Capabilities / Overmolding Services

Overmolding Services

SUDACNC delivers professional two-shot 2K and pick-and-place overmolding multi-material injection molding. We mold soft elastic TPE/TPU/silicone over rigid plastic or metal substrates in one integrated component, eliminating secondary assembly while improving anti-slip grip, waterproof sealing, vibration damping and soft-touch ergonomics. Full DFM material compatibility analysis, custom overmold tooling and adhesion peel test validation included for stable mass production.

What Is Overmolding?


Overmolding is a specialized multi-material injection molding process that forms a hard structural substrate first, then injects a second soft elastic material over targeted surfaces to form a single bonded composite part.

Two mainstream production methods: Rotary two-shot (2K) molding uses a rotating mold platen in one press for high-volume consistent output; pick-and-place overmolding produces the base part separately then transfers into a secondary soft mold, ideal for small batches and metal insert substrates. Compatible material pairs create chemical or mechanical interlock bonding, widely used for hand tool grips, waterproof electronic housings, medical soft-touch devices, automotive interior control knobs and shock-absorbing consumer hardware.





Learn More About Overmolding Technology

Our Overmolding Advantages

Pre-production material compatibility DFM, strong interlayer bonding, two production process options, adhesion testing & one-stop mold + molding mass production.

Integrated Single-Part Design
Remove glue, clip and assembly labor, lower total manufacturing cost

Two Overmolding Process Choices
Rotary 2K for mass production / Pick-and-place for low batch & metal inserts

Reliable Interlayer Bonding
Chemical compatible resin matching + mechanical interlock groove design prevent delamination

Multi-Functional Soft Layer
Anti-slip grip, IP waterproof sealing, shock absorption, vibration isolation and soft ergonomic touch

Overmolding Basics & Two Main Process Types

Overmolding combines rigid structural substrate and soft elastic overmold layer into one unified component via dual-stage injection molding. Two mature manufacturing workflows fit different volume and substrate types: Rotary two-shot 2K molding for high mass production, pick-and-place overmolding for small batches and metal insert base parts. Our engineering team runs pre-project DFM simulation to verify material bonding, cooling balance and shut-off geometry before mold cutting to eliminate delamination, flash and substrate deformation risks.

Core Advantages of Our Overmolding Service

  • Eliminate Secondary Assembly: Remove adhesive bonding, clip fitting and multi-part assembly steps, reduce BOM and labor cost
  • Two Flexible Production Routes: Rotary 2K high-speed mass run; pick-and-place low-volume flexible molding compatible with metal cast inserts
  • Dual Bonding Mechanism Support: Chemical compatibility resin matching + mechanical interlock groove design to maximize peel resistance
  • Multi-Functional Soft Layer Performance: Custom TPE/TPU layer for anti-slip grip, IP waterproof sealing, shock absorption and vibration damping
  • Full Quality Validation: Peel adhesion test, water immersion IP test, thermal cycle aging test for medical & automotive compliance

Two Standard Overmolding Production Processes

Rotary Two-Shot (2K) Overmolding

  • Single injection press with rotating mold platen, full automated cycle
  • First shot rigid substrate molded, mold rotates 180° to second cavity for soft elastomer injection
  • Tight positional tolerance, no manual part transfer error, stable mass production over 100k pcs
  • Ideal for plastic-on-plastic dual color/dual hardness consumer & automotive serial parts

Pick-and-Place Overmolding

  • Separate mold for rigid substrate, finished base parts manually/robotically loaded into secondary soft mold
  • Supports pre-manufactured metal die cast, stamped metal and complex multi-component inserts
  • Lower upfront mold investment for prototype validation and small batch under 50k pcs
  • Flexible material switching, widely used for medical equipment and custom industrial grips

Overmolding Dimensional Tolerance & Wall Thickness Specification

Design Parameter Overmolding Standard Requirement
Rigid Substrate Wall ThicknessMinimum 1.5mm to resist overmold injection pressure deformation
Soft TPE/TPU Overmold Layer Thickness0.8–2.0mm recommended; ratio soft : hard = 1 : 2 to prevent warpage
Minimum Shut-off Groove Depth0.5–1.0mm groove on substrate edge to eliminate feather edge peeling
Overall Part Dimensional Tolerance±0.03 ~ ±0.08mm per ISO 2768 for two-shot 2K precision parts
Minimum Draft Angle For Soft Layer1.5° minimum; textured surface requires 3° draft to avoid sticking
Quality Inspection ItemsInterlayer peel strength test, dimensional CMM scan, IP waterproof aging test

Submit Overmold CAD Drawing For Free DFM Thickness & Tolerance Analysis

Compatible Rigid Substrate & Soft Overmold Elastomer Material List

Material matching directly determines chemical bonding strength; low-compatibility pairs must add mechanical interlock grooves to avoid delamination.

PP Substrate + PP-based TPE / TPR: Excellent fusion, low cost grip components

ABS / PC+ABS + General TPU / TPE: Strong chemical bond for consumer electronics housings

Aluminum Die Cast Metal + Universal TPE: Reliable mechanical grip bonding for tool handles

PA6 / PA66 Nylon + Modified TPE: Interlock grooves mandatory to prevent layer separation

PC Polycarbonate + Hard TPU: Suitable for transparent sealing parts with structural undercut locks

POM Acetal + Special Adhesion TPE: Only for small local overmold areas

Medical Grade Biocompatible TPE: Skin contact surgical instrument soft touch layers, sterilization resistant

Food-Grade Silicone Overmold: Sealing gaskets for kitchen appliance and medical fluid channels

High-hardness / Low-hardness TPU Shore A 30~95: Custom elasticity for shock absorption and anti-slip grips

Material Compatibility Matching Consultation For Your Overmolding Project

Overmolding Mold Tooling Design & Critical Shut-off Specifications

Dual-cavity rotating mold plate integrated in one mold base, independent hot runner system for hard and soft material respectively. Precision positioning lock prevents substrate shift during second shot injection. S136 / NAK80 mold steel standard for high gloss cosmetic overmold parts, built-in dedicated vent channels to eliminate air trap burn marks at material interface.

