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Precision Plastic Injection Molding for Custom Parts
Karry Precision provides precision plastic injection molding for custom parts, supporting projects from prototype tooling and low-volume production to repeat manufacturing. We work with standard and engineering-grade thermoplastics and provide insert molding, overmolding, multi-cavity molding, tooling development, dimensional inspection, and assembly support.
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Custom plastic parts manufactured to drawings and specifications -
Insert molding, overmolding, and multi-cavity molding capabilities
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Support for standard and engineering-grade thermoplastics
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Tooling development, molding, inspection, and assembly support
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From Prototype Tooling to Production Injection Molding
Typical Plastic Injection Molding Parts
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Precision Housings -
Shafts -
Bushings -
Flanges -
Brackets -
Valve Bodies -
Manifolds -
Connectors -
Mounting Plates -
Custom Mechanical Components
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Precision Plastic Injection Molding Capabilities
Custom Plastic Parts
Custom injection-molded components produced according to customer drawings, material requirements, tolerances, and application needs.
Insert Molding
Metal inserts, threaded components, or electrical contacts are placed into the mold and permanently bonded with plastic during molding.
Overmolding
A secondary material is molded over an existing plastic or metal component to improve grip, sealing, impact resistance, or appearance.
Multi-Cavity Molding
Multiple identical parts are produced in one molding cycle, improving production efficiency and reducing unit costs for volume orders.
Materials for Precision Plastic Injection Molding
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Engineering Plastics-
ABS
A versatile thermoplastic with good impact resistance, dimensional stability, and surface quality. ABS is widely used for housings, covers, brackets, enclosures, and other injection-molded components that require a balance of strength and appearance.
Cost Efficiency:
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Polypropylene (PP)
Lightweight, chemical-resistant, and cost-effective. PP is suitable for living hinges, containers, covers, clips, automotive components, and other molded parts that require flexibility and moisture resistance.
Cost Efficiency:
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Polycarbonate (PC)
A strong engineering plastic offering excellent impact resistance, dimensional stability, and transparent grade options. PC is commonly used for protective housings, electronic components, covers, and structural plastic parts.
Cost Efficiency:
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POM (Acetal)
POM provides high rigidity, low friction, good wear resistance, and excellent dimensional stability. It is well suited for precision injection molded gears, bushings, clips, mechanical components, and moving parts.
Cost Efficiency:
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Nylon (PA)
Strong, wear-resistant, and suitable for demanding mechanical applications. Nylon is commonly used for gears, brackets, fasteners, structural components, and precision molded parts requiring strength and fatigue resistance.
Cost Efficiency:
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TPU / TPE
Flexible thermoplastic materials suitable for grips, seals, protective components, soft-touch surfaces, and overmolded parts. Different hardness grades are available depending on application requirements.
Cost Efficiency:
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Explore our full material list or contact our engineering team for recommendations.
Surface Finishing Options
We offer a variety of surface finishing options to enhance the appearance, durability, and performance of your CNC machined parts.
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Sanding
Removes layer lines, support marks, and minor surface imperfections to create a smoother and more uniform finish.
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Polishing
Refines the printed surface to improve smoothness, gloss, and visual quality, particularly for display models and cosmetic parts.
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Painting
Adds customized colors and protective coatings to enhance appearance, branding, and environmental resistance.
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Spray Coating
Applies a consistent protective or decorative layer to improve surface texture, wear resistance, and overall part appearance.
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Dyeing
Colors nylon and other compatible printed materials while maintaining dimensional details and surface texture.
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Vapor Smoothing
Uses a controlled chemical-vapor process to reduce visible layer lines and create a smoother, more sealed surface on compatible thermoplastics.
*Not sure which finish is right for your part? Explore our complete guide
Plastic Injection Molding Tolerance Guide
Dimensional control is essential in plastic injection molding because it directly affects part fit, assembly performance, appearance, and functional reliability. At Karry Precision, molding tolerances are evaluated according to resin type, part size, wall thickness, shrinkage rate, mold structure, and production requirements.
A practical tolerance strategy helps reduce tooling complexity, molding defects, inspection costs, and part rejection rates.：
- Apply tight tolerances only to critical mating features
- Maintain consistent wall thickness where possible
- Allow suitable draft angles for smooth part ejection
- Avoid abrupt thickness changes that may cause warpage
- Consider material shrinkage and moisture absorption
- Use ribs and supports instead of excessively thick walls
| Tolerance Type | Typical Tolerance | Suitable Materials | Cost Impact | Molding Considerations |
| General Linear Dimensions | ±0.20–0.30 mm | ABS, PP, PE, PC | Low | Suitable for non-critical dimensions and standard molded parts |
| Precision Linear Dimensions | ±0.10–0.20 mm | ABS, PC, POM, PA | Medium | Requires stable tooling, controlled processing, and dimensional inspection |
| Critical Mating Features | ±0.05–0.10 mm | POM, PC, PBT, reinforced plastics | High | Depends on part size, mold accuracy, shrinkage, and environmental conditions |
| Hole Diameter | ±0.10–0.20 mm | Most thermoplastics | Medium | Core-pin design, material shrinkage, and feature depth affect accuracy |
| Hole Position | ±0.15–0.30 mm | Most thermoplastics | Medium | Influenced by mold alignment, part warpage, and datum selection |
| Flatness | 0.20–0.50 mm | ABS, PC, PP, PA | Medium | Large or thin parts may require looser tolerances due to warpage |
| Insert Position | ±0.10–0.20 mm | Insert-molded components | Medium to High | Insert fixtures and molding pressure must be carefully controlled |
These values are general references. Final achievable tolerances depend on material shrinkage, part dimensions, geometry, wall thickness, mold design, process stability, and inspection requirements.
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Our Plastic Injection Molding Process
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STEP 1
Design Review -
STEP 2
Mold Design -
STEP 3
Tooling Production -
STEP 4
Material Preparation -
STEP 5
Injection Molding -
STEP 6
Quality Inspection
Precision Plastic Injection Molding FAQs
Ready to Start Your Injection Molding Project?
Upload your 2D drawings or 3D CAD files with material, color, quantity, tolerance, surface texture, and assembly requirements for engineering review and quotation.
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Why Choose Karry for Precision Plastic Injection Molding?
Karry Precision combines mold engineering, material expertise, controlled molding processes, and reliable quality inspection to produce consistent plastic components. From design review and tooling development to injection molding, assembly, and final delivery, we support projects from prototypes to volume production.
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Engineering support for moldability and part design optimization
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Insert molding, overmolding, and multi-cavity molding capabilities
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Support for standard and engineering-grade plastic materials
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Efficient transition from prototype tooling to production molding
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Stable process control and consistent part quality
