used by businesses across the world. Learn more about our manufacturing capabilities:

3D printing

Fast, scalable, and cost-effective 3D printing technology for a variety of industrial applications.

CNC machining

Precision computer-controlled machining processes, utilizing rotating drills, end mills, and lathes.

Injection molding

Cost-effective plastic injection molding for precision, high-volume production runs.

Urethane casting

Versatile mold-casting for the production of urethane parts customizable with colors and textures.