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Author Topic: The Laser Project.  (Read 831362 times)

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Offline Tweakie.CNC

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Re: The Laser Project.
« Reply #660 on: August 25, 2012, 02:11:21 AM »
Hi Jammerm,

In creating the photons (laser beam) atoms in the gas mixture get consumed - bit like a battery, it has to run out one day.  :'(

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline Tweakie.CNC

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Re: The Laser Project.
« Reply #661 on: August 26, 2012, 06:46:56 AM »
My family had great plans for the holiday weekend but, fortunately, the poor weather forecast came to my rescue and I was able to take a day out to construct the extension to my laser tube enclosure. This did not exactly go down too well with them but they now have my full attention for the next couple of days.  ;D

The new tube will sit on the two existing mountings, held in position by the elastic bungee cords and the laser beam will exit through the small hole in the far end of the enclosure. Although the mountings are adjustable, from underneath, I am hopeful that the alignment will not be too much of a drama.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: The Laser Project.
« Reply #662 on: August 30, 2012, 11:16:30 AM »
Tweakie,

Have you ever tried to vary the power of any of your lasers with analog modulation to engrave a picture with g-code in Mach3 to get shades instead of pulsing your laser to get the allusion of shades? I have perfected a process to do it using PhotoVcarve software and an absolute shaft encoder with analog 0-5V output.

Read this thread and it will explain how I was able to do it. 

http://www.vectric.com/forum/viewtopic.php?f=16&t=13405&start=60

and here

http://www.vectric.com/forum/viewtopic.php?f=16&t=15161

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

Offline Tweakie.CNC

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Re: The Laser Project.
« Reply #663 on: August 30, 2012, 11:41:01 AM »
Hi Jeff,

I have been following your progress on the Vectric forum with great interest - Very nice work you are producing.

Art's Mach3 Impact / Laser plugin does just as you describe, producing the shades of gray by a PWM method of varying the laser on time. This is OK for certain materials (such as wood) but many other materials just do not accept shade.
After many trials and comparisons I prefer the half-tone method but, as you have shown, each method has it's own merits.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: The Laser Project.
« Reply #664 on: August 31, 2012, 07:48:25 AM »
Thanks for the compliment Tweakie.

I do have to say though, technically by using PWM in Art's plugin is still pulsing the laser on and off to get shades. It's not really varying the power like I am with the MA3 analog absolute encoder and the PhotoVcarve software. My laser never turns off until the engraving is finished.

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

Offline Tweakie.CNC

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Re: The Laser Project.
« Reply #665 on: August 31, 2012, 08:11:57 AM »
Hi Jeff,

How does your laser vary it's output power when you input the analog 0 - 5 Volt input ??

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: The Laser Project.
« Reply #666 on: August 31, 2012, 09:20:34 AM »
Hi Tweakie.

I have one of these driving the 445nm laser diode. http://hacylon.case.edu/ebay/laser_diode/FlexModP3.php. It has analog and TTL modulation I'm using the USB port to power one of these. http://usdigital.com/products/encoders/absolute/rotary/shaft/MA3 I purchased the analog output version instead of the PWM output one and it's attached to the Z axis stepper motor by a timing belt and pulley setup with a 6-1 ratio. With these ratios, when my Z axis motor moves from Z0.00 to Z-.016" the encoder outputs 0-5V. With a 2-1 ratio to my Z axis screw the laser only moves .008" and it's not enough to go out of focus. I'm not using any special code, but just like the PhotoVcarve software outputs for a Lithophane or rotary bit engraving with the X Y & Z g-code moves. Darker areas with a deeper depths of cut, it throttles up the power of the laser and lighter areas it throttles back so it is truly variable and proportional with all shades in between. This could be done with a more powerful CO2 laser if there was a way to vary the output power of it. I was planning on down the road to build my larger CNC router into one, when my finances with allow. I guess the tube would have to be mounted vertically to make it work properly. That way it could still move up and down based on material thickness so the beam would still stay in focus.

Jeff
« Last Edit: August 31, 2012, 09:29:01 AM by JJWMACHINECO »
Extensivly Re-worked/Re-designed/Modified Servo K2CNC KG-3925 and the Mini Laser Engraver

Offline Tweakie.CNC

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Re: The Laser Project.
« Reply #667 on: August 31, 2012, 12:53:08 PM »
Hi Jeff,

Thanks for the information, most interesting.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline Tweakie.CNC

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Re: The Laser Project.
« Reply #668 on: September 19, 2012, 11:34:53 AM »
Based on the excellent results Jeff (JJWMACHINECO) has achieved with burning ‘shades of grey’ into wood…

There are those that have converted imported CO2 laser machines to operate with Mach3 who do not actually have a motorized Z Axis and others who perhaps do not wish to add an encoder to their existing Z Axis. For this scenario I submit the following design idea which is primarily aimed at CO2 lasers with 40 Watts (or more) available output power.

Because the Mach3 internal PWM generator cannot easily be controlled ‘on the fly’ with the S*** commands blended with X Axis movement, or at least not fast enough to be useful, another approach has been considered.

It is perfectly feasible to construct a ‘stand alone - step / direction’ controlled PWM generator the output of which is easily converted to a voltage with a simple DAC (digital to analogue converter). Then by using 2 voltage dividers, one to set the lower voltage at which the wood is just marked and the other to set the higher voltage at which the maximum burn is achieved the laser output power can be fully controlled (via its PSU), with 8 bit resolution, from a lithophane type GCode tool-path.

I threw out the initial idea of connecting an encoder to a stepper motor and then using a standard stepper motor driver in favour of an all electronic solution which will enable ‘on the fly’ adjustment of the minimum and maximum thresholds whilst still maintaining an 8 bit resolution of  voltage over a typical 2mm depth of tool-path.

My design may well be a bit theoretical at this stage but so far I have established that a PIC microprocessor, clocked at 20MHz, can be configured within Mach3 as an Axis which can then be driven at a typical feed-rate of 1000mm/min with 127.5 steps/mm and produce a continuously updated PWM output between 0 and 100%.
Referring to my very basic schematic, this PWM is then opto-isolated, to remove the GND constraint and place the 255 step output potential between the maximum and minimum voltage settings of the two potential dividers. A simple DAC is then used to drive the emitter-follower output voltage to the laser PSU.

For the initial testing and for convenience, I am using a partially populated pcb from my RF Laser controller design (mentioned many posts back) purely because the display is useful, at the software design stage, to be able to observe the various settings and values. The final design will be a lot less complicated.

As always, early days yet but it all looks promising.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: The Laser Project.
« Reply #669 on: September 20, 2012, 06:06:43 AM »
That's cool Tweakie.

Can't wait to see some pictures with shades you engrave using that setup. I'm getting allot better and consistent results with John's PicEngrave Pro software then before using PVC. Here is one I did the other day and the detail is amazing.   8)

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