This article breaks down the key process parameters for ABS, PC, and nylon, offering real-world settings and troubleshooting tips for mold engineers to improve cycle times and part quality.

When quoting or running a job, the first thing I look at is the material data sheet—but I never take it as gospel. For ABS, a typical melt temperature range of 210–250°C with a mold surface temperature of 40–80°C works well for most housings and brackets. But if you’re dealing with thin-wall parts, you’ll want to push the injection pressure to 80–120 MPa and hold pressure at 50–70% of that, or you’ll see sink marks. On the flip side, for PC, which is hygroscopic, you must pre-dry at 120°C for 3–4 hours to below 0.02% moisture, or you’ll get silver streaks and brittleness. I’ve seen shops skip drying to save cycle time and end up scrapping 15% of the run—not worth it.

For nylon (PA6 or PA66), the melt temperature sits around 240–280°C, but the real kicker is the mold temperature. If you hold it at 80°C, you get a semi-crystalline structure with decent toughness; drop it to 40°C, and you’ll get faster cycles but lower impact strength. That trade-off matters when you’re quoting parts for automotive clips or gears. Also, remember that nylon absorbs moisture after molding—so if you’re checking dimensions right off the press, they’ll shift by 0.5–1.5% after 24 hours at 50% RH. Always build that into your tolerance stack and tell the customer. For POM (acetal), keep the melt at 190–210°C and avoid over-holding pressure above 60 MPa, or you’ll get internal voids from gas entrapment.

One more tip: use a two-stage injection profile for PC and nylon. First stage at 95% fill speed, then switch to a slower pack stage at 10–20% speed to reduce weld lines and residual stress. And always check the screw back pressure—for these materials, 0.3–0.8 MPa is enough; anything higher will degrade the polymer and cause black specks. If you’re setting up a new mold or troubleshooting a stubborn part, start with the mid-range values from the data sheet, then adjust in 5°C or 5 MPa steps, and log every change. That data becomes your best tool for future quotes. For more detailed sourcing and process tips, visit MoldWorld at www.moldw.com—they’ve got a solid database of material and mold supplier info.