Introduction to Injection Molding Parameters
Injection molding parameters are critical for achieving high-quality plastic parts with consistent properties. These parameters include barrel temperatures, melt temperatures, mold temperatures, injection pressures, holding pressures, back pressures, injection speeds, screw speeds, metering strokes, residual amounts, pre-drying conditions, recovery rates, shrinkage rates, gating systems, machine shutdown procedures, and equipment requirements. Proper selection and control ensure optimal flow, cooling, and solidification, minimizing defects such as warping, voids, or surface imperfections.
This guide covers parameters for common plastics, based on industry standards and best practices. Each material has unique thermal, rheological, and mechanical characteristics that influence processing. For instance, crystalline polymers like HDPE require precise temperature control for crystallization, while amorphous ones like PS focus on viscosity management. Engineers should adjust parameters based on part geometry, machine capabilities, and environmental factors to enhance productivity and part performance.
Key considerations include safety, energy efficiency, and sustainability. Always verify parameters with material data sheets and conduct trials for new setups. This approach reduces scrap rates and improves cycle times, contributing to cost-effective manufacturing.
High-Density Polyethylene (HDPE)
HDPE is a semi-crystalline thermoplastic known for its excellent chemical resistance, low moisture absorption, and high impact strength. It is widely used in containers, pipes, and toys. Processing requires careful temperature management to achieve uniform crystallization and avoid warping.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 30-50°C; Zone 1: 160-250°C; Zone 2: 200-300°C; Zone 3-5: 220-300°C; Nozzle: 220-300°C |
| Melt Temperature | 200-280°C |
| Mold Temperature | 20-60°C |
| Injection Pressure | 80-140 MPa (up to 180 MPa for thin walls) |
| Holding Pressure | 30-60% of injection pressure |
| Back Pressure | 5-20 MPa |
| Injection Speed | Medium for general; high for thin-wall packaging |
| Screw Speed | Up to 1.3 m/s linear velocity |
| Metering Stroke | 0.5-4D |
| Cushion | 2-8 mm |
| Pre-Drying | Not required; 80°C for 1h if stored poorly |
| Recovery Rate | Up to 100% |
| Shrinkage | 1.2-2.5%; high shrinkage, potential warping; no further shrinkage after 24h |
| Gating System | Point gate; hot runner (heated or insulated); small cross-section sufficient for thin parts |
| Machine Shutdown | No special cleaning needed; HDPE withstands temperature rise |
| Equipment | Standard screw; three-section screw for general; special mixing/shear sections for packaging (L=25D); straight nozzle, check valve |
For optimal results, ensure 4D metering stroke for sufficient melt residence time. High screw speeds are permissible if plasticization completes before cooling ends. Adjust for thin-wall parts to prevent flow hesitation.
Polypropylene (PP)
PP is a versatile semi-crystalline polymer with good chemical resistance, fatigue strength, and low cost. It is ideal for automotive parts, packaging, and consumer goods. Processing focuses on managing shrinkage and ensuring uniform cooling to avoid sink marks.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 30-50°C; Zone 1: 160-250°C; Zone 2: 200-300°C; Zone 3-5: 220-300°C; Nozzle: 220-300°C |
| Melt Temperature | 200-280°C |
| Mold Temperature | 20-70°C |
| Injection Pressure | 80-140 MPa (up to 180 MPa for thin-wall packaging) |
| Holding Pressure | 30-60% of injection pressure; ~30% of cycle time |
| Back Pressure | 5-20 MPa |
| Injection Speed | High for thin-wall packaging (with accumulator); medium for others |
| Screw Speed | Up to 1.2 m/s linear velocity |
| Metering Stroke | 0.5-4D |
| Cushion | 2-8 mm |
| Pre-Drying | Not required; 80°C for 1h if stored poorly |
| Recovery Rate | Up to 100% |
| Shrinkage | 1.2-2.5%; high shrinkage; no further shrinkage after 24h |
| Gating System | Point or multi-point gate; hot runner (heated or insulated); gate at thickest part to avoid sink marks |
| Machine Shutdown | No special cleaning needed; PP withstands temperature rise |
| Equipment | Standard screw; three-section screw for general; special mixing/shear sections for packaging (L=25D); straight nozzle, check valve |
Long holding times are essential to prevent sink marks in thick sections. Gate placement at the thickest point minimizes shrinkage variations. Use accumulators for high-speed filling in packaging applications.
