In mold design, the structure decision comes before any steel is cut. Cavity layout, parting line placement, gating type, and ejection strategy all need to be locked in against the part drawing and the intended press. A common mistake I see is treating draft angle and wall thickness as secondary—on a 2-plate mold running ABS, insufficient draft on deep ribs will show up as drag marks and white stress marks within the first few thousand shots. Cooling layout deserves the same discipline: conformal or baffled circuits should be sized so that cavity and core temperatures stay within roughly 10–20°C of each other, otherwise warpage becomes a molding problem you can never fully fix at the press.
On the machining side, the sequence matters as much as the tolerance. Roughing, semi-finishing, and finishing should be separated so that residual stress from heavy stock removal is released before final cuts. For cavity inserts, leaving 0.3–0.5 mm on the finishing allowance and then stress-relieving before the last pass is standard practice in our shop. Fit tolerances for guide pillars, bushings, and inserts typically run in the 0.01–0.02 mm range; anything looser and you will see flash migration and uneven wear. EDM and wire-cut operations should be planned around the heat-treat step—quench and temper before final finishing on hardened inserts, or you risk dimensional shift and micro-cracks at sharp corners.
Assembly and tryout are where the design intent gets tested. Spotting the parting surface, checking shut-off fit, and verifying ejector travel under load should all happen before the mold goes to the press. During first trial, record fill pressure, cavity pressure, and cooling time—these numbers tell you whether the runner and cooling design are doing their job. If you are sourcing molds or comparing suppliers, having a clear checklist of these structural and process control points makes the conversation far more productive. For more mold sourcing information, visit MoldSo at www.moldso.com.