My laser engraver from 0 knowledge to 32.461% .... probably

[BobbyW]

2)
     Auggie can only send numbers from 0-100 as power. So when you limit it to 32% by the laser power
in auggie you can get only 32 different PWM levels. This is unfortunate for high power lasers as it reduces the
resolution as you lower the laser power %.   I use an arduino to receive the pwm and allow me to adjust its
% before it goes to the laser. The arduino can subdivide in 100 steps. SO I set laser power to 100%, then
tell the arduino to adjust down to 20%. The output is then 100 steps from 0 - 20 instead of only the 20
steps Auggie can do by itself. The arduino project is published on this board as well if youd like to make
a similar board. This allows you to override the 0-100 steps the pokeys can do to be 100 steps of any %.
  So this arduino takes in 0-100% pwm from auggie set to 100%, and outputs 0-xx% as set on a lcd
connected to the arduino and sends a new pwm to the laser.

  You can see the project in the auggie topic I think under pwm control.

Hi Art
Ahh ok, i got it now, you use the trick to get a good resolution. I never work with arduino still i was developer for years on dsPIC products a while ago. I think i have a board here with one microcontroller , i can write a small code for that in a moment . I never think on that . Thanks.
Right now is midnight here , so i need to sleep , but tomorrow i will do some test .
I will let you know.
Bobby

[BobbyW]

Hi Art
I can't stop myself to go on sleep, i made some fast and small test's.
1: First i connect the PWM to TL input and on analog input on the source i set the voltage on 200mv . I play with some feedrates and here we go , some result arrive .
First on you image and after on my . Laser was able to increase the power. I listen you advice and i put 100% at maxim , and of course the laser itself was limited by input analog vcc.
2: I found only the PIC 16F684 here , and i made a very small code , programed in real time with Pickit3 and i made some adjustments.
Like you see was pointed laser , on same image .
Also PWM set matter in my case in ouggie. If i set to high i get only full power , to low , the annoing noise from low frequency and resonances around 2khz  :o (probably was source reflection on they chinese drivers). Also when than noise come out , the laser remain stuck with fixed power (maxim alowed by analog input )
The picture say everything.
Also i think the material matter . That's a regular mdf , i cant find any different here around my city and i didn't has the time to search.
Thanks Art , i will let you know what happen .
Bobby

[ArtF]

Much better. I see more steps.

In my PWM processor I take it in, and measure it based on the 5khz I use. I then have an LCD
display that allows me to pick a %. If I pick 50% on the lcd for example, I will change an incoming
100% to an outgoing 50%.  If the arduino see's a 25% PWM, it puts out a 12.5% ( 50% of incoming).

This allows 100 steps of any power level set by the arduino as long as Auggie stays on 100%.

( Actually, do not go above 99% as i seem to have a bug at 100% that I am tracking down, it may
be in my arduino code but I need to be set to 99% in Auggie on my system for it all to work.
Now if I run a grey scale at 100%, I can set my LCD to 10% and get 0-10% power in 100 steps. )

Art

[BobbyW]

Hello everyone.
I was a little busy but now i have some free time again to play .
So , I figure out everything about feedrate , jerk limits and other stuff.
About my laser power , for the moment i programmed a dsPIC to deal with my PWM , I give up the idea to control the laser over analog input ,
and i use TH input and adjustable analog input . Like that i have 100 scale control and i notice if i convert the frequency to low frequency pulses
like 400Hz , the result are different , with fast speed on en my laser.
I attach below, the picture have some missing lines and that because i don't have the compressed air installed and the smoke keep gluing on my laser nose.
That is not a problem now.I will try for sure on analog input after my order with DAC converter will arrive , next week probably.
That's it for now.
Thanks
Bobby

[tweakie]

Nice work Bobby, you are making excellent progress and I look forward to following your thread.

Tweakie.

[BobbyW]

Nice work Bobby, you are making excellent progress and I look forward to following your thread.

Tweakie.

Thank you Tweakie , i remember you has the first one who give me the advice about laser engrave.
Yesterday arrive my order with DAC and some optocouplers. The DAC working perfect (at least measured , not tested on laser) and let me to adjust the min-max voltage level from 0 - 100 PWM.
That's very useful for different materials and operations.
Still, connected to my stupid laser source the output become at maxim according with my reference set on 90% PWM. I think i will use an OP to follow the voltage with high current. Also like that i will be sure my input laser source will stay at 0 point all time.
And i manage to tune my motors how Art explain me.
https://youtu.be/a3QQo0dvWFU
That's for now.
Bobby

[ArtF]

Very nice. :)

It looks like your coming along well. Let us know how the regulation circuit works out.
The photos are showing nice progress.

