| Material Selection Criteria |
| Commodity Thermoplastic |
Polypropylene (PP) |
Density: approximately 0.90–0.91 g/cm³
Typical mold shrinkage: approximately 1.0–2.5%
Typical melt temperature: approximately 200–250°C
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Low density, good chemical resistance, good fatigue resistance, and relatively low material cost. Suitable for containers, household parts, caps, and living hinges.
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Confirm grade suitability for food contact, impact requirements, UV exposure, flame rating, and the expected shrinkage direction.
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| Engineering Thermoplastic |
Acrylonitrile Butadiene Styrene (ABS) |
Density: approximately 1.03–1.07 g/cm³
Typical mold shrinkage: approximately 0.4–0.8%
Typical melt temperature: approximately 220–260°C
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Provides a useful balance of impact strength, stiffness, dimensional stability, and surface appearance. Common for housings, control panels, and interior components.
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Check impact grade, required surface finish, color stability, flammability classification, and drying requirements before molding.
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| Engineering Thermoplastic |
Polycarbonate (PC) |
Density: approximately 1.20 g/cm³
Typical mold shrinkage: approximately 0.5–0.7%
Typical melt temperature: approximately 280–320°C
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High impact resistance, good transparency options, and strong dimensional performance. Appropriate for protective covers, optical housings, and safety-related parts.
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Verify drying control, maximum service temperature, stress-cracking resistance, optical requirements, and compatibility with mold release agents.
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| Moisture-Sensitive Material |
Polyamide 6 (PA6) |
Density: approximately 1.12–1.15 g/cm³ when unfilled
Typical mold shrinkage: approximately 0.7–1.5% when unfilled
Typical melt temperature: approximately 230–280°C
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Good wear resistance, strength, and chemical resistance. Moisture absorption can significantly affect dimensions, toughness, and processing stability.
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Require documented drying conditions, moisture measurement, glass-fiber content if applicable, and dimensional testing at the intended humidity condition.
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| High-Dimensional-Stability Material |
Polyoxymethylene (POM) |
Density: approximately 1.41 g/cm³
Typical mold shrinkage: approximately 1.8–2.2%
Typical melt temperature: approximately 190–220°C
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Low friction, good fatigue resistance, and excellent dimensional repeatability. Suitable for gears, bushings, clips, and precision mechanical parts.
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Confirm the material safety data, avoid excessive residence time, and verify venting because thermal degradation can generate hazardous formaldehyde gas.
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| Reinforcement |
Glass-Fiber Content |
Common reinforcement levels: approximately 15–50% by mass
Fiber-filled materials generally reduce bulk shrinkage but increase anisotropic shrinkage and warpage risk.
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Improves stiffness, strength, and heat resistance, but may increase tool wear, weld-line sensitivity, and directional dimensional differences.
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Confirm fiber percentage, fiber orientation risk, gate location, mold-flow analysis, abrasion-resistant inserts, and allowable dimensional tolerances.
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| Recycled Content |
Regrind and Recycled Resin |
Use only when permitted by the product specification. A controlled regrind ratio is often required because repeated thermal history can affect viscosity, color, and impact performance.
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May reduce material cost and environmental impact, but uncontrolled reuse can reduce consistency and increase visible defects.
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Define the maximum regrind ratio, lot traceability, contamination controls, moisture limits, and acceptance tests for mechanical and visual properties.
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| Mold Selection Criteria |
| Mold Structure |
Parting Line and Ejection |
Place the parting line where flash can be hidden or controlled. Use adequate ejector-pin area and provide draft on molded surfaces.
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Correct parting-line and ejection design reduces visible mismatch, deformation, sticking, and ejection marks.
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Review parting-line drawings, draft analysis, ejection simulation, ejector-pin locations, and the maximum acceptable flash specification.
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| Draft Angle |
Release from the Mold |
A common starting point is approximately 0.5–1° per side for polished surfaces. Textured surfaces generally require additional draft, depending on texture depth.
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Sufficient draft prevents drag marks, scuffing, core damage, and excessive ejection force.
