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Fórum » Only in English » Technologies » CO2 Lasers. (Anything relating to CO2 Lasers can be discussed here.)
CO2 Lasers.
mbarosevic Dátum/Date: Péntek, 2015-01-23, 09:01 | Üzenet/Post # 441
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Hi all!
I whant to tell you, that i have solved the problem with my laser machine. Main problem was aluminium elastic couplers, and with faster feedrate, machine maked mistakes. Without couplers, it works perfect.
Next what i need to do is fireing laser with M10/M11 command, and putting laser beam to work with spindle pwm output.
Vectric aspire is what i am useinh to generate g code, and i have already made changes to postprocessor.
I dont have pictures of new cutting with me, so i will post it later. I have tried to cut some 3mm mdf, and 3mm acrylic. Feedrate for acrylic was approximately 0,4 m/min.
 
Amatőr Dátum/Date: Péntek, 2015-01-23, 11:31 | Üzenet/Post # 442
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Marko, It's good to hear that You find the problem. Our intuition about a mechanical problem wasn't wrong.
What program do You use to drive the machine? Mach3? What is Your laser wattage? 0,4m/min cutting speed is really good.


H1i.hu
 
mbarosevic Dátum/Date: Péntek, 2015-01-23, 18:28 | Üzenet/Post # 443
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It is 40w laser tube, mach3 used, g code generated with vetric aspire, 3stepper motors nanotec 4.2a, chinese drivers 2m542.

There are some pic:







 
Amatőr Dátum/Date: Péntek, 2015-01-23, 19:21 | Üzenet/Post # 444
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Marko, nice job! Do You use air assist to cut MDF?

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mbarosevic Dátum/Date: Péntek, 2015-01-23, 23:54 | Üzenet/Post # 445
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@Amator Yes, i have used air assist. I have air pump ACO-005 70l/min

Hozzáadva (2015-01-23, 23:54)
---------------------------------------------
There are few pictures with M11/M10 switching laser.http://i67.photobucket.com/albums/h304/marcobc/laser/IMG_20150123_231012.jpg
http://i67.photobucket.com/albums....242.jpg
There is engraving, but i work that as pocket toolpath with 0,5mm stepover.
http://i67.photobucket.com/albums....038.jpg

 
tweakie Dátum/Date: Szombat, 2015-01-24, 06:45 | Üzenet/Post # 446
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Nice work Marko  ok

Tweakie.


Success consists of going from failure to failure without loss of enthusiasm.
 
Amatőr Dátum/Date: Szombat, 2015-01-24, 16:14 | Üzenet/Post # 447
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Marko, Your machine seems professional, good job on design and building.

H1i.hu
 
mbarosevic Dátum/Date: Szombat, 2015-01-24, 19:17 | Üzenet/Post # 448
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I have one question for tweakie!
I have tried to make laser work with pwm spindle output, as you described, with el. Circuit with two optocuplers. Only i have modified circuit with one pullup resistor on laser trigger(low).
Everything seems to be ok, but i can not make the beam works. I think that mach setup is ok, but g code maybe do not have command for spundle. Do you have postprocessor file that support m11/m10 and pwm?
Can you please send me. Thanks, Marko!

Hozzáadva (2015-01-24, 19:17)
---------------------------------------------
P.s. this el schematics:
http://www.openbuilds.com/attachments/a1-jpg.3093/

 
tweakie Dátum/Date: Vasárnap, 2015-01-25, 07:16 | Üzenet/Post # 449
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Hi Marko, The basic PWM / Power circuit will only work if your laserPSU trigger is Active Low (ie. It has a pull-up to 5V and operates when taken
low or 0V).
 I have not yet got around to creating the Vectric post-processorwhich incorporates the Sxxxx command for changing the PWM – it’s on my to-do
list but may be a while as I am pretty busy with other stuff just at the moment.
 Tweakie.


Success consists of going from failure to failure without loss of enthusiasm.
 
mbarosevic Dátum/Date: Vasárnap, 2015-01-25, 09:32 | Üzenet/Post # 450
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Thank you for reply!
I have been tested the circuit with multimeter, and it is working correctly. It is connected to active low. I have realized that voltage on the active low trigger is always off, than i have added 10k pullup resistor. 

I thought that you have already written pp file for vectric. I'll try to solve it myself, maybe it is not problem with g code, maybe it is something with my wiring.

What is situation with dotG? It has no command for m10/m11. I'll try to change pp file, as i understand (every thime when Z axes is going down, with M11/p1: G0 X [xa]Y [ya]Z[za]; G1 Z [zd]F [fz])

Marko
 
Amatőr Dátum/Date: Vasárnap, 2015-01-25, 14:36 | Üzenet/Post # 451
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Marko, there is already a laser plugin for DotG with M11P1 and M10P1 commands, Tweakie wrote it.