Custom positioning fixture cavity to fully support thin substrate against injection pressure bending. Multi-point clamping locators lock metal inserts without surface scratch, precise shut-off edges to stop soft elastomer flash overflow onto rigid base part surfaces.

Prohibit zero-thickness feather edge soft material termination; design 0.5~1mm depth circumferential shut-off groove on substrate where TPE layer ends. Vertical wall shut-off surface hardness HRC48+ to resist long-term flash wear during mass production cycles.

Custom Two-Shot & Pick-and-Place Overmold Tooling Quotation

DFM Critical Design Guidelines To Avoid Overmolding Defects

Design Feature Overmolding DFM Best Practice
Soft Overmold Layer Termination EdgeAdd 0.5–1mm shut-off groove; never design feather thin zero-thickness edge
Mechanical Interlock For Low Bond MaterialsCircular/rectangular through holes or undercut recess 1–2mm deep distributed evenly on bonding surface
Substrate Anti-Deformation ReinforcementAdd internal ribs for substrate thinner than 1.8mm to resist second shot injection pressure
Air Vent Layout At Bond Interface0.015–0.02mm thin vent at end of soft material flow path to eliminate air trap burning
Internal Fillet Radii All CornersMinimum R0.3mm for soft layer to avoid stress crack under repeated bending

Free Pre-Molding DFM Risk Analysis For Overmolding Parts

Main Industry Overmolding Application Scenarios

Consumer Power Tools & Handheld Devices
Two-shot overmold ergonomic anti-slip handles, shock-absorbing power tool housings, wireless charger soft grip frames with integrated TPE non-slip layer.
Medical Devices & Healthcare Equipment
Biocompatible TPE overmold surgical instrument grips, catheter soft sealing joints, portable diagnostic device skin-contact overmolded surfaces with sterilization resistance.
Automotive Interior & Electronic Components
Control knob soft touch overmold, door handle anti-slip trim, wire harness waterproof overmolded sealing sleeves, vibration-damping interior plastic parts.
Consumer Electronics & Industrial Equipment
IP67 waterproof electronic enclosure TPU seal overmolding, robot gripper shock absorption soft layer, kitchen appliance food-grade silicone overmold sealing gaskets.

Custom Overmolding Solution For Your Industry Product

Overmolding Typical Defect Solutions & Frequently Asked Questions

1. Delamination / Layer Separation: Incompatible material pairs, cold substrate temperature, surface oil contamination; fix by upgrading matched resin, preheat substrate and add mechanical interlock grooves.

2. Soft Material Flash Over Substrate: Worn shut-off edges, excessive injection pressure; repair mold shut-off surface and optimize molding process parameters.

3. Substrate Warpage Deformation: Thin base wall without ribs, high second shot injection pressure; reinforce substrate ribs and reduce melt injection speed.

Rotary two-shot 2K uses single mold with rotating plate inside one injection machine, fully automated cycle, high consistency and fast cycle time for mass plastic-on-plastic serial production, higher mold upfront cost. Pick-and-place uses separate molds for substrate and overmold, supports metal inserts, lower mold investment, longer per-part cycle time, ideal for prototype and low-volume batches.

Yes, matching compatible substrate and soft TPU/silicone with continuous full-circumference overmold sealing layer and tight shut-off interface can reach IP65~IP67 waterproof rating, widely applied for outdoor electronic device housing and wire harness connectors.

STEP, IGES, SLDPRT, X_T, CATPart, STL, 3MF solid files are fully supported; native solid 3D models are recommended for accurate material bonding and mold flow simulation analysis.

Simple pick-and-place overmold: 22–32 working days including trial samples; rotary two-shot 2K complex mold with hot runner system: 35–48 working days with multi-round adhesion testing and cosmetic adjustment.

Two-Shot 2K Overmolding VS Pick-and-Place Overmolding Full Comparison

Swipe to view full table columns
Comparison Factor Rotary Two-Shot 2K Overmolding Pick-and-Place Overmolding
Mold & Equipment Requirement Single integrated rotary mold, dedicated dual-shot injection molding press required, higher initial tooling cost Two independent simple molds, standard single-shot injection machines, lower upfront mold investment cost
Supported Substrate Type Only rigid plastic substrate molded in same mold cycle, cannot integrate pre-made metal inserts Fully compatible with plastic, aluminum die cast, stamped metal and pre-assembled multi-component inserts
Production Cycle Efficiency Full automatic one-machine cycle, 30–50% faster output for large batch mass production over 100k pcs Requires manual/robot transfer between two molds, longer single-part cycle time, low throughput for mass runs
Dimensional & Positional Consistency No substrate secondary handling shift, ultra-tight positional tolerance, uniform cosmetic overmold edge alignment Substrate positioning deviation risk during transfer, larger tolerance stack for multi-batch long-term production
Best Matching Production Volume High-volume serial mass production over 50,000 units, long-life stable product lines Prototype validation, small batch under 50k pcs, custom low-volume special metal insert composite parts
Material & Design Flexibility Limited to plastic-plastic dual material combination, fixed mold cavity geometry hard to modify Flexible material switching, easy substrate design iteration, wide range of hard/soft/metal multi-material combinations

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