Polystyrene (PS)
PS is an amorphous thermoplastic with high clarity, rigidity, and low cost. It is suitable for packaging, toys, and disposable items. Processing emphasizes fast injection to achieve good surface finish and minimize weld lines.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 30-50°C; Zone 1: 160-250°C; Zone 2: 200-300°C; Zone 3-5: 220-300°C; Nozzle: 220-300°C |
| Melt Temperature | 200-280°C |
| Mold Temperature | 15-50°C |
| Injection Pressure | 80-140 MPa |
| Holding Pressure | 30-60% of injection pressure; short holding time |
| Back Pressure | 5-10 MPa |
| Injection Speed | Fast, multi-stage based on part shape; very fast for thin-wall packaging (with accumulator) |
| Screw Speed | Up to 1.3 m/s linear velocity; slow plasticization to match cooling time |
| Metering Stroke | 0.5-4D |
| Cushion | 2-8 mm |
| Pre-Drying | Not required; 80°C for 1h if stored poorly |
| Recovery Rate | Up to 100% |
| Shrinkage | 0.3-0.6% |
| Gating System | Point gate; hot runner (heated or insulated); small cross-section sufficient |
| Machine Shutdown | No special cleaning needed; PS withstands temperature rise |
| Equipment | Standard screw; straight nozzle, check valve |
Low back pressure prevents air entrapment, avoiding streaks. Slow plasticization ensures good melt quality for high-gloss parts. Vent molds properly to prevent burning.
Polyvinyl Chloride – Unplasticized (PVC-U)
PVC-U is a rigid amorphous polymer with good chemical resistance and flame retardancy. It is used in pipes, fittings, and profiles. Processing is sensitive to heat, requiring low shear to avoid degradation.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 30-50°C; Zone 1: 140-160°C; Zone 2: 165-180°C; Zone 3-5: 180-210°C; Nozzle: 180-210°C |
| Melt Temperature | 210-220°C |
| Mold Temperature | 30-60°C |
| Injection Pressure | 80-160 MPa |
| Holding Pressure | 40-60% of injection pressure; based on part and gate |
| Back Pressure | Up to 30 MPa |
| Injection Speed | Low to avoid shear; multi-stage if needed for edges or degradation-prone areas |
| Screw Speed | Lowest possible; up to 0.2 m/s linear velocity; delay plasticization if necessary |
| Metering Stroke | 1.0-3.5D |
| Cushion | 1-5 mm |
| Pre-Drying | 70°C for 1h if stored poorly |
| Recovery Rate | Allowed if no thermal degradation |
| Shrinkage | 0.5-0.7% |
| Gating System | Direct, fan, or diaphragm gate; point gate for small parts; rounded transitions |
| Machine Shutdown | Close heating; allow melt to reside 2-3 min, then extrude slowly; repeat until barrel at 160°C, empty |
| Equipment | Rigid PVC screw; barrel with heating/cooling; grooved screw head; straight nozzle |
Heat from screw friction is preferable to barrel heating due to thermal sensitivity. Ensure minimal barrel clearance for tight fit. Monitor for degradation signs like color change or odor.