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Confirm draft by surface finish, texture depth, shrinkage behavior, and the direction of ejection.
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| Steel Selection |
Tool Steel and Corrosion Resistance |
Pre-hardened mold steel is commonly used for general-purpose tooling. Hardened tool steel is preferred for high wear, high-volume, or glass-fiber-filled applications. Stainless mold steel is advantageous for corrosive materials or humid environments.
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Steel selection affects tool life, polishing quality, corrosion resistance, repairability, and maintenance cost.
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Request steel grade certificates, hardness records, heat-treatment documentation, cavity and core material details, and corrosion-protection procedures.
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| Cavity and Core Count |
Production Volume and Cycle Balance |
Single-cavity molds generally simplify development. Multi-cavity molds can reduce unit cycle cost when demand is high and cavity-to-cavity balance is controlled.
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More cavities increase initial tooling cost and balancing complexity but can improve output and reduce cost per part.
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Compare forecast volume, required annual output, machine capacity, cavity balance, filling consistency, and maintenance access.
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| Gate Design |
Gate Type and Location |
Common options include edge gates, submarine gates, pin gates, and hot-runner gates. Gate location should support uniform filling and minimize weld lines, sink marks, and visible gate vestige.
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Gate design controls filling pattern, packing efficiency, cosmetic quality, cycle time, and ease of automated degating.
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Require mold-flow results or filling analysis for complex parts and define gate vestige, weld-line, and cosmetic acceptance limits.
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| Cooling System |
Cooling Channel Layout |
Cooling channels should be distributed uniformly around thick sections and positioned to maintain consistent mold temperature. Baffles, bubblers, or conformal channels may be used where access is limited.
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Balanced cooling is essential for cycle time, warpage control, dimensional stability, and consistent surface appearance.
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Check cooling-circuit diagrams, pressure-drop data, inlet and outlet temperatures, flow rate, leak testing, and temperature mapping during trials.
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| Venting |
Air Evacuation |
Provide vents at the end of fill, around inserts, and near weld-line risk areas. Vent dimensions must suit the resin and mold surface without causing flash.
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Effective venting reduces burn marks, short shots, trapped air, weld-line weakness, and injection-pressure spikes.
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Inspect vent locations, vent depth control, vacuum or gas-assist requirements, and evidence from short-shot and full-fill trials.
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| Tool Life and Maintenance |
Expected Shot Count |
Tool-life requirements should be stated as a target shot count, supported by wear-resistant design, replaceable inserts, lubrication access, and preventive maintenance intervals.
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A defined tool-life target helps buyers compare initial tooling cost with long-term production reliability.
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Require a maintenance schedule, spare-part list, cavity identification, inspection checkpoints, and ownership of mold repair data.
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| Machine Selection Criteria |
| Clamping Capacity |
Required Clamping Force |
A preliminary estimate is commonly calculated from projected molded area multiplied by a material- and geometry-dependent pressure factor. A practical starting range is approximately 0.3–0.8 metric tons per cm² of projected area, followed by validation through molding trials.
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Insufficient clamp force can cause flash. Excessive clamp force can increase mold wear, energy use, and stress on the mold and machine.
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Calculate projected area including runners, apply an engineering safety margin, and confirm platen size, tie-bar spacing, mold height, and maximum opening stroke.
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| Injection Unit |
Shot Size |
The required shot weight, including runner and sprue, should normally use a controlled portion of the machine's rated shot capacity rather than operating continuously at the maximum limit.
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Correct shot-size matching improves melt residence time, weighing accuracy, pressure control, and material stability.
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Compare actual shot weight with the machine rating, screw diameter, check-ring condition, cushion stability, and material density.
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| Plasticizing System |
Screw Design and L/D Ratio |
General-purpose thermoplastics commonly use screw length-to-diameter ratios around 18:1–24:1. Abrasive or heat-sensitive materials may require specialized screw, barrel, and mixing designs.
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Screw geometry affects melting quality, color dispersion, fiber damage, plasticizing rate, and residence time.