Art

[BobbyW]

It looks like your coming along well

Yes and no. First of all i was needed to clear some things. One of them was to see linear on what analog voltage my source will delivery maxim power.
So surprise , surprise, on 2.68V input i get 25ma, on my Fluke , so was very calibrated measurement.
My first test with what i buy , was completely fail. Not because analog device is not good , because Bobby was a idiot ,
order in hurry and didn't read entire PDF. At least i made a good choice on optocoupler
https://pdf1.alldatasheet.com/datasheet-pdf/view/598737/CEL/PS9151.html
The PWM to DAC converter was fail , because dont let me to control the VCC in full scale reference by REF pin.
https://tz.infinite-electronic.hk/datasheet/73-LTC2644IMS-L10-TRPBF.pdf
Whatever soon my stupid source has that residual voltage input (the chinese creator let her like that , is written in PDF) i was force to deal with that.
So next help me the optpcoupler a log potentiometer and the most loved OP LM324 .
Now i can deal in full PWM range on any level. We will se if the laser respond in the same way >
Bobby

[BobbyW]

I forgot to say , the small potentiometer in the picture , is used to set the max power of laser , is conected to the external one (have 20 micro steps on full jog).
Now i thinking what simple was to use a pre-amplifier IC controlled by voltage . Ahh , but is ok like that , i will test later .
Bobby

[ArtF]

Ill be interested in hearing how the linear input affects output..

Art

[BobbyW]

Ill be interested in hearing how the linear input affects output..

Yes , i will made some test's tonight , to see how that work properly.
I have a question , i try to find a good answer but , i didn't found any.
My lens are ZnSe 20mm 50.8 focus , and i think it is on middle scale , i mean is not perfect for engrave also not perfect for cutting.
In my head is like , shorter focus length = engraving and longer focus length = cutting .
I have right ? Because i found on my lens , don't have a perfect fixed point , i mean can be tolerated 2-3mm ( i didn't see the proper difference between that interval , the tiny point remain the same)
Thanks  :)
Bobby

[ArtF]

Bobby:

  Your right but situations vary widely.  A short focal lens ..say 25-50mm
has a very hot tip and very shallow depth of heat. As it gets longer focus
the heat lessens but goes deeper.

  I think of it as a needle being heated. In short focus the center of the needle glows
white hot for maybe 1mm on either side of center. As focus distance increases the length
of the glowing part of the needle increases, but its the same amount of heat
so it doesnt glow as much..

  As to which you need.. depends.

To cut thin pieces a 50mm is great. To cut thick pieces its nice to have a 3" or even 4"
Some materials help you on their own. Acrylic as it burns creates a waveguide for the
radiation and cuts deeper than the focus can really account for. Wood wont do that.

My main laser has a 3" on it and cuts great. It will also engrave up to .25" deep or so
for 3d engraving. My Galvo laser has a focus lens 265mm long ( very long) but can 3d
engrave to at least 1" or more in depth. (Though it cuts my 50 watt to 20watt or so equiv at
the surface. )

  So when it comes to focus, I like to have a short ( 50 or so) and a long( 75 - 100) for
3d engraving. Normal engraving like a photo can be done with pretty much any focus
length with simple adjustment of power and speed. Highest res though is in theory
with the shortest focal length as the tip dot is smallest.

  This is all if your picky.. Ive found almost any focus can do almost any job
but with varying quality of output.

 
Art


 

[BobbyW]

Yea , so i will buy the most long i will get , just to test some differences . On that lens i have the point on simple 10ms shoot at some low power to pass trough paper , is just pass trough but almost invisible in one focus point , i need a magnifier to see the hole, so i think is good for engraving.
Now about my linear vcc circuit , it works realy great , more nice than i expect
The "magic" is done by optocoupler , he work so nice , https://pdf1.alldatasheet.com/datasheet-pdf/view/598737/CEL/PS9151.html the operational i use to filter , voltage folower and to adjust the power , is in full range , i let auggie at 100% power, is so nice to have now so many option to adjust . I was afraid my laser is to powerful to engrave , but was definetly my fault. My first try " just import a photo and generate " no any filter or any adjustment's , and still is decent on that shit material.
I have another question , i buy here a piece of plexiglas , but i think is not acrylic , because i try to cut him and on almost 80% power , he don't pass trough more than 1mm , he just melt him and very bad cut after 3 passes (with or without air assist don't matter on different pressure) . Maybe he's not IR absorbant ? I don't know , i didn't try on other . Is what i found here in France in one storage.
Bobby

//~~~~~~~~~~~~~~~ edit later ~~~~~~~~~~~~~~~~~~~~
Ahh , and now i notice that raster on the end of black region , i forgot to turn more higher frequency on auggie , lol.  Roll Eyes
Remain me on 300Hz on my last test before to change the interface , i rise up to 10k . I will see next how that will work
Thanks for now, i keep testing , i will try on glass and mirror soon.
Bobby

[ArtF]

Hi:

>>Maybe he's not IR absorbant ?

Yeah, some materials look like acrylic, but dont cut at all.. Beware their smoke..

Art

[BobbyW]

Yeah, some materials look like acrylic, but dont cut at all..

Hi Art
Yea i figure out that .
What about that material PMMA, is that acrylic ? They say are acrylic but they have a "special" way to spell the words .
https://www.plaqueplexiglass.com/perspex-chilli-red-frost-s2-4t50/
I made some test on glass , what i can say , working very well .
And.... on 3D engrave , wow , what i can say , working realy well , a realy nice texture .
You will notice the great job on last pass , if they are more than 3 .
Thanks
Bobby