Yesterday I ordered 2 25mm ball screws to start the xy conversion. I have a couple of weeks to think about the next step. I want to use steppers. I am torn between quill and knee z. I have a lot of backlash in my acme knee z. I am worried that this will cause major problems.
This is for a hobby machine to cut aluminum. I contacted Keling and told him I wanted to use a 2:1 belt drive. He recommended 570oz xy motors and 1200 oz knee
I want to start making motor brackets but need to get motors. Looking at other build threads mills half my size are using larger motors. I was thinking of oversizing the drivers with KL-9082 or KL-8070D and going with the smaller xy motors. If I need more power I could use the motors on my next project. What am I missing?
I would like some input before I buy
The right way to go about this is to put in the ballscrews, then *measure* the torque required to move each axis, and design the drives around those measurements. Every machine will be slightly different, and taking someone else's recommendation may, or may not, work for your machine. FWIW - on my BP-clone, I'm using DC servos, rated at 140 oz-in continuous, 850 oz-in peak, with 5-pitch screws, and 2.5:1 belt reducers. I easily get 350IPM rapids, and more than adequate thrust (i.e. - I can snap off a 1/2" endmill without losing position).
As for the knee vs quill - If you're only going to do one, I'd do the quill. Moving the knee will be slow, though it is a much simpler conversion. Also, if you keep the leadscrew, it will wear quickly. Totally impractical if you intend to do any 3D work, however. My machine has both knee and quill CNC'd - I use the quill for all cutting, and the knee for applying tool-length compensation, so full quill travel is always available for all tools. If you search the archives about two years back, you'll find info I posted on my quill drive, on which I used a simple mounting approach I've never seen anyone else use. It was really very easy to build, and works flawlessly - great performance, and accuracy.