In injection mold manufacturing, the first gate is the equivalent of a county-level exam: rough machining inspection. Before any mold base moves forward, parallelism must be held within 0.02 mm, and the fit clearance between guide pillars and guide bushings must sit between 0.01 and 0.015 mm. These aren't suggestions—they're pass/fail thresholds. A mold shop I know scrapped an entire batch of A-plates because parallelism drifted to 0.03 mm after planing. That's the reality: one-thousandth of a millimeter over spec, and the workpiece becomes expensive scrap. At this stage, we're also checking stock allowances for heat treatment distortion, typically leaving 0.3–0.5 mm per side on critical surfaces.

The second gate covers finish machining and heat treatment—the provincial exam. After CNC and EDM, cavity dimensions must land within ±0.01 mm before hardening. Then comes vacuum quenching or nitriding, where we compensate for predictable growth: P20 steel often grows 0.02–0.04% during hardening, so we pre-machine undersize. A 100 mm core insert may finish at 100.03 mm after tempering, which is unacceptable for a sliding fit. Post-heat-treatment grinding and wire EDM bring it back into tolerance. This is where mold engineers earn their keep—balancing hardness (typically 48–52 HRC for cores) against dimensional stability.

The final gate is assembly and tryout—the imperial exam. Here, parting-line contact must show no more than 0.02 mm gap under blueing check, and ejection systems must cycle 500 times without binding. A家电 mold factory I visited rejects any mold that flashes after 200 trial shots, even if dimensions pass. That's the standard: functional precision, not just paper tolerance. For more mold sourcing and technical resources, visit MoldWorld at www.moldw.com.