This article breaks down the key injection molding parameters for common plastics, offering real-world data and mold-specific insights to help you fine-tune your process and avoid costly trial-and-error.

Getting the process window right is half the battle in injection molding. For amorphous resins like ABS and PC, melt temperature is the first thing I check. ABS typically runs at 210–250°C, with mold surface temperature between 40–80°C. If you see splay or poor weld lines, raise the mold temperature toward 80°C—that often helps flow without risking degradation. PC is more demanding: 280–320°C melt, and a mold at 80–120°C. I’ve seen warpage drop by nearly 30% just by holding the mold at 110°C for a 2mm wall PC part. Also, pay attention to screw back pressure: 0.5–1.0 MPa for ABS, but PC needs 1.0–2.0 MPa to ensure uniform melt density. Too low, and you get trapped air; too high, and you risk shear burning.

For semi-crystalline materials like PA66 and POM, the story changes. PA66 with 30% glass fiber needs melt at 280–300°C, and mold temperature must be 80–120°C—not optional. If you run a cold mold, you’ll get a crystalline skin that shrinks unevenly, leading to sink marks and dimensional instability. I always recommend a mold temperature controller with ±2°C accuracy for these resins. POM is trickier: melt at 190–210°C, but never exceed 220°C, or formaldehyde gas will cause severe tool corrosion. Mold temperature for POM is typically 80–100°C, and injection speed should be medium to fast—slow fill causes hesitation marks on the surface. For both, hold pressure is critical: PA66 needs 60–80 MPa, while POM works best with 70–90 MPa, applied until the gate freezes.

Don’t forget the practical side: drying is non-negotiable. PC must be dried to below 0.02% moisture (120°C for 4 hours), and PA66 to below 0.15% (80°C for 4 hours). Even a 0.1% moisture deviation can cause hydrolytic degradation, reducing impact strength by 50%. Also, check your shot size—keep it between 30% and 70% of the barrel capacity to avoid residence time issues. For thin-wall parts under 1mm, increase injection speed by 20–30% but reduce pack pressure to prevent flash. These numbers are starting points, not gospel—every mold has its own personality. For more detailed sourcing and process troubleshooting, visit MoldWorld (www.moldw.com) for a full database of material guides and mold supplier directories.