New CNC Mill: What is CNC Anyway?

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The MakerSpace has more CNC machines than ever before, including a brand new Tormach CNC Mill. So what are these machines for, and how do you choose the right one for your project?

What is CNC?

CNC is short for Computer Numerical Control. CNC is used automate all sorts of tools and tasks in manufacturing, prototyping, and even hobby applications. If you have used our 3D printers or Laser cutters, you have already seen CNC in action. Just like on those machines, most CNC machines use stepper or servo motors to move a tool in multiple directions, or axes. Most often these are represented with X and Y, and Z representing the tool moving up and down. With 3 axes, the tool can move in 3D, or 2D at multiple levels (sometimes referred to as 2.5D). The computer controlled movement allows extremely precise and complex parts to be made.

Subtractive Manufacturing

3D Printers are sometimes referred to additive manufacturing, the opposite of which is subtractive manufacturing. Subtractive starts with a solid block of material, and a tool cuts away until the desired shape is achieved. With CNC, the desired shape can be created in CAD (Computer Aided Design), then CAM (Computer Aided Machining) is used to convert that into tool paths, which are exported as a set of instructions (G-code) for the CNC machine.

CNC Milling vs Routing

We have both CNC Routers and a CNC Mill. The routers are made by ShopBot, and the mill is made by Tormach. Both are 3-axis machines that use a rotating cutting bit, but are built for different purposes. The ShopBots are made to cut wood products, so the machine rotates the cutting bit at very high speeds, between 10,000 and 21,000 RPM. ShopBots have a large work area, with the Desktop model having a bed of 18”x24” and the Buddy model having a bed of 24”x32”. The Tormach is built for cutting all types of metals, so the frame is very robust and it has an even better positional accuracy. The Tormach’s spindle has a range of 300 to 10,000 RPM, with good torque. It has a smaller work area, which is 6.5” x 10”. Plastics can actually be cut on both machines, so the choice may come down to a question of size, accuracy, or cutting speed needed. These machines have a wide range of cutting speeds, because every combination of cutting tool and material has an optimal feed and speed. Feed is how fast the tool moves across the axes, speed is how fast the tool is rotating. Too slow, too fast, or a bad combination will lead to poor cuts and damaged cutting tools.

Interested in learning more? Talk to our staff about what you can do with these machines. ShopBot training is offered weekly on the training calendar, and training for the Tormach is offered by appointment. Due to the complexity of these machines, expect training to be longer than our other training sessions.