Painting
Applies color for protection and uniform appearance.
What Is Overmolding?
Overmolding is an injection molding process that combines a rigid plastic substrate with a second material—typically TPE or TPU—to add grip, sealing, cushioning, or protection. Typical process includes:
- Mold the substrate
- Place it in the overmold tool
- Inject the overmold material
Our Engineering-Led Overmolding Process
At RPWORLD, we see ourselves as an extension of your engineering team. Our overmolding
process focuses on material compatibility,
interface design, substrate control, tooling
performance, and repeatable part quality.
Overmolding DFM Review
Before tooling begins, our engineers review the part design, proposed materials, and substrate–overmold interface to identify potential manufacturing risks.
- Substrate and overmold material compatibility
- Bonding areas and mechanical interlocks
- Shut-offs, wall thickness, draft, gates, and flash risks
Outcome for You: Earlier visibility into material, bonding, and interface risks—before tooling changes become costly.
Mold Design & Manufacturing
Based on the approved DFM, the substrate and overmold tools are developed as one coordinated tooling system.
- Design cavities, parting lines, shut-offs, gates, vents, and cooling
- Engineer substrate locating and retention features
- Manufacture and inspect both tools before molding trials
Outcome for You: Fewer tooling corrections and trial-stage adjustments, helping your project move more predictably from T1 to production.
Substrate Molding & Overmolding
The rigid substrates are molded and inspected before the second material is injected in the overmold tool. T1 trials are then used to refine the molding process.
- Mold and inspect the rigid substrates
- Position and secure each substrate before overmold injection
- Run T1 trials and optimize molding parameters
Outcome for You: Fewer molding-related adjustments and a more predictable transition from T1 approval to repeat production.
Quality Assurance & Functional Verification
Finished parts are inspected for dimensional accuracy, overmold quality, appearance, and specified functional performance.
- Dimensions, coverage, alignment, flash, and appearance
- Bond, peel, pull, sealing, or functional tests as specified
- FAI, in-process and final inspection, and traceability
Outcome for You: Greater confidence that parts meet agreed dimensional, interface, appearance, and functional requirements.
Match Your Project Needs with Our Overmolding Capabilities
Whether you're validating material bonding or scaling up production, RPWORLD supports overmolding projects with coordinated substrate molding, overmolding, and quality control. Our flexible manufacturing solutions adapt to your project’s development stage and volume requirements.
Overmolding Support by Project Development Phase
Functional & Validation Builds
Objective:
Verify material compatibility, interface design, and part-level performance
before repeat production
Key Focus:
Bonding, sealing, grip, fit, appearance, and functional performance
Industry
Applications:
Medical and scientific equipment components, consumer product grips and
housings, cable protection, and other functional multi-material parts
Pilot & Bridge Production
Objective:
Confirm process stability, batch consistency, and production readiness before
repeat manufacturing
Key Focus:
Substrate positioning, bond consistency,
assembly fit, and inspection requirements
Industry
Applications:
Medical and scientific equipment pilot builds, consumer electronics launch
batches, automotive pre-production and more
Low- to Mid-Volume Production
Objective:
Support repeat production with consistent quality, flexible quantities, and
reliable delivery
Key Focus:
Material traceability, substrate, critical
dimensions, and batch-to-batch consistency
Industry
Applications:
Repeat production of medical, scientific, industrial, automotive, and consumer
product components
RPWORLD Overmolding Technical Specifications
Capability Category
Specification
Note
Part Capacity
Max Part Size: 300 × 300 mm
Depending on part geometry, substrate, and materials
Max Part Depth: 150 mm
Final feasibility reviewed during DFM
Max Part Weight: 1,600 g
Depends on molding-machine and tool requirements
Mold Capacity
Max Mold Size: 800 × 800 mm
Supports two-stage overmolding workflows
Typical Mold Lead Time: 1–6 weeks
Varies with complexity, materials, and validation scope
Overmolding Material Compatibility
Choose substrate and overmold materials based on bonding performance, hardness, chemical resistance, appearance, and end-use requirements. The chart below shows representative material pairs supported by RPWORLD.
