Custom Injection Molding, From Tooling to Production
Turn your part design into consistent plastic components, from pilot runs to repeat production. Hexamold’s custom injection molding services combine tooling, process validation, and quality inspection to meet your dimensional, appearance, and performance requirements. Assembly and packaging can be coordinated alongside molding, simplifying the path from approved samples to finished products.
The Right Material and Process for Your Plastic Part
Material selection and process control work together to achieve the required fit, strength, and appearance. We review your part design, resin requirements, tolerances, and expected order volumes, then establish molding parameters through trials and validation. Production checks focus on agreed critical features and cosmetic requirements, helping maintain consistency across repeat orders.
Design Guidelines for Injection-Molded Parts
Effective design for injection molding reduces defects, shortens cycle time, controls unit cost, and extends mold life. Hexamold reviews part geometry, resin, tolerances, appearance, assembly, and production volume during DFM before tooling begins.
A professional injection molding DFM review helps identify these risks before mold manufacturing, reducing engineering changes and supporting a smoother transition from prototype to high-volume production.
Maintain Consistent Wall Thickness
Uniform wall thickness promotes balanced filling and cooling. It helps prevent sink marks, warpage, voids, and internal stress while reducing cycle time. When thickness changes are necessary, use gradual transitions instead of abrupt steps.
Add Appropriate Draft Angles
Draft helps molded parts release cleanly without scratching or deformation. A typical starting point is 1–2 degrees, while deeper textures often require additional draft. The final angle should be confirmed according to the resin, surface finish, texture depth, and part geometry.
Use Radii & Fillets
Sharp corners restrict material flow and concentrate mechanical stress. Rounded internal and external corners improve filling, impact resistance, and long-term durability. As a general starting point, the internal radius can be approximately half the nominal wall thickness.
Strengthen Parts with Ribs & Gussets
Ribs increase stiffness without making the entire part thicker. Rib thickness is commonly designed at approximately 50–60% of the adjacent wall to reduce sink marks. Rib height, spacing, draft, and base radii should be evaluated through DFM.
Design Bosses for Reliable Assembly
Bosses support screws, inserts, and locating features but can create sink marks if they are too thick. Core the boss, maintain consistent surrounding wall thickness, and use ribs or gussets when additional support is required. Boss dimensions should match the selected fastener, resin, and assembly load.
Optimize Snap-Fit Features
Snap-fits can reduce hardware and assembly time when strain remains within the material’s allowable limit. Lead-in geometry, retention angle, arm length, thickness, and travel stops should be designed according to the resin and expected number of assembly cycles.
Minimize Undercuts & Mold Complexity
Undercuts may require sliders, lifters, or collapsible cores, increasing tooling cost and maintenance. Where possible, shut-offs, pass-through features, or geometry changes can provide the same function with simpler tooling. Unavoidable witness lines should be positioned away from critical cosmetic areas.
Engineer Living Hinges Carefully
Living hinges are commonly molded in flexible materials such as polypropylene. Hinge thickness, flow direction, gate position, radius, and processing conditions must be tightly controlled to achieve repeatable flexing. The correct dimensions depend on the material and required service life.
The Custom Injection Molding Process
Hexamold converts thermoplastic resins into precision plastic components through a controlled, repeatable injection molding cycle. Mold engineering, material preparation, processing parameters, cooling, and inspection are coordinated to maintain dimensional accuracy, surface quality, and production consistency.
This repeatable injection molding process supports prototyping, bridge production, and scalable high-volume manufacturing for B2B plastic components.
1. Custom Injection Mold Manufacturing
Each project begins with a custom mold manufactured from aluminum or tool steel according to the approved CAD data, resin, tolerances, surface finish, production volume, and expected tool life. Accurate tooling provides the foundation for repeatable part quality.
2. Resin Melting & Injection
Plastic pellets are dried when required and fed into a heated barrel. A rotating screw melts and mixes the resin before injecting it into the closed mold under controlled pressure. Injection speed, melt temperature, and holding pressure are adjusted to fill thin walls and detailed features while reducing molding defects.
3. Packing, Cooling & Solidification
Holding pressure compensates for material shrinkage as the part begins to solidify. Cooling channels then remove heat from the mold until the component becomes dimensionally stable. Balanced cooling helps reduce sink marks, warpage, internal stress, and cycle time.
4. Ejection & Quality Control
After cooling, the mold opens and ejector pins or automated handling equipment remove the part. The cycle then repeats under monitored processing conditions. Depending on the project, parts may undergo dimensional, visual, functional, or assembly inspection before secondary operations and packaging.
Injection Molding Material Selection
Selecting the correct injection molding resin affects part strength, appearance, chemical resistance, operating temperature, service life, cost, and regulatory compliance. Hexamold evaluates the product application, mechanical loads, environment, assembly method, and production requirements before recommending a thermoplastic.
PP — Polypropylene
Properties: Lightweight, fatigue-resistant, chemically resistant, and suitable for living hinges.
Common applications: Closures, containers, packaging, household products, and automotive interior components.
