Raster Laser Engraving software and methods

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Raster Laser Engraving software and methods

Postby lasersafe1 » Fri Nov 27, 2009 9:34 pm

First let me congratulate you on the fine build log you created on the buildlog.net web page. It looks like you and I are very close in the time span of getting a machine in operation. I started with an ebay 40W engraver. It came with the Moshidraw software and a controller that would accept the print job over the parallel port and then raster it. I played with this software for about 1 day before I decided to junk the whole thing. I tore all the chips off the controller and wired my own Allegro chips to the lone remaining parallel port connector. I already owned Mach3 because I bought it for a mini-mill that I run with it.

1. We can agree that the raster engraving program in Mach3 is not yet adequate. It needs help from a smart programmer.
2. Mach 3 works quite nicely for vector cutting. I was using the Z direction bit and very shallow Z movements for my laser ON/OFF control. I know that you and others have used the machine codes.
3. I can't get Mach3 to raster worth a damn. If you use a machine code to turn the laser on and off it momentarilly pauses as it runs the VB script. I think that it might be more advantageous to use the Z direction bit because it is loaded into the trajectory planner ahead of time. That being said, I'm still not getting good results.
4. I thought that perhaps EMC2 on Linux would be better. I have tried it but I still get odd results. I find that the M64 and M65 commands still pause the motion of the X sweep. I've got people telling me that I need to use the G64Px.xxx code to smooth out the motion, but for some reason I can't see any change in behaviour of the EMC2 run whether I have this code set or not.
5. I contacted LinkMotion and downloaded the Virtual CO2 Laser Driver. I have it set up on my Windows XP machine with the proper speed, RAM, PS2 Keyboard and mouse, etc. I am able to jog my X and Y stages and fire the laser, but when I print from a document to this new "virtual printer", it throws out an access violation warning(tried to write to some odd memory address) and crashes the linkmotion software. I only get 15 tries with this demo software, so I'm just about expired. I think I need to junk it and go back to testing EMC2. The linkmotion "virtual" printer software was going to be $600 if it worked. I am not opposed to spending that kind of money if I get a reliable result, but right now it is not working.
I have two other threads going on two other forums, but the answers aren't coming too clearly.

http://www.cnczone.com/forums/showthread.php?t=93949

http://www.linuxcnc.org/component/optio ... 6/lang,en/

Please jump in on any of them if you have anything to add.
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Re: Raster Laser Engraving software and methods

Postby bdring » Fri Nov 27, 2009 11:08 pm

That is a good "State of the Union" post. I agree with all of it. I can add a few details.

As best as I can figure, in it's present form Mach3 will never do real engraving, because it does not store the grayscale information. The plugin can store a single bit per step. It then tries to use that to dither a gray across multiple steps, but it only fires the laser for a few microseconds per step, so the duty cycle is too low for a decent engrave. This is a limitation of the Mach3 pulse engine not the plugin. We need to set a full 8 bits per step for 256 level grayscale. Even more at the power control level if we want accel/decel compensation.

EMC2 does a better job of control for cutting for me, but has no provision for engraving.

If anyone knows more about the LinkMotion controller, please chime in. It looks like it needs a ton of memory. how much do you have? Describe what you were trying to engrave..resolution...size...steps/in. Anyway, I agree $600 is a non-starter.

I wonder if a second parallel port could be used in parallel to set the power level. That way each step could have it's own full 8 bit or more power level. A simple parallel to voltage or PWM circuit would be very easy. Now someone needs to write the software. I might give it a shot in Linux after my microcontroller based engraver is done.
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Re: Raster Laser Engraving software and methods

Postby lasersafe1 » Sat Nov 28, 2009 3:48 pm

Well last night I did some more experimentation. I had to put a more powerful computer on my laser engraver in order to try out the LinkMotion software. The LinkMotion was a bust even with a fast computer and 1 Gig of memory, but now that I had a 3.4Ghz machine in the shop I decided to load Mach3 on it and see what improvements can be made. My old machine was 1GHz.
1. Mach 3 runs quite well on this machine. I can now set the pulsing engine up to 100kHz.

2. I feel bad that I had previously bashed the laser engraver plugin. Yes, it does have issues with short pulse period and it will fold the output in two if you don't insert a perfectly square image, but at least it runs and runs quite fast. This in itself is proof to me that a computer parallel port can indeed spit out the signals fast enough to do a quick engraving. Everyone is trying to sell us cards that have FPGA's and memory to load the raster and then send it directly to the machine. The computer can do it on its own if the software is written properly. I will try to make a Youtube video shortly of the Mach3 laser engraver plugin running on my laser.