| Substrate Material Overmold Material | ABS | PC/ABS FR3010 or C2950 |
PC LEXAN 945 or CHIMEI 110 |
PCTG Tritan TX1001 |
PP | PA66 |
|---|---|---|---|---|---|---|
| TPV 101-87 (Santoprene) | — | — | ||||
| TPV 101-64 (Santoprene) | — | — | ||||
| TPE OM1040X-1 | — | — | ||||
| TPE OM1060X-1 | — | — | ||||
| TPE TA-65AN-019 | — | — | ||||
| TPU TU-70AT-W00 | — | — | ||||
| TPE TC-50AN-055 | — | — | — | — | — | |
| TPE TA-50AN-019 | — | — | ||||
| TPETA-65AN-N33 | — | — | — | — | — |
= Recommended material pair based on our current material and processing experience.
Material note: final bonding depends on the selected materials, part design, and molding conditions.
Need help selecting the right material pair for your application? Discuss Your Material Requirements
Finishing, Texture & Pre-Assembly Support for Overmolded Parts
RPWORLD supports mold textures, custom material colors, part marking, secondary finishing, and selected pre-assembly for overmolded parts.
Surface Finishing Options
EMC Coating
Shields electronics from electromagnetic interference.
Plating
Adds a metal layer for conductivity or corrosion resistance.
NCVM
Non-conductive metal texture and functional characteristics.
Laser Marking
Marks logos or codes with sharp, permanent detail.
UV Printing
Achieve complex graphics and gradient effects.
Silkscreen Printing
Prints logos or text using a mesh screen for consistent branding.
Pad Printing
Transfers ink onto curved or uneven surfaces for clear markings.
Hot Melting
High-strength permanent connection of plastic parts.
Ultrasonic Welding
Achieve high-efficiency precision welding with beautiful surface.
Overmolding Texture Board
SPI Polish Board
Ref:SPI-SPE:A1
3# DIAMOND
Ref:SPI-SPE:A2
6# DIAMOND
Ref:SPI-SPE:A3
15# DIAMOND
Ref:SPI-SPE:B1
600# GRIT PAPER
Ref:SPI-SPE:B2
400# GRIT PAPER
Ref:SPI-SPE:B3
320# GRIT PAPER
SPI Polish Board
Ref:SPI-SPE:C1
600# STONE
Ref:SPI-SPE:C2
400# STONE
Ref:SPI-SPE:C3
320# STONE
Ref:SPI-SPE:D1
DRY BLAST GLASS
BEAD 11#
Ref:SPI-SPE:D2
DRY BLAST 240#
OXIDE
Ref:SPI-SPE:D3
DRY BLAST 24# OXIDE
VDI 3400 EDM Standard Board
Ref-VDI 12
Ra0.4/Rt1.6/0.3°
Ref-VDI 15
Ra0.6/Rt3.2/0.5°
Ref-VDI 18
Ra0.8/Rt5.0/0.6°
Ref-VDI 21
Ra1.1/Rt7.5/0.8°
Ref-VDI 24
Ra1.6/Rt12.0/1°
Ref-VDI 27
Ra2.3/Rt16.0/1.5°
VDI 3400 EDM Standard Board
Ref-VDI 30
Ra3.1/Rt20.0/2°
Ref-VDI 33
Ra4.5/Rt25.0/3°
Ref-VDI 36
Ra6.3/Rt37.0/4°
Ref-VDI 39
Ra9.0/Rt46.0/5.5°
Ref-VDI 42
Ra12.5/Rt60.0/7°
Ref-VDI 45
Ra18/Rt85.0/10°
MT Texture Board
MT-11000
.0004
DEEP
10um
DEEP
MT-11010
.001
DEEP
25um
DEEP
MT-11020
.0015
DEEP
45um
DEEP
MT Texture Board
MT-11030
.002
DEEP
50um
DEEP
MT-11040
.003
DEEP
75um
DEEP
MT-11050
.0045
DEEP
110um
DEEP
Pre-Assembly Support
RPWORLD provides selected pre-assembly for compatible overmolded parts, including hardware installation, ultrasonic joining, and simple component fitting where required.