Polyvinyl Chloride – Plasticized (P-PVC)
P-PVC is flexible with good weather resistance and electrical insulation. It is used in wires, hoses, and seals. Processing involves lower temperatures than PVC-U to preserve flexibility.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 30-50°C; Zone 1: 140-160°C; Zone 2: 150-180°C; Zone 3-5: 160-220°C; Nozzle: 160-220°C |
| Melt Temperature | 200-220°C |
| Mold Temperature | 30-50°C |
| Injection Pressure | 80-120 MPa |
| Holding Pressure | 30-60% of injection pressure |
| Back Pressure | 5-10 MPa |
| Injection Speed | Not too fast for good surface; multi-stage if necessary |
| Screw Speed | Medium; up to 0.5 m/s linear velocity |
| Metering Stroke | 1.0-3.5D |
| Cushion | 2-6 mm |
| Pre-Drying | Not required; 70°C for 1h if stored poorly |
| Recovery Rate | Allowed if no thermal degradation |
| Shrinkage | 1-2.5% |
| Gating System | Point gate for small parts; rounded transitions |
| Machine Shutdown | Close heating; no back pressure, extrude cycles |
| Equipment | Standard screw; check ring, straight nozzle |
Avoid high speeds to prevent poor surface quality. Monitor for plasticizer migration during storage. Use for flexible applications requiring durability.
Polyamide 6 (PA6)
PA6 is a semi-crystalline polyamide with high toughness, abrasion resistance, and moisture absorption. It is used in gears, bearings, and automotive parts. Processing requires drying to control moisture for consistent properties.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 60-90°C; Zone 1-2: 230-240°C; Zone 3-5: 240-250°C; Nozzle: 230-240°C |
| Melt Temperature | 240-250°C |
| Mold Temperature | 60-100°C |
| Injection Pressure | 100-160 MPa (up to 180 MPa for thin long runners) |
| Holding Pressure | 50% of injection pressure; short time |
| Back Pressure | 2-8 MPa |
| Injection Speed | Fast; good venting to avoid burning |
| Screw Speed | Up to 1 m/s; low to match cooling |
| Metering Stroke | 0.5-3.5D |
| Cushion | 2-6 mm |
| Pre-Drying | 80°C for 4h; moisture <0.25% |
| Recovery Rate | Up to 10% |
| Shrinkage | 0.7-2.0%; 0.3-0.8% with 30% glass fiber |
| Gating System | Point, latent, fan, direct; blind pockets for cold slug; hot runner with closed-loop control |
| Machine Shutdown | No cleaning; melt residence up to 20 min |
| Equipment | Standard screw with high plasticizing capacity; check ring, straight nozzle; bimetallic barrel for glass-filled |
Slow cooling reduces post-mold shrinkage and internal stress. Use steam for annealing if needed. Check stress with solvents. For glass-filled, use wear-resistant equipment.
Polyamide 66 (PA66)
PA66 offers higher melting point and stiffness than PA6, with good heat resistance. It is used in under-hood automotive components and electrical connectors. Drying is essential to prevent hydrolysis.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 60-90°C; Zone 1-2: 260-290°C; Zone 3-5: 280-290°C; Nozzle: 280-290°C |
| Melt Temperature | 270-290°C |
| Mold Temperature | 60-100°C |
| Injection Pressure | 100-160 MPa (up to 180 MPa for thin long runners) |
| Holding Pressure | 50% of injection pressure; short time |
| Back Pressure | 2-8 MPa |
| Injection Speed | Fast; good venting to avoid burning |
| Screw Speed | Up to 1 m/s; low to match cooling |
| Metering Stroke | 0.5-3.5D |
| Cushion | 2-6 mm |
| Pre-Drying | 80°C for 4h; moisture <0.25% |
| Recovery Rate | Up to 10% |
| Shrinkage | 0.7-2.0%; 0.4-0.7% with 30% glass fiber |
| Gating System | Point, latent, fan, direct; blind pockets for cold slug; hot runner with closed-loop control |
| Machine Shutdown | No cleaning; melt residence up to 20 min |
| Equipment | Standard screw with high plasticizing capacity; check ring, straight nozzle; bimetallic barrel for glass-filled |
Gradual cooling improves dimensional stability. For glass-filled grades, higher mold temperatures enhance surface finish. Store in moisture-proof containers.
