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Author Topic: The Laser Project.  (Read 806566 times)

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Offline Dan13

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Re: The Laser Project.
« Reply #1010 on: January 18, 2018, 07:10:27 AM »
Tried to adjust the laser out of focus slightly. Can't say that it helped to produce more shades of grey. If find that trying to engrave a photo on wood is inconsistent and since the wood is not uniform I usually see different tones for shades that had to be the same. The darker shades work better the lighter usually are not seen at all. Increasing power burns the dark spots too deep.

Dan

Offline Tweakie.CNC

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Re: The Laser Project.
« Reply #1011 on: January 18, 2018, 08:22:59 AM »
Hi Dan,

Hopefully third time lucky trying to attach everything to this post. :)

The .zip file has my .aug and .tap files for this image that I have engraved onto Birch ply. Please try it and see if you can get similar results.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline ART

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Re: The Laser Project.
« Reply #1012 on: January 18, 2018, 08:38:00 AM »
Hi Dan:

 Variations caused by wood grain are usually desirable as they identify the wood its on. Your problem may be more
related to absorption profile. UV lasers dont work the best on organic matter. The higher the frequency
or shorter the wavelength of a laser the less it is used for organics, and more for marking metal.
  CO2 and Yag ( either end of the infra red spectrum) are easily absorbed by organic matter like wood ( or skin
or corneas) while UV  absorbs differently than the others. For example if you hit your
eye with a CO2, its probably fixable as the burn occurs on the outside of the eyeball, whereas UV will go
through the first layesr and damage the retina at the back of your eyeball, and may not be fixable.

   So while UV will burn wood, its a smaller portion of the energy that's doing the burning. Its why UV is used more for
engraving a photo on metal than wood, and you may find the photo looks better on an aluminum plate or metal
surface of some kind, though grey scale may suffer as that's a property of the surface material.

  UV lasers also suffer from optics, an LED isnt easy to focus to a tight focal spot, the optics are difficult
so the typical lower end laser dont have great optics on them usually. This can limit its ability to get sharp
results. You may want to try on a white painted surface and finding the power levels that best produce a
grey scale. Paint tends to darken on a more linear scale.

   If your using Auggie, in its config there is a setting of minimum power and max power. Setting that properly, by setting
minimum to the level at which you begin to see burn, and max to the power where its dark enough will allow Auggie
to create a grey scale that's best for that laser as it will scale power to between those two levels.

  I'm sure a UV can do photos, but I suspect you need to treat the wood with something that assists the absorption
like a resin or paint ( wood conditioner maybe), then using the proper power range should allow a grey scale.

  I don't use UV yet, I'm all CO2 here, so I'm no expert on such matters, but all this may give you some things
to consider. I'm just hooking up my third CO2 laser now ( I have a 10w and a 40w, I'm adding a 48w)
 and building a new cabinet for it, so Ill be playing more with photos myself in the future,
though I'm more interested in cutting paper with my new one, than burning it.
    :)

Art



Offline ART

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Re: The Laser Project.
« Reply #1013 on: January 18, 2018, 08:38:55 AM »
Nice photo Tweakie. :)

Offline Dan13

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Re: The Laser Project.
« Reply #1014 on: January 18, 2018, 09:06:19 AM »
Thanks. That was my guess too regrading the wavelength. It's not UV here, but just violet at 450nm.

I am using the software that came with the laser. The controller doesn't seem to work with any other sowftare. It either does photo or accepts Gcode. But the way it uses Gcode is not common to all others - on G1 moves the laser turns ON and on G0 it turns OFF. This is the only way to switch the laser on and off from within Gcode. I will look into the gcode you sent Tweakie and see if it I can adapt it.

Dan

Offline ART

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Re: The Laser Project.
« Reply #1015 on: January 18, 2018, 10:06:11 AM »
>>on G1 moves the laser turns ON and on G0 it turns OFF.

  Auggie works the same. It saves a lot of switching statements and I find it preferable
to other types of control statements. As your probably ocked into a set power range for a photo
unless you can set the power level range, you may want to experiment with various treatments to
the material to perhaps get a better range.

Art

Offline Dan13

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Re: The Laser Project.
« Reply #1016 on: January 19, 2018, 06:33:51 AM »
That's good to know Art. I have never used Auggie. Have had Gearotic since its first days, but never got to see what Auggie was all about.

Tweakie, I cannot understand the Gcode you attached. There doesn't seem to be any laser control commands, just G1 moves side to side. No G0's or anything.. either I am missing something in the way you control your laser, or it is the wring file.

Dan

Offline ART

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Re: The Laser Project.
« Reply #1017 on: January 19, 2018, 07:46:45 AM »
Dan:

>>There doesn't seem to be any laser control commands, just G1 moves side to side.

  Its because the Gcode loads an Augment file at the start and that sets photo mode.

   Thats standard GCode for Auggies Photo engraving setup. The laser in Auggie's photo
mode only turns on in G1 mode moves AND only when the x,y position is in the extents
of a loaded photo. This allows one to accelerate toward the photo with burning starting
automatically as the laser enters the photo and stopping as it leaves. This allows for constant speed
photo engraving which smooths out any aberrations caused by accel and decel of the laser head.
  Since power and speed are semi-linearly related in laser cnc, having a constant velocity can
help when burning a photo. Although in general use Auggie will vary the power as a linear function
of actual velocity, the correction is not quite linear enough on most lasers for photos, so for photos
we do this acceleration rejection method to make them clearer.

Art


Offline Dan13

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Re: The Laser Project.
« Reply #1018 on: January 19, 2018, 08:14:46 AM »
I see. Pretty neat. But afraid I will not be able to use it. My laser has a USB dongle which does the communication between the machine and PC. So can only use their supplied software. Which would accept Gcode file as input or images.

Dan

Offline ART

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Re: The Laser Project.
« Reply #1019 on: January 19, 2018, 08:41:42 AM »
 Yup, typical problem. Best to just keep playing with material and such to find one that gives a
good grey scale on your machine, then photos shoudl start to look better.

Art