05.16 CNC Basics
CNC or computer numeric control is a great way to fabricate precise parts. CNC tools very based on the type of material they cut, the dimensions and directions they are able to cut in, and the type of cutting head.
Common CNC machines are three axis machines, 5-axis machines and multiple access machines that even tilt the stock that is being cut to allow for undercuts.
Often, CNC machines use a spinning cutting tool. This limits the insides of corners from being perfectly square.
Is important to consider tolerances when making tool paths for CNC machining. A 3D model is made to nominal dimensions, meaning the ideal perfect dimensions of the piece. If something has a 2-in hole and it is made 2 in then it will not fit. Either. The hole needs to be slightly larger or the part needs to be slightly smaller.
Best practice is to design a 3D model to nominal dimensions, and then build in the tolerances based on the materials and the design into the tool paths before cutting out the part.
ShopBot Two Axis CNC Machine
A ShopBot is a brand of 2 Axis CNC machine. It is relatively user friendly and affordable. Models can be made in 3D modeling software and then converted to G-Code toolpaths. The tool paths are loaded into the ShopBot for cutting.