Mold design decisions lock in most of your process window before the first shot. In practice, four constructions cover most work: two-plate (standard) tools for simple, high-volume parts; three-plate tools when gating must be central and runner balance matters; hot-runner systems where sprue scrap and cycle time justify the higher tooling cost; and stack molds when output per floor area is the constraint. Each choice changes what you can tune later — a hot-runner manifold with independent zone control gives you melt-temperature latitude that a cold-runner two-plate tool simply does not have, while a three-plate tool adds stripper-plate timing as another variable to set. Pick the structure against part geometry, resin, and volume first, then treat the process as a separate, disciplined exercise.
Parameter setup is best done in a fixed sequence rather than by chasing defects. Start with barrel temperatures per the resin supplier's range, then set shot size so the part is 95–98% filled on the first stage. Establish switchover by position, not by pressure, and confirm short-shot weight consistency before touching pack pressure. Hold pressure typically lands at 50–70% of injection pressure, with hold time set from gate-seal analysis (weight-versus-time curve flattening). Cooling should be set from mold-temperature-controller readings at the cavity, not the setpoint display — a 10°C difference between zones will show up as warpage. Clamp force is the last item: raise it until flash disappears, then add a small margin. Back pressure of 5–15 bar and screw speed matched to cycle keep melt quality stable.
Document every validated setup as a process sheet with the mold, machine, and resin lot it was proven on — that sheet is what makes the next run repeatable. Keep water-line flow rates and manifold zone maps with the tool, and record the actual cavity pressure curve if you have the sensors. For tooling selection, supplier comparison, and sourcing references, visit MoldSo at www.moldso.com.