Precision Issue

[Jason Chancellor]

I have a new Red and Black laser and am trying to cut a design I have cut numerous times on a different laser without issue.

Here is the RDWorks design I am cutting:

scaleissue.jpg

However, when I cut the piece, the two pieces dont line up correctly. See how the holes are off by a couple of mm.

cutalignmentissue.jpg

I double checked the stepper calibration by creating a simple design that was a known length and then cutting that on both x and y axis, and it appears that the machine can cut a known size line properly.

Any other ideas what might cause this?

[Jeffrey Aley]

Perhaps some kind of backlash issue? Have you calibrated out the machine's backlash? You might also try ticking the "backlash reapy optim" on the output tab of the right-hand pane. For what it's worth, "reapy" is a typo for "repay", which in turn is Chinglish for "compensation" (because compensation and payment have similar meanings in English).

Another thing I'd try is to lower the speed and the acceleration.

[Pete Cyr]

1. Perform the measurements in the topic below
viewtopic.php?f=105&t=3528

Re-perform the cut - if it is good I think your done

2. If it is bad then review the guidance in this link.
https://cartonus.com/how-to-improve-eng ... r-machine/

Please post back on what you learn and or what resolve the issue - or if none of this helped. But once competing these steps you will have eliminated the most probable issues.

[Jason Chancellor]

Thanks for ideas. I'm traveling so it will be a few days, but I'll post back after following advice here...

[Doug Fisher]

Did you cut each piece at different locations on the cutting bed? If so, try cutting the pieces separately but placing the material for each one so each part is cut on the exact same spot on the cutting bed.

[Jason Chancellor]

1. Perform the measurements in the topic below
viewtopic.php?f=105&t=3528

Please post back on what you learn and or what resolve the issue - or if none of this helped. But once competing these steps you will have eliminated the most probable issues.

Ok, so I did the test as shown in this link and made some changes to calibration. But what I noticed is that the machine is out of square.

On a 100mm square cut it is .5mm out of alignment from corner to corner. I'm ASSUMING you extrapolate that across the entire bed and that is my problem?

If yall agree thats my issue, any links on how to square one of these ebay machines?

[Pete Cyr]

1. Perform the measurements in the topic below
viewtopic.php?f=105&t=3528

Please post back on what you learn and or what resolve the issue - or if none of this helped. But once competing these steps you will have eliminated the most probable issues.

Ok, so I did the test as shown in this link and made some changes to calibration. But what I noticed is that the machine is out of square.

On a 100mm square cut it is .5mm out of alignment from corner to corner. I'm ASSUMING you extrapolate that across the entire bed and that is my problem?

If yall agree thats my issue, any links on how to square one of these ebay machines?

So, now you have to determine if the bearing rails are parallel or not and if parallel are the perpendicular to the gantry.
AND you have determine if the gantry is racked...ie not perpendicular to the bearing rails

The easiest way is to cut as large a piece of of thin wood and measure each side as well as measure the angle of each corner (cut a large square or rectangle as the bed permits)

[Jeffrey Aley]

One alternative to cutting a large rectangle is to use a suitably large piece of plywood (any thickness) and just mark a rectangle with the laser (you don't have to cut it out). This is slightly easier because you probably have a scrap of plywood laying around, and if you don't it's easy to get. And you can re-use the plywood (mark it several times, on each side as needed) as you make adjustments.

A framing square (roofing square) will be extremely handy for this.

If you're lucky, the two Y-axis rails are parallel, and it's the gantry that's out of whack (because the gantry is easier to adjust). But we can help you fix either problem.

[Pete Cyr]

Good point Jeffery

[Jason Chancellor]

Ok thanks for everyones help, so I tested cutting on a large piece of material as suggested and using a large square I have and its pretty square. It could probably use some very minor tweeks, but I don't think thats my problem.

I ran a bunch more experiments, and I'm basically even more confused now. LOL. I tried running some tests just along the X axis to see if could narrow down the potential issues and take the Y axis our of the picture. Heres what I did:

First, I went into CAD and created a basic ruler with 1in lines and then cut that on a known laser cutter that I use all the time.
I then ran that same ruler job on my new red and black laser, and from end to end its is consistent. But I did notice some variations in the middle where an inch wasn't consistent but it was tiny amounts, 1/64th of an inch for example

laser-ruler.jpg

Then I just focused on the holes in my design in case it was getting off traveling the path cutting the full design. Even when just creating 4 simple holes, I can't get this dang thing to line up.

laser_holes_pic.jpg

Any other ideas I could test?