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Fórum » Only in English » Technologies » CO2 Lasers. (Anything relating to CO2 Lasers can be discussed here.)
CO2 Lasers.
Dave Dátum/Date: Hétfő, 2013-07-15, 21:38 | Üzenet/Post # 301
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If I'm understanding what the book says about vector cutting wacko .... I've always used the 100% setting for tube current (without really understanding why) - according to the lcd display that's about 19ma. so using 0.5% should get a 19ma spike of really short duration for vector engraving.
Rastering is a bit different. I can see the depth of cut is dependant on their power% setting, and ends up with something looking like a relief carving but it doesn't really darken the wood all that much.
This is starting to get a bit too technical for my feeble mind.:D I gotta go downstairs and try it out.....
Dave
 
Muk Dátum/Date: Kedd, 2013-07-16, 02:44 | Üzenet/Post # 302
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Hmmm...now I wish I wonder if "power setting" on my PSU is the same as "amperage level" on your DSP.

I did a test on leather, using my pot there is no way to get the laser to produce a 'mark'. It fires inside the tube...but I see nothing emerge from the tip. Not sure why (on super low settings).

Hozzáadva (2013-07-16, 00:55)
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Gah, I can't find specifically what frequency is best for feeding PWM into the power side.

I've been digging around and I think tweakie posted it once, but I lost it. 20 khz? 25 khz?

------------------------------

So, after writing all that and reading another pile of articles I came to this with no....finality to it. He finished this article and that was the last of talk about it.

http://www.buildlog.net/blog....-system

This last article here...really hits the nail on the head. I think he has it really spot on...but the electronics of it have me kind of confused to be honest. I think someone with more MC experience needs to look at this and say what sort of viability there is to this...

Hozzáadva (2013-07-16, 02:44)
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After reading up on PPI (including that some of the engineering guys contact FSE about the spike power) that the spike power of firing the laser gives it the full 'bam' for that short second without the 'drop' aftewards...being 22kV pop then the 15kV stay power.

Using the 22kV pop constantly over and over gives a higher power shot, less burn damage, greater accuracy, infinitely more precision control over repeatability and actually makes a silky smooth edge at the cut vs a black char mark.

I haven't wanted to add a feature nearly as badly as this...few folks out there have boards they have made use of but nothing 'open'. They use Mach 3's modbus connection to send out the feedrate to make the PPI actually based against the distance of the head moved rather than the messy 'quick math' without knowing true movement.

Az üzenetet módosította/Modified by Muk - Kedd, 2013-07-16, 02:18
 
Dave Dátum/Date: Kedd, 2013-07-16, 03:18 | Üzenet/Post # 303
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OK, did some vector engraving with the speed set to 100%, vector current set to 100% and the power (pwm width??) set to 0.2% and it cuts regular paper nicely without any burn marks. If I back off the vector current to 50% or so, it marks without cutting. I can see the laser tube light up (dimly) even at this low setting.
I may have a mirror alignment issue, as the marking is noticeably lighter in the lower right corner of the work area (i.e. farthest from the laser tube. Time to get out the thermal paper again and recheck the alignment....  smile
Dave
 
tweakie Dátum/Date: Kedd, 2013-07-16, 17:21 | Üzenet/Post # 304
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Idézet
I've been digging around and I think tweakie posted it once, but I lost it. 20 khz? 25 khz?


There is no problem with pulsing the tube faster but the high voltage PSU's should not be pulsed at frequencies above 20kHz unless the PSU manufacturer specifically says it is safe to do so.

Tweakie.


Success consists of going from failure to failure without loss of enthusiasm.
 
Muk Dátum/Date: Szerda, 2013-07-17, 01:11 | Üzenet/Post # 305
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Doing some more reading...things like PPI and "On the fly" PWM control is available using LinuxCNC using a particular configurations done by guys who re-wrote stuff on the HAL side of things. No extra hardware needed, just a PC that can handle it.

I will be testing this tomorrow hopefully and be able to report on it.
 
tweakie Dátum/Date: Szerda, 2013-07-17, 17:52 | Üzenet/Post # 306
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Muk,

Phil seems to be getting on quite well with LinuxCNC http://oplaser.co.uk/opsupport/viewtopic.php?f=74&t=773 so I would be most interested to hear of your progress if you give Linux a try.

Tweakie.


Success consists of going from failure to failure without loss of enthusiasm.
 
