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Re: The Laser Project.
« Reply #860 on: July 24, 2014, 12:46:52 PM »
Tweakie, have you seen this article. A diode laser that is strong enough to cut steel. I haven't read it all but it sounds promising. I wonder if any cooling is required. I'll look at it closer when I get back from town.

http://phys.org/news/2014-07-direct-diode-laser-bright-weld-metal.html

Offline Tweakie.CNC

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Re: The Laser Project.
« Reply #861 on: July 27, 2014, 07:42:38 AM »
Hi Jammer,

Thanks for posting the link – there is no doubt that laser development, new thinking and technology advancement is cracking on at an alarming pace and that article made very interesting reading.

One thing that’s often not made very clear in press releases is that laser beams do not actually contain any heat – they are just a coherent stream of photons (having no mass) and it is the reaction of the molecules in the material they come into contact with which actually creates the heat. Another point that is often overlooked is that when cutting metals it is the high pressure assist gas (often Oxygen) which actually does the cutting (much like oxy-acetylene or plasma work) and the laser beam is merely the catalyst.

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

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Re: The Laser Project.
« Reply #862 on: July 27, 2014, 08:02:46 AM »
Just a short 1 minute video of the combined engraving / cutting toolpath using a logical AND between PWM and laser trigger as described in posts #856 / #857


https://youtu.be/8fUg6ebWut0

Tweakie.
« Last Edit: May 14, 2019, 05:01:07 AM by Tweakie.CNC »
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline ART

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Re: The Laser Project.
« Reply #863 on: August 06, 2014, 02:04:24 PM »
Hi Guys:


   Im starting to monitor this thread as Im finally doing laser experiments myself. I have my synrad
running on my workbench. It stopped lasing the other day and I found by slightly tweaking the
frequency with the cap that it works again. I tuned for 6 amps at 100% duty cycle. ( If anyone can tell
me the actual draw of a synrad j48 at 100% duty Id appreciate it, or a tuning proceedure. :).

   This project Im doing starts with a diagnostics and remote control panel ,now built ,and ends with a new engraving plugin
for Mach3/4 or any CNC system. (We'll see how that goes :) ). The control panel seems to work fine, It does 1us
tickle pulses, any frequency and pulse count can be dialed up by buttons, and a fire button starts to blink. You can
dial up from 1 - 5000 pulses or CW mode. Pressing fire shows the count countdown till 0, at which point laser shuts off,
and the counter reads zero. This shot pattern counts down at the dialed up frequency.. then Tickle resumes. Removing your finger from the button stops the test fire and it can resume by repressing. A reload button reloads the last count for another run. A photo is attached before a mask is applied over the top. (It will end up resembling a wooden control panel. :) )

   Internally, the PWM is controlled in 3192 steps from 1 - 99% power. (Though I suspect the synrad will probably make that 100 steps internal to itself.). Everything seems to be firing well, so Ill be starting the next phase to allow an engraving algorithm to
be uploaded for any engraving. The panel is built from an arduino YUN, the 400mhz unix system takes care of the SD card and will accept engraving command files wirelessly. The 16mhz arduino will control all firing pulses. This allows me to send a large file of commands for an enraving run OR simply use the panel as a smart spindle controller for on/off types of work.

  The plan is to connect the Yun to the step/dir inputs to any breakout board on X, Y and A. They will be monitored by the Arduino which will then reach into a command file to find the power level, frequency or dither pattern to be put out for the current virtual location of the laser in cartesian space. This means Ill have to write an engraving command program to take a photo and create a command file for various types and resolutions of engraving. It will also put out a GCode file which really will be nothing more than a raster scan with perhaps high and low res areas in that scan. The command file, already sent wirelessly in to the SD card of the YUN will interpret current location of that raster scan from the step pulses and make a very high res, multi power level engraving step by step. It may have to use fractalization to make an image larger to match the step count for the highest res. possible.

