This site is a place where you will find useful and important information about building your CNC machine out of aluminum extrusion.
Why go CNC
I must admit, DIY CNC machine is not the cheapest project in the world. In fact, it can be one of the most expensive projects one will ever undertake. There must be a serious reason behind the decision of buying or building the CNC machine. Often there is one or several of such reasons. I do not know about your particular case, but I always wanted to be able to fab one-off parts (also called prototypes) without having to pay unholy amount of money. I am sorry, mister “big manufacturer”, but it is not my fault that I do not need production runs; I am not interested in hundreds and thousands of useless parts lying around; dumping them at e-bay for almost nothing is not something I would like to do regularly too.
Once, browsing through the internet, I came across a great site devoted to all machinists. You have probably heard of it: www.cnczone.com. This is where I started to gather small bits of information about how to retrofit a manual machine, or even how to build the CNC machine myself. Why anybody would attempt such an experiment with his or her time and money? Well, there are several reasons:
- If you design the machine yourself, you can make it fit your tasks exactly. Maybe you need a working area of 3’ x 4’? Or you do not want that ballscrews on your machine because to buy a 2’ ballscrew assembly you will have to sell your house? Or maybe you want your machine to be as cheap as possible and you would like to cut it out of MDF and use M8 allthread rods as leadscrews? You name it. You can do whatever you want – nobody will say you a thing (well, maybe except your wife, asking to “take that thing out of the garage, because I need to park my car somewhere”, but that is another story all together).
- It is not a top secret that most machine shops will charge you hourly rate, and often a setup fee. The total may grow to an unacceptable amount quite fast. For example, one shop quoted me around 500$ for making one 19” x 3.5” aluminum front panel (without material costs) – that is plain ridiculous, considering that they just had to drill several holes, mill a couple of cutouts and engrave text on the 0.16” aluminum plate. With your own CNC machine at home, you can make anything you want and spend whatever time it takes fine-tuning the process and getting great results. This will cost you just a bit more than the materials.
- If you are a curious DIYer you may find it very interesting to go through all stages of design and manufacturing yourself. It is always a small miracle when a part from the screen of a CAD program turns into something real: something, that you can touch and feel yourself.
- If you build the machine yourself, you get an invaluable experience and a deeper understanding of how it works. You will then be able to adjust all manufacturing processes to your particular machine quickly.
- You can build the machine for almost half the money than commercially available one. Sometimes even cheaper than that. Nothing is free, however – you will spend much more time researching, designing and assembling the machine. I prefer to look at these steps as a self-education, though. The information and experience you get will have extreme value.
Actually, this list can go on and on. I have mentioned only the few things.
Please note, however, that this is not applicable to those big 100k$ monsters that can cut steel like butter. It is at least unwise to attempt to build that kind of machine yourself without a bunch of engineers sitting around you and a large factory ready to spit out high precision parts for you. What I am talking about is 3k$-7k$ range CNC machines that are often as simple as a steel or aluminum frame with some linear motion components bolted to it, and a router. That is exactly the kind of CNC machine (sometimes it is called hobby CNC machine) that I am aiming at.
It is very important to be realistic about your CNC machine. Do not think that it will cut steel or even aluminum, if you have made the frame out of wood or MDF. I mean, it will eventually cut something harder than wood if you insist, but the quality of the cut will be plain unacceptable. Do not think that a long ACME screw will turn faster than approximately 100-150 rpm (exact number depends on the leadscrew diameter and length). You need higher rpm – go buy a ballscrew. Etc, etc… There are many more small (and not that small) things you need to consider before you even run your CAD program for the first time and start designing. And this leads us to another important question:
What do you want your CNC machine to do?
Well, you probably have a good reason to build your own CNC machine. However, you should fully understand your needs. For example, if you want to build a PCB drilling and routing machine, you probably will not need it to have a frame as heavy and rigid as a milling machines one. The same is true for plasma cutting machines – there is hardly any load present, so there is no need to enforce the frame. Of course, if you are going to machine soft metals or steel, than you should find out (and calculate) if your frame is rigid enough for such loads.
Another thing to consider is the working area of the machine. Would you like to fab only small aluminum parts (say, 10” x 8” x 5”), or you need a large cabinet router that has 3’ x 4’ working area? The first machine is a good candidate for incorporating moving table design. The second one is probably better designed with a moving gantry though.
One more thing to consider is what router you are going to use. For woodcutting, there are a lot of high speed router motors (up to 25000-30000 rpm). For metals, however, you will need lower speed (or rather thin mills). Thus, you need to find a spindle that has a speed range that will suite your needs, or find a way of modifying existing router to make it rotate slower (this will void your warranty though).
You need to decide what motors to choose: servos or steppers; will your machine use gearing or will it be direct driven; ACME screws or ballscrews; and a dozen more questions of that kind.
Designing and building your CNC machine
After you have made all the decisions and answered all the questions it is time to start designing your machine. Now, not everybody is ready to design a CNC machine from scratch. In this case you can base your design on some well-known and well-documented build, or you can use one of CNC machine plans that are available on the internet (some of them are free, some are very reasonably priced). Now, while committing yourself to a particular design or buying a set of plans for a CNC machine it is very important to consider what tools and machines do you have at hand. Almost all plans that I browsed through required some sort of precision machining (cutting, drilling, turning or milling). This means that if your parts will not meet the precision needed, your CNC machine may turn out not that precise either!
Not having a mill or a lathe is a big disadvantage, because you will have to order custom parts somewhere, and prepare to pay considerable premium for that. But what will you do if you have no drill press, cutting saws and other machines? What will you do if you cannot cut and drill material precisely enough? Would you buy expensive tools and machines for a one-off project? I do not know about you, but I personally would not. Because it is cheaper to buy a ready available CNC machine than to buy all those tools required to build a DIY one.
Imagine, though, that you can build a CNC machine without all those expensive special tools and machines, having only a set of regular screwdrivers and hex wrenches – all those common tools that you can find in almost every garage? Sounds too good to be true? Then I will tell you how to...
Build your CNC machine with a set of basic tools
I am not kidding and not trying to cheat you. I have built my CNC machine using literally several common tools. I had a cheap set of tools from IKEA that had a screwdriver with common bits, a wrench, pliers and a hammer in it. I also had a set of imperial hex keys and some three or four clamps. The only special tools I had to buy were calipers and a dial test indicator. Keep in mind that these special tools are necessary if you plan to do serious machining work later (and you probably do, otherwise why in the world would you build a CNC machine). How did I manage to do that? You can read it on the How to build a CNC machine page.