Thanks guys,
The majority of what I'll be doing is wood or even foam with the ocasional aluminum bit here and there. While accuracy is very important, when cutting foam, you need to get some speed for sure or it just melts rather than cuts. Consider also that there will be no lead screws on this machine as it will be completely belt driven from motors to linears.
I think my laser demonstrates that darn good (0.001") repeatable accuracy can be had at 1.5 turns per inch of travel resolution with great speed too (300 IPM). Again there is only the small load of the linears for the system to overcome on that machine. It cuts very acurately at 15 IPM to 200 IPM depending on material and engraves acurately at 300 IPM all day. Clearly Robert has limited the speed in the software to stay below 300 IPM at 1.5 turns to an inch. That is only 450 motor RPM.
In reading the Geckodrive FAQ, 1200 RPM isn't out of the question for a stepper motor with a top speed threshold of around 1350 RPM so at 4 turns to 1 inch, 300 IPM is possible at 1200 RPM in rapids. Whether it's advisable or efficent is another story. it seems that steppers have a resonance problem between 300 and 900 RPM that Gecko have incorporated a damper in their drive to counter also. Another thing I can think of in the feed speed question is the acceleration / deceleration capabilities of the motors and drives.
What does all this mean to me at this point? So far there is a fairly strong case for fewer motor turns per inch to retain the motors torque and make rapid and cutting speeds higher as well as a better ability to change or stop direction of travel. Also a motor to shaft belt drive ratio of 4:1 puts the linear ratio at 2 turns per inch and removes the need for a compound reduction setup so less complexity there.
Bud  |