H1i.hu
 
Amatőr Dátum/Date: Vasárnap, 2015-01-25, 18:40 | Üzenet/Post # 452
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Today I tried to cut plywood with air assist. I never had this before and I found it really effective.
The 3mm plywood was cut through in one pass with 4mm/s speed.



Unfortunately after some minutes my compressor stopped, maybe the motor burnt down. It worked for long time, now finished.

What do You guys think about this one? 70l/min must be enough but the pressure is low, isn't it?
Csatolások/Attachments: 4328564.jpg(363Kb)


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tweakie Dátum/Date: Hétfő, 2015-01-26, 07:07 | Üzenet/Post # 453
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Hi Zoltan,

Excellent progress my friend.

I use a koi pump (similar to the one linked) for general work - it is good and will run continuously but it really does not have enough volume and pressure for cutting MDF / ply etc.
The type of compressor that has become popular (because it is oil-less) is similar to this (unfortunately not cheap).

Tweakie.

Csatolások/Attachments: 1797782.jpg(16Kb)


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Amatőr Dátum/Date: Hétfő, 2015-01-26, 18:01 | Üzenet/Post # 454
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Thank You tweakie!
I had no idea that air assist can be so helpful. I mean it is just a few air, but the result is so dramatically better.
If I google "laser air pump" I find a lot electomagnetical pumps with low pressure. What can be more interesting for air assist: volume or pressure? I have a 3mm ID tube, leading to the lens, I think it needs pressure to push the air through.
Now I'm looking for piston type compressors in local ads.


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tweakie Dátum/Date: Kedd, 2015-01-27, 06:55 | Üzenet/Post # 455
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Hi Zoltan,

That is the benefit of our forum - sharing all our experience / knowledge - we all learn together and certainly have all come a long way over the last few years - from humble beginnings to great works (especially your mirrors).  

Regarding air assist...
The larger the internal diameter of the tubing and shorter the length (between compressor and nozzle) the better. Also smooth bore tubing rather than concertina is best.
As the object of the air assist is to remove the carbon deposit I would have thought that high pressure is best but my nozzle diameter started out at 1.5mm and I had to increase it to 3mm to allow sufficient volume of air to pass so perhaps it is both volume & pressure that is required.

Tweakie.


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Amatőr Dátum/Date: Kedd, 2015-01-27, 15:56 | Üzenet/Post # 456
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tweakie, You are right, I couldn't reach many things without the help from this forum.

I found two possible business in the ads, now I'm in conversation with the sellers about the techical parameters. The lowest pressure offered was 1,5 Bar, the other is higher. After collecting all the info I need, I hope I can get a good compressor.

Have You info about the theoretical minimum diameter of the focused beam? I think it mostly depends on the lens, now I cannot get less than 0,3mm.


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tweakie Dátum/Date: Kedd, 2015-01-27, 19:09 | Üzenet/Post # 457
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Hi Zoltan,

0.3mm is probably the best that can be achieved with a standard Chinese lens.
With a high quality lens (made in the USA) 0.2mm and with a multi-lens (beam expander type) 0.1mm is possible. 
(It is a law of physics that the beam can never be focused to a spot size smaller than the wavelength which for a CO2 is 10 microns (0.01mm) and in reality impossible to achieve).

Tweakie.


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Amatőr Dátum/Date: Péntek, 2015-01-30, 16:43 | Üzenet/Post # 458
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tweakie, thanks, that can be the cause why I cannot write 1mm letters with the beam. Do You think the same law can be true when people writing tiny letters with a blue laser? Maybe its beam is focusable in a smaller diameter.

Other thing that I built in the flow meter into the coolant, and with my multimeter I measure 23~24Hz output signal. I'm searching for a circuit that can stop the laser if the frequency goes down to the half of normal flow.


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tweakie Dátum/Date: Péntek, 2015-01-30, 17:31 | Üzenet/Post # 459
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Hi Zoltan,

That’s it precisely and the reason red laser DVD was replaced by blue-ray – smaller spot size = closer tracks and more information
on the DVD.
The blue wavelength is around 473nm making the theoretical minimum spot size around 0.004mm.

You may need to set minimum power but you should be able to write 1mm high characters (just) with your CO2 laser.

With regard to the flow-sensor I would be inclined to use aPIC microprocessor such as the 12F683 (I use them for just about everything now). It’s the same physical size as the 555 and can read a frequency on a pin and set an output if the frequency falls below a set value. They can sink / source enough current to drive TTL logic and would be ideal for your application if you can find someone locally who can program one for you.
Alternately the programmers are cheap to buy (ebay from China) and you could learn a whole new hobby.  biggrin

Tweakie.


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Amatőr Dátum/Date: Szombat, 2015-01-31, 07:59 | Üzenet/Post # 460
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tweakie, thanks. I will try again with less power. At last try the beam size was too big to draw small things.
I had experience with 16F628, used to manage the heating in the house. I found PIC programming harder than Arduino. I wasn't thinking in programmable device, but this type You offered is not a waste of components. Yes, it's a good hobby, especially on a long winter afternoons. smile


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