3. The source code for the plugin is freely available. Perhaps the EMC2 coders might want to take a closer look at it. I think ultimately EMC2 can beat Mach 3 in a timing performance race on any given machine because Linux has tighter control over latency issues.

4. I never did get the Mach 3 or the EMC2 to raster quickly using standard Gcode. I can't seem to get around the fact that the X sweep wants to slow down to activate and deactivate the laser. It doesn't seem to matter whether I play with G64 or not. I must be doing something wrong. Attached is the file I have been playing with. This was created using a program called BMPtoCNC.

5. I am actually where I need to be right now with my laser and Mach3 running the engraver plugin. I am using the laser to raster an image across an optical film to simply "kiss" the film and burn it off the substrate in select locations. Since I am not interested in grey levels, the plugin works. In the longer term I would love to actually be able to do this in Gcode where I could do the raster and then do a cutout all within the same run.

I actually have a product to produce now, so I need to dedicate some time to cleanup of the laser hardware. Today I will pop a hole in the shop wall to put in a dryer vent for this laser. After that I'm going to build the air assist nozzle that you were kind enought to provide the drawing of. I have a cool "spring loaded" capillary tube (1/8") that will be perfect for introducing the air flow. Finally I will replace the single turn potentiometer that my laser power supply uses for power setting with a 10 turn pot with readout for higher precision. Longer term I might go digital with a keypad entry to a DAC.
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Re: Raster Laser Engraving software and methods

Postby lasersafe1 » Sat Nov 28, 2009 3:54 pm

Looks like we can't add .nc or .txt files to the posts. If you want to try my file it is posted over at the CNC zone under as linked above.
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Re: Raster Laser Engraving software and methods

Postby lasersafe1 » Sat Nov 28, 2009 4:07 pm

Forgot to mention.

I did put together a simple power controller for the laser that is based on Z motion. It uses a DS1804 digital pot that works directly off the step and direction bits to give 100 steps in power. I had to use another physical pot and opamp to set the lower threshold for starting power and I used the original pot on my power supply to set the upper threshold for max power. The digital pot would then accept standard Gcode to provide 100 steps in power between these min and max settings. I will draw up a schematic later when I get a chance. I also played around with an old V/F and F/V chip. The purpose of this chip was to switch it inline with the laser ON/OFF ttl command for super fine tuning of the laser power. I would have done this with a PIC, but I needed some very short pulses at first and I had to go Old School.

Again, I've got the 40W laser but I need to turn it way down to kiss the optical film I am machining. Who knows? Perhaps I shouldn't be using my CO2 at all, but a simple DVD burner diode instead.
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Re: Raster Laser Engraving software and methods

Postby bdring » Sat Nov 28, 2009 9:05 pm

There is a better version of the mach plugin on this thread

http://www.machsupport.com/forum/index.php/topic,11996.0.html
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Re: Raster Laser Engraving software and methods

Postby bdring » Sat Nov 28, 2009 9:20 pm

I think I fixed the settings to allow uploading that file type. Are these the files you were talking about?
Attachments
rugerflood.txt
(257.86 KiB) Downloaded 1536 times
ruger.txt
(281.75 KiB) Downloaded 1717 times
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Re: Raster Laser Engraving software and methods

Postby bdring » Sat Nov 28, 2009 9:32 pm

Please post a screen shot of your Mach3 engraving and a screen shoot of the plugin screen to show the settings before the engrave started.
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Re: Raster Laser Engraving software and methods

Postby lasersafe1 » Sun Nov 29, 2009 3:02 am

bdring wrote:There is a better version of the mach plugin on this thread

http://www.machsupport.com/forum/index.php/topic,11996.0.html


I tried that one and it didn't work for me. Perhaps now with my new PC it will run.
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Re: Raster Laser Engraving software and methods

Postby lasersafe1 » Sun Nov 29, 2009 3:06 am

Yes indeed those were the files. One used the Z direction bit for laser on off. The other used the flood relay which was a huge mistake. The M-codes take a long time to process and stall the X axis sweep. I simply use the find and replace function of notepad to try out different things.

I will post a shot of the engraver plugin soon, along with a Youtube video of the engraving.
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