Polybutylene Terephthalate (PBT)
PBT is a semi-crystalline polyester with excellent electrical insulation and chemical resistance. It is used in electrical connectors and automotive parts. Processing involves narrow temperature ranges to avoid degradation.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 50-70°C; Zone 1: 230-250°C; Zone 2: 240-260°C; Zone 3-5: 250-260°C; Nozzle: 250-260°C |
| Melt Temperature | 250-260°C; narrow range, below 240°C condenses, above 270°C degrades |
| Mold Temperature | 60-80°C |
| Injection Pressure | 100-140 MPa |
| Holding Pressure | 50-60% of injection pressure |
| Back Pressure | 5-10 MPa; avoid friction heat |
| Injection Speed | High due to fast solidification; good venting to prevent burning |
| Screw Speed | Up to 0.5 m/s |
| Metering Stroke | 0.5-3.5D |
| Cushion | 2-5 mm |
| Pre-Drying | 120°C for 4h |
| Recovery Rate | Up to 10% for flame-retardant; 20% for non-flame-retardant; pre-dried, no degradation |
| Shrinkage | 1.4-2.0%; 0.4-0.6% with 30% glass fiber; higher mold temp increases shrinkage |
| Gating System | Avoid direct/point for glass-filled; hot runner with closed-loop control |
| Machine Shutdown | Close heating; extrude until empty; restart with purge until no bubbles |
| Equipment | Standard screw; check ring, straight nozzle |
Limit residence time to <0.5 min to prevent overheating. For flame-retardant grades, lower recovery rates. High crystallization rate demands fast filling.
Polyethylene Terephthalate (PET)
PET is a semi-crystalline polyester with high strength and barrier properties. It is used in bottles and fibers. Processing requires strict drying to avoid hydrolysis.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 50-70°C; Zone 1-2: 240-260°C; Zone 3-5: 250-290°C; Nozzle: 250-290°C |
| Melt Temperature | 270-280°C |
| Mold Temperature | 120-140°C |
| Injection Pressure | Up to 160 MPa for thin sections |
| Holding Pressure | 50-70% of injection pressure; adjust time to minimize stress |
| Back Pressure | 5-10 MPa; avoid friction heat |
| Injection Speed | High due to fast solidification; good venting |
| Screw Speed | Up to 0.5 m/s |
| Metering Stroke | 0.5-3.5D |
| Cushion | 2-5 mm |
| Pre-Drying | 120°C for 4h |
| Recovery Rate | Up to 20%; pre-dried, no degradation |
| Shrinkage | 1.2-2.0%; 0.4% with 30% glass fiber; varies with mold temp and holding |
| Gating System | Any standard; hot runner with closed-loop control |
| Machine Shutdown | Close heating; extrude until empty; clean with PE or PP if changing materials |
| Equipment | Standard screw; check ring, straight nozzle |
High mold temperatures promote crystallization. Limit residence time to <0.5 min. For non-crystalline grades, longer holding reduces impact strength.
Polycarbonate (PC)
PC is an amorphous thermoplastic with high impact strength and transparency. It is used in lenses, helmets, and electronics. Processing requires high pressures due to high viscosity.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 70-90°C; Zone 1: 230-270°C; Zone 2: 260-310°C; Zone 3-4: 280-310°C; Zone 5: 290-320°C; Nozzle: 300-320°C |
| Melt Temperature | 250-310°C |
| Mold Temperature | 80-110°C |
| Injection Pressure | 130-180 MPa |
| Holding Pressure | 40-60% of injection pressure; lower for reduced stress |
| Back Pressure | 10-15 MPa |
| Injection Speed | Based on flow length and thickness; fast for thin walls, multi-stage slow for surface quality |
| Screw Speed | Up to 0.6 m/s; match plasticization to cooling |
| Metering Stroke | 0.5-3.5D |
| Cushion | 2-5 mm |
| Pre-Drying | 120°C for 3h; moisture <0.02% |
| Recovery Rate | Up to 20% |
| Shrinkage | 0.6-0.8%; 0.2-0.4% with glass |
| Gating System | Gate diameter 60-70% of max wall thickness, min 1.2 mm; point for small uniform walls |
| Machine Shutdown | Air shot to 200°C; clean with high-viscosity PE, remove screw and brush |
| Equipment | Standard screw; check ring, straight nozzle |
High torque screws are needed for viscosity. Lower holding reduces stress. Dry thoroughly for optical clarity.
