Quote Originally Posted by i2i View Post
I wouldn't put two motors on one driver.

I don't see that using the c axis and the x axis would be more reliable or accurate than using the port output to supply two drives. Have you experienced problems doing this.?
Yes it's down to timings in the drives with one drive seeing the signal before the other and accumulative errors creep in, The higher the micro stepping and harder the PP is working the worse it can be. The PP needs to be very good with strong signal and still it can happen depending on drive quality,opto speeds etc.
If your working at low feed rates then it can work and indeed the RepRap boys often use this method but they are only using low feed rates with no stress on PP. But any decent CNC machine that wants reasonable feed rates and uses MS to help with smoothing motors will potentially fall foul of using this method.!!
While this can and does happen with Each drive having it's own signal it's far far less likely to happen even at high micro stepping if the PP is only even half decent as it's not sharing and virtually Nil chance with good PP.

The other problem with this and twin motors on one axis is you can't control one motor individually for homing and squaring the Gantry etc so has the dropped steps start accumulating eventually racking the gantry there's nothing you can do about it other than Manually loosen the couplers and reset square.

With 2x motors sharing one drive there's problems from features like Mid band resonance or other correction features. The drive doesn't know which motor to apply the compensation too so only one drive gets it this then throws the other into resonance and it can stall. Which drive gets current reduction etc all bad news and not worth the trouble IMO.

So all in all it's a shite idea and not required really has most BOB's are 5 axis and the software allows for slaving motors. The PP provides enough output signals so why take the risk of accumulative errors creeping in to what should be an accurate system.!!

Think about this.?? . . . .If 2 drives where ok to be run from one signal don't you think the likes of Lead shine and other drive manufactures would have produced a two drives in one package for those that needed them.!!