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Fórum » Only in English » Technologies » CO2 Lasers. (Anything relating to CO2 Lasers can be discussed here.)
CO2 Lasers.
tweakie Dátum/Date: Csütörtök, 2014-06-26, 12:02 | Üzenet/Post # 381
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Something I keep getting asked about is CO2 laser output power control by using the Mach3 generated PWM signal and the Sxxx command in the GCode program. This is not something I prefer to do as I always treat engraving and cutting toolpaths as two different operations separated by a tool change. However, PWM control had to be done.

Well, pre-set laser output power is not a constant – it will vary dependant on tube temperature and it’s cutting / engraving ability will also vary dependant on ambient temperature as well as the type of material and it’s moisture content etc. etc. As a result a GCode program with a defined power setting may run just fine today but may need some adjustment to run just as well tomorrow.

There is always more than one way to accomplish anything but this is the best solution I have come up with so far. It does however need a bit of extra hardware to function but this is simple enough to make and just fits inline with the LPT cable to the machine.
The maximum laser power is still manually set and the GCode Sxxx command controls the actual laser output power between (approx.) 0% to 100% of the maximum that has been set. This allows for the laser output power variations, mentioned above, to be compensated for and adjusted on a day-to-day basis without having to make any changes to the GCode program.

This method basically gates together the Mach3 PWM signal with the M11P1 / M10P1 command codes on Output# 1 just by using a pair of opto-couplers and the LED series resistor values have been chosen to present a loading on the LPT port of no more than 5mA per pin which is well within it’s capability.
This method negates the set-up time delay associated with switching the PWM signal with the M3 / M5 commands by leaving the Mach3 PWM signal constantly running then just applying it as required with the M11P1 / M10P1 commands. Provided any changes to the laser output power are commanded by entering the Sxxx command on a separate line in the GCode no delays in changing power levels have been noticed and engraving / cutting within the same program is easily accomplished.

The circuit is extremely basic and can be easily made and fitted to an existing machine (which is controlled by the LPT port, of course) and the following pics. Show just what I have done.

My Mach3 set-up is as follows (please note - your pin numbers may be different).

PWM base frequency 500
Minimum PWM 0
Relay – M3 Output #2
Spin up / down delays all 0
Spindle √ 17 0 X X 1 1
Output #1 √ 1 16 X
Output #2 √ 1 9 √
Spindle pulley 1 Min speed 0 Max speed 100 Ratio 1

The GCode program uses M3 followed by Sxxx (0 to 100) which is essentially percentage of full power. Thereafter changing power by entering a new Sxxx command and the laser is switched on / off by the M11P1 / M10 P1 commands. The program then has M5 at the end.

Nice little project for a rainy day perhaps ?

Tweakie.



Csatolások/Attachments: 0668000.jpg(21Kb) · 9311003.jpg(55Kb) · 2045992.jpg(55Kb) · 5822904.jpg(91Kb)


Success consists of going from failure to failure without loss of enthusiasm.
 
picengraver Dátum/Date: Péntek, 2014-06-27, 01:19 | Üzenet/Post # 382
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Tweakie,
You always make things look easy.  prof

Thanks,
John


I paint with a blue light beam.
 
tweakie Dátum/Date: Péntek, 2014-06-27, 08:16 | Üzenet/Post # 383
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Thanks John. smile

Tweakie.


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Amatőr Dátum/Date: Péntek, 2014-06-27, 18:46 | Üzenet/Post # 384
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tweakie, thanks for posting Your solution, I think it's very clever to set AND relation between PWM and laser trigger.

H1i.hu
 
tweakie Dátum/Date: Szombat, 2014-07-05, 12:03 | Üzenet/Post # 385
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Just a short video demonstrating the PWM control of laser power (as detailed in post #381) enabling seamless engraving and cutting operations using Mach4 with the Darwin driver.

video

Tweakie.


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tweakie Dátum/Date: Hétfő, 2014-07-07, 11:09 | Üzenet/Post # 386
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Some further thoughts on this…

By changing the active state of Output #1 to ‘active low’ the circuit can be simplified as shown below.

Tweakie.

Csatolások/Attachments: 8318317.jpg(29Kb)


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Amatőr Dátum/Date: Kedd, 2014-07-08, 18:12 | Üzenet/Post # 387
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tweakie, good idea, I suppose this can not be more simple. Effective solution!

H1i.hu
 
tweakie Dátum/Date: Szerda, 2014-07-09, 11:07 | Üzenet/Post # 388
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Thanks Zoltan.