Acrylonitrile Butadiene Styrene (ABS)
ABS is an amorphous terpolymer with good impact resistance and surface finish. It is used in automotive interiors and electronics. Processing aims for high gloss and strong weld lines.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 40-60°C; Zone 1: 160-180°C; Zone 2: 180-230°C; Zone 3-5: 210-260°C; Nozzle: 210-260°C |
| Melt Temperature | 220-250°C |
| Mold Temperature | 40-80°C |
| Injection Pressure | 100-150 MPa |
| Holding Pressure | 30-60% of injection pressure; short time |
| Back Pressure | 5-15 MPa |
| Injection Speed | Multi-stage from slow to fast for gloss, min weld lines; vent at flow meetings |
| Screw Speed | Up to 0.6 m/s; low to match cooling |
| Metering Stroke | 0.5-4D |
| Cushion | 2-8 mm |
| Pre-Drying | Optional; 80°C for 3h if moist to avoid streaks or bubbles |
| Recovery Rate | Up to 30%; no degradation |
| Shrinkage | 0.4-0.7% |
| Gating System | Point gate, hot runner; min wall 0.7 mm |
| Machine Shutdown | No special cleaning |
| Equipment | Standard screw; check ring, straight nozzle |
Multi-stage injection improves surface and weld strength. Dry if moist to prevent defects. Suitable for plated parts.
Acrylonitrile Butadiene Styrene/Polycarbonate (ABS/PC)
ABS/PC blend combines ABS toughness with PC heat resistance. It is used in automotive and electronics. Processing balances the blend’s properties.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 50-70°C; Zone 1: 230-250°C; Zone 2-5: 250-270°C; Nozzle: 250-270°C |
| Melt Temperature | 260-270°C |
| Mold Temperature | 70-90°C |
| Injection Pressure | 80-150 MPa |
| Holding Pressure | 40-50% of injection pressure; low for min stress |
| Back Pressure | 5-10 MPa; avoid friction heat |
| Injection Speed | Medium; multi-stage from slow to fast for some parts |
| Screw Speed | Up to 0.4 m/s |
| Metering Stroke | 1.0-3.0D |
| Cushion | 2-5 mm |
| Pre-Drying | 80°C for 4h |
| Recovery Rate | Up to 20%; pre-dried, no degradation |
| Shrinkage | Nearly isotropic 0.5-0.7%; 0.2-0.4% with glass |
| Gating System | Any standard; hot runner with closed-loop control |
| Machine Shutdown | Close heating; extrude to clean barrel |
| Equipment | Standard screw (50 mm dia); low compression for larger; check ring, straight nozzle |
Limit residence time to <6 min. For large screws, use low compression geometries. Ideal for parts requiring impact and heat resistance.
Styrene Acrylonitrile (SAN)
SAN is an amorphous copolymer with high clarity and rigidity. It is used in housewares and cosmetics. Processing focuses on fast injection for gloss and strength.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 30-50°C; Zone 1: 160-180°C; Zone 2: 180-230°C; Zone 3-4: 210-260°C; Zone 5: 220-260°C; Nozzle: 220-260°C |
| Melt Temperature | 220-250°C |
| Mold Temperature | 40-80°C |
| Injection Pressure | 100-150 MPa |
| Holding Pressure | 30-40% of injection pressure; short time |
| Back Pressure | 5-15 MPa |
| Injection Speed | Fast for gloss, color, min weld lines |
| Screw Speed | Up to 0.6 m/s; low to match cooling; medium torque |
| Metering Stroke | 0.5-4.0D |
| Cushion | 2-8 mm |
| Pre-Drying | 80°C for 4h if moist |
| Recovery Rate | Up to 30%; no degradation for high quality |
| Shrinkage | 0.4-0.7% |
| Gating System | Any standard and hot runner |
| Machine Shutdown | No special cleaning |
| Equipment | Standard screw; check ring, straight nozzle |
Dry to avoid surface defects. Fast injection enhances aesthetics. Suitable for transparent applications.
