| 1. Conventional Thermoplastic Injection Molding |
Thermoplastic pellets are melted, injected into a closed mold, packed under pressure, cooled, and ejected as a solid part. |
PP
ABS
PE
PA
PC
POM
PBT
Filled grades may contain glass fiber, mineral filler, or flame-retardant additives.
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Hardened or pre-hardened steel molds for high volume; aluminum or soft steel may be used for prototypes and low-volume production. Requires runners, gates, cooling channels, ejectors, and suitable draft angles.
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Standard reciprocating-screw injection molding machine, material hopper, dryer when required, mold temperature controller, cooling unit, and auxiliary granulator or material loader.
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Housings, automotive components, consumer products, electrical parts, packaging closures, industrial components, and general-purpose precision parts.
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High scalability
Usually the lowest unit cost at medium-to-high volumes. Material drying, shrinkage, weld lines, warpage, and mold cooling must be controlled.
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| 2. Insert Molding |
Metal, ceramic, or preformed plastic inserts are positioned in the mold before thermoplastic material is injected around or onto them. |
Thermoplastics such as PP, PA, PBT, PC, ABS, and POM; inserts commonly include stamped metal, machined metal, threaded components, terminals, or magnets.
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Mold must securely locate and support each insert while allowing material to flow around it. Requires insert pockets, retention features, venting, insulation where needed, and allowance for thermal expansion.
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Standard injection machine plus manual loading, pick-and-place automation, robotic insertion, or rotary indexing equipment. Vision inspection may be used for insert presence and orientation.
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Electrical connectors, threaded components, bushings, sensor housings, structural brackets, knobs, and parts requiring reinforced attachment points.
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Medium automation complexity
Improves assembly efficiency but requires accurate insert tolerances, reliable placement, strong mold retention, and controls to prevent short shots or damaged inserts.
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| 3. Overmolding |
A second material is molded over a previously molded substrate to create a combined part with functional, protective, or ergonomic layers. |
Rigid thermoplastics combined with TPE, TPU, silicone, or a second compatible thermoplastic. Material compatibility and surface adhesion are critical.
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Two-stage or modular tooling with accurate substrate location, shut-offs, sealing surfaces, and controlled overmold thickness. The mold must prevent flash along the substrate interface.
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Single-material machine for sequential molding, or two-material machine with rotary, transfer, or movable-core tooling. Requires precise temperature and process control between shots.
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Soft-touch handles, grips, seals, protective covers, medical components, wearable products, cable strain reliefs, and vibration-isolation parts.
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Material compatibility required
Bond strength, shrinkage differences, substrate cleanliness, cycle time, and cosmetic transitions should be validated through adhesion and durability testing.
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| 4. Two-Shot or Multi-Component Molding |
Two or more materials or colors are injected in a controlled sequence within one integrated production cycle. |
Compatible combinations such as rigid thermoplastic plus TPE, two compatible thermoplastics, or multiple colors of the same polymer family.
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Rotary, index-plate, core-back, transfer, or movable-cavity tooling. Requires accurate alignment, separate flow systems, independent cooling zones, and reliable sealing between material areas.
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Two-component injection molding machine with separate injection units, synchronized controls, and specialized mold rotation or transfer mechanisms.
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Multi-color consumer parts, illuminated controls, sealed assemblies, ergonomic handles, automotive interior components, and integrated functional surfaces.
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Specialized equipment
Reduces secondary assembly but has higher mold and machine costs. Gate location, shot balance, material bonding, and color contamination require close control.
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| 5. Gas-Assisted Injection Molding |
Partially filled polymer is followed by pressurized inert gas, usually nitrogen, which forms internal channels or pushes material against the mold wall. |
Commonly PP, ABS, PC/ABS, PA, POM, and other thermoplastics with suitable melt strength and processing stability.
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Gas injection nozzles or pins, controlled gas passages, suitable venting, and mold geometry designed for gas penetration. Mold sealing and pressure resistance are important.
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Injection molding machine with gas controller, high-pressure nitrogen supply, gas injection valves, pressure sensors, and process monitoring software.
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Thick or hollow handles, large automotive parts, structural components, tubing-like parts, and products requiring lower weight without completely foamed material.
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Process-sensitive
Can reduce weight, sink marks, and clamp-force requirements, but gas pathways, wall-thickness transitions, and pressure profiles must be developed carefully.