  Well, thats the plan.. we'll see what works or if it all just drives me nuts.. :) . Ill be posting the source code and schematics as open source,as well as any program thats written to create command files.. its all pretty cheap with the exception of the YUN, but one could use a simple leonardo... I just wanted mine to be wireless for ease of use..and the unix side makes it very powerfull for any size file to be used up to 100gig or so... you can even remote mount the sd card for this arduino onto your desktop.

  The whole point here is to give the pulsing and power waveform performance of a DSP laser system with just Mach or other cnc doing the motion...

Heres the panel as a photo... comments or suggestions welcome. Should be interesting..


Art


  

Offline Tweakie.CNC

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Re: The Laser Project.
« Reply #864 on: August 07, 2014, 02:08:47 AM »
Hi Art,

That Gearotic laser control looks like a very interesting project indeed and I look forward to following your progress.

Regarding the engraving plugin you may be interested in work by TomTom in Japan - he has produced raster and vector plugins (based on your original engraving plugin) and these videos relate...

https://www.youtube.com/watch?v=o-BHEPkvaVI

https://www.youtube.com/watch?v=5L_xaxfXNjM

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

Offline ART

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Re: The Laser Project.
« Reply #865 on: August 07, 2014, 07:08:47 AM »
Tweaky:

   He's done very well.  My problem with the current way fo doing things is the limits on power. At 5Khz you get only
4 -5 power levels from Mach. I think we need much more if we want to do 3d sculpting type of engraving. For that
Id like to see at least 50 -100 levels of power. The question is always how to get the power functions into
the motion stream. The trick of sending in a stream of 1's and 0's as I did with that original plugin was OK..
but I really want to see what happens when you get much greater control of the power and trigger stream.

  SO instead of 1's and 0's, I propose a stream of byte data for power, combined with a set of variables that
control the ratio'ing of that power from point to point.  Kind of a curve fitting for engraving lines.. It may cause a small
delay at each end of a engraved line.. but we'll see. My main concern is if a Arduino can control the changes
fast enough during an engraving. Perhaps Darwin could send data over an output line or something..

Anyway..thanks for the links, it shows great stuff has been done, and that theres interest for such things, all
things I like to see when I start down such a road. :)

Art

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Re: The Laser Project.
« Reply #866 on: August 07, 2014, 11:48:48 AM »
Hi Art,

I agree, the 4 – 5 power levels will not be enough. Just a thought but could you not just run at 10kHz and limit the duty cycle to 50% (the original plugin only achieves, at best, a 50% duty cycle at 12.5khz).

Quote from Synrad docs…
In most cases, the laser does not achieve full depth of modulation when driven by Command signal frequencies over 5kHz at duty cycles greater than 50%.

Scrub that thought - it would not enable more power levels in just half the band.

However, I don't understand quite how you are going to do it but I like the idea of byte streaming power levels.  :)  External PWM generator ??

Tweakie.
« Last Edit: August 07, 2014, 12:02:01 PM by Tweakie.CNC »
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline ART

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Re: The Laser Project.
« Reply #867 on: August 07, 2014, 12:27:38 PM »
Tweakie:

 >> the laser does not achieve full depth of modulation when driven by Command signal frequencies over 5kHz at duty cycles greater than 50%.

Im really not sure what to make of that statement, like many of their statements on PWM its a bit ambiguous. I "think"
it means that above 5khz and as you appraoch 20khz the modulation turns into an average of the pwm incoming width. So
running 50% at 10Khz for example would still only give 1/2 power output. Im experimenting here to see how true all that is,
its why the panel I built had to have the capability of repetative pulseing by pulse count, width and frequency..so I could see
the effect on various materials.

