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

[MartinS]

-Nick

I WOULD want a machine "the best that it can be". My 40+ years of Engineering has instilled in me the importance, no, necessity of (appropriate) machine precision, accuracy and rigidity.

I am currently trying to get my head around ALL of the elements of what many you guys have been doing for that long that it is probably second nature.

So, expanding on what you have said:

If a machine is not rigid enough such that it needs twin homing squaring, do the belts in the single motor approach keep an adequate squareness?


Can anybody put um numbers on this?


- Martin

[magicniner]

Look up belt manufacturers specifications on length change versus temperature and tension and combine that with your pulley diameters and screw pitches to get a number.
Using a tensioning system which applies equally to two both upper and lower belt runs will almost eliminate errors from temperature and tension, good grade ground ball screws with pre-tensioned ball nuts will help too.

- Nick

[MartinS]

Thanks Nick

..............yes I'll do just that.

[magicniner]

You can get belts with various reinforcements, fabric, more exotic fibres and steel wires which will all perform differently with changes in temperature and tension.

[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