How We Machine Molds at AOOM

CNC mold machining looks simple from the outside. A block of steel goes in, a mold cavity comes out. Anyone who's actually run mold work knows different. Every step — from CAM programming to finishing passes — affects the final part quality. I've spent years refining this process at our shop. Here's how we do it.

The Process Step by Step

We start with 3D CAD models and program them in advanced CAM software. Tool paths for molds are different from standard parts. We need smooth transitions, constant chip load, and minimal tool engagement changes. Sharp corners in a tool path leave witness marks on the cavity surface. Our programmers eliminate those before the machine starts.

Material selection comes next. Tool steels like P20, H13, and S7 are common for injection molds. For aluminum molds used in prototype or low-volume production, we use 7075-T6. Each material dictates its own cutting parameters. H13 at 45 HRC requires slow speeds and robust tooling. Aluminum 7075 cuts fast but needs chip clearance.

Rough machining removes the bulk material efficiently. We leave 0.5 to 1 mm for semi-finishing. Semi-finishing brings the surface close to final geometry. Precision finishing does the last pass — typically 0.1 mm radial engagement with a ball-nose end mill running 12,000 RPM or higher.

Quality Checks at Every Stage

After finishing, we verify the mold cavity on a CMM. Every critical dimension is measured and recorded. Surface finish is checked with a profilometer. For injection molds, we can also run mold flow analysis in our engineering software to predict filling patterns. This catches potential sink marks or short shots before you cut steel.

Types of Molds We Build

We machine injection molds, die casting dies, and stamping tools. Injection molds for consumer electronics need fine detail and good polish. Die casting dies face thermal cycling and need hot-work tool steels. Stamping tools need wear resistance and impact toughness. We handle all three in our facility without subcontracting.

One recent project was a two-cavity injection mold for a medical device housing. The cavity had a 0.3 mm rib detail and required Ra 0.2 μm surface finish on the A surface. We held ±0.01 mm on cavity dimensions and delivered the mold in 12 working days. The client's production parts came out clean on the first shot.

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