View Full Version : Laser lens, upside down vs rightside up

Kev Williams
05-11-2014, 4:42 PM
Been wanting to do this, had some time today :)

I ran 2 identical ramp and cut tests today, one with the lens correct, one with the lens upside down.
raster was 500 mm/s at 55 power, vector was 100mm/s at 25 power.

When I found the optimum focus distance, I ran some cut tests.

Ok, here's ramp test "A" (note the extra markings above the letters, that's how to tell them apart ;) )


And here's test "B"...


Using a magnifying glass I determined the best focused areas, and marked the areas with the arrows.

Here's closeups



and "B"--


OK, so which one is which? I'm curious at to your picks, and the reason(s)!

And finally, I ran a few cut tests. What I found was the power/speed necessary was nearly identical for either lens position.
In this pic, both were ran at their prime focus points, speed was 100 mm/s, power was 50. No air. In both cases they both ALMOST made it all the way thru but not quite-
But the surface of the bottom plastic has less residue after the cut than the other... Which was which?


Regardless of which is which, I would think there would be a much more noticeable difference than I'm getting?

Dan Hintz
05-11-2014, 4:53 PM
I can see individual dots (stair-stepping) in 'A' (like in the comma), but 'B' looks smoother... my first guess is 'B' was upside down and it caused some smoothing of curves. That said, I also see a lot of minor wiggling (like under the KLD in 'B') that makes quality tough to measure, not to mention we're talking about a JPG image that tends to add ringing at color transition edges, so making a determination based upon these images is pretty close to a complete guess.

Kev Williams
05-11-2014, 7:32 PM
One thing I've found with this Chinese machine is that some of the anomalies are just part of the fun-- Look at all the "D"s, every one has a small bump in the 'hole' on the bottom near the middle.

Kev Williams
05-12-2014, 5:44 PM
well, to answer the question, A=rightside up, B=upside down. Red plastic, the bottom, cleaner piece was cut with the lens upside down. Not sure why that is, but the first time I ever cut laminate I had the same results.

On the black, I got a bit thinner vector line rightside up, but overall the engraving results are nearly identical...

Walt Langhans
05-13-2014, 1:27 AM
Ok stupid question of the day... Would which side was 'up' affect the life of the lens?

Kev Williams
05-13-2014, 3:28 AM
All any lens does is bend light waves. My thinking is that lens life is proportional to 'outside influences', such as cleaning with a dirty rag, flying debris (no more black onyx!), dropping it on the floor, etc... My 11 year old LS900 and 18 year old ULS are still working fine with their original lenses...