4018
« on: October 03, 2011, 07:10:44 PM »
1m/min is really much too slow for cutting wood. On our big commercial router at work, we cut at 20m/min. For a home built machine, I'd shoot for 3-5m/min minimum.
When using steppers, you have to trade resolution for speed, since they lose torque as rpm increases. So you can go very fast and have lower resolution, or very slow and have really good resolution.
With your screw length approaching 2m, I'd recommend 2 turns/inch (12mm lead). 4 will get you a little more resolution, but you'll probably get whipping at higher speeds.
I have 60" 4tpi screws on my router (1/2" acme), and screw whip limits my maximum speed to 150ipm (3.8m/min). My shorter Y axis can get to 4.8m/min, and it's still really a lot slower than I'd like.
I really have to question the need for .01mm accuracy. Most mid grade acme leadscrews here in the US have a tolerance of ±.009"/ft, which is .2mm/300mm.
Unless your screws will be precision ground to much better than .01mm tolerance, you'll never see that.
.01mm is .00004". Don't you need a temperature controlled machine and room to maintain those kinds of tolerances?
Also, wood will easily move more than 25-50x your target accuracy with changes in humidity.
I'm hoping you meant to say .1mm, in which case the 2tpi screws will be more than precise enough.