Quote Originally Posted by peteeng View Post
Hi TiBoy - I'm guessing the ratio, as in the video the belt is closed up in a casing. Unless its a gearbox but unlikely to be a gearbox. The quote max speed is 8000rpm so maybe its a 5000rpm servo and smaller ratio? They do steel with light cuts. The vids look good but there are machine aspects that are poor. Like they run the ballscrews directly to the motors with no thrust bearing, so motor life is at risk specially if shock loaded. They use a leadscrew for the Z for some reason as well. The machine assembly videos are quite good so you see how they are doing various bits of the machine. I suppose if its in a commercial environment and gets a few 1000 hrs on it the owners will know. It does have some vibration as in one vid you can clearly see the chatter in the finish then it gets cleared in the spring cut...

In regard to the pulley diameter you pick a small pulley that works then get a big pulley to suit. 3:1 is common on various things. So you must have a space problem
Thanks for your thoughts on the MR-1 and how it gets away with cutting steel. Doing super-slow baby cuts in steel isn’t really a problem for the home gamer if it means being able to make a part as versus not being able to make a part.

My mill uses 5M HTD pulleys and belt. The motor pulley is 63 teeth (94.7mm flange OD and 24.6mm inside flange width) and the spindle pulley is 38 teeth (64mm flange OD and 17.5mm inside flange width) with a 17mm wide HTD belt. The servo motor is 3000 rpm and 1.2kW.

I was told by Novakon that the spindle pulley couldn’t get any smaller because “the power of the servo motor is significant and to properly transfer the motor torque to the smaller pulley, the diameter and the number of teeth engaging the belt drive is a factor. There is not much room to enlarge the motor pulley and the size of the smaller spindle pulley can’t be reduced for practical reasons. To make the ratio any larger would also limit the maximum size that can be tapped due to loss of available torque delivered to the spindle”.

I would happily trade away some rigid tapping capability for increased rpm.