Originally Posted by
JoeHarris
Further to my previous post I have some questions:
1) to drive the two ball screws on the x axis I am using a belt driven by one stepper and driver. I am doing this because of fear of missed steps. If I use digital drivers (not closed loop) does this issue go away?
No, even digital drivers can miss steps. A stepper only misses steps if you're asking it to perform outside its torque curve. As long as the torque available at the speed/acceleration you are operating it at is sufficient to move the motor onto the next step, or prevent it moving to the next step when inertia comes into play on deceleration then it'll be fine. Microstepping makes it much harder and the risk much higher esp if you go over 1/4step.
2) if I stick with the belt drive arrangement shown does it matter where the motor is placed in the belt loop. I have shown it off to one side currently, I had it in the middle previously? I figure it shouldn't make a difference? Probably need to add in another idler though.
Shouldnt make any difference as long as belt tension is sufficient to maintain meshing with the pulleys, tho avoiding long unsupported runs of belt reduces the possibility of skipping a tooth due to belt 'flap'
3) the four sides of the base of the machine is comprised of two aluminium plates fixed to the ends of two aluminium profiles. These sit onto a series of aluminium box sections. I have no cross bracing in this frame. Would it be prudent to add some in??
If you mean diagonal bracing, then yes it wouldnt hurt
I intend to build the timber table next so I have a base to work up from - any comment would be greatly appreciated before it is too late!!