A few years ago, I bought a small chinese CNC machine on eBay. It was a 3020, meaning about 30 × 20 cm of travel, with an 800 W water-cooled spindle, a variable frequency drive, and control through an old-school lpt port from a computer. Since the spindle was water-cooled, the setup even came with a small fish tank pump. 🐟
In hindsight, I probably should have taken the word engraver more seriously.
The machine worked, but it was far too unstable for any real milling. Cutting soft plastics was possible, but the whole structure was simply not rigid enough. So, of course, the small “cheap” CNC machine slowly turned into a much larger project.
The first big step was reinforcing the gantry. I also replaced the original mounting plate, which was made from aluminum extrusion profiles, with a solid 10 mm thick aluminum plate. I drilled and tapped M6 holes every 4 cm across the plate. Doing all of that by hand was a real tour de force.
To make the whole thing more stable, I mounted the machine on a granite garden tile from the home improvement store. This helped quite a bit: it added mass, reduced vibrations, and most importantly stopped the machine from slowly wandering off the table while running. I also upgraded the ball screws to make the motion more solid.
In the end, the amount of money I spent improving the machine was well above the roughly 700 € I had paid for the initial purchase. But I learned a lot about milling, and why cheap CNC machines are usually cheap for a reason.
So is it a good machine? Not really.
Was it a fun project? Absolutely.