Do you think this driver will be poor quality?
https://www.ebay.ca/itm/203996840791
Should I buy one first to test if it is cheap junk and then buy 2 more if the first is good?
It's a 'DM556' and as stated above, it should work well as a remplacement of the defective genuine drivers.
Of course, for C$22, you get probably only a copy of the 'DM566', which was originally
manufactured by Leadshine. User manual V1
here.
The Leadshine unit, currently in version 3, also features a programmable smoothing filter and other improvements (sertup performed via dip switches SW9 to SW16). User manual for v3
here.
If you don't want to take an excessive financial risk, it is certainly a good idea to buy only one unit and hook it on each axis motor, to see if it always behaves well.
A suitable test is to apply very slow accelerating ramps to identify all of the resonance points.
You may also try some fast moves back and forth to check if there's no step loss.
In case of resonance, if the motor driver cannot cope with it, some CNC software can be setup to avoid dedicated displacement speeds where this situation occurs (which often leads to bad surface roughness during the milling process).
You may also mount the steppers by using dedicated rubber dampers or even use an oil resonance damper directely fitted on the axis.
https://www.cnczone.com/forums/stepper-motors-drives/32284-take-stepper-damper-8.html#post534256https://www.cnczone.com/forums/diy-cnc-router-table-machines/103920-cnc.htmlUpdate #1 : contents enhanced by describing differences between ebay motor driver model and genuine Leadshine part.
Update #2 : tackling mechanical resonance