Dave Dátum/Date: Csütörtök, 2013-07-18, 02:56 | Üzenet/Post # 307
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Did some more playing today. I'm finding that on hard materials like glass, mirrors, granite tile, ceramic tile etc, the image quality is very good. Wood, though, is another story entirely. The laser vaporises the wood (deeper with increased power), but doesn't darken it very much. Instead, it looks more like a lithophane carved with a rotary bit. I think I've got a way around this by sealing the wood first with shellac or sanding sealer, lasering through the coating, reseal it, apply some wood stain, wipe off the excess (just gets the high spots), let dry and sand a bit. Gel stain would probably work better, but don't have any right now. Here's a sample on some poplar scrap at a stepover of 0.002".
Dave

Csatolások/Attachments: 1644758.jpg(61Kb)
 
tweakie Dátum/Date: Csütörtök, 2013-07-18, 13:27 | Üzenet/Post # 308
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Nice work Dave and very interesting information regarding the wood pre-treatment and post-laser finishing. Keep up the good work my friend. ok

Tweakie.


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JJWMACHINECO Dátum/Date: Csütörtök, 2013-07-18, 19:56 | Üzenet/Post # 309
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Idézet (Dave)
I think I've got a way around this by sealing the wood first with shellac or sanding sealer, lasering through the coating, reseal it, apply some wood stain, wipe off the excess (just gets the high spots), let dry and sand a bit. Gel stain would probably work better, but don't have any right now. Here's a sample on some poplar scrap at a stepover of 0.002". Dave

Darn Dave,

Would not it be easier and quicker just using your 445nm laser diode? It sure would come out allot better running that image analog?  smile

Jeff


Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver
 
Dave Dátum/Date: Csütörtök, 2013-07-18, 22:15 | Üzenet/Post # 310
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At just under 5 minutes of laser time, probably not as slow as the diode laser. I'll admit that the diode darkens wood more than the co2 laser does, but it also takes a lot longer. I'm planning to stick mostly to the harder materials. btw, at the local home despot today I did find some 4x4 colored glass tiles. Only found two colors in stock though, light blue and whitish green.They have a thin white coating on the back side so I'll have to fill the lasered area with a contrasting color. I'm not sure if the diode laser would work for them or not. Planning to try them out later on the co2 laser.
Dave
 
Muk Dátum/Date: Péntek, 2013-07-19, 13:52 | Üzenet/Post # 311
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Heh, you know how building a laser from scratch is quite a test of patience...then when you get it all rolling you feel really accomplished? Tossing in a custom config'ed edition of LinuxCNC on a foreign operating system really pushes you back into that boiling vat of challenge...

Anyway, I've got my homing switches back online, custom config running, now I need to make the PP for CamBam and I think I'll be able to test it in a few hours. Whew!
 
tweakie Dátum/Date: Péntek, 2013-07-19, 16:15 | Üzenet/Post # 312
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Excellent smile looking forward to seeing the results.

Tweakie.


Success consists of going from failure to failure without loss of enthusiasm.
 
Muk Dátum/Date: Péntek, 2013-07-19, 19:50 | Üzenet/Post # 313
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Just a quick update...

I have the custom config 100% functioning. PWM is still a bit flaky for figuring that out (I'm sure it works, I just need to decipher it).

So far, I was able to make a cut at 3.00v @ 351mm/m (instead of 4.80v @ 351mm/m as I usually use) and have a perfect through cut w/ having almost NO charring at all. I rubbed my finger and had no residue. I will post some pics in a little while, I need to run a few chores.

Very, very exciting results so far.

Hozzáadva (2013-07-19, 19:30)
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Ok so while I wait for some pictures to come through (working on a raster right now)...I'll write up the necessary bits.

First things first, this is the custom linux config I'm basing this against: https://github.com/jv4779/2x_laser

If you don't have a basic knowledge of Linux, it's not too bad to get used to...all the instructions are there. Here is where you download it: http://www.linuxcnc.org/index.php/english/download

You can test run Linux via LiveCD, 'install' it like a program through Windows, or install to it's own separate partition for best performance. The disc comes pre-loaded with LinuxCNC and Ubuntu 10.04 ready to fly. I suggest updating it though via the update manager, as well going into the BIOS and disabling HyperThreading if you have Intel and "Cool and Quiet" for AMD. These cause problems with latency and that is a big thing for using this program.

There is a great guide that I only found much later...read through it then return here.

http://www.cnczone.com/forums....sp.html

Now, after reading through that you should have a pretty good feel for what's going on.

