Insert Molding Services | Metal and Plastic Assembly Services
Insert molding skips the whole assembly process by embedding metal or plastic components right into your injection-molded parts while they’re being made. We run the full gamut—prototype tooling through high-volume production—with ISO 9001:2015 and ISO 13485:2016 certifications backing everything we do. Need overmolding, insert molding, or some CNC work on top of that? We handle it all under one roof.
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What is Insert Molding?
Insert injection molding integrates pre-formed components—typically threaded inserts, stainless steel bushings, or copper electrical contacts—into plastic part assemblies during the molding process to create unified components. The component is placed into the mold cavity before plastic injection, allowing molten thermoplastic material to flow around the insert and encapsulate the metal or substrate for superior mechanical bonding. This process eliminates post-molding assembly operations while achieving retention strengths that exceed pressed-in or heat staking methods.
Manufacturing Process Steps
The molding process follows five distinct phases:
- Insert placement into the cavity
- Mold closing under clamping force
- Plastic material is injected at controlled temperature and pressure
- Cooling until solidification
- Part ejection with permanently embedded insert
We work with threaded metal inserts from PEM, Dodge, and Spirol manufacturers, along with custom-designed brass, stainless steel 316/304, aluminum, and copper components machined in our facility.
Compatible Thermoplastic Materials
- Polycarbonate: Impact resistance and optical clarity for medical devices
- Nylon (Polyamide 6, Polyamide 66): Mechanical strength and wear resistance
- ABS: Dimensional stability and surface finish quality
- Polypropylene: Chemical resistance and flexibility for injection-molded parts
- PET: Barrier properties and recyclability
- PEEK: High-temperature performance to 260 °C with superior durability
- LCP: Ultra-low thermal expansion and chemical resistance
| Injection Mold Inserts | Insert Molding Applications | Key Properties |
|---|---|---|
| Brass | Thread reinforcement, electrical contacts | High conductivity, corrosion resistance |
| Stainless Steel | Bushings, structural components | Superior part strength, durability |
| Aluminum | Lightweight assemblies, heat sinks | Weight reduction, thermal conductivity |
| Copper | Electrical connectors, grounding | Excellent conductivity, ductility |
What Insert Molding Capabilities does Yijin Hardware Offer?
We manufacture insert molded parts across five tool classifications, ranging from Class 105 prototype tooling (under 500 cycles) to Class 101 production molds (over 1,000,000 cycles). Our aluminum prototype tooling delivers first articles in 7 to 10 days for design validation with tight tolerance control to ±0.02 mm through high-volume production runs. Engineering support includes CAD design review with upload your CAD file capability, design for manufacturability (DFM) analysis, finite element analysis (FEA) for stress distribution, and computational fluid dynamics (CFD) for plastic flow optimization.
Material Selection and Certifications
Custom plastic material selection spans FDA-compliant thermoplastics for medical device applications, UL-listed plastic resin for electrical components, and engineering polymers meeting regulatory requirements. We maintain material certifications traceable to FDA 21 CFR requirements and UL yellow card specifications. Metal insert molding compatibility includes standard threaded fasteners, custom brass components, stainless steel bushings, and specialized electronic contacts.
Advanced Manufacturing Technologies
- Two-Shot Molding: Sequential injection of two different materials for multi-component assemblies
- In-Mold Assembly (IMA): Component assembly during molding cycle reducing production time
- 3D Printing Integration: SLS, SLA, and FDM prototyping for rapid design validation
- Cleanroom Molding: Contamination-controlled environment with on-demand production
- Automated Vision Inspection: Real-time defect detection and dimensional verification
- Overmolding Services: Elastomer overmolding to protect metal components from vibration and shock
| Mold Class | Cycle Life | Tolerance | Lead Time | Production Parts Use |
|---|---|---|---|---|
| Class 105 | Under 500 | ±0.02 mm | 7-10 days | Prototype validation |
| Class 104 | Under 100,000 | ±0.02 mm | 10-15 days | Low-volume production |
| Class 103 | Under 500,000 | ±0.02 mm | 10-15 days | Bridge manufacturing |
| Class 101 | Over 1,000,000 | ±0.02 mm | 10-18 days | High-volume production runs |
Which Industries Benefit from Insert Molding Services?
Automotive manufacturers, medical device companies, and more benefit greatly from insert molding services.
Industry-Specific Applications
- Electronics: Circuit breaker assemblies with copper contacts, switch mechanisms with brass terminals, actuator housings providing EMI shielding
- Consumer Products: Power tool housings with thread reinforcement, recreational equipment with steel bushings, game components with embedded fasteners
- Aerospace: Lightweight assemblies reducing size and weight, structural components with aluminum inserts
- Industrial Equipment: HVAC system components with brass fittings, agricultural machinery housings, power tool assemblies
- Food and Beverage: FDA-compliant equipment parts with stainless steel contacts protecting against contamination
What Quality Standards Ensure Insert Molding Precision?
ISO 9001:2015 certification guarantees quality management throughout our injection molding capabilities from incoming material inspection through final dimensional verification. ISO 13485:2016 certification enables medical device manufacturing with documented design controls, process validation, and risk management protocols. Material certifications include FDA 21 CFR approval for thermoplastics used in food-contact and medical applications.