Quality Assurance for Overmolded Parts
Inspection Equipment & Technology
- CMM & 3D Scanning – Dimensional verification of substrates and finished parts
- Optical & Flash Measurement – Fast inspection of dimensions, coverage, and edge transitions
- XRF Scanner – Rapid elemental screening for material verification
- Functional Test Equipment – Bond, peel, pull, torque, sealing, or other specified tests
Expert Quality Engineering Team
- Extensive Experience – 10+ years in overmolding quality assurance
- Advanced Training – Skilled in dimensional, visual, interface, and functional inspection
- Certified Excellence – Operating under ISO 9001, 13485 & 14001 systems
Comprehensive Inspection Process
- Incoming Quality Control (IQC) – Verifies resins, substrates, and material records
- First Article Inspection (FAI) – Validates dimensions before mass production
- In-Process Quality Control (IPQC) – Monitors molding parameters and overmold consistency
- Outgoing Quality Control (OQC) – Confirms finished-part quality before shipment
Detailed Quality Documentation
- FAI Reports – Dimensional and visual verification of first-off parts
- COA & Material Records – Supports material and batch verification where required
- RoHS & REACH Documentation – Supports applicable material compliance requirements
Related Overmolding Resources
Overmolding FAQs
Overmolding adds a second plastic or elastomer material over a previously molded substrate, commonly to provide grip, sealing, protection, insulation, or soft-touch features. Insert molding places a preformed component—often a metal insert, fastener, or electronic component—into the mold before plastic is injected around it.
The right process depends on the materials, part function, interface design, production volume, and assembly requirements. RPWORLD, owned by Innorapid, can review the part design and recommend the appropriate molding approach.
Common combinations include TPE, TPU, or TPV over substrates such as ABS, PC/ABS, PC, PCTG, PP, and PA66. However, compatibility cannot be determined from the material family alone.
The exact grades, hardness, additives, colorants, operating environment, and required bonding performance must also be evaluated. Material-pair review, molding trials, and project-specific testing may be recommended before production.
Reliable bonding begins with compatible material grades and controlled molding conditions. Bond strength can also be improved through:
- Proper substrate drying, cleanliness, and surface condition
- Suitable melt and mold temperatures
- Controlled gate location, flow direction, and overmold thickness
- Mechanical interlocks, undercuts, or through-holes where appropriate
- Edge transitions designed to reduce peeling forces
For critical applications, peel, pull, torque, sealing, or other functional tests can be specified to verify interface performance.
The main cost factors include:
- Whether both substrate and overmold tools are required
- Part geometry, tooling complexity, and cavity quantity
- Substrate positioning and retention requirements
- Manual, semi-automated, or automated substrate placement
- Material selection and molding cycle time
- Inspection, functional testing, finishing, and production volume
A project review is required to determine the appropriate tooling strategy and provide an accurate quotation.
Overmolding can support functional and validation builds, pilot and bridge production, and low- to mid-volume manufacturing. The appropriate tooling and production approach depends on part complexity, substrate placement, material combination, required testing, and expected annual volume.
RPWORLD, owned by Innorapid, can recommend a tooling and molding strategy based on the current project stage and future production requirements.
Overmolding lead time depends on whether the substrate tool already exists, whether one or two molds are required, part and tooling complexity, material availability, molding trials, testing requirements, and production quantity.
For suitable projects, tooling and initial trial parts can be completed in as fast as 7 days. Production lead time is confirmed after the trial parts have been evaluated and approved.
Get a Free Overmolding DFM Review
Upload your CAD files to receive feedback on material pairing, bonding strategy, interface
design, shut-offs, substrate location,
and molding feasibility—together with a project quote
from our injection molding team.