Quote Originally Posted by Jonathan View Post
From the machining marks in the picture it looks like the bearing bores were milled? If this is the case then it's a bit concerning - if their milling machine doesn't have zero backlash then the bore will be less round, which would distort the outer ring. It's also generally less accurate than boring, which is why bearing housings are usually bored.
When I make these I bore them on the lathe and make the bearings a light press fit, to get better rigidity and ensure the outer rings don't creep. Also, if you get more made I'd be inclined to increase the axial spacing of the angular contact bearings, as it's currently insufficient to get the best stiffness. You'll probably be OK, but the critical speed should be higher if the bearing spacing is increased a little.


I was so tired yesterday, cause i had a flue, that i missed that. I guess i was overexcited .They were told to bore it on the lathe and i was promised that even it would be done in one pass without turning the block. I hope they did it right. Now i am worried a bit.


Quote Originally Posted by Jonathan View Post
Regarding the pulley selection, you know the dimensions of the rotating ballnut shaft and the rest can be estimated well enough, so work out the inertia with aluminium and steel pulleys and see if aluminium is worthwhile? Or post the following numbers here and I'll show you:
  • Mass of gantry (i.e. mass that both rotating nuts are moving).
  • Desired rapid feedrate.
  • Ballnut size (RM2510?).
  • Motor ratings.

I think you'll find aluminium pulleys aren't worth it, due to the relatively high inertia of the ballnut - but no point speculating...
RM2510 nut
20t:30t
400w Samsung AC servo each side,
~100-120kg gantry


Decided to drivel all 20:30t, only the Z is 20:20t. This after exausting 3 day calculations, belt lengths,inertia, tooth engagement, speeds, etc. and at the end -common sense.
This is a separate thread of its own. I believe this the wisest decision between speed, acceleration, precision.

The rotating ball nut assembly. 20:30t hence 1.5:1 driven. Compromise due to common sense. At the end precision and power at the same time is the aim.

2048 encoder on the motor, so more or less 20m/min. I see on the motor specs that it can go up to 4500rpm, just the curve is straight till 3000rpm. The resolution will be ~0.003mm on all axis , 0.001mm on the Z/ 1605 screw and 2500ppr encoder/. That without any artificial gearing or micro stepping which is not needed it seems. Thats good, cause the Galil board is not micro stepping board.