Q1: How to accurately control injection position? How to determine if residual amount is reasonable?
A: Injection position determines melt filling endpoint. Insufficient residual amount will lead to pressure holding failure, while excessive residual amount easily causes flash.
- Technical Details:
- Residual Amount Calculation: Residual amount = Total stroke - Injection position. For example, with a total stroke of 150mm and an injection position set to 140mm, residual amount is 10mm.
- Dynamic Calibration: Use "short shot method" test (gradually increasing injection volume to 98%) and observe screw end pressure curve. If pressure curve shows a steep rise at the end (e.g., a sudden increase from 80Bar to 120Bar), it indicates insufficient residual amount, and position setting needs to be increased.
- Case Study: In production of a car bumper (PP material), original injection position of 145mm (5mm residual amount) caused shrinkage at the end. After adjusting to 148mm (2mm residual amount), shrinkage depth decreased from 0.4mm to 0.1mm.

 

Q2: How to balance filling efficiency and weld line control in segmented injection speed settings?
A: Segmented speeds must match mold runner structure and material properties.
- Technical Details:
- Gating Section: Speed ≤ 30% (e.g., Φ50 screw) to prevent cold slug from entering cavity. For example, in production of a PA66 gear, increasing gate speed from 25% to 35% reduced fiber breakage rate by 20%.
- Body Section: Speed = Maximum allowable shear rate of material * 0.7. Maximum shear rate of PC material is 10⁵Pa·s, and recommended speed is 70mm/s (corresponding to a shear rate of 7 * 10⁴Pa·s).
- End Section: Speed reduced to below 50% to avoid overheating of melt front (e.g., when end speed of PC material is > 60%, surface temperature rises by 8-10℃).
- Case Study: A transparent PC lampshade (1.5mm wall thickness) produced using a three-speed injection (30%→70%→30%) system reduced weld line whitening by 60%.
Q3: What problems arise from switching pressure holding point (V/P switching) too early or too late?
A: - Premature switching (e.g., 80% fill): Insufficient holding pressure, leading to shrinkage and deformation.
- Late switching (e.g., 99% fill): Insufficient screw residual weight, holding pressure failure, and increased risk of flash.
- Solution: Determine switching point using "short-shot method," retaining a 5-8mm material pad.
- Case Study: In production of a PC lampshade, adjusting V/P switching point from 90% to 95% reduced shrinkage depth from 0.3mm to 0.1mm.
Q4: What are differences in injection parameters between different materials (e.g., PP, PC)? How to adjust them?
A: Material viscosity and flowability determine parameter selection:
- PP: Injection speed 70-80%, pressure 40-50%, holding pressure 30-40%. Suitable for daily necessities, such as using high speed (70%) to reduce flash in production of cosmetic bottle caps.
- PC: Injection speed 30-50%, pressure 60-70%, holding pressure 50-60%. In an optical lens case, low speed (40%) combined with high pressure (65%) eliminates internal stress cracks.
- ABS: Injection speed 50-70%, pressure 50-60%, holding pressure 40-50%. In production of electronic casings, three-stage holding pressure (P1=50%, P2=30%, P3=10%) improves dimensional accuracy.
Q5: How does Haitian Machinery achieve pressure gradient control through multi-stage holding pressure?
A: By simulating material cooling and contraction curve through three-stage pressure reduction.
- Technical Details:
- P1 (Main Holding Pressure): Pressure = Injection Pressure * 60%, Time 60% (e.g., 9 seconds out of a total holding pressure of 15 seconds), rapid shrinkage compensation.
- P2 (Transition Holding Pressure): Pressure decreases to 40%-50% of P1, Time 30% (4.5 seconds), stress balance and release.
- P3 (Final Holding Pressure): Pressure decreases to 10%-20% of P1, Time 10% (1.5 seconds), eliminating residual stress.
- Case Study: After applying three-stage holding pressure to a certain automotive interior part (PP material), dimensional fluctuation coefficient decreased from 0.15% to 0.08%.
Q6: How to solve "flash" problem through parameter optimization?
A: Flash is mostly caused by excessive holding pressure or insufficient mold closing force.
- Technical Details:
- Pressure Reduction Method: Reduce holding pressure from 70% to 50% and observe whether the flash decreases.
- Clamping Force Compensation: Haitian injection molding machines utilize "Dynamic Clamping Force Distribution" function to increase parting surface pressure by 10% (e.g., from 1500T to 1650T).
- Case Study: In production of cosmetic bottle caps (PP material), holding pressure decreased from 65% to 55%, and flash rate decreased from 15% to 3%.

 

Q7: How do intelligent injection molding systems (such as Haitian iQ) achieve parameter self-adaptation?
A: Based on MOLDFLOW mold flow analysis and real-time data closed-loop.
- Technical Details:
- Data-Driven: Input material parameters (e.g., PA66 melting point 260℃) and mold temperature (80℃), and system automatically generates initial parameters.
- Real-Time Feedback: Monitor mold cavity pressure curve (sampling rate 100Hz), and trigger pressure compensation for 0.5s when pressure drops by 10%.
- Case Study: After application on a PET preform production line, cycle time was shortened by 18%, and energy consumption was reduced by 25%.
Q8: What is effect of mold temperature on injection parameters? How to optimize process?
A: Mold temperature directly affects melt viscosity and cooling rate.
- Technical details:
- High mold temperature (e.g., 80-100℃ for PC molds): Injection speed needs to be reduced (30%→20%) to prevent material degradation.
- Low mold temperature (e.g., 40-60℃ for PP molds): Injection pressure needs to be increased (50%→60%) to compensate for decreased fluidity.
- Case study: For an ABS shell (2mm wall thickness), raising mold temperature from 70℃ to 85℃ improved surface gloss by 30%.