laser raster engraving

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23 Jul 2017 21:26 #96321 by vre
vre created the topic: laser raster engraving
I have a chinese CO2 laser machine with glass tube and ruida controller.
I want to retrofit it to linuxcnc so i plan to buy a Mesa 7i93.
The machine works ok except of engraving that is poor quality.
I have seen an other machine that has the same glass tube and PSU with mine
but has a proprietary controller optimized for raster engraving and this machine gives perfect photo engraving results.
So the controller is the key to achieve good engraving this is the reason why i want to retrofit my machine.
The question is possible to do with linuxcnc raster engraving ?
I have seen this wiki.linuxcnc.org/cgi-bin/wiki.pl?Rastering_With_A_Laser but is old and some links not working.
I don't know rubby & python (i know java) to check the code but this old code (is from 2009) will work with linuxcnc 2.7 ?
Have anyone do with success a conversion like this and has good raster engraving ?
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23 Jul 2017 23:28 #96326 by skunkworks
skunkworks replied the topic: laser raster engraving
This is a good thread (printer port rasterizing..)

www.buildlog.net/forum/viewtopic.php?f=1...94599e5ac6cba9de2872

sam
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24 Jul 2017 21:07 #96366 by vre
vre replied the topic: laser raster engraving
Thanks.
Iam interested in a mesa solution for laser not parport..
Is there a similar project with linuxcnc raster engraving and mesa hardware ?
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24 Jul 2017 22:53 #96368 by rodw
rodw replied the topic: laser raster engraving
It probably won't make any real difference once you have the motion sorted out. Assuming your machine is stepper driven, the 7i76 or 7i76e (ethernet version) is probably going to be perfect for you. From there it would just be renaming pins to suit the mesa card. I'd look at some of the plasma posts as it explains how to use M67/M68 to control various components via Gcode. Eg./ how to turn the laser on and off and adjust power levels.
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24 Jul 2017 23:19 #96369 by skunkworks
skunkworks replied the topic: laser raster engraving
Not yet - there isn't currently a way to get the laser trigger information streamed to the mesa card... I think it has been thought about - but no one has implemented it.
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24 Jul 2017 23:23 #96370 by rodw
rodw replied the topic: laser raster engraving

skunkworks wrote: Not yet - there isn't currently a way to get the laser trigger information streamed to the mesa card... I think it has been thought about - but no one has implemented it.


Is that sending pulses per mm of movement or something like that?
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25 Jul 2017 02:02 #96371 by rodw
rodw replied the topic: laser raster engraving

skunkworks wrote: This is a good thread (printer port rasterizing..)

www.buildlog.net/forum/viewtopic.php?f=1...94599e5ac6cba9de2872

sam


I read this. Interesting. On Page 14, he starts to use Mesa hardware.... He said it was easier becasue the PWM signals are generated on the Mesa board... Good luck!
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25 Jul 2017 09:48 #96377 by vre
vre replied the topic: laser raster engraving
It starts using mesa hardware for cutting..
For raster engraving image he not finished because he says that this function must embedded to fpga
and modified linuxcnc code.
parport is useless because the speeds are low and engraving needs high speeds.
In raster engraving the speed of x axis must be constant and the laser fire synchronized with motion.
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25 Jul 2017 10:29 #96381 by rodw
rodw replied the topic: laser raster engraving
I am a little bit interested in this topic but I have a lot more to do to finish my current machine before I can buy into it. I'm not sure he has taken the right approach talking about programming the FGPA. I don't understand why he wanted to retain the base thread which is not usually used in a Mesa config. I think if I was going to do this I would write a HAL component that was installed on the servo thread. This would mean it was called every millisecond. He says he was working at 0.5ms pulses but the maths did not indicate that to me and I can't see how a parallel port could generate pulses at that frequency.

I would save the current position and compare the distance moved since the last pass through the component (or simply check the current velocity). Either way, you can calculate the distance moved in real time so you can synchronise the laser pulses with motion and turn a pin on and off to pulse the laser.

So now if you could take control of one of the Mesa stepgens (which is probably a simple as commanding an unused axis to run at a given velocity) you could pulse the laser at speeds of up to 10 Mhz until you tell it to alter the velocity. So as you run through the servo thread, check if the velocity has changed then alter the stepgen frequency from your custom component.

Another crazier idea might be to use one of the $69 Mesa THCAD-10 cards which converts a 0-10 volt signal to a frequency. The frequency alters from card to card but mine peaks at 925 kHz. I think though that maintaining a PWM 10 volt signal might not be as responsive as a stepgen.
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25 Jul 2017 12:12 #96383 by skunkworks
skunkworks replied the topic: laser raster engraving
The problem is currently - with external hardware (mesa) you can only change the laser intensity once every servo cycle (1 to 5khz give or take)

With the printer port rastering running a base thread - you can up that to 20 -40khz.

The only way around this is to somehow offload the raster information to the mesa card. Again - I know it has been discussed but no one has coded it. PCW would have more info.

sam
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