GRBL CNC Retrofit

Wow. What an undertaking this was. It almost happened off a whim too. I’ll keep it short and sweet. I wanted to start fooling around with CNC in my own basement, so I looked immediately to my father’s old milling machine. I took it apart, cleaned it up, and got it ready for the second step of adding motors.

I looked to Solid Edge ST10 next to put together some easy mount-on brackets that would by simple attachments to the existing hardware. My 3d printer allowed me to mock everything up before moving on.

After searching long and hard for software that could run the steppers, I decided to fall back upon what I knew, which was arduino. The GRBL library is amazing to say the least. It’s free, decently documented, and has run everything I’ve thrown at it. So with that I ordered some NEMA 34 steppers off of eBay and fixed everything together.

I played around with the feeds and speeds and found an envelope both the machine and I were happy with. There’s quite a bit of backlash in the system, about .005″ worth, so some cuts can get rather choppy. That’s what can be expected from a 30+ year old machine that’s still running on the same lead screws. The emphasis here being on lead screws. A future sub-project will be removing the old screws and putting in some nice pre-loaded ball screws. With that upgrade I’ll be able to shift the motors closer to the table and remove them from that strange cantilever I have going on now.


Overall I am very satisfied with what I have working now. There’s always more to be done, but getting something working is a good first step in my mind. Many engineers I’ve met are more concerned with the theoretical than the actual. They’ll spend a whole meeting throwing around ideas –excellent ones I might add– but at the end of the day nothing was done except throw around fancy words. I believe in both means, but I sway more towards the ‘let’s get it done’ side.

Anyway, with this accomplished I’m on to something beautiful!



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