Control of 40w desktop laser

Gallery for images of work cut using PhotoVCarve
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inchgreen
Posts: 5
Joined: Sun Jan 04, 2009 11:19 pm

Control of 40w desktop laser

Post by inchgreen »

Gents
I have transferred the 40w laser tube c/w power supply cross to my older 600x400 gantry and can now move x/y using Mach 3
My laser is the £300 unit from ebay K40 I believe. With regard to the switching/triggering of the laser my unit has on the top paned a meter and pot to adjust power a push to test laser switch (non latching) which fires the laser as long as you keep it pressed and another latched on push to make 'Laser On' switch

It seems to me that to switch the laser on and off all i need to do is use the circuit of the 'push to test' on a relay driven by the output of the Mach 3 pins - ie laser on then Mach 3 energizes output pin??? and triggers relay and then goes 0v and opens relay on command from mach3
My query is what pins to drive relay with - what relay (high speed) to use
- and how do I include the commands in the G code

Now be kind to me I know enough to have built my router and sort problems with help from here \ but really am a dumb ass when it comes to programming or anything more tech than using a multimeter-----so can i ask the following questions and get straight answers as otherwise I get cerebral meltdown trying to understand your language

1) Is this feasible
2) What pins should I use for the relay
3) what relay should I use
4) How do I put in the commands into Gcode do I just replace Z codes
For info all my drivers are Routout CNC 3.5 Amp and power supply is 24v
Thanks for your patience guys
paulj :?

dlgabry
Vectric Craftsman
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Location: Olivebridge, NY

Re: Control of 40w desktop laser

Post by dlgabry »

Hi Paul,
I'm using Vectric software and Mach3 to control my much much smaller laser. I use a separate Mach3 profile that defines plasma mode and Pin 14 as the C-axis direction line, and a modified Mach3 postprocessor that replaces all the gcode "Z" references with the letter "C".
The C-axis direction line drives a 4N25 opto-isolator that in turn drives the laser's modulation input. It looks like Mach3 leaves the direction lines in the state of the most recent move, so a one-step move down on the c-axis turns the laser on, and is stays on until the next move in the up direction turns it off. This leaves the X, Y, and Z stepper definitions as they were so I can use the Mach3 jog keys to move to the right position. Have a look at this thread http://www.vectric.com/forum/viewtopic.php?f=16&t=13405

The opto-isolater doesn't have enough beef to directly drive a relay, but you could use it to drive a transistor that controls the relay. I didn't need to do that since my laser has a TTL level modulation input.

Dave

Greolt
Vectric Wizard
Posts: 992
Joined: Fri Sep 21, 2007 1:44 pm
Model of CNC Machine: UCCNC Router, Plasma, Laser
Location: Australia 3781

Re: Control of 40w desktop laser

Post by Greolt »

I am going to, for the most part, give the same answer as Dave.

Not sure about your particular laser power supply but most will fire the laser with a TTL (5v) signal that can be provided directly from your controller board.

For Mach3 laser control I use M11P0 and M10P0 to turn the laser on and off. These commands switchs the Digital Output.

I have a Vectric post processor to produce these commands in the gcode in response to Plunge and Retract.

One of the advantages of using "Digital Output" for laser control in gcode, is that this is the output that the engraving plugin uses. So one profile suits all.

Greg

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JJWMACHINECO
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Posts: 143
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Model of CNC Machine: Re-worked/Modified K2CNC KG-3925
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Re: Control of 40w desktop laser

Post by JJWMACHINECO »

Greg,

Do you have any picture engraving examples you have done using your setup that you can post?

Jeff
Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver

dlgabry
Vectric Craftsman
Posts: 104
Joined: Sun Apr 13, 2008 2:20 pm
Location: Olivebridge, NY

Re: Control of 40w desktop laser

Post by dlgabry »

I just tried a modified postprocessor for photovcarve with the plunge_move and retract_move sections containing the M codes as above. While photovcarve doesn't flag the postprocessor as containing invalid sections, it does not include their commands in the gcode file either. So it sounds like this isn't a workable approach for photovcarve engraving with a laser.
The same postprocessor used with vcarve pro does properly insert the retract and plunge M-codes in the gcode file.

