Russ' focus test- pulse, up 1mm, pulse, up 1mm...

[Gene Uselman]

I have seen Russ use this test a number of time to determine the best [smallest] burn size and the best focus. I am not aware that he has ever mentioned it? Anyway, I like it and want to replicate it. I use Lightburn now and there is a Z offset setting which I believe would work with different layers for each Z level but how does he program a pulse on each layer? I am struggling with this- anyone have any ideas? Thanks Gene

[Pete Cyr]

I don’t know how he does it but why don’t you perform a ramp test

viewtopic.php?f=97&t=3439
Focus ramp.dxf

[Philipp Pap]

When doing the z offset by hand the laser mode can be set to a fixed time (up to 999ms) by pressing the pulse button once.
On a ruida 6445 it can be found under "menu-button", "function+", "laser set+".
The automated focus test is done with lines as far as I know.

[Gene Uselman]

I have seen him do the line focus test too, sometimes he does a test with just pulses. I have had the ramp that he designed for years and use it a lot, Philipp - that will set a time for the pulse but I don't think you can do a pulse from the software?
I was always wondering how he did the 'autoMagic' one for a quick check. Thanks Guys. Gene

[Pete Cyr]

Gene - I ran several ramp test to narrow the measurement for the focal distance AND then I did individual pulse tests at 0.2mm increments, measuring my spot size until I was satisfied I had found my ideal spot size - it only took about 15 min.(after the ramp test narrowed the band to evaluate)

[Gene Uselman]

Did you automate the pulse tests? that is more of less what I am trying to do. Old and in the Way [it's a band and seems to be my new motto].

[Gene Uselman]

Turns out that Lightburn has a built in focus test [doncha hate people who think they can just pick up a program as they go... and then ask stupid questions?] to do more or less what I want to do. Here is my exploratory tests on that focus test. I measure my focus in mm and the program is set up in inches so I need to fine tune it into mm, and fine tune my Z axis too. The Mighty Oz does it again!

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lightburn focus test.jpg

[Pete Cyr]

Did you automate the pulse tests? that is more of less what I am trying to do. Old and in the Way [it's a band and seems to be my new motto].

Nope - all manual...but it appears in the follow on post you figured it out

[Danny Miller]

I recommend a few very close parallel lines for this. They can be vector lines, OR raster lines with slightly excessive line interval.

You can really pick out where the line is in best focus, as it leaves the space between the lines. When out of focus, the lines widen and leave less space, or merge entirely. I have sometimes done a few lines at different line intervals and repeat for each Z height and you can objectively grade the spot size, it's pretty obvious where it merges and eats up the space between lines.