Y-Axis Homing Consistency

When I first got my Shapeoko running I used a dial indicator to test the homing switch on the X Axis. Every homing cycle ended with the X Axis at the exact same position.

I figured the homing cycle was consistent and did not give it a second thought.

Then I noticed that my Y Axis was not consistent. I had to adjust my fence Y Axis origin a couple of times.

Tonight I put a dial indicator on the left end of the X Axis gantry to measure how consistent the Y Axis was at the end of the homing cycle.

New photo by Andrew Hood

I found that depending on whether I pushed the gantry into position on the left or right side, the left end would vary up to 0.080" at the end of the homing cycle. i was hoping for better.

My solution was to take a thin strip of wood and place it between the gantry and end support, and push the gantry back into the spacer before powering the system on. This way the gantry would be in the exact same position each power cycle.

I noticed that when I powered the system on the gantry jumped a little. So i shaved the ends of the stick down a bit until it jumped very little and I could easily remove the stick after power was applied.

New photo by Andrew Hood

With this solution I am finding that the Y Axis homing cycle varies about 0.001".

I was wondering how other people dealt with this issue?

That’s one of the downsides of the Y-axis w/ dual belt drives — the teeth on the belt aren’t necessarily aligned exactly the same, and during operation, things will get out of synch.

On more sophisticated (expensive) machines) there will be separate drivers for the Y-axis motors which can then be homed independently — I addressed this on my SO1 by instead implementing a drive shaft: https://www.shapeoko.com/wiki/index.php/Drive_Shaft