Why is Y axis "squaring" necessary only with twin motors?

[Neale]

I have a machine with an approx 1000mm long gantry, driven at each end. Couple of ways in which it can get out of square:

One motor stalls for some reason, or sometimes when I hit the e-stop button. If the two motors do not stop at the same time, or come to a halt at slightly different rates, you have lost sync.

When you first power on the stepper drivers, the motors may or may not be at a full-step point. If not, it's likely that the driver will initialize it to the nearest full step, although I believe that some drivers are supposed to remember the last state when powered down. It's possible that if this happens often enough, the gantry may drift slowly out of square, a tiny amount each power-down/power-up cycle.

Homing both ends to a known position gets round these problems; on my machine it will hold these settings for an entire session unless one of the above happens.

[MartinS]

So Neale

One motor stalls for some reason, or sometimes when I hit the e-stop button. If the two motors do not stop at the same time, or come to a halt at slightly different rates, you have lost sync.

When you first power on the stepper drivers, the motors may or may not be at a full-step point. If not, it's likely that the driver will initialize it to the nearest full step, although I believe that some drivers are supposed to remember the last state when powered down. It's possible that if this happens often enough, the gantry may drift slowly out of square, a tiny amount each power-down/power-up cycle.

whether it is motors jumping sync/steps, and/or the movement of a less than stiff gantry/endplate/bearing setup, the TWIN homing switches correct the gantry squareness.

Makes sense.

And presumably, within a single motor/twin belt system, the "stiffness" within the drive belt arrangement tends to hold the gantry square.


Great got it thanks.

-Martin

[Clive S]

So Neale



whether it is motors jumping sync/steps, and/or the movement of a less than stiff gantry/endplate/bearing setup, the TWIN homing switches correct the gantry squareness.

Makes sense.

And presumably, within a single motor/twin belt system, the "stiffness" within the drive belt arrangement tends to hold the gantry square.


Great got it thanks.

-Martin

Yes that is correct, but with using one motor you have to use a bigger one like a nema34 which usually requires a bigger volatage to drive it. The single motor setup does not go out of square, and using 2 motors hence the duel switches you also.need stall detection etc in case one drive packs up etc

[MartinS]

Yes that is correct, but with using one motor you have to use a bigger one like a nema34 which usually requires a bigger volatage to drive it. The single motor setup does not go out of square, and using 2 motors hence the duel switches you also.need stall detection etc in case one drive packs up etc

Noted Clive, thanks

[Neale]

Yes, stall detection is important with a two-motor setup. Modern digital stepper drivers will do this for you.

As Clive says, a typical single-motor setup will need a Nema 34, where my machine (gantry with spindle, etc, is probably around 40-50kg) is driven by two 3Nm Nema 23 motors with 2005 ballscrews. Not an optimum configuration, but it works ok up to about 5000mm/min.