Make sure you've run the latency test (I've found that if you open a program for the first time since boot, you'll have higher latency then compared to it having been opened once already). Write down the numbers. Now run through the LinuxCNC Stepconf wizard to get all your numbers written down and put into config files. These will help you when you transfer the numbers over to either my config file or to Jarvis's file.

Next up is to install the COMP files. You'll need to be in the 2x_laser folder to install them (as per the Git page).

Now you should drop the 2x_laser config folder into your LinuxCNC config folder (you need to run the Stepconf wizard to create the folder first).

Now we transfer over the necessary info over. This is basically around the Axis velocities for your INI file, and the port/pin numbers in the HAL file. It looks scary but it's not too bad. My config was built around 1/16th steppers, 2000 steps per inch, slight delay to accomodate for optocouplers in my BoB. It's also built around having homing switches in the bottom left hand corner. If your homing switches are elsewhere, change the 'homing velocity' to a positive number instead of a negative one so the axis moves in the right direction.

This page helps explain what "duty cycle" is all about as compared to simply PPI. http://www.buildlog.net/forum/viewtopic.php?f=4&t=1303

For now, I am getting some wild results (like being able to cut through 3mm MDF with only 1.6v on my power scale) but I have not gotten a "formula" down yet as to how to positively modify my results. So if anyone else is wanting to join in on experimenting with Duty Cycle + feedrate + power, that would be fantastic. I can now "mark" paper using 0.8v on my power using analog power, PWM is still an option if you want it allowing for combined Etching + Vector cutting in 1 file (awesome) but again...needs some play.

Note: in the config file if you see a # then writing, it's commented out and isn't being used. So modifying that line will do nothing.

There is also a built in Raster file conversion utility. Well worth playing with as well. It's actually quite feature filled from what I was initially expecting.

Sorry if this post seems all over...lots of info in my head and having trouble organizing it cleanly.

I've attached my working 2x laser profile folder, the only two files that you change in it are the 2x_laser.HAL and 2x_laser.INI. Everything else is...well part of the system.

Hozzáadva (2013-07-19, 19:50)
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K, here's that raster I was working on. The included example from Jarvis I did with 1.5v power on cheap MDF (my test sheet, came out actually really really good). I gave it a wipe with a wet sponge to pull out the dust and soot to give it better contrast.

Csatolások/Attachments: 2x_Laser.hal(7Kb) · 2x_Laser.ini(3Kb)


Az üzenetet módosította/Modified by Muk - Péntek, 2013-07-19, 22:26
 
Dave Dátum/Date: Szombat, 2013-07-20, 00:47 | Üzenet/Post # 314
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Looking good Muk!
Dave
 
Muk Dátum/Date: Szombat, 2013-07-20, 03:46 | Üzenet/Post # 315
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tweakie Dátum/Date: Szombat, 2013-07-20, 06:36 | Üzenet/Post # 316
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Muk,

Nice work and excellent write-up. ok

Tweakie.


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Muk Dátum/Date: Vasárnap, 2013-07-21, 15:46 | Üzenet/Post # 317
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As an addendum, to run the 'raster' section of the Custom configs..you need to run the raster.py script via "open" then loading the picture after it runs the python script. It's crazy but...wow, wild work done from it.

Running the 'standard' raster is garbage.

Hozzáadva (2013-07-21, 15:46)
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For the first time ever, I was able to do this, with leather, with this level of detail without a DSP. I finally feel like I own a truly remarkable piece of hardware and not just "a homemade laser".

Csatolások/Attachments: 8094312.jpg(123Kb)
 
Dave Dátum/Date: Hétfő, 2013-07-22, 01:27 | Üzenet/Post # 318
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That's awesome Muk!!!
My experimenting with glass tile didn't come out very well. The home depot glass tiles are actually clear glass with a colored ceramic backing that's really hard to burn through without lowering the speed to around 20%. The laser's much quicker burning through the glossy front of ceramic tiles, and filling in the halftone dots with a contrasting color. Did 4 tiles today, might make interesting coasters if I can find some cork pads for the backs.
Dave

Csatolások/Attachments: 8062554.jpg(226Kb)
 
picengraver Dátum/Date: Hétfő, 2013-07-22, 01:34 | Üzenet/Post # 319
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Dave,
Well done.

I prefer felt pads instead of cork.  I buy them from Walmart, Lowes, etc.

John


I paint with a blue light beam.
 
Muk Dátum/Date: Hétfő, 2013-07-22, 01:50 | Üzenet/Post # 320
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Wow Dave, those look fantastic!

I'm going to go scouting out Home Depot...I want to try that out. You just did a 'color fill' and wipe off the excess?
 
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