Deep draw stamping.
The enclosure is drawn through a series of dies that progressively stretch the aluminum into something approaching the final shape of a Mac Pro
The initial ingot of material
Apple uses a CNC center to profile the outside shape of the Mac Pro. This step brings the part into high-precision tolerances and removes the relatively rough surface finish produced in the deep draw process.
Profiling
Robots spin the Mac Pro's enclosure around polishing wheels to produce a near-mirror surface finish.
Internal surface
External surface
Milling
In order to prevent damage during the upcoming milling operations, the freshly polished enclosure is coated with a surface protection film.
The enclosure is back in a CNC center where the I/O slot is cut out.
Anodizing
Electrical current is run through aluminum in an acid bath, causing oxygen molecules to bond to aluminum producing a thin, uniform layer of aluminum oxide.
In this process, robotic blast system uses air pressure to force glass beads to uniformly rough up the surface.
This is a triangle cooling tower inside the Mac Pro. It is extruded from aluminum and has features like holes and threads added later.