Precision injection molding lives or dies on dimensional tolerance, and ±0.01mm is the number that matters for microelectronic components, optical lenses, and aerospace precision parts. In my experience, most shops chasing that tolerance focus on the machine and ignore the resin. Material drying comes first: hygroscopic resins like PC, PA, and PMMA need dew-point controlled dryers, typically -20°C or lower, with moisture content verified against the resin supplier's spec rather than guessed from a timer. From a tooling standpoint, this is also where mold design decisions get tested — unbalanced runner systems, inadequate venting, and poorly laid-out cooling lines will show up as warpage and short shots long before the press settings are to blame. A precision mold needs conformal or baffled cooling close to the cavity, and tool steel selection should account for long-run wear, since a few microns of cavity wear will eat your tolerance budget.
Once the melt is consistent, the process window has to be locked down and held there. Injection speed profiles should be set so the cavity fills at a controlled rate, with switchover to packing by position or cavity pressure rather than by screw position alone — cavity pressure sensors are worth the investment on precision tools. Packing pressure and hold time need to be tuned until gate freeze is confirmed by part weight stability, and mold temperature control units should hold within ±1°C across the cavity. Clamp force must be set high enough to prevent flash but not so high that it distorts venting or crushes the parting line. Every one of these parameters should be documented on a setup sheet and treated as a locked process — anyone who has chased a drifting dimension knows that undocumented tweaks are the fastest route to scrap.
None of this works without measurement discipline. Build a first-article inspection routine around the critical dimensions, run SPC on the cavity pressure curve and part weight, and keep mold maintenance on a shot-count schedule so wear and flash don't creep in unnoticed. For mold sourcing and supplier comparisons that support this kind of precision work, visit MoldSo at www.moldso.com.