Quality Control Methods
Dimensional inspection follows ANSI B4.1 tolerance standards, ASME Y14.5 geometric dimensioning and tolerancing (GD&T) specifications, and ASTM D638 testing protocols. We implement Six Sigma methodology to reduce defects and maintain statistical process control (SPC) at 1.33 Cpk minimum. Insert retention testing validates pull-out strength with stake testing to ensure proper encapsulation around an insert.
Inspection and Verification
- First Article Inspection: Complete dimensional verification against part size specifications
- In-Process Monitoring: Cavity pressure sensors and molten material temperature verification
- Vision Inspection Systems: Automated detection ensuring inserts are placed correctly before plastic around injection
- Material Traceability: Resin lot numbers through molded part serial identification
| Standard | Application | Verification Method |
|---|---|---|
| ISO 9001:2015 | Quality management | Third-party audit |
| ISO 13485:2016 | Medical devices | Regulatory audit |
| ANSI/ASME Y14.5 | Dimensional tolerancing | CMM inspection |
| ASTM D638 | Material properties | Tensile testing |
How does Engineering Support Optimize Insert Molding Design?
Finite element analysis (FEA) simulates stress distribution around embedded inserts preventing plastic cracking under mechanical loading or thermal cycling. Computational fluid dynamics (CFD) modeling predicts plastic flow patterns when injected into the mold to optimize gate location, eliminate weld lines near inserts, and prevent void formation. Design for manufacturability review identifies potential defects including sink marks, warpage, and insert displacement before tooling design begins.
Design Optimization Guidelines
Wall thickness optimization ensures uniform flow while maintaining structural integrity—typically 1.5 mm to 3.0 mm depending on injection molding design requirements and part geometry. Insert molding allows minimum 2x insert diameter embedment for adequate retention. Gate location analysis prevents direct impingement on insert surfaces that could cause displacement or incomplete encapsulation.
Material Compatibility Analysis
Insert molding needs consideration of thermal expansion coefficient matching between insert and thermoplastic to prevent stress cracking. Brass inserts with 19 × 10⁻⁶ /°C expansion pair well with nylon at 80 × 10⁻⁶ /°C, while stainless steel at 17 × 10⁻⁶ /°C matches polycarbonate at 65 × 10⁻⁶ /°C. Insert molding is used with advanced pre-form techniques where material selection provides design flexibility for complex geometries. We provide CAD modeling with online quote capability, tolerance stack-up analysis, and mold flow simulation reports.
What Manufacturing Process and Timeline does Insert Molding Require?
Prototype tooling fabrication requires 7 to 10 days using aluminum mold construction with Class 105 specifications suitable for under 500 production cycles. Production tooling extends to 10 to 18 days for tool steel molds rated Class 101 with over 1,000,000 cycle life expectancy reducing molding costs per unit. Tooling design incorporates insert locating features including pins, pockets, or magnetic holders positioning components within ±0.1 mm before molten plastic injection.
Injection Molding Cycle Parameters
The injection molding process begins with insert placement where inserts are placed using automated pick-and-place systems for production volumes. Mold closing applies clamping force from 25 tons to 850 tons depending on projected part area and design considerations. Plastic injection occurs at material-specific temperatures: polycarbonate at 290 °C, nylon at 270 °C, ABS at 240 °C, with injection pressures reaching 15,000 psi to 25,000 psi for complete cavity filling.
Secondary Operations
- Ultrasonic Welding: Hermetic sealing for multi-component assemblies
- Pad Printing: Surface graphics and product identification
- Hot Stamping: Brand identification and decorative elements
- Blanking: Precision trimming of molded products
- Assembly: Multi-part integration with automated handling
- Packaging: Custom packaging solutions with protective materials
Why Choose Yijin Hardware for Insert Molding Services?
Our integrated facility combines CNC machining with insert molding and overmolding services, enabling us to fabricate custom brass, aluminum, and stainless steel inserts alongside the injection molding process. ISO 9001:2015 and ISO 13485:2016 certifications ensure quality management for commercial and medical device applications with full material traceability. Engineering support includes FEA stress analysis, CFD flow simulation, and DFM optimization before tool fabrication begins.
From Class 105 prototype tooling delivering first articles in 7 days to Class 101 production molds supporting 1,000,000+ cycle life, we scale with project requirements maintaining ±0.02 mm tolerances. In-house secondary operations—ultrasonic welding, pad printing, hot stamping, blanking, and automated assembly—eliminate coordination with multiple vendors.
What Our Clients Say
Insert Molding Services FAQs
Insert molding places pre-formed components into the mold cavity before plastic injection, creating a single-shot process where plastic encapsulates the insert. Overmolding requires two sequential operations—first creating a substrate component, then molding a second material layer over the existing part. Insert molding typically uses metal components while overmolding combines two plastic materials or adds elastomer layers over rigid substrates.
Injection molding forces molten plastic into closed mold cavities under high pressure for complex geometries. Blow molding inflates heated plastic tubing inside molds to create hollow containers. Compression molding places material into heated mold cavities where pressure forms the final shape. Rotational molding tumbles plastic powder inside heated molds to coat interior surfaces. Transfer molding uses a plunger to force material through runners into mold cavities for thermoset plastics.
Casting inserts are pre-positioned metal components placed into sand molds or permanent molds before molten metal pouring. The liquid metal flows around the insert and solidifies, permanently embedding the component through metallurgical bonding or mechanical interlocking. Common applications include cast iron engine blocks with steel cylinder liners and aluminum transmission housings with bronze bushings.
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