ABS — Acrylonitrile Butadiene Styrene
Properties: Good impact strength, dimensional stability, processability, and surface appearance.
Common applications: Electronic housings, consumer products, equipment covers, and non-implantable medical-device enclosures where an appropriate grade is specified.
PC — Polycarbonate
Properties: High impact resistance, optical clarity, dimensional stability, and good heat resistance.
Common applications: Transparent housings, safety components, lighting parts, lenses, and technical enclosures.
PA — Nylon
Properties: High tensile strength, wear resistance, low friction, and good thermal performance. Moisture absorption must be considered during design and processing.
Common applications: Gears, bearings, bushings, clips, brackets, and under-hood automotive components.
TPU and TPE — Thermoplastic Elastomers
Properties: Flexible, impact-absorbing, vibration-dampening, and suitable for soft-touch surfaces and overmolding.
Common applications: Seals, gaskets, grips, protective components, flexible connectors, and wearable products.
What Determines Injection Molding Cost?
The total cost of injection molding includes two main components: the initial mold investment and the unit production cost.
Injection Mold Cost: Tooling is a one-time investment covering mold design, engineering, machining, assembly, and validation. Pricing depends on part complexity, mold size, cavity count, sliders or lifters, steel grade, tolerance, surface finish, and expected production life.
Unit Production Cost: The price per molded part is influenced by resin type and weight, machine size, cycle time, labor, quality inspection, secondary operations, packaging, and order volume. Engineering plastics and specialized materials generally cost more than commodity resins.
Higher production volumes usually reduce the unit price because the mold investment is distributed across more parts and the manufacturing process can be optimized for repeatable production. Hexamold reviews the CAD files, material, annual volume, and quality requirements to provide an accurate tooling and injection molding quotation.
Injection Molding Quality Control and Defect Prevention
Hexamold applies documented injection molding quality controls aligned with ISO 9001 quality-management principles. Inspection requirements are defined according to the part drawing, tolerance, material, application, and customer-approved quality plan.
Dimensional Inspection: CMM, optical measurement, gauges, and other inspection methods can verify critical dimensions, tolerances, and assembly features against approved drawings.
Process Monitoring: Key parameters—including injection pressure, melt and mold temperature, cycle time, and holding conditions—are monitored to improve process stability and batch-to-batch consistency.
Visual and Functional Inspection: Parts are checked for sink marks, warpage, flash, short shots, weld lines, color variation, surface defects, texture consistency, and parting-line quality.
These controls help prevent defects, maintain traceability, and support reliable production from first-article validation through high-volume injection molding.
Injection Molding Project Checklist
To prepare an accurate injection molding quotation and manufacturing plan, Hexamold reviews the part design, material, production volume, appearance, and functional requirements. Please provide:
Design Files: STEP, IGES, or X_T files plus 2D drawings showing critical dimensions and tolerances.
Material Requirements: Preferred resin or details about temperature, UV exposure, chemicals, strength, flexibility, color, and regulatory requirements.
Production Volume: Prototype quantity, initial order, and estimated annual volume to determine the appropriate mold material, cavity count, and expected tool life.
Appearance Standards: Surface finish, texture, color, cosmetic areas, and acceptable locations for gates, ejector marks, weld lines, and parting lines.
Assembly and Secondary Operations: Requirements for overmolding, inserts, machining, printing, labeling, assembly, inspection, and packaging.
This information helps Hexamold optimize mold design, cycle time, part quality, tooling durability, and unit production cost.
Injection Molding FAQs
What is injection molding?
How much does custom injection molding cost?
Which materials can Hexamold injection mold?
Hexamold works with materials such as PP, ABS, PC, nylon, TPU, TPE, and other engineering thermoplastics. Resin selection depends on strength, flexibility, heat, chemicals, appearance, regulations, and cost.
What production volumes are suitable for injection molding?
Injection molding is best suited to repeat production because the initial mold investment is distributed across each part. Hexamold supports pilot runs, bridge production, and scalable volume manufacturing based on project requirements.
What tolerances can injection molded parts achieve?
How does Hexamold prevent injection molding defects?
What information is needed for an injection molding quotation?
Please provide STEP, IGES, or X_T files, 2D drawings, resin requirements, order quantity, annual forecast, tolerances, surface finish, color, testing, assembly, packaging, and delivery requirements.
Does Hexamold support international injection molding projects?
Yes. Hexamold coordinates DFM, tooling, injection molding, quality inspection, assembly, packaging, export preparation, and global delivery for international customers.
Where does Hexamold provide injection molding services?
Hexamold provides custom injection molding from its facility in Zhangjiagang, Suzhou, Jiangsu, China, supporting OEM and B2B manufacturing programs for customers worldwide.
Can Hexamold manage the complete injection molding project?
Yes. Hexamold provides product DFM, custom mold manufacturing, tooling validation, process development, injection molding, inspection, secondary operations, assembly, labeling, packaging, and export preparation.
Share your part files, material requirements, tolerances, finish, production volume, and quality standards with Hexamold. Our team will review manufacturability, tooling, process requirements, and unit-cost factors to prepare a tailored injection molding solution.