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Verify screw material, non-return valve design, compression ratio, wear protection, maximum injection rate, and compatibility with the selected resin.
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| Injection Pressure |
Pressure Capability |
Required pressure depends on resin viscosity, flow length, wall thickness, gate design, mold temperature, and filling speed. Thin-wall or long-flow parts generally require higher pressure capability.
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Adequate pressure capacity prevents short shots and allows stable packing without operating permanently at the machine limit.
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Review the pressure-versus-speed profile, peak pressure during trials, pressure reserve, and the influence of actual material moisture and temperature.
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| Mold Compatibility |
Platen, Tie-Bar, and Mold Height |
The mold must fit within the machine's minimum and maximum mold-height range, tie-bar spacing, platen dimensions, and locating-ring requirements.
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Mechanical incompatibility can prevent installation even when clamp force and shot size are adequate.
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Confirm mold dimensions, locating-ring size, ejector position, nozzle radius, platen hole pattern, and available opening stroke.
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| Process Control |
Closed-Loop Control and Repeatability |
Closed-loop control of injection speed, pressure, screw position, and temperature generally provides better repeatability than open-loop control.
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Stable process control reduces part-to-part variation, flash, sink marks, short shots, and weight fluctuation.
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Request repeatability data for part weight, injection position, peak pressure, barrel temperature, and cycle time under production conditions.
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| Energy and Utilities |
Power, Cooling, and Compressed Air |
Confirm electrical supply, motor power, cooling-water temperature and flow, hydraulic or servo requirements, compressed-air demand, and ambient operating conditions.
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Utility compatibility affects installation cost, cycle stability, energy consumption, and the ability to maintain process conditions.
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Obtain a complete utility schedule and verify that the factory infrastructure can support peak load, cooling capacity, drainage, and air quality requirements.
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| Automation |
Part Removal and Process Integration |
Automation may include sprue pickers, robots, conveyors, vision inspection, insert loading, leak testing, and packaging. Interface standards should be defined before machine purchase.
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Proper integration improves labor efficiency, cycle consistency, operator safety, and traceability.
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Confirm robot reach, mold-safe signals, safety circuits, end-of-arm tooling, cycle synchronization, communication interfaces, and emergency-stop behavior.
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| Quality and Validation Criteria |
| Dimensional Validation |
Critical-to-Quality Dimensions |
Define nominal dimensions, upper and lower tolerances, datum references, measurement temperature, and inspection equipment before tooling approval.
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Clear measurement rules prevent disputes caused by different inspection methods or uncontrolled environmental conditions.
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Require a dimensional report from first-off and production samples, including measurement method, equipment calibration, and sample identification.
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| Process Validation |
Trial and Capability Study |
Validate filling, packing, cooling, ejection, cycle time, part weight, appearance, and dimensional stability over multiple consecutive cycles.
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A single acceptable sample does not demonstrate sustained process capability or cavity-to-cavity consistency.
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Request trial records, process windows, cavity balance results, defect analysis, and capability data for critical characteristics.
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| Documentation |
Technical File and Traceability |
The production package should include approved drawings, material certificates, mold drawings, process parameters, inspection standards, maintenance records, and change-control history.
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Complete documentation supports repeat orders, troubleshooting, regulatory review, and long-term production continuity.
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Define document format, revision control, retention period, approval workflow, and the procedure for material, mold, or process changes.
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| Export Readiness |
Packaging and Shipment Protection |
Protect molds against corrosion and mechanical shock. Drain and seal cooling circuits where appropriate, secure moving components, and use moisture-resistant packaging.
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Proper export preparation reduces transit damage, rust, contamination, and installation delays at the buyer's facility.
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Confirm packing photographs, corrosion protection, lifting points, spare-parts packaging, shipping dimensions, gross weight, and installation instructions.
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Note: The numerical values shown are typical engineering ranges for preliminary selection only. Final material grades, mold dimensions, processing windows, clamping force, and machine capacity must be confirmed through the approved part design, resin data sheet, mold-flow analysis, and production trials.
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