Hi folks,
before I ran through this procedure my lens was nearly calibrated correctly.
I have a 175-mm-lens and chosen a 160-mm range. But the 9 squares were way too small. Every measurement at about 55 mm.
After dialing in all the measurements my scaling was totally off and a test-square appeared at almost double size. Running the procedure once again I got almost the same size of these 9 squares (so they are evidently not affected by the new scaling factor).
Any ideas, how this could happen / what went wrong?
CU Thomas
You have two lenses?
What do you mean, chosen the 160mm range – same 175mm lens?
There is little difference between these lenses lengths as far as performance.
Can’t say I’ve seen an F175mm or an F160mm – closest I’ve seen is an F163mm.
Might need to help us understand what you are doing.
Hello,
I have only one Lens with F175.
160 mm is the length and width that I have chosen for the 9 squares. They should have been 80mmx80mm each but were lasered narrow 55 mmx55mm.
If it’s an F175mm, the focal length is 175mm. You can’t change a 175mm lens and focus it to 160mm. An F163mm has a coverage of 112x112mm. It can’t do a larger area than it’s scan will allow.
An F100mm lens has a coverage of 70x70mm.
Where are you attempting to changing this, in the calibrate galvo lens function?
My lens has a working area of 175 mm x 175 mm.
The recommended size for the over all width and length is 85 to 90%.
I typed in a square of 160 mm x 160 mm, which is about 91 % of the maximum working area.
Now I follow the issue… thanks for taking to time to clarify.
I’ve never used the internal galvo lens correction, so I’m not clear how it works…
Can you measure the distances with good accuracy?
Any short lens is going to produce a smaller 9 point system.
Maybe @gilaraujo from Lightburn can help or @Albroswift, not from Lightburn can assist.
If the 4 squares are too small but correctly proportioned, complete the 9 point correction and next step is the scale utility. Make sure you are perfectly focused and run these two, one at a time.
I looked for documentation “Calibrate Galvo Scale” didn’t find anything, but it basically asks for input actual, input correct and makes the adjustment. Could do the same with a calculator or slide rule I suppose… 
Hello Al,
the proportions and angles are o.k., so I´ll proceed with calibrating the scales tomorrow.
Thank you for your answer.
I hope, that anyone could find out, why the automated lens correction does not work well in some cases and the issue will be solved.
Have a nice day
Thomas
I don’t know why that is, I re-calibrated all my lenses when 9 point first came out, was almost dead on, only like 0.5mm off on the 300x300. 175x175 and 110x110 required nothing. How far off were you on actual measurement vs designed measurement?
Hello Al,
I drew an 60-mm-square and lasered it.
It was clear, that I should recalibrate or rescale my settings next week, so I did not measure exactly anything. Maybe it was about 87mm*87 mm. But that is just, what I can calculate from here:
80/55x60=87.27272727
Now I am curious shall measure the outcome exactly tomorrow back in my “clean room” :-)) LOL
I would be glad to hear about any solution for this issue, because I really enjoy the simple way to get through the procedure.
Other users with lenses of 300mmx300mm and bigger, seamed to have similar problems. But these posts are closed.
Have a nice week
Thomas
on “Pfingstmontag”-evening at 20-14
I don’t know how exactly LB does this, have heard issues IIRC about the 300x300. I didn’t have the issue so just lucky. I didn’t even know about the “Scale” buttons when I did mine, but I was as close as the original markcfg7 file.
Original markcfg7 from factory, LB 9 point.
Interesting thing, the markcfg7 file from the factory trapezoid and skew no corrections, both 1.000 for all 3 of my lenses.
LB 9 point trapezoid has corrections.
As far as skew, I don’t think LB 9 point or corefile2 can calibrate skew without a corner to corner measurement. It has to be done manually.
I have never installed something like ez-cad or the software, what came with the lazer. So I am not so accustomized with corfile -stuff so far.
But there are the original settings for the scaling factors to read on the plate or in the manual.
Think, I should start from these settings and then go for the perfect lens correction 
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I drew a 60mm x 60 mm rectangle and it was lasered to 106mm x 105 mm
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You would think 9 point would get you closer then that.
When I calibrated mine last time, I covered the bed with black painters tape, made sure I was focused, (IIRC) the framing/ bounding box was octagon shaped, corners were cut off, but when I burned it came out a square. Used the recommended scale. Been a while. Another user / forum reported not getting the framing/ bounding box to show at recommended scale but ran it anyway and worked.
After rescaling I have this for 120-mm-square
It is not really perfect, but I will be patiently waiting for correction of the buck by the team of lightburn or LMA
Maybe it’s just me, but the top line doesn’t look too square.
It does appear curved.
It bears repeating:
1.) perfectly flat test piece. I like to just cover the bed with the black painters tape.
2.) scan head is perfectly level to the bed in both directions. Digital level seems to work best for me, but I am concerned the lens may not screw into the galvo head squarely so a straight edge across that in conjunction with the level as well to double check.
3.) a large digital caliper is more accurate then a rule. accuracy matters!
Hello Jack, t
hat is exactly, what I wanted to show.
The ruler is just a reference for the photo.
The measurement is of course done with a caliper.
Do you think, I have a chance to get it better?
Is anyone going to erase the misfunction out of the 9-squares-utility, so that it will work with every setup?
Here is a video from Laser Everything that shows how to manually modify the corrections.
It’s about 37:40 into the video.
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