Getting started with CNC

After 3D printing for awhile now, I got the itch to start playing around with CNC machines. I’ve had things made by CNC shops before, and had a pretty good idea of the process, but there’s nothing quite like jumping right in and doing it yourself. In the next few blog entries, I’ll describe some of the elements of CNC operations.

CNC machines come in a wide variety of forms. Some are meant for engraving, some are meant for woodworking, and still others are designed to machine large parts made of steel and other hard materials.

One thing common among them all is that they all have at least one “axis”, or direction that the work piece or tool can move in. In fact having one axis wouldn’t do you a whole lot of good, though I suppose that a CNC drill press might be an exception.

Most CNC machines are probably of the 3 axis type. That’s about the minimum you need in order to do useful work. A common setup for a 3 axis machine is to have a table where the work is placed, and a mechanism that can move a tool over the table in the X and Y directions, while controlling the height of the tool using the Z axis. A CNC machine to cut a sign from a piece of plywood may well have a woodworking router attached to the Z axis mechanism, allowing different types of cuts to be made using different bits.

Here’s a picture of a small 3 axis CNC machine. This type of arrangement is very popular. There is a flat work table, and a “gantry” mechanism that allows the tool to be positioned precisely over the work. The tool is then raised and lowered under control of the CNC program while also moving in the X and Y directions to cut out your design from the piece of stock material.

If you’ve been 3D printing for awhile, you’ll find yourself spoiled by the ease at which 3D printing can be accomplished compared to CNC machining. With 3D printing, you add layers of material to end up with a part that might need a little cleaning up after removal from the build platform. However as you’ll see, a CNC machined part needs to be set free from the stock material. That is not always an easy task, and you’ll find yourself giving more thought to how you’ll machine each part in order to minimize the amount of time and effort needed to finish your machined part.

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