Variable laser power

[Blueyonder]

Hello, first time on this forum so please correct me if I do anything wrong. I currently have a chinese laser running LaserDRAW and I'm verry happy with it but while LaserDraw does what it says on the tin it is limited in function so replacing the current controller with a Pokey card and running Auggie is verry apealing. One issue i have with my current setup is that if I set the laser power to the minimum required to cut material when the head is in minX,minY position, i.e. shortest laser path, this same laser power setting is not sufficient to cut the same material when the head is in the maxX,maxY position, i.e. longest laser path. For this reason i have to set laser power higher to the worse case setting. Is it or will it be an option in Auggie to dynamically increase lasor power in proportion to the length of the lasor beam path or is more of a problem with my setup and not general to all Co2 lasors?

[ArtF]

Hi:

    It will probably be possible to correct for that, but I think you may have an aiming problem
because your trouble should be reversed. A CO2 laser needs distance for its beam to expand,
the longer the better, when it hits the longest path, the beam has expanded the most, and the
lens will be that much more efficient. Its more normal to have less power in the short distance path
from what I understand. I use a beam expander in fact to widen my beam due to a very short path.

    Have you carefully tested your entry to the mirror at both extremes? Is it centered at both ends,
or perhaps more out of center at the long distance end? Since many laser suffer from the distance
problem I will probably add a linear corrector for the distance effect, cant say when exactly. (Though
I would have though Id need to reduce power a touch at the long end..

    Im currently adding DXF import for cutting vectors , so the next release will have more for the user
to select from for a burn or cut operation.  We dont know much yet about how CO2 laser high voltage
supplies work under Auggie, hopefull we'll know more over time. From what Ive read they should
be quite adapatable to Auggie and give as good a control or better than the cheaper co2 dsp driven
units .. time will tell.

Art

[Blueyonder]

Thanks Art, Very interesting. I'll spend some time re-checking the beam geometry.

[Joakim]

Hi.

I have a 40W Chinese CO2 laser (the cheap ones). Alignment of laser beam helps, but it still have less power in the far end (longest light travel). Only laser glass tube, mirrors and lens (no beam expanding).

(Not converted to Auggie yet...)

[ArtF]

  Hi:

        How much less power? It woudl be interesting to gather how everyone finds their lasers, how
much power it seems to take to cut what material , and any strangeness you find.

  Generally, from what Ive read, its recommended to have 6' of laser travel, but of course, most of us have
no such thing. I do use an expander on one, but not on the other. My chinese laser isn't the cheap one, but its not
far different either. It could be normal for that effect to happen, just seemed strange.. Rounded part of the
lens is facing upwards, right? ( Believe it or not Ive seen it work upside down.. just not as well. ).

  Mine i supposed to be a 50 watt in the shop, it takes 100% power at about 6mm/sec to cut 4mm acrylic
in one pass, Ive heard  of both better and worse from 50 watts. ( Personally, I suspect mine is really about
40 watts ). My inside laser on Auggie is rated 10, and I suspect is running 15 or so..
(Synrad 10 watts usually give up to 30 at best)

    Power differences may be geometry, or perhaps its normal depending on the laser.. but I cant see a laser losing
power over such a short distance for just reasons of distance.. provided the beam doent get too large.

Another interesting question, how large is the dot as it enters the final mirror port? Any different far or close?

    I do think we can make a correction calibration for it at any rate. My plan is to make things similar to the
delay calibration in the video,the type of calibrations where you select numbers that look best after burning
a test. So far, its all working good, next phase is vector cutting work... Im deep into its code already..

Art

[Joakim]

Hi.

My laser is half disassembled at present... I would like to take measurements when it's running with PoKeys+Auggie.
May be weeks as other projects has to be finished first.

[ArtF]

Hi:

    No problem, and no rush. Nice to know projects are in the works.., when your ready Auggie
will be that much further along..

      Im in a slower portion of code at the moment anyway so updates will be slow over
the next couple weeks as I implement a kind of mini-cam system into Auggie for creating
libraries of commonly used shapes. I find with my laser I tend to cut multiple copies over time
of the same shapes for various projects, but I may want differing sizes and such, so the library
is my attempt to make a scale-able object list for rapid recall and burning at various scales and
angles. Im trying to add Gcode as an input to that as well, so that one can modify Gcode files or
just copy bit of them for future use.. ( grab a single roadrunner and store it as an
object for example..)

  Then Ill begin vector calibration type of work to see how well we can control things for
even cuts across the workspace.. ( that is still an issue on my workshop one at times, but
Im convinced a calibration could cure it.. )..

  It will be interesting when some of you power up with the high voltage units, Im curious
how they respond to PWM control and what kind of tolerance we'll have to adjust things..

Yell when you get to your project..

Art

[Blueyonder]

Art, I tend to leave the laser power the same and compensate by adjusting the speed. As a general observation, If I need to cut at the longest beam length I have to reduce the speed to approx 60% of the speed I would use if I only needed to cut at the shortest beam length. My bed is 300mm x 200mm.

[Blueyonder]

For added info. My Chinese laser (and it is one of the cheap ones) is supposed to be rated at 40W. I have no way of knowing how accurate this is. It's analogue meter reads from 0 - 15mA. I find it takes 1.5mA to fire the laser. I don't really know if its best to use high laser power and fast speeds or low power and slow speed in order to prolong the life of the tube but I tend to use low power and set slow speeds. For 4mm Acrylic (at longest beam length) I can cut fine using 2.5mA @ 4mm/S. The thickest material I've cut is 6mm MDF using 5mA @ 2.5mm/S.

[ArtF]

Hi:

  Well, for CO2 lasers, keeping them below 95% current is recommended to prolong their life.
You should be safe using 12ma most of the time. I tend to use near 100% most of the time. I
dont have an ma meter, but mine wont fire below 27%, and fires up to 100%. Keeping mine
at 95% woudl probably be smarter. But yours sounds way low at 2.5, Id go crazy and bump to
10ma if the manual says you can max at 15ma. ( which is typical). On the other hand, your getting
pretty good results for only 5ma.. 6mm mdf isnt easy to cut. Is that a short focal lens?

  I suspect your cutting way too low a power for most things, bump your speed up and bump power 90% of max
and I suspect youll find it better.

Good info ,
Thx

Art