Definitely machining should follow the confirmed 3D data of the bumper injection mould design, and then there should be some tips as followed for processing some specific surface areas.

Core&Cavity Part Area: fine machining to blade R1 with allowance 0 for front and 0.2mm for side under tolerance of 0~ +0.05mm. To keep the surface smooth with no clear steps and blade marks, and shifting blade for clean corners within 0~0.02mm and no higher than processed surface.3+2 five axis machining at last for surface smooth.

Parting Surface: fine machining to blade R0.5 with allowance 0 for front and 0.15mm for side under tolerance of ±0.02mm. To keep the surface smooth with no clear steps and blade marks, and shift+ing blade for clean corners within 0~0.02mm and no higher than processed surface.3+2 five axis machining at last for surface smooth.

Spigot Surface: Tolerance to be controlled within 0~ ±0.02mm. Side lock / interlock areas to be machined at last for smooth by one step after fine machining, only one stroke same blade. Self-check and quality control are necessary.

Kiss-off and Shut-off Surface: blue in the middle area of mold, convex part to be machined with allowance of 0.08mm.

Tick mark and radar hole line of the part on the corresponding mold surface should be processed by CNC 3+2 milling machine, with depth minus 0.05mm-0.08mm to avoid re-process.

Of course there are many other specific tips for plastic bumper mould surface processing or those may be different for other injection mould surface machining that we are not going to detail here.

http://www.automotive-mold.net/