Dave

Greolt
Vectric Wizard
Posts: 992
Joined: Fri Sep 21, 2007 1:44 pm
Model of CNC Machine: UCCNC Router, Plasma, Laser
Location: Australia 3781

Re: Control of 40w desktop laser

Post by Greolt »

dlgabry wrote:I just tried a modified postprocessor for photovcarve with the plunge_move and retract_move sections containing the M codes as above. While photovcarve doesn't flag the postprocessor as containing invalid sections, it does not include their commands in the gcode file either. So it sounds like this isn't a workable approach for photovcarve engraving with a laser.
The same postprocessor used with vcarve pro does properly insert the retract and plunge M-codes in the gcode file.
Yes it seems that Photovcarve does not recognise Plunge and Retract. That makes sense as Photovcarve toolpaths are really 3D.

Plunge and Retract as applied to switching a laser, is really only applicable to 2D toolpaths like profiling. Vcarving or other 3D would not be applicable either.

If you want to use Photovcarve for laser then perhaps you should follow along with Jeff's methods.

Apart from a few experiments when I first made my laser, I don't engrave photos. And when I did, I used the Mach engraving plugin. Within its limitations it worked quite well.

At present I have a dedicated laser controller running my laser. I have switched back and forth a few times.

Mach is, IMO, better for vector cutting work than the dedicated laser control. It has superior motion control.

Greg

dlgabry
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Posts: 104
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Re: Control of 40w desktop laser

Post by dlgabry »

Hi Greg,
With my low power laser, the engraving plugin doesn't work well since its pulse width is just too short to get a good burn. I find that photovcarve works great for burning black and white as well as halftone images. And vcarve pro handles 2d vector work just fine too with the setup I'm using.

Dave

Greolt
Vectric Wizard
Posts: 992
Joined: Fri Sep 21, 2007 1:44 pm
Model of CNC Machine: UCCNC Router, Plasma, Laser
Location: Australia 3781

Re: Control of 40w desktop laser

Post by Greolt »

When using Mach3 on my laser, I use Aspire to create the 2D toolpaths. Does a great job as you would expect.

Users who do not come to lasers from a CNC background expect to be able to to artwork in something like CorelDraw and send it straight to the laser.

Nothing wrong with that. They typically see the Mach route as too long and complicated.

On the other hand, users like me, with long experience with CNC and gcode, are very accustomed to going through the, CAD - CAM - Controller, route. And we like the level of control that that gives us.

My laser is a purpose built 60w glass tube CO2 laser. The Mach plugin works fairly well with it, but its not as versatile as the dedicated laser controller for engraving.

As I said I haven't been doing photographs, so have not attempted to use Photovcarve.

Greg

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JJWMACHINECO
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Joined: Tue Aug 04, 2009 2:15 pm
Model of CNC Machine: Re-worked/Modified K2CNC KG-3925
Location: Deep South

Re: Control of 40w desktop laser

Post by JJWMACHINECO »

I just ordered a new small 4 axis benchtop CNC router with steppers and ball screws. I will be getting back to my original plan implementing the analog modulation of my other laser like Dave has. I already know I can get shades using the PVC software and the 3D g-code it creates. I figured out how to use a shaft encoder this time to sense the Z axis motion very precisely to varying the voltage for the analog modulation. I will continue to leave Mach out of controlling the laser with output pins and a modified PP.

When I get everything in and work out the bugs and get the process down, I will post some pictures and the details on how I did it.

Paulj, you really have not said what you are planning on doing with your 40W laser. You started this thread in PhotoVcarve Gallery, so are you planning on doing photo engravings with the PVC software? If you are mounting your Laser tube horizontally in the back of your gantry and reflecting the beam to the front, then I don't think you want the Z axis to move when pulsing your laser on and off. If you mount your Laser tube vertically in front, then my way of pulsing the laser will work. As you have read in both threads, there are different ways to control your laser with Mach 3.

Jeff
Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver

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