Mold Machining and Repair — Two Different Skills

Cutting a new mold and repairing an old one are not the same job. CNC mold processing for new tools is about speed and accuracy. CNC mold repair is about patience, measurement, and matching existing geometry. At AOOM Technology, we do both, and I'll walk through what each requires.

New Mold Processing: Get It Right the First Time

For new molds, we start with the steel selection. H13 for hot work, P20 for plastic injection, S7 for high-impact tools. Each needs different roughing and finishing strategies. We rough with coated carbide at high MRR, then switch to finishing tools with stepover under 10% of tool diameter.

A client needed a 16-cavity mold for bottle caps in H13. First article had one cavity .008mm out. We caught it on the CMM, adjusted the CAM offsets for that specific cavity, and requalified. All 16 cavities ran within .005mm on the second try. That level of control comes from having skilled programmers who know how molds behave during cutting.

Mold Repair: Measuring Is Half the Job

When a mold comes back for repair, the first thing we do is scan the worn surfaces. We compare against the original CAD model and map how much material needs to come off. Then we weld-build the worn areas, stress-relieve, and remachine to the original specs.

The biggest mistake in mold repair is overshooting. Cut too deep and you're welding again. We take light finishing passes — .1mm DOC maximum — and check with a CMM after each pass on critical surfaces.

Common Mold Issues We Fix

Edge wear on shut-off surfaces is the most frequent problem. Next is gate erosion from high-pressure plastic flow. We also see cracked cores from thermal cycling — these need careful weld repair and stress relief before remachining.

Post-Repair Surface Treatment

After machining, we polish mating surfaces and apply release coatings if specified. Surface finish on repaired sections should match the original — we profile the area and adjust the polishing sequence until it does.

Send your CAD files to chen@aoomtech.com for a quote within 24 hours.