I have been doing some testing with Mach4 and laser cutting / engraving - this little device provided a very easy solution to 'logic AND' the two signals. There are, no doubt, other ways in which it can be done but this method suits me. smile

Tweakie.


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Amatőr Dátum/Date: Hétfő, 2014-12-15, 18:11 | Üzenet/Post # 389
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Hello friends!
I had a little time to prepare my cooler for the CO laser, here are some pictures.
I know it seems a bit chaotic, but theoretically it is correct, tests will come soon.




Csatolások/Attachments: 8406339.jpg(227Kb) · 7639298.jpg(237Kb) · 6749459.jpg(232Kb) · 8417677.jpg(173Kb)


H1i.hu
 
tweakie Dátum/Date: Kedd, 2014-12-16, 06:37 | Üzenet/Post # 390
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Wow !
That looks really neat Zoltan - excellent job my friend.  respect

Tweakie.


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Amatőr Dátum/Date: Kedd, 2014-12-16, 18:18 | Üzenet/Post # 391
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Thank You tweakie, it will turn out how fine the Nutella jar will work as a surge tank smile

H1i.hu
 
tweakie Dátum/Date: Szerda, 2014-12-17, 06:47 | Üzenet/Post # 392
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Hi Zoltan,

I am sure that will work just fine and it will certainly cool to ambient, but please let us know how it performs.

Tweakie.


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Amatőr Dátum/Date: Csütörtök, 2014-12-18, 18:01 | Üzenet/Post # 393
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Today afternoon I had time to work on the coolant for the laser.
I filled up with a mixture of 50% distilled water and 50% antifreeze. I had a little problem to fill the tubes and the pump without air inside, so the pump wasn't able to suck up the water. Forunately I could make a little pressure in the jar to make the liquid go through the pump, after that it was working. Now the pump is still running to surely remove the rest air.





The flow switch had a leak, so I had to remove from the system.
Csatolások/Attachments: 6977360.jpg(385Kb) · 2469786.jpg(378Kb)


H1i.hu
 
tweakie Dátum/Date: Péntek, 2014-12-19, 15:52 | Üzenet/Post # 394
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Hi Zoltan,

I think a flow-switch is a necessary safety precaution for protection of the laser tube.

Tweakie.


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Amatőr Dátum/Date: Szombat, 2014-12-20, 06:15 | Üzenet/Post # 395
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tweakie, You're right, the flow switch is necessary, I'll take it back as soon as I found the leakage and could repair it.

H1i.hu
 
Amatőr Dátum/Date: Vasárnap, 2014-12-21, 16:04 | Üzenet/Post # 396
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I found the leakage on the flow switch, was not hard to repair. Unfortunately it does not close its terminals. Turned out that the pump is very slow, I cannot measure but it takes ca. 2~3min to flow 0,5l. This flow isn't enough to push the flow switch. I have to change the pump or take a hall-effect flow meter and a circuit?

H1i.hu
 
tweakie Dátum/Date: Vasárnap, 2014-12-21, 16:25 | Üzenet/Post # 397
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Just a thought, but my flow-switch has to be mounted vertically to operate properly.

Tweakie.


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Amatőr Dátum/Date: Vasárnap, 2014-12-21, 17:06 | Üzenet/Post # 398
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Thanks Tweakie, I demounted the switch to see what happens in vertical position, but it still wants more flow. Earlier when I repaired the switch, I was shortening the spring to be more sensitive, seems it couldn't help. Worked fine on dry, swithed by just blowing air into the tube. I thought the liquid will push enough.
I was searching the datasheet of the pump, and it says at 0m height the flow is max. 11 l/min. Although it maybe would be enough to cool, I'm sure the current performance is much weaker. Maybe the impeller is too used.


H1i.hu
 
tweakie Dátum/Date: Hétfő, 2014-12-22, 07:07 | Üzenet/Post # 399
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Hi Zoltan,

The CO2 tubes do not need a vast circulation of coolant so I am guessing that your pump will be OK. Perhaps, as you mentioned earlier, a different type of flow-sensor is needed. ?

Tweakie.


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Amatőr Dátum/Date: Hétfő, 2014-12-22, 09:43 | Üzenet/Post # 400
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Tweakie, I agree, the coolant is enoug, the only problem is that I cannot detect the flow. If I choose another sensor, I think this kind will detect slow flow rate. The question is how to build a circuit what can sense if the impules slowing or lost.

H1i.hu
 
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