Author Topic: Grrr, weird smearing! (still, t2laser)  (Read 223 times)

stevepax

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Grrr, weird smearing! (still, t2laser)
« on: May 18, 2017, 09:22:01 PM »
I'm still having some trouble with my laser. Zac has been helping, but it's still not reliable. Thought I'd check in to see if anyone else has gotten this problem.

Take a look at the attachments. Both engraved from the same jpg file, same speed, same power, just black and white. Cranberry 1 is a bit smaller than I would like, so I reloaded the image, sized it a bit bigger than before (both were still reduction in size from original jpg image), and engraved again, got Cranberry 2. See those weird smearing/ghosting artifacts at the top of the glass? Why did it do that? It doesn't show up in the original image, of course, and doesn't appear in the gcode simulated viewer in t2laser, either. But it means when I try to engrave the final piece, I don't know what I'm gonna get.

Anyone ever seen this? The artifacts were on the second engraving. Was the laser just too tired to turn off quickly or something?  :)

Zax

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Re: Grrr, weird smearing! (still, t2laser)
« Reply #1 on: May 19, 2017, 04:45:38 AM »
That's a new one for me too. Very odd, since it was black/white the laser should have been on or off.

Perhaps heat in the wood caused resins to bleed or something ???

ggallant571

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Re: Grrr, weird smearing! (still, t2laser)
« Reply #2 on: May 19, 2017, 08:12:38 AM »
Can you post the original source, before and after scaling.  I have seen similar effects when working with 32-bit RGBA color where the Alpha get interpreted as Black. Assumed it was my strictly host etch utility.
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Zax

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Re: Grrr, weird smearing! (still, t2laser)
« Reply #3 on: May 19, 2017, 08:48:45 AM »
I convert 32-bit to 24-bit at import, and depending on the setting the background is converted to solid white or black. All code generation is using a 24-bit or lower image.

He is also using B/W mode so only laser min and laser max are output.

stevepax

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Re: Grrr, weird smearing! (still, t2laser)
« Reply #4 on: May 19, 2017, 09:34:07 AM »
In case anyone is interesting, I attached the original jpg file here. I did the resizing in t2laser, and B/W mode is selected (as you can see, it's just a B/W image anyway...).

Zax

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Re: Grrr, weird smearing! (still, t2laser)
« Reply #5 on: May 19, 2017, 03:12:02 PM »
Does the "view" look correct?

ggallant571

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Re: Grrr, weird smearing! (still, t2laser)
« Reply #6 on: May 20, 2017, 08:48:48 AM »
I looked at IMG_7185.JPG using gimp on Linux and observed a few oddities relative to my etching experience. BTW - I am a novice with an entirely home-brew setup.

1. The resolution is 300x300dpi.
2. It is gray scale.
3. There are a lot of low intensity/density pixels.

Do you get the same result with slower X/Y travel?

Attached is a version with some of the "clutter" removed. It renders clean on my tools but is larger than my A5 work surface so I do not know what it etches like.


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Zax

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Re: Grrr, weird smearing! (still, t2laser)
« Reply #7 on: May 20, 2017, 02:32:09 PM »
Double check you have laser min at 0, as I verified there is no software issue so the "smearing" must either be due to the material or a laser issue (which you would think should be more repeatable).

The left simulation "view" is using blue (max) and white (min) but to confirm I displayed the laser off (yellow) and also ran the top part of the image 3 times and confirmed no output.

stevepax

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Re: Grrr, weird smearing! (still, t2laser)
« Reply #8 on: May 20, 2017, 04:59:28 PM »
So, see the attached photo. I went out to the shop, connected the laser and hit send on the gcode, and it engraved the bottom image perfectly. Black and white mode, speed 1000, power 75.

Then to test it, without exiting at all, I just jogged the laser up a few centimeters and hit send again, exactly the same gcode (because I did not regenerate the gcode, just hit send again). The top part of the attached is the first bit of that carve, and you see those smears appearing there again. They are not shaped the same as before exactly, but do appear on the same areas as before.

This makes no sense to me at all.

ThothLoki

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Re: Grrr, weird smearing! (still, t2laser)
« Reply #9 on: May 20, 2017, 05:14:50 PM »
Try a different wood. That may be the problem.

Honestly, I like those stains. I think it looks cool.
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Zax

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Re: Grrr, weird smearing! (still, t2laser)
« Reply #10 on: May 20, 2017, 06:34:54 PM »
It looks like the wood, see the staining in the vertical line down the glass.

The only thing I can think to try is a slightly lower burn, either up the feed rate or reduce power if you have a TTL laser. That may prevent the heat build up and whatever is happening to the wood.

stevepax

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Re: Grrr, weird smearing! (still, t2laser)
« Reply #11 on: May 20, 2017, 07:25:58 PM »
It's not the wood. The laser is physically on for those sections, if it is not the first burn of the day. Also, it happens in exactly the same places on the image. It's definiely the laser.

ggallant571

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Re: Grrr, weird smearing! (still, t2laser)
« Reply #12 on: May 20, 2017, 07:34:26 PM »
You might want to try the burn using card stock at much lower power. I find that the neon yellow and green react very nicely. If you could capture and post the gcode during the failure I would give it a try. Please just post the small failing segment!!
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Zax

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Re: Grrr, weird smearing! (still, t2laser)
« Reply #13 on: May 21, 2017, 05:20:36 AM »
I wonder if you add a pull down resistor on the laser module or controller, if that would shut it down quicker although it's more likely the laser driver doesn't switch correctly.

As I said, it's not only the top of the glass the same over burn is visible in other areas where the laser needs to transition from an area of solid black to white. You could test with a black square or thick outline and get the same result.

ggallant571

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Re: Grrr, weird smearing! (still, t2laser)
« Reply #14 on: May 21, 2017, 07:44:14 AM »
It looks like the laser is weakly powered. You can get that by PWM, supply voltage, or faulty power transistor.
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