Polymethyl Methacrylate (PMMA)
PMMA is an amorphous polymer with excellent optical clarity and weather resistance. It is used in lenses and displays. Processing requires high pressures and slow speeds for thick parts.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 60-80°C; Zone 1: 150-200°C; Zone 2: 180-220°C; Zone 3-5: 200-250°C; Nozzle: 200-250°C |
| Melt Temperature | 220-250°C |
| Mold Temperature | 40-80°C |
| Injection Pressure | 100-170 MPa |
| Holding Pressure | 40-60% of injection pressure; long for thick parts (2-3 min) |
| Back Pressure | 10-30 MPa |
| Injection Speed | Low for thick; multi-stage from slow to fast near gate for quality |
| Screw Speed | Slow to match cooling; up to 0.6 m/s |
| Metering Stroke | 0.5-3.5D |
| Cushion | 2-6 mm |
| Pre-Drying | 80°C for 4h; high absorption |
| Recovery Rate | Allowed if dried and colored; reduced optical quality |
| Shrinkage | 0.3-0.7% |
| Gating System | Large gates; short round or square cross-section; avoid sharp edges |
| Machine Shutdown | No cleaning |
| Equipment | Standard screw; special for optics; check ring, straight nozzle |
High back pressure avoids voids. Dry thoroughly for clarity. For lenses, long holding ensures uniformity.
Polyoxymethylene (POM)
POM is a semi-crystalline acetal with low friction and high stiffness. It is used in gears and fasteners. Processing focuses on stable shrinkage for precision parts.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 40-50°C; Zone 1: 160-180°C; Zone 2: 180-205°C; Zone 3: 185-205°C; Zone 4-5: 195-215°C; Nozzle: 200-250°C |
| Melt Temperature | 205-215°C |
| Mold Temperature | 40-120°C |
| Injection Pressure | 100-150 MPa; 100 for thick, 150 for thin |
| Holding Pressure | 80-100 MPa; long for min shrinkage (~30% cycle) |
| Back Pressure | 5-10 MPa |
| Injection Speed | Medium; low if low mold/melt temp to avoid pores |
| Screw Speed | Up to 0.7 m/s; match to cooling; medium torque |
| Metering Stroke | 0.5-3.5D |
| Cushion | 2-6 mm |
| Pre-Drying | Not required; 100°C for 4h if moist |
| Recovery Rate | 100% for general; 20% for precision |
| Shrinkage | ~2%; stops after 24h |
| Gating System | Point for small uniform; 50-60% of max wall; against obstacles; hot runner possible |
| Machine Shutdown | Close heating 5-10 min before end; zero back pressure, empty; clean with PA or PC, then PE |
| Equipment | Standard screw; check ring, straight nozzle |
Optimize holding for stable dimensions. For precision, monitor part weight to 100% for min shrinkage. Vent well.
Cellulose Acetate (CA)
CA is a biodegradable amorphous polymer with good clarity and toughness. It is used in eyeglass frames and tools. Processing is sensitive to moisture and heat.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 30-40°C; Zone 1: 140-160°C; Zone 2: 160-185°C; Zone 3-5: 170-200°C; Nozzle: 170-200°C |
| Melt Temperature | 200-210°C; color change if too high, poor gloss if low |
| Mold Temperature | 40-80°C |
| Injection Pressure | 80-120 MPa |
| Holding Pressure | 40-100% of injection pressure; long for thick to avoid stress |
| Back Pressure | 5-10 MPa |
| Injection Speed | Fast for thin; slow for thick |
| Screw Speed | Medium; up to 0.6 m/s |
| Metering Stroke | 1.5-3.5D |
| Cushion | 3-8 mm |
| Pre-Drying | 70°C for 3h |
| Recovery Rate | Up to 20%; pre-dried, no degradation |
| Shrinkage | 0.4-0.7%; anisotropic (0.4% flow, 0.6-0.7% transverse) |
| Gating System | Point/latent; spring-loaded ejectors to avoid jetting |
| Machine Shutdown | Close heating; no back pressure, extrude to empty |
| Equipment | Standard screw; special if needed; check ring, straight nozzle |
Adjust speed for wall thickness. Dry to prevent defects. Suitable for bio-based applications.
