UC300ETH: UCBB Vs UB1 breakout board ?

[Neale]

I don't know if this is just an academic quibble, but is there an issue with the concept of two steppers driving a single, very rigid, axis with no possibility of adjusting their relative position? I'm thinking that the typical micro-stepping driver (although possibly not the latest and greatest) will reset to the nearest full step at switch-on, and there is no reason to suppose that the "full-step" positions on both steppers will align. In the case of the typical both-ends-of-a-gantry setup, there is enough give to allow for this (and we are taking about quite small mis-alignments - a full step with a 5mm pitch screw is only 0.025mm) but auto-squaring takes this out anyway. But if this dual-drive Z axis is going to be much stiffer, is this an issue? Maybe this will be addressed at initial setup?

I believe that some newer stepper drivers will maintain micro-step position across switch off/on, which might help.

[JAZZCNC]

I don't know if this is just an academic quibble, but is there an issue with the concept of two steppers driving a single, very rigid, axis with no possibility of adjusting their relative position? I'm thinking that the typical micro-stepping driver (although possibly not the latest and greatest) will reset to the nearest full step at switch-on, and there is no reason to suppose that the "full-step" positions on both steppers will align.

I agree with Neale on this (even though I'm probably talking myself out of a sale...Lol), the motors will always jump to the nearest full step on startup or when drive powers down and you won't know if they both go the same way. Over time this will accumulate and twist up the axis. Loosening the coupler will only work that one time and without some way to home each motor to a known location, you will need to loosen the coupler every time to be accurate or at least every other power down/up.!.

[routercnc]

OK sounds like I will have to do some testing on the steppers and see how they behave over multiple startups (w/o couplers connected).