Both 3D printing and subtractive manufacturing are CNC machining processes. This means a computer controls the process. The major difference is that 3D printing is additive. This is why it has the name “additive manufacturing”. Source
A 3D printer creates objects by adding material in successive layers. The material used is a thermoplastic. This is a type of plastic that melts when heated and can be reshaped into an object that solidifies when cooled.
There are several types of 3D printing techniques. The most commonly used are Fused Deposition Modeling (FDM), Stereolithography (SLA) and Selective laser sintering (SLS).
3D printed objects do not have the same material strength as objects made from traditional manufacturing methods. This is largely down to how an object is created using 3D printing and the inherent weaknesses it creates.
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How Does Subtractive Manufacturing Work?
Subtractive manufacturing, as you might have already guessed, works in the opposite way. Typically, we start off with material that is cut away to produce the final object.
The raw material can be a block, bar or rod of metal or plastic that is shaped through drilling, cutting, or grinding. There are several types of processes used including water jet cutting, laser cutting, electrical discharge machining and of course CNC machining.