Polyphenylene Oxide (PPO)
PPO is an amorphous engineering plastic with high heat resistance and dimensional stability. It is used in pumps and valves. Processing requires good flow for long paths.
| Parameter | Value |
|---|---|
| Barrel Temperature | Feed: 40-60°C; Zone 1: 240-280°C; Zone 2-5: 280-300°C; Nozzle: 280-300°C |
| Melt Temperature | 270-290°C |
| Mold Temperature | 80-120°C |
| Injection Pressure | 100-140 MPa |
| Holding Pressure | 40-60% of injection pressure |
| Back Pressure | 3-10 MPa |
| Injection Speed | Fast for long flows; ensure venting |
| Screw Speed | Medium; up to 0.6 m/s |
| Metering Stroke | 0.5-3.5D |
| Cushion | 3-6 мм |
| Pre-Drying | 110°C for 2h |
| Recovery Rate | Allowed if no degradation |
| Shrinkage | 0.8-1.5% |
| Gating System | Point/latent for small; direct/fan for others; hot runner |
| Machine Shutdown | Close heating; low back pressure, metering cycles to empty |
| Equipment | Standard screw; check ring, straight nozzle |
Good venting for long flows. Dry to prevent hydrolysis. Ideal for high-heat applications.
Practical Applications and Guidelines
Injection molding parameters must be tailored to specific applications. For packaging with HDPE or PP, high speeds and accumulators ensure thin-wall filling. In automotive with PA66 or PBT, high mold temperatures enhance mechanical properties. For optics with PMMA or PC, stringent drying and slow speeds minimize defects.
Guidelines include monitoring moisture for hygroscopic materials like PA and PET, using closed-loop controls for hot runners, and conducting DOE for optimization. Safety measures involve proper venting to avoid gas buildup, and sustainability through maximizing recovery rates without compromising quality.
- Start with material supplier recommendations and adjust based on trials.
- Use process monitoring tools for real-time parameter control.
- Ensure machine calibration for consistent cycles.
- Avoid overpacking to reduce stress in amorphous materials.
- Implement cooling channels for uniform temperature distribution.
These practices lead to high-quality parts, reduced waste, and efficient production.
Часто задаваемые вопросы (FAQ)
- Why is pre-drying essential for materials like PA6 and PET?
- These hygroscopic materials absorb moisture, leading to hydrolysis during processing, causing defects like bubbles or reduced strength. Drying to <0.25% moisture ensures quality.
- How does injection speed affect part quality in PP molding?
- High speeds for thin walls prevent premature freezing; medium for general avoids shear degradation, ensuring uniform fill and min sink marks.
- What is the impact of mold temperature on shrinkage in HDPE?
- Higher temperatures allow slower cooling, increasing crystallinity and shrinkage (1.2-2.5%); control for dimensional stability.
- Why use multi-stage injection in PS processing?
- It optimizes fill for complex shapes, improving surface gloss and weld line strength while preventing overpacking.
- How to handle thermal sensitivity in PVC-U molding?
- Use low shear speeds, friction heat preference, and max back pressure of 30 MPa to avoid degradation and ensure uniform melt.
- What adjustments for glass-filled PA66?
- Use bimetallic barrels for wear resistance, higher mold temps for finish, and check for reduced shrinkage (0.4-0.7%).
