Lightburn Focus Ramp Test - How to get the best focus

[PMoore1st]

Hi Rich;
I finally got around to doing this test and your video is great!
I did notice that my laser "spot" is rectangular. I'm using the Ortur LM2 Pro2 with the LU2-10A Laser; specs say the MIN spot size is 0.05mm x 0.1mm. The smaller dimension is along the X-axis and the larger on the Y-axis.
The normal tendency, I think, is to orient the ramp test along the X-axis from right to left. Because of the rectangular spot size, I found it easier to draw the line vertically on the Y-axis, as it used the larger dimension of the laser image in the line. That seemed to make it easier to find the narrowest point along the line.
Thanks as always...

Pat

[Eds100]

Thanks for a great video. A GREAT tip indeed..

[lynnchas]

I have a Two Trees TS2 20 Watt Auto Focus lens How to you use the Focus Test in Lightburn to check the focus.

[SkyBlu63]

Gonna try this, cause I followed Rich's video ( I think) and I got results that my Ortur LM3 leg was right. But I can't cut 2mm cardboard @ 1000-100.

[Wyked]

A ramp test should be mandatory as way to many manufacturers quote optical focus not intensity focus, eg my Atomstack is quoted as 2mm, this is actually OPTICAL focus not Intensity focus which from my ramp test turned out to be 3.4mm which makes to "Focus" block they supply just an indicator of where to start looking for your true INTENSITY focus, a laser works based on Intensity of the beam more so than the optical focus point, bearing in mind also that the lenses in most lasers sold are the cheaper ones (plano-convex) they can get for mass production, with a moniscus lens in a 20w would probably be able to cut 2" hardwoods in a single pass, unfortunately a quality Moniscus lens would go close to doubling the price of a diode laser. Oh and the flat side down is a whole other topic. (Physics Rant Off)

[erikdoyle]

Great. After I know the focal length how do I easily replicate it on my work?

[cggorman]

Most people note the measurement from work surface to a convenient fixed point on the laser module, like the bottom of the nozzle or safety shield, then make a spacer at that size. Some make them with steps to accommodate other focus distances for different effects/materials/cutting thicknesses/etc.

[AceWickwire]

Found this and performed the test. Sure enough my xTool wasn't quite right. Now use a spacer between work piece and laser head focus foot. Much cleaner and better cuts. Thanks Rich for sharing this procedure. Everyone should do this, it will improve the performance of the laser.

[joejones]

I did not read through this entire thread, but the way I set my focus is to place a piece of identical material on the work surface, and begin burning a simple design. AS the laser is trying to burn the design, I dial the laser head height UP or DOWN.

USE LASER SAFE GOGGLES!

When the laser is at the correct height, the material will instantly begin to burn and emit smoke. you might even HEAR the laser burning the material.

This is how we did it as kids, with a magnifying glass! We moved the lens closer to the wood until we got the sharp, blinding white focused sun spot on the material and it began to burn! I blame this seemingly harmless childhood activity for a generation of people whose eyes now FAIL in their 40s.

Joe

[joejones]

What about something like this? I drew it up, but I do not have the ability to cut it just yet to test it.

"What?!? With all of those lasers in your FrankenBarn?!"

I know. They mock me.

To use this gauge, place material on the slope and burn a line.

Say your material is 3mm thick, and the best part of the test line falls above 30mm

30mm + (3 x 1.054) = correct focal length = 33.162mm

Joe

AGIT RAMP TEST.lbrn2