Hi everyone, I am designing a small CNC lathe attachment that will go on my Schaublin 102 lathe. (Mid size (102mm from bed to center and 400mm between centers) If you don't know the machine they are accurate Swiss tool room/instrument lathes that do not use a lead screw. Anyway I will keep the manual functions and add a CNC option with a totally separate system for cutting threads etc. The machine has some nice features such as full length T-slots on the the top and both edges of the bed. The mechanical side of things is under control.
For electronics I have ordered a pair of G723-400-4 (5amp 400oz-in Gecko motors and a pair of G203V drives and will be running with a 48v power supply. I also have a Mesa 5i25+7i76 for interfacing with the drives and plan on using Linuxcnc.
I am kicking around a number of different designs but need to pick a motion solution. My preference is to run or at least have the option of running the steppers directly on screws (so what I am calling a 1:1 drive ratio)
Looking at the documentation It seems clear I don't want to spin the steppers too fast while cutting (say less than 17Hz (1000rpm). This isn't the issue, the question is what is the minimum stepper speed I should be aiming to cut at? I am far more concerned with finish quality, accuracy etc than production rate as this is just for personal use. Once I have this detail I can figure out the ideal ratio between the stepper motor and movement but I can't run my optimization without this lower bound. Reading the Gecko site it looks like maybe this lower bound is 5Hz but I would like to get more info.
The drive design (at least on the Z axis) is open so I can use lead screw, rolled ball screw, belts etc. I am not going to pay for ground ball screws but everything else is open.
thanks
Luke