Shenhui SH-G1290 Not Cutting Square

[Kevin Looker]

I'm getting my Shenhui SH-G1290 set up, finally got the mirrors aligned but now it won't cut square - see pic.

It's off by approximately 0.031" over a 6.125" (or .8mm over 155.6mm for the rest of the world).

I emailed Shenhui & they said that the rails are out of square. Their solution is to loosen one side of the Y-axis belt, push the rail a little then re-tighten the belt.

I've checked my rail alignment & they are only off by less than 0.125" (3 mm) over 48" (1,219mm). Taking my measured misalignment from the cut piece & extrapolating, the rails are out of alignment by 0.24" (6.1mm) over 48" (1,219mm).

Isn't there a way to correct for this in the controller setup?

Thanks in advance.

[Kev Williams]

Could be a rail out misaligned to the other rail, which would skew Y-axis travel, could be the Y-axis belt alignment, which would skew X-axis travel...

Could be a little of both.

Try this test: cut something cheap (paper, cardboard) in a 10" square, measure it for square, and measure the distance from corner to corner on all four sides.

This is exaggerated, but- if your square comes out like this:

http://www.engraver1.com/erase2/sq1.jpg

That's an indication one of the rails is misaligned---


If it looks like this

http://www.engraver1.com/erase2/sq2.jpg

this indicates the gantry isn't square to the rails, and the Y-axis belts/drive shaft need to be adjusted to square things up...

<edit> And your alignment being out less than .125" across 48", you want to bring that to zero, or it'll never cut square...

[Rich Harman]

I've checked my rail alignment & they are only off by less than 0.125" (3 mm) over 48" (1,219mm).

How did you measure this? Are you measuring the parallel-ness of the Y rails or the location of each end of the gantry on the rails, or something else?



Isn't there a way to correct for this in the controller setup?

Thanks in advance.
No.

My laser came with it very much out of alignment. I loosened one side of the torque tube on the Y axis and adjusted accordingly. It took several iterations to get it dialed in.

Additionally, the two Y rails did not lie on the same plane. It was necessary to shim up the far end of the left rail in order to fix it.

[Kevin Looker]

I should correct my terminology.

I was referring to the "gantry" being square with the LH rail - it is within 1/8" of square over 48". I made a big 36" X 48" carpenters square & checked it against another square along with checking the trig & it's pretty accurate, off by less than 1/16". I put the 36" leg against the LH rail & the 48" leg below the gantry.

It's cutting like the second illustration - a parallelogram.

I have not checked the Y-rails for parallel. I assumed the gantry would bind if they weren't parallel.

Thanks again!

[Dave Sheldrake]

Make sure you are checking the PMI's Kev or you will be chasing your tail.

cheers

Dave

[Kevin Looker]

What are PMI's?

[Dave Sheldrake]

sorry Kev....guide rails, sometimes they aren't mounted level on the gantry so measuring from the gantry will give an incorrect figure.

cheers

Dave