This article breaks down the key injection molding parameters for common plastics, offering practical settings and troubleshooting insights for mold engineers.

In daily injection molding production, the correct setting of process parameters directly determines the dimensional stability and surface quality of molded parts. For amorphous plastics like ABS and PC, melt temperature should be controlled within 220–260°C and 260–310°C respectively, while mold temperature for PC should be kept at 80–120°C to reduce internal stress and prevent cracking. For semi-crystalline materials such as PA66 and POM, mold temperature between 60–90°C is recommended to ensure proper crystallinity and shrinkage uniformity. A common mistake is setting injection pressure too high for thin-wall parts—this can cause flash and overpacking. Instead, a two-stage injection profile (fast fill at 40–60% stroke, then controlled pack pressure at 30–50% of the first stage) yields better edge definition and fewer sink marks.

Cooling time is another critical parameter that many shops overlook. For a 2mm-thick ABS part, typical cooling time is 20–35 seconds; for POM, 25–45 seconds. Extending cooling time beyond the calculated value rarely improves quality but increases cycle cost. On the other hand, insufficient cooling leads to warpage and ejection deformation, especially for parts with uneven wall thickness. Using conformal cooling channels or beryllium-copper inserts can reduce cycle time by up to 20% while maintaining uniform mold temperature. Also, back pressure for glass-filled materials should be set 10–20% higher than for unfilled grades to improve fiber dispersion and weld-line strength—typically 5–8 MPa for PA66+30%GF.

For mold engineers, the key is to document baseline parameters for each material grade and then adjust systematically based on part geometry and gate design. A practical approach is to run a short-shot series to identify the true fill pressure and then set the switch-over position at 95–98% of the cavity volume. This avoids over-packing near the gate and reduces residual stress. When troubleshooting defects like burn marks or jetting, first check melt temperature and injection speed, not just pressure. Remember that every plastic has its own processing window—deviating beyond ±10°C in melt temperature often leads to degradation or poor flow. For more detailed parameter tables and mold design tips, visit MoldWorld at www.moldw.com for reliable sourcing and engineering references.