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| 6. Water-Assisted Injection Molding |
High-pressure water is injected into a polymer melt to create hollow sections or displace material from the center of a thick part. |
Suitable thermoplastics include PP, PA, PBT, and selected engineering polymers with adequate melt strength and controlled moisture behavior.
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Mold must accommodate water injection pins, drainage or recovery paths, corrosion-resistant components, and sealing features capable of handling high-pressure water.
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Injection molding machine with water pressure unit, high-pressure pump, water reservoir, temperature control, filtration, recovery system, and process sensors.
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Hollow tubes, fluid-carrying components, long automotive parts, handles, lightweight structural sections, and parts requiring internal channels.
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Specialized infrastructure
Offers efficient hollowing and short cooling times in suitable geometries. Corrosion control, water management, sealing, and process repeatability are essential.
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| 7. Structural Foam Injection Molding |
A physical or chemical blowing agent creates a cellular core while the outer surface forms a relatively dense skin. |
PP, ABS, HDPE, PA, PC/ABS, and other thermoplastics compatible with the selected foaming system.
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Mold should provide controlled filling, suitable venting, robust part ejection, and sufficient cavity pressure tolerance. Gas counter-pressure tooling may be used for improved surface quality.
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Injection molding machine with plasticizing capability for the foaming system, gas dosing or chemical-agent feeding equipment, and optional gas counter-pressure controls.
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Large housings, pallets, equipment covers, automotive structures, furniture components, and parts requiring reduced weight and increased stiffness.
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Moderate-to-specialized process
Reduces material consumption and clamp-force demand, but surface appearance, dimensional stability, cell structure, and density distribution must be specified.
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| 8. Micro Injection Molding |
Very small, lightweight, or highly precise components are molded using extremely small shot sizes and tightly controlled process parameters. |
Engineering thermoplastics such as PA, PEEK, PC, POM, LCP, PPS, and medical-grade or specialty grades where applicable.
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High-precision mold inserts, micro-gates, fine venting, polished or textured micro-features, and specialized ejection systems. Mold alignment and cavity wear must be tightly controlled.
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Micro-injection machine or precision machine with a small injection unit, accurate screw or plunger metering, high-resolution sensors, and automated part handling.
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Medical devices, miniature gears, micro-connectors, laboratory components, optical parts, electronics, and precision fluidic components.
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High precision requirement
Tooling cost can be high relative to part size. Buyers should define dimensional tolerances, gate vestige limits, contamination controls, inspection method, and yield targets.
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| 9. Reaction Injection Molding (RIM) |
Two or more low-viscosity reactive liquid components are metered, mixed, and injected into a mold where they chemically react and cure. |
Mainly polyurethane systems, including rigid, semi-rigid, elastomeric, and reinforced grades. Other reactive resin systems may be used for specialized applications.
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Large, relatively low-pressure molds made from aluminum, steel, or suitable tooling materials. Requires controlled vents, overflow areas, seals, and mold temperature management.
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Metering and mixing unit, heated chemical storage tanks, high-pressure or impingement mixing head, temperature controls, mold handling equipment, and ventilation systems.
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Large automotive body parts, equipment housings, enclosures, architectural components, protective structures, and low-to-medium-volume large parts.
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Suitable for large parts
Provides low injection pressure, good surface area capability, and relatively low tooling cost. Chemical ratio, moisture control, cure time, and worker safety require strict management.
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| 10. Liquid Silicone Rubber (LSR) Injection Molding |
Two liquid silicone components are metered and mixed, injected into a heated mold, and rapidly cured into an elastomeric part. |
Liquid silicone rubber in different hardness levels, including transparent, pigmented, electrically insulating, medical, and high-temperature grades.
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Highly polished or textured steel molds with cold runners, precise shut-offs, fine venting, and controlled flash-prevention features. Mold temperature uniformity is critical.
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LSR metering and mixing system, cooled material supply, static mixer, heated injection mold, automatic demolding equipment, and clean production area where required.
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Seals, gaskets, valves, diaphragms, keypads, baby-care products, medical components, wearable parts, and heat-resistant electrical protection components.
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Specialized material handling
Excellent temperature resistance, flexibility, and durability. Buyers should verify cure chemistry, post-curing needs, flash limits, cleanliness requirements, and pigment compatibility.
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