   The original plugin was binary really. It sent a string of 1's and 0's that turned the laser on or off at each step location, but the
power was always at the PWM frequency of the S word. 1 of 8 levels or so( I know you know this, I mention it so it will be in the
 record of the thread..)
  My thought at the time was that by triggering on step with a dithering frequency or other method of injecting grey scale the
engraving would be the best we could do. So basically what Im looking at doing with this panel is uploading a file into it before
the scan. ( The original plugin kinda did this too, it sent one line of binary to the printer port driver to use as triggers of off
or on , one for each step. ).  A printer port driver ( Darwin included) can do that , but its only control is on or off. So what
Im doign is adding a level between Darwin ( Or the m3 pp driver) and the laser. This panel is smart, so Darwin ( or m3) wont send that
digital stream anymore, instead we'll send a file before the scan. TO illustrate.. heres the old method..

 
 1) Plugin loads photo and calculates a line of binary off/on data. Sends data to printer port driver.
 2) Plugin sends one line of motion to CNC. Memory limited to one line of scan data as binary
 3) During motion, port driver uses binary stream on a per step basis to turn laser on or off.
 4) Plugin repeats process for each scan line till end of photo..
 
 Heres what Im trying to do.
 
 1) Standalone program loads photo. Creates entire x/y cartesion scan power levels file for each step of a
    scan of the photo. File may be up to 8Gig or so in size. Its sends this wirelessly to the SD card in the smart
    panel.
 2) Program puts out scan Gcode file. A simple raster file, with tighter closer scan lines where hiresolution is desired,
    and looser scan lines where less lasing needs to be done. This makes the raster scan faster overall.
 3) As the Gcode runs ( In mach3, 4 whatever..) the panel is tied to the step and direction lines. Its interrupt driven
    so it knows whenever the CNC system moves an axis. It looks into the SD card file and figures out what power level to
    shoot on each step ( X or Y..). the file has 3000 power levels possible per step location. Since its created by a standalone program
    the data levels can be quite complex. For example nonlinearity of the beam can be considered with more power in certain grey
    levels. For 3d scupting, you coudl use a calibrated power curve for depth.. a lot of things can be done with a smart control panel.
 4) Mach ( or whatever) has no idea a laser is running, doesnt have to control power levels at all, it just has to turn on the laser output
    which tells the arduino panel that it must lookup a value for each step and fire the laser at that power. The CNC unit simply runs
    Gcode of an XY raster.. or spiral raster..or whatever shape one wants..
   
    Well, thats the thought.. Im not sure my arduino can do all this fast enough, but I think it can. It also means youd simply build a smart
    panel for alaser, hook it up to a breakout baord so it gets the step/dir signals paralleled from the stepper driver. Of course
    a secondary mode will simpyl do on/off for traditional laser usage..
     
    Hope that explains it better.. Hope even more its all possible. :)
   
    Art
   

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Re: The Laser Project.
« Reply #868 on: August 07, 2014, 01:08:18 PM »
Hi Art,

Thank you for the detailed explanation - you make it all sound so simple  ;D

Seriously though, I think I understand your intention and it seems just terrific - I especially like the possibility of a non-linear response curve, as you say different materials behave differently and certainly not all in a linear manner. Another thing comes to mind - when raster scanning, ignoring the areas where the laser is not firing (not scanning those areas) speeds up through-put a great deal.

Keep up the good work my friend - I wish I had your brains when it comes to software development  :D

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

Offline ART

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Re: The Laser Project.
« Reply #869 on: August 07, 2014, 03:22:09 PM »
>>I wish I had your brains when it comes to software development

 I think its more lack of brains that makes on jump into this type of project. :)

Seriously, it will be interesting to see the effects of several things once we have
a greater level of power control.. Ill be implementing a test pattern to try to show the effects
of power, frequency and pulse count on various materials. Ive searched the forums and I see
all kinds of questions about the three variables and their effects, but with frequency ranging from
 0-5000, power from 0-100 and pulse count per pixel perhaps as much as 1000 pulses per location
( a function of speed vs frequency) , that's about 500 million variable combinations. Im always
 interested  when I get to explore things like that.  So as long as this laser continues to work Im
really interested in what we can do.

Art