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About Pexco
Injection Molding
Overmolding/Insert Molding
Where Ideas Take Shape
Pexco’s overmolding and insert molding capabilities combine multiple materials into integrated components that eliminate assembly operations, improve performance, and enable designs not achievable through conventional single-material molding. We specialize in molding high-performance thermoplastics around delicate inserts and complex geometries that other molders consider too thin or intricate to process reliably.
Our proprietary tooling designs, robotic material placement systems, and thermal management expertise enable consistent production of overmolded assemblies using challenging materials like PEEK, PFA, FEP, and Torlon—not just commodity elastomers. Whether integrating metal hardware, sensors, or pre-molded substrates, we deliver components with robust bonds between dissimilar materials while maintaining the tight tolerances your application demands.
Insert Molding for Delicate Components
Insert molding places metal or pre-molded plastic components into the mold cavity before injecting polymer around them, creating a single integrated part. This eliminates secondary assembly operations, improves mechanical integrity, and enables designs that combine the properties of multiple materials.
Pexco has developed capabilities significantly more advanced than conventional insert molders:
- Proprietary tool designs and fixturing for inserts commonly considered too thin or complicated to mold
- Robotic material placement ensuring accurate, consistent positioning of complex inserts
- Thermal management systems controlling polymer flow around insert features without displacement or damage
- Dimensional stability maintained through process controls that prevent insert shifting during injection
Metal Insert Capabilities: We regularly mold around brass, steel, and stainless steel inserts. Knurled surfaces and specialized geometries provide mechanical retention, while our process expertise ensures proper polymer encapsulation and bond integrity. Applications include threaded fasteners, electrical contacts, structural reinforcements, and wear-resistant bearing surfaces.
Multi-Material Overmolding
Overmolding adds a second polymer layer onto a pre-molded substrate, combining materials with complementary properties into a single component. Pexco’s multi-shot molding capabilities use multi-barrel injection systems to mold substrate and overmold materials in sequence, creating strong bonds through chemical adhesion or mechanical interlocking.
High-Performance Overmold Combinations
Unlike molders limited to commodity TPE and TPU overmolds, Pexco processes advanced thermoplastics in both substrate and overmold applications:
| Substrate Materials | Overmold Materials |
|---|---|
| Polycarbonate, ABS, Nylon | TPE, TPU, Silicone, Santoprene |
| PEEK, Ultem (PEI), Ryton (PPS) | PEEK, Ultem, fluoropolymers |
| Metal (brass, steel, stainless) | FEP, PFA, fluoropolymers |
This capability enables overmolded components for demanding applications where both materials must withstand high temperatures, aggressive chemicals, or sterilization cycles.
Bonding Considerations
Material selection determines whether bonds form through chemical adhesion or mechanical interlocking. Our engineering team evaluates melting temperatures, coefficients of expansion, and adhesion characteristics to recommend optimal material combinations. For challenging material pairs, we design mechanical interlocking features that ensure reliable long-term performance.
Design Engineering Support
Successful overmolding requires careful attention to material compatibility, gate locations, and insert positioning from the earliest design stages. Pexco’s engineering team provides comprehensive support including:
Material selection guidance
for substrate and overmold combinations optimized for your application requirements
Mold flow analysis
predicting fill patterns, weld line locations, and potential issues before tooling investment
Insert retention design
incorporating knurls, undercuts, or geometric features that ensure mechanical bond integrity
Gate location optimization
minimizing visible witness marks while ensuring complete cavity filling around inserts
Our 6 in-house tool and die centers handle mold design, fabrication, and rapid modifications throughout development. For critical dimensional requirements, our Industrial CT Scanning & Metrology capabilities verify internal features and bond interfaces non-destructively.
See Design Engineering Services for complete engineering support capabilities.
Materials & Resins
Pexco’s overmolding capabilities span the full range of high-performance thermoplastics:
Substrate Materials
Engineering Thermoplastics
Polycarbonate (PC), ABS, Nylon (PA), Acetal (POM)
High-Performance Thermoplastics
PEEK, PEI (Ultem), PPS (Ryton), PSU (Polysulfone)
Metals
Brass, steel, stainless steel inserts
Overmold Materials
Elastomers
TPE, TPU, Silicone, Santoprene
Advanced Thermoplastics
PEEK, PEI (Ultem), EXTEM
Fluoropolymers
FEP, PFA, PVDF, ETFE
Why Choose Pexco?
Proprietary tooling for inserts too thin or delicate for conventional molders
Robotic insert placement for consistent positioning and high-volume production
High-performance overmold materials including PEEK, Ultem, and fluoropolymers
Metal insert molding with brass, steel, and stainless steel
Multi-shot overmolding capabilities for plastic-on-plastic applications
6 in-house tool and die centers for rapid mold development
Industrial CT scanning for non-destructive verification of internal bonds
Tolerances as tight as ±0.0003″ on critical features
ISO 9001:2015 certified, ITAR registered
Full design engineering support from concept through production
Get Started
Contact Pexco’s engineering team to discuss custom tooling requirements for your application.