Detailed description of the injection molding grade nylon PA6 injection molding process operation requirements nylon PA6 is milky white or yellowish transparent to opaque keratinous crystalline polymer, molding processability is excellent: injection molding, blow molding, casting, spraying, powder molding, machining, Welding, bonding, etc. Since the nylon PA6 has good moldability, the following describes the injection molding process.
Melt temperature: 240-250 ° C
Barrel constant temperature: 220 ° C PA6
Mold temperature: 60-100 ° C
Drying treatment: The injection molding grade nylon PA6 should be dried before processing. If the material is supplied in a waterproof material, the container should be kept closed. If the humidity is greater than 0.2%, it is recommended to dry in hot air above 80 °C for 16 hours. If the material has been exposed to air for more than 8 hours, it is recommended to dry at 105 ° C for more than 8 hours.
Melting temperature: 230-280 ° C, for enhanced varieties 250-280 ° C.
Mold temperature: 80-90 ° C. The mold temperature significantly affects the crystallinity, which in turn affects the mechanical properties of the part. Crystallinity is important for structural components, so it is recommended that the mold temperature be 80-90 °C. It is also recommended to apply a higher mold temperature for thin-walled, longer-flowing plastic parts. Increasing the mold temperature increases the strength and stiffness of the part, but reduces the toughness. If the wall thickness is greater than 3mm, a low temperature mold of 20-40 °C is recommended. For glass fiber reinforced materials, the mold temperature should be greater than 80 °C.
Injection pressure: generally between 750-1250bar (depending on material and product design) Injection speed: high speed (slightly lower for reinforcement) Runner and gate: For injection molding grade nylon PA6, the setting time is very short, so the gate The location is very important. The gate aperture should not be less than 0.5*T (where T is the thickness of the plastic part). If a hot runner is used, the gate size should be smaller than with a conventional runner because the hot runner can help prevent premature solidification of the material. If a submerged gate is used, the minimum diameter of the gate should be 0.75 mm.
Injection pressure: 100-160 MPa (1000-1600 bar), if it is processing thin surface long runner products (such as wire tie), it needs to reach 180MPa (180bar).
Holding pressure: 50% of the injection pressure; due to the relatively fast condensing of the material, a short holding time is sufficient. Reducing the holding pressure reduces the stress inside the product.
Back pressure: 2-8MPa (20-80bar), need to be accurately adjusted, because the back pressure is too high will cause uneven plasticization.
Injection speed: It is recommended to use a relatively fast injection speed; the mold has good ventilation or coking has appeared on the product.
Screw speed: The screw speed is high and the line speed is 1 m/s; however, it is better to set the screw speed lower, as long as the plasticizing process can be completed before the end of the cooling time; lower screw torque is required.
Measuring stroke: 0.5-3.5D
Residual amount: 2-6mm depends on the metering stroke and screw diameter.
Pre-baking: drying at 90 ° C for 4 h, except for feeding directly from the charging container; injection molding grade nylon PA6 is absorbent, should be stored in a moisture-proof container and a closed hopper; water will contain more than 0.25% Causes molding changes.
Recovery rate: 10% return material can be added.
Shrinkage: 0.7%-2.0%; or 30% glass fiber reinforced, shrinkage 0.3%-0.8%; if the temperature provided exceeds 60 °C, the product should be gradually cooled; gradually cooling can reduce shrinkage after molding. That is, the product exhibits better dimensional stability and small internal stress; the steam method is recommended; the nylon product can be inspected for stress by welding the flux.
Gate system: point type, latent type, chip type and sprue can be used; it is recommended to use blind hole and gate socket to cool the material point; hot runner can be used; due to the narrow processing temperature range of the melt, the hot runner should be Provides closed loop temperature control.
Barrel equipment: standard screw, high plasticizing capacity for special geometry; anti-reverse ring, straight-through nozzle; for the addition of glass fiber reinforcement, high wear-resistant bimetallic barrel
Machine downtime: no need to clean with other materials; the melt remains in the barrel for up to 20 minutes, after which thermal degradation is easy to occur.
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