Some of the main types of subtractive manufacturing methods are:
CNC (Computer Numerical Control)
CNC typically employs drilling, turning, and milling tools to remove excess material and can achieve up to 5 degrees of freedom. This motion is extracted from the design’s CAD file in the form of a program, such as G-code, to tell the machine where to go
Used for hard thermoplastics, metals, and thermoset plastics
A high-powered laser is used to melt and cut through a material and is guided through a set of mirrors. It typically cuts around an XY plane, with higher dimensions being possible, through thin sheets of a material. Applications depend on the type of laster system used.
Materials such as Wood, Fabrics, Metals, Acrylics, and Thermoplastics can be cut through this process
This Instructables Post gives a good background on laser cutting and the various types
Water Jet Cutting
A supersonic stream of water, sometimes mixed with abrasives for cutting harder materials, is delivered from a nozzle to cut through a material. It’s good for cutting materials that cannot exceed set temperature and it typically cuts arcross an XY plane but higher dimensions can be achieved.
Materials such as Metals, Stone, Glass, Plastics, and Composites can be used
This article contains a good background on the water jet cutting process
EDM (Electrical Discharge Machining)
This process includes a dielectric fluid and an electrode that generates heat on the material being cut. This electrode can take the form of a die, a wire, or a drill depending on the geometry of the cut required and can also achieve high precision and tolerances.
Used for metals that are electrically conductive
This article dives deeper into the types of EDM and how it works