If you haven't seen part 1, your CNC may look like a three legged dog. This is a multi-part instructable that demonstrates how to build a CNC Router (a computer controlled router) from scratch.
CNC Machines can come in many shapes and sizes. Just look at these cool instructables on building a CNC. This is a cool new instructable how to make a CNC using pipes, which blew me away. There is also this one that includes plans.
This instructable is based on a logical process of construction where measurements are made during certain steps to achieve any size CNC machine. Whether you want to build a mini mill for PCBs, or a large sign making device. It's up to you. With power tools, I believe that this machine can be made in one weekend. I built mine within two weeks with kids, wife and a job. I just wish I had a table saw to replace my miter box (you see me cranking away in the videos). The cool aspect of this build is that you can put the thing together as you create the pieces.
So, we left off with the z-axis assembly and now we can get started with the y-axis.
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Step 1: Make the Y-Axis Bearing Supports
Generally, the bearings, and supports are designed to hug the rail supports, using compression around two aluminum angles and a piece of MDF. This gives the machine it's rigidity.
First I will cut the y-axis rail support piece by taking a 7" wide piece and chamfering the four long edges to receive aluminum angles. The 7" measurement will dictate the z-axis travel. If you want more z-axis travel, use a wider piece. We will need this piece to make other measurements.
The two bearing supports for the y-axis will be cut about 5" to 6" in length using a 4" piece of MDF. These two pieces will slide along what I call the y-axis rail support. The bearing supports will hold the bearings with grooves cut out of the MDF.
Step 2: Measuring and Completing the Y-axis Assembly
This is the critical part. A quick and dry assembly with a clamp is necessary to measure for the y-axis back support and the z-axis rail support. The z-axis rail support was chamfered in part 1 and now we will cut that piece to the correct length. The length of one of the support pieces (z-rail support, or the y-axis back support) pieces should be slightly shorter (about 1/32") that the other so the whole assembly can be tightened around the rail support.
Step 3: The Z-Axis Transmission Nut
To get the z-axis moving with some sort of mechanism, a nut and a screw will be used. This video will show you how partly this is done. Also, I sow you a good technique to hold the nut in a piece of MDF. For the motor to be able to turn a screw and move the z-axis assembly up and down, the holes that are drill need to have a pretty good alignment.
First, you will get a glimpse of how the y-axis assembly will be positioned around the y-axis rail support piece.
Step 4: X-Axis Cutting Surface and Stands
Let's get to the meat of this project and skip ahead to the X-Axis for a minute (well, actually 8 minutes). It's important to mention that the x-axis rail support (the table or cutting surface) should have a double ply of MDF, if it is made as large as mine. My table measures about 2' x 4' which could be cut down a little if the application is for small sized projects. However, MDF is real cheap, so douple plying it should break the bank.
Note: if you do go the route of doubling the MDF, a larger aluminum angle will be necessary. Mine measured 1 1/4" x 1/8".
Step 5: Finishin Up on the Z-Axis Assembly
It's time to get a lead screw into the z-axis assembly to complete the mechanical portion of the linear movement. I will also get started on the x-axis rails in this video.
In the next part, we will start working on the gantry assembly.