It seems like a great idea to build your own DIY CNC machine. Whether you shoot for a basic router for MDF profiles or a more advanced milling type machine for Non-Ferrous or even Ferrous Metals, there seems to be some underlying supernatural force that drives the project in directions not originally intended. Well there was if my experience is anything to go by. It’s like an ever increasing addiction before you have even sampled the drug in question (don't do drugs!!). It may be better described as a fever that grips you that you just can't shake. From the moment you decide to build and commit your grey matter to begin thinking of designs, you are enroute to building a heavily over budget nuclear powered CNC Aircraft carrier with an action camera bolted to it, so you can watch it making you rich from the house while you fill your face with sausage rolls. With the exception of the last point, everything else above is likely to be completely true in your project. I will try to explain this in more detail as the tale unravels.

So, in the very beginning I had only set my eyes on first building a basic CNC router. I was looking at approximately a metre square working foot print, mainly to be used to cut sheet material profiles, with some basic 3D detailing and engraving. Let’s not forget that even after 5 years with Schneider Electric as the Industrial Engineering Manager for Medium Voltage Switchgear, I have very little understand of electronics, electrics, and wiring in general.

The plan was that I would explore different designs for a CNC Router without taking any particular machine, type or brand as a baseline for the design. Unfortunately I had some early designs that I am unable to share as I had them on a laptop running a basic CAD package on which I would tinker in my leisure time. The hard drive died, and I lost them all. Other than some laughing gear material and nostalgia, I didn't really lose anything of any value. The majority of them involved the round type bearing rails and were literally as basic and useless as you could possibly imagine. The next step involved the project migrating to a larger size footprint. I was now looking at something around 1500mm in the X-Axis. I didn't want to build something so big that it would take full size timber standard sheets at 8`x4`, but I figured if I could at least achieve a 1200 wide cutting footprint, I could somehow join cuts or at in the very least be able to router quite large items. That was it, the project plan was set. I had budgeted my floor space within reason. I had abandoned any idea of using round rails (and so should you), and instead decided to use 'a' type of linear rail.

I learnt very quickly that you become obsessed with what you believe is a balance between rigidity and the speeds you will be able to achieve. To be very honest, it was a really helpful experience to research and read results and opnions of all the various systems. It really gave me a very strong background of the pitfalls that you can easilt fall into without a design plan.

Key Learnings....

• Forget round rails. Even basic Alibaba Linear Rails will perform better than the round rail systems for similar prices...
• You become obsessed with not loosing 30mm of Y axis and try to compromise your design to maximise your cutting space. Agree with yourself what the minimum is you need and work outwards.
• Almost all the decisions you will make in the design process will be at the expense of something else. There is no perfect all signing all dancing CNC Router design, because it goes against the laws of physics really. I nevver really became obsessed with achieving lightening speeds, but reading many of the group conversations, it is obvious many people think this is their ultimate goal. If you want it to race around like a lunatic on Alu 40/80 extrusion, don't expect 0.1mm accuracy.
• Don't expect perfection with Steppers. Accept that you will occasionally ruin a job from lost steps.
• And lastly at this stage I would jump forward to a learning really and say that if you don't think about the design details like cable routing, limit switch locations and mounting before you buy your aluminium extrusion and EBay torque wrench, expect to have problems further down the line.
• Oh yes, the world does not need more American Flag engravings.