Custom Plastic Overmolding Services
AdvancTEK’s plastic overmolding molds a soft-touch or protective layer directly onto a rigid substrate. The result is one finished part – a grip, seal, or housing – that no longer needs assembly or secondary finishing.
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Key Takeaway
The AdvancTEK team performs overmolding at our Concord, North Carolina plant, and we also have the capability at our Saltillo, Mexico facility as well. Common work includes:
What Overmolding Is and How the Process Works
Overmolding – sometimes called injection overmolding – is an injection molding process that combines two materials into one part. A rigid base – the substrate – is molded first. A second material is then molded over it, bonding to the substrate to form a finished component.
AdvancTEK’s core in-house method uses two separate molds. Our overmolding process covers:
Because the substrate and the overmold run in two standard tools on standard horizontal injection molding machines, the overmolding process stays flexible and portable. It can move between presses, or between plants, without a machine dedicated to a single program.
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Two-Mold Overmolding vs. Two-Shot Molding
There is more than one way to produce an overmolded part, and the right method comes down to annual volume and tooling investment.
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The bottom line: Choosing between the two is a routine part of AdvancTEK’s quoting process, and we will guide you to the correct overmolding process for you.
Overmolding Materials
The overmold – the outer skin – is most often a thermoplastic elastomer. TPE and TPU are the two materials AdvancTEK runs most. The substrate underneath can be almost any rigid resin.
Substrate and overmold have to be compatible enough to hold together, and that is where material selection gets technical:
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AdvancTEK’s approach is often to design for both at once: a chemical bond reinforced by a mechanical one. Leaving the substrate surface slightly rough allows you to get not only a chemical bond but also a mechanical bond to the substrate. It’s a belt-and-suspenders method that protects against adhesion failure.
Inserts and Loading
AdvancTEK’s insert overmolding covers a wide range of inserts, all hand-loaded into the tool. Typical inserts include threaded and nut inserts, metal components, and bus bars – for example, a T-bar bus bar where the plastic encapsulates the body and leaves the electrical contacts exposed.
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Applications and Components Best Suited to Overmolding
Overmolding is ideal for a broad range of industries and part types. Representative AdvancTEK applications include:
| Component | Representative Work |
|---|---|
| Grips and handles | Soft-touch grab handles for heavy-duty trucks, and grips for hand tools where a knurled surface alone is not comfortable enough |
| Bus bars and electrical components | A plastic body molded around a metal bus bar, exposing only the contacts – this work now extends into data center programs |
| Powersports components | Overmolded bars and hip restraints for golf cars, plus brake and accelerator pedals with internal bracing |
| Bushings, compression limiters, and inserts | Metal hardware encapsulated in plastic to eliminate a downstream assembly step |
Industries that regularly use overmolding include powersports and recreation, telecommunications and data centers, battery and energy storage, industrial, medical, and heavy-duty transportation.
Advantages of Overmolding
The most common reason customers choose overmolding is tactile – it supplies a soft, ergonomic grip that a hard molded surface cannot match. It also gives an engineer real design freedom. Beyond feel, overmolding delivers several practical advantages, such as:
Insert Molding vs. Overmolding
The two terms are often used interchangeably, and you will hear both in the same meeting to describe the same result. In practice:
- Insert molding – Usually refers to placing a component (a brass or steel insert, a bracket, a brace) into a part
- Overmolding – Usually refers to adding a soft-touch or cosmetic layer over a substrate
Key insight: Inserts do not always have to be loaded into the tool. In many cases, AdvancTEK recommends installing them as a post-molding operation using heat staking or an ultrasonic (sonic) horn, which can shorten cycle time and reduce part cost.
For the full picture on inserted components, see AdvancTEK’s insert molding capabilities.
Design and Development for Overmolding
With overmolding, the engineering happens before the press ever runs. The development and the planning of an overmolded part is critical to its success.
AdvancTEK’s in-house design and development team works through the failure modes up front:
- Differential shrinkage and warpage – An overmold cooling over a substrate can pull a slight twist into a part that measured perfectly on its own. AdvancTEK’s experience across injection molding and reaction injection molding means the team knows to design for it.
- Wall thickness and standoffs – The substrate has to be held centered in the overmold cavity to keep the skin at a consistent wall thickness. Thin spots are where a soft overmold can break through.
- Mold flow analysis – Overmold behavior often takes several mold-flow iterations to predict, especially around the gate and point of entry.
- Substrate accuracy and insert survival – A plastic substrate has to be dimensionally correct before it enters the overmold tool, and any insert has to withstand the temperatures and injection pressures of the second shot without crushing, moving, or being damaged.
AdvancTEK also has experience fully encapsulating a component in an overmold – a genuinely difficult job that many molders will not take on, A good, successful DFM – design for manufacturing – will get you a more robust process to keep that part consistently centered in the overmold.
Prototyping, Volumes, and Quality Validation
- Prototypes – AdvancTEK supports overmolding prototypes through established prototype partners.
- Production volumes – Overmolding does not change what AdvancTEK can produce; it changes how the work is planned. Because an overmolded part is essentially two parts for part of its life, it uses more machine time and more work-in-progress space than a single-shot component.
suited to specialty and reaction injection molding processes.
- Quality and validation – Overmolding carries a higher level of inspection than a standard molded part. Since the substrate often becomes invisible once encapsulated, AdvancTEK uses destructive testing – sectioning parts to confirm wall thickness is consistent and the bond is sound – as part of the quality plan.
Request an Overmolding Quote
As a custom plastic overmolding company, AdvancTEK combines in-house design, tooling, and molding under one roof. Send your part requirements and the team will help you determine the right method, materials, and validation plan.
Overmolding FAQs
What is overmolding?
Overmolding is an injection molding process that molds a second material over a rigid substrate to form a single finished part. It is used to add soft-touch grips, seals, and protective layers, or to encapsulate metal inserts and bus bars.
What is the difference between overmolding and insert molding?
The terms are often used interchangeably. Insert molding generally means placing a component, such as a threaded insert or a bracket, into a part, while overmolding generally means molding a soft-touch or cosmetic material over a substrate. AdvancTEK performs both.
What materials are used in overmolding?
The overmold is most often a thermoplastic elastomer: TPE or TPU. The substrate can be most rigid resins, with nylon and polypropylene among the most common. Material pairing matters, because some combinations bond chemically while others require a mechanical bond feature.
Does AdvancTEK support overmolding prototypes?
Yes. AdvancTEK supports overmolding prototypes through established prototype partners and can advise on the right production method as volumes scale.