I think for what you have there its Ipk=Vref/(8*Rs) where Rs=0.11 (?) and therefore should try a setting of Vref=0.50v to start with. So try setting vref to half a volt and see if Z movement gets better. This value i think links to where the motors are peaked already and setting vref higher might is useless, and might freak the microsteps levels, probably where the "judders" comes from.
Also could try something like Vref=0.35volts but thats probably kind of low already. If things get better when vref is 0.5, then could also tweak the microsteps like 1/4 for Z and 1/8 for X and Y. It should be possible to get those motors working at least, but its probably better to change them if you can.
Also could try something like Vref=0.35volts but thats probably kind of low already. If things get better when vref is 0.5, then could also tweak the microsteps like 1/4 for Z and 1/8 for X and Y. It should be possible to get those motors working at least, but its probably better to change them if you can.