laser engraving in photo negative?

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Joethegasman
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Joined: Sun Mar 11, 2018 2:16 pm

laser engraving in photo negative?

Postby Joethegasman » Sat Mar 17, 2018 3:35 pm

I amy be overlooking something simple and I did poke around a bit with a search but I did not find anything pertaining to my issue, that being my lights are dark and my darks are light.

I did try checking "negative colors" to no avail. perhaps that is not what I needed.

I am runniNG A JTECH 2.8W laser on an xcarve with the original arduino/gshield.

I'm still trying to get my head wrapped around all of this, new to me terminology, techniques, etc but that sort of thing is what keeps the gray matter elastic.

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Picengravertoo
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Re: laser engraving in photo negative?

Postby Picengravertoo » Sat Mar 17, 2018 4:12 pm

Hi Joe,

Are you using the Analog/PWM engraving profile? That is the best profile to use with grbl. You should set the Max 3D Axis Depth to 255 for the Black Shades and the Min 3D Axis Depth can be set above 0 to where the lightest shades just start to burn.

Are you using Larry's MultiMode grbl 1.0c, or the latest grbl 1.1f?

If you are using either of those grbl firmware versions, make sure to set these settings like this:

$30=255
$31=0
$32=1

Joethegasman
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Joined: Sun Mar 11, 2018 2:16 pm

Re: laser engraving in photo negative?

Postby Joethegasman » Sat Mar 24, 2018 4:17 pm

Well I am finally able to get back to this,
I am using the settings you replied with, except for the max 3d axis depth is only at 130 or so.
I was able to determine that the photo negative issue was something to do with the way the image I was using was saved.
I started over with a fresh copy of the file and all was well in that regard.
On to the current conunderum.
On my burned image, I have areas tha should be black but for some reason they are straight white like the lasser was shut off or it skipped these areas for whatever reason.I have included the original for reference.
Any ideas what this is?

I am going to do a test run of something else while awaiting your reply to see if it occurs there as well.

Thanks ,
Joe

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Picengravertoo
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Re: laser engraving in photo negative?

Postby Picengravertoo » Sat Mar 24, 2018 6:40 pm

Hi Joe,

I recommend you use as much of the Min 0/Max 255 PWM range as you can. Theoretically, every PWM voltage change will burn a different shade level. If you limit the PWM range, you will limit the shades that can be burnt. The Feed Rate Change (variable feedrate) feature will expand the shade range even more. Try a setting between 20-25%. If a Max 255 setting burns too dark, increase the Feedrate.

You may need to make these changes to your grbl settings to increase the performance.

$0=30
$1=255
$11=0.005
$120=4000.000
$121=4000.000

It looks like you may have the Pixel Resolution (axis step over) set too high. The Pixel Resolution setting will ensure your laser's burn lines will lay down next to each other without any overlapping or leaving gaps between them. With the 2.8w, you should be around a .006"-.007" Pixel Resolution. You will have to resize your image in the PEP6 image editor using the Auto option. Instructions are on Page 8 in the Tutorial.

I did some editing to your image in the PEP6 editor. I used a Gamma setting of .8 and sharpened it to 20. It will lighten the image slightly and sharpening it will bring out more detail when it's laser engraved.

zak1.jpg
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As far as the white spots, does your laser's PWM modulation wires have an intermittent connection somewhere? What type of material are you lasering on?

Jeff

Joethegasman
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Re: laser engraving in photo negative?

Postby Joethegasman » Sun Mar 25, 2018 10:16 am

Thanks for the help Jeff,
Every time I work on all this the light bulb above my noggin gets a little brighter.

I pulled a random JPG image from the interne and ran it yesterday after posting here, looking to see if I could replicate the "blotching" issue. (as i will call it now for lack of a better term). and it did not show up.
My settings could have been better but this was mostly a test for blotching. the color vertical variation in burn density is due to the wood as it is a glued up panel. I'll deal with that a little later.

I'll adjust my GRBL settings to what you have posted hrere ad see what it produces and report back.
Also, I need to educate myself on "gamma" , sharpening is a bit self explanatory.

Thanks again for the assistance.
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Picengravertoo
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Re: laser engraving in photo negative?

Postby Picengravertoo » Sun Mar 25, 2018 9:43 pm

Joe,

Have you seen our laser focusing instructions in our Laser Setup PDF? Select the Help button in PEP6 and look on Page 22.

Joethegasman
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Re: laser engraving in photo negative?

Postby Joethegasman » Mon Mar 26, 2018 8:34 pm

I have now read page 22. I came across a variation of focusing on another orum and have had some success in getting my focal spot as small as possible.

Ive putzed around some more with a different image aqnd am noe getting some decent results. Once my phone recharges and I can get back into the shop I'll get some pics to post here. The blotching issue is apparently isolated to the one image I have posted here previously. I was beginning to think it was some sort of artifact of the jpg compreassion but even after resampling and converting to a bmp the blotching still appeared. so i gave up on that particular image and went with a different on taken by the same camera. No blotching.
i'mgetting a bit more familiar with the image settings and am starting to see major improvements.

I look forward to putting my successes up here soon!


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