If you’re interested in a homemade CNC machine, the best way to go about it is to download or purchase a design plan. There are many such guides online you can try, and the process varies. However diverse the approach is, the steps for building a router / milling machine is generally the same.
If you want to build the machine from scratch, start with some sketches. Once you have a good idea of the shape and dimensions, create a 3D model of the machine in a 3D CAD program. A parametric CAD modeler is ideal for custom built machines, and the more technical drawings you can make, the more detailed your CAD model will be.
The frame stabilizes the machine and makes it easy for you to use. With the sliding rails in place, you’ll mount the gantry, after which it’ll be set on the working surface. This is also where you’ll place the X axis spindle and the stepper motor.
You can construct this with a square piece, four corner plates, two 10 mm thick endplates, and 40 x 80 mm profiles. The profiles should be cut at right angles and milled to a square.
Use a heavy frame to bolt the pieces, while the square frame can be built from four milled aluminum blocks within the profiles. If the frame is under the work surface, dust and other debris could end up on the guide rails. To avoid this you have to build dust covers.
The gantry acts as the bridge for the rails of the X axis, and it also provides motor support. The higher the gantry, the thicker the parts you’ll be able to work with. Do not make the gantry too high however, as it could become impractical.
Most routers / milling machines are used for aluminum part milling. If you’re going to work with 60 mm high aluminum blocks, the space for the metal piece and the workspace can be 125 mm.
A U-profile 5 mm thick can be used to stabilize the guide rails for the Y axis, and with a couple of mounting blocks you can set it up between the side plates. Within the U profile is the spindle for the Y axis, using the same blocks for the other axis, and they’re also mounted outside the side plates.
The housing for the Z stepper motor can be built with a back plate, a motor mount, a couple of reinforcement plates, and a front plate set on the Y axis guide rails. At the front plate you can put the Z axis guide rails. Lastly you put runner blocks there along with the stepper motor.
If the motor has the Z axis spindle bearing, there’s no need to use a bearing block. In some DIY designs, the low end hangs by the motor’s mounting plate, and the spindle nut is bolted. As for the Y axis spindle, you mount in on the back plate.
The guide rails guide the machine as it travels in the X, Y and Z axes. It is these guide rails which make the router rigid, and it’s what allows you to control the machine so it moves where you want.
For the best results, go with runner equipped profiled linear guide rails, as they are built to absorb force regardless of direction. For the guide rails to be parallel and perpendicular to one another, they have to be designed with a difference of no more than 0.01 mm. This is an aspect that will take some time, but it’s worth it.
The spindles turn the rotational movement to linear. There are many ways to build a spindle, but the basic choice comes down to ball screws and lead screws either in imperial or metric configurations.
The difference between the two is ball screws are more accurate, though they’re also more expensive. The problem with lead screws is compared to ball screws, they’re not as precise and produce friction.
If you’re going to use lead screws, look for those with drive nuts that minimize friction. Remember too that the X and Y axes ends have to be adjusted to fit the clamping nuts, pulleys and bearings. If necessary, the pulleys have to be drilled to fit the parameters.
This is the part of the machine where you’ll clamp the material pieces. In commercially made machines, you’ll see a T-slotted bed, which allows you to use nuts and bolts to secure your materials. A less expensive surface would consist of a squared birch plywood exactly 18 mm.
You just screw the materials in. You can also use an MDF with bolts and anchor nuts, but don’t use nails and screws on an MDF because the grip isn’t as good.
Once you’ve constructed the main body, it’s time to build the electrical system. The major components are:
You can buy these components online, and they come with instructions on how to install them in a CNC machine. You may need to add more electrical parts depending on how complex your machine is.
To shape the material on the work surface, you need to install a motor which to run the cutter at high or low speeds. Motor power is measured in kilowatts, and your choice should be based on what you’re planning to build and your budget.
You use a 3D CAD program to create the design. There are a lot of free CAD programs online, and also professional quality CAD software. Once you’ve created the design, you use a Computer Aided Machining (CAM) program to translate it into G-Code or the language the CNC machine knows.
Once your CNC machine has been built, connect it to a power supply. Get some wood pieces and work them over, using the various features on the machine. In no time at all you’ll be able to maximize its potential.