Overmolding Services

Overmolding typically involves two types of materials: a substrate (base layer) and an overmold (outer layer). At Kemal, we support a wide range of thermoplastics and elastomers for both layers.

✅ Common Substrate Materials (Rigid Base):

• ABS – Good dimensional stability and adhesion
  
• PC (Polycarbonate) – High impact resistance, bonds well with TPU
  
• Nylon (PA6, PA66) – Strong and heat-resistant, requires proper surface prep
  
• PBT – Excellent for electrical applications
  

✅ Common Overmold Materials (Soft Layer):

• TPE (Thermoplastic Elastomer) – Ideal for grip, flexibility, and comfort
• TPU (Thermoplastic Polyurethane) – Durable, abrasion-resistant, good chemical resistance
• Silicone (LSR) – Used in medical and high-temperature applications

Kemal also offers material compatibility testing and can recommend the best pairing for your product’s functional, visual, or bonding needs.

Yes, absolutely. Material compatibility is one of the most critical factors in successful overmolding. At Kemal, our engineering team provides:

• Expert guidance on selecting compatible substrate and overmold materials
  
• Access to our material compatibility chart, based on industry-proven pairings
  
• Bonding trials upon request, to test adhesion before production
  
• Advice on surface treatments or primers if required (e.g., Nylon + TPE)
  

Whether your goal is soft-touch comfort, structural strength, or environmental sealing, we’ll help you choose the right material combination to ensure strong bonding and reliable performance.

Lead time depends on several factors, including part complexity, tooling type, and order volume. At Kemal, we offer flexible timelines to meet both prototyping and production needs.

• Rapid Tooling & Prototype Runs:
  Typically 2–3 weeks from mold kickoff to T1 samples
  
• Production Tooling & Low- to Mid-Volume Orders:
  Usually 3–5 weeks, depending on part complexity and material availability

We also provide T0, T1, and T2 trial samples to validate the tooling before mass production. If you have a specific deadline, our team can work with you to meet critical delivery targets.

Yes, Kemal supports both two-shot (multi-shot) and insert-based overmolding processes.

• Two-Shot Overmolding
  Involves molding two materials in a single machine cycle using a rotating mold or multi-barrel press. Ideal for high-volume production and consistent alignment.
  
• Insert-Based Overmolding
  Involves placing a pre-molded plastic or metal insert into a second mold cavity, then overmolding a new material around it. Suitable for prototypes, metal-plastic assemblies, or lower-volume runs.

Our engineering team will recommend the best process based on your part design, material combination, and production goals.

We accept a wide range of 3D CAD and 2D drawing formats to support your overmolding project.

✅ Supported 3D formats:

• STEP (.stp / .step)
• IGES (.igs / .iges)
• Parasolid (.x_t / .x_b)
• STL (.stl) – for reference or 3D printing only

📝 Supported 2D drawings:

• PDF (.pdf)
• DWG / DXF – for dimensional tolerances and critical callouts

If you’re unsure which file to send, just upload what you have—our engineers will review it and get back to you promptly.

No, Kemal does not require a minimum order quantity. 

• We accept orders from a single part to high-volume production
  
• Ideal for startups, pilot runs, and bridge tooling
  
• Pricing will be adjusted based on volume, but there’s no restriction to get started

Just upload your design, and we’ll provide a tailored quote—no matter the quantity.

Absolutely. Kemal provides free Design for Manufacturability (DFM) reviews for all overmolding projects—before you commit to tooling or production.

Our engineers will evaluate your design for:

• Material compatibility
• Wall thickness and flow behavior
• Undercuts and mechanical locking features
• Gating, venting, and mold parting line placement

You’ll receive expert feedback and optimization suggestions to ensure your design is ready for efficient and reliable overmolding.

✅ Upload your CAD file today and get your free DFM review within 24–48 hours.

Overmolding is a specialized injection molding process used to combine two or more materials into a single, unified part.

It involves molding a second material—usually a soft or flexible thermoplastic—over a pre-formed substrate, which can be plastic or metal. This technique enhances functionality, grip, aesthetics, and sealing, all without adhesives or secondary assembly.

At its core, overmolding builds on standard injection molding but requires additional tooling, material compatibility control, and precise process setup.

Overmolding and 2K (two-shot) molding are both used to produce multi-material plastic parts, but the key difference lies in the process and equipment used:

🔄 Overmolding (Two-Step Molding)

• Involves two separate molding steps
  
• The substrate is molded first, then transferred to another mold or machine for overmolding
  
• Can be done manually or with automated transfer
  
• More flexible, suitable for small to medium volumes or insert-molding scenarios
  

⚙️ 2K Molding (Two-Shot Molding)

• Both materials are molded in a single cycle using a special multi-barrel injection machine
  
• Requires rotating or indexing molds
  
• Ensures perfect alignment and is ideal for high-volume, high-consistency production
  

At Kemal, we support both methods and can recommend the best process based on your part design, materials, and production volume.

Overmolding tolerances depend on the material combination, part size, and mold precision. In general, tolerances for overmolded parts are slightly looser than for single-material injection molding due to material shrinkage differences and bonding layer variation.

At Kemal, our typical overmolding tolerances are:

• ±0.05 mm to ±0.10 mm for general features
  
• ±0.025 mm for critical dimensions (when substrate and overmold are tightly controlled)
  
• Tighter tolerances may require special material pairing and precision tooling
  

We evaluate tolerance requirements during the DFM review and will advise if adjustments are needed to meet function and manufacturability.

🧩 Note: Tolerances may vary between two-step and two-shot overmolding due to alignment factors.

The minimum overmold thickness depends on the material type, part geometry, and bonding requirements. If the overmold is too thin, it may not flow properly or adhere well to the substrate.

At Kemal, our general recommendations are:

• Minimum overmold thickness:
  0.5 mm (0.020 in) for rigid plastics
  0.8–1.0 mm (0.031–0.039 in) for soft materials like TPE or TPU
  
• Ideal range for soft overmolds:
  1.5–2.5 mm (0.06–0.10 in) – to ensure proper flow, bonding, and durability
  
• Thin sections below 1 mm may require:
  
  • Higher injection pressure
    
  • Optimized gating and venting
    
  • Material with low viscosity and high flow rate
    

Our engineers will assess wall thickness and advise during the DFM review to ensure manufacturability and bonding performance.

Designing for overmolding requires attention to material compatibility, wall thickness, bonding surfaces, and moldability. Here are the key factors to consider:

✅ 1. Material Compatibility

Choose substrate and overmold materials that chemically or mechanically bond well. Poor compatibility can lead to delamination.

✅ 2. Wall Thickness

Keep overmold walls between 1.5–2.5 mm for elastomers to ensure proper flow and adhesion. Thin walls (<1 mm) may cause short shots or weak bonding.

✅ 3. Bonding Surface Area

Maximize the surface contact between layers. Avoid sharp corners or sudden transitions that could interrupt material flow or adhesion.

✅ 4. Mechanical Interlocks

Use features like grooves, holes, or undercuts to strengthen the bond, especially if materials are not naturally adhesive.

✅ 5. Parting Line and Gate Placement

Avoid placing parting lines or gates in critical bonding zones or cosmetic surfaces to prevent flash or visible defects.

✅ 6. Ventilation and Flow Paths

Ensure proper venting in overmold areas to avoid air traps and achieve full fill.

At Kemal, our team reviews all designs during the DFM phase and provides guidance to optimize for strong bonding, accurate molding, and high production efficiency.