Couple of funnies - revisited

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MarkW
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Couple of funnies - revisited

Post by MarkW »

Back in Mar 2020 I started a post wherein I questioned PWM and M30 problems.

I'm happy to let you know that I figured out the "double M30" problem we discussed already. In the Edit Pro/Epilogue config pulldown there was an Epilogue line of text showing an M30 and some comment that I can't remember just now.    I deleted that Epilogue text string and all is good.

The PWM is still bothering me a bit.  When I issue an M3 command and watch the PWM output with my o'scope I see that there are PWM pulses output from the Pokeys57CNC at 1% of the PWM freq BEFORE I even hit the fire button or move an axis.  This happens regardless of the PWM frequency. It just happens to light my laser at the lower PWM freqs and I noticed it lites my diode because my control board is spec'd at between 500 and 1KHz.  When I get above 2KHz my control board doesn't light the laser (that I can see). 

My tickle is set to 0 (even went negative number with no difference) as you recommended yet the Pokeys board still outputs a 5uS wide pulse (at 2Khz PWM freq).  Why?  Min power is set to 0. Max is set to 97%. 

Is there a way to set a minimum output in the Pokeys board that I haven't discovered?  I'd like to set to zero.

I'm chasing this because I'd like to run my PWM freq at the laser control box spec of 500-1000Hz without the dang laser lighting up when I issue an M3 command alone.  Also trying to improve my raster engraving of lighter gray parts of my image.  Different discussion/investigation.  Trying to optimize machine first and this "1% always on" bothers me.

Mark
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5uSec 2KPWM.jpg
MarkW
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Re: Couple of funnies - revisited

Post by MarkW »

A couple of other interesting things I've noticed.  Some of the Engine/Planner Config parameters don't seem to change my observed results at all.

The PWM Period does in fact change the PWM frequency observed on my scope.  So that's good news.

Now the bad news.

Changes to the MinPWM(Tickle), MaxPWM, and MinPWM(PowerOn) have no effect on my laser function. I set Tickle to 10.  No changes seen.  I set MaxPWM and MinPWM to 50 and 10 respectively.  The PWM waveform on my scope show expected pulse widths for values higher than 50 and also lower than 10.  Confirmed by my diode current meter and visual observations of the light intensity.  So it appears that these limits are not affecting my Pokey board output signal. Something else is controlling max and min power.

Next, I stumbled around in the SpindleLib-Laser script.  Just looking.  These lines below from it seem to me (uneducated in programming) to set the max power to 100%, pwm freq to 5KHz and sets the channel to 4.  These are contrary to what I'm trying to use: channel 2, max power at 97 and 1KHz for PWM freq (0.001 period).  Do I need to edit the script to use my values.  (the ones I set in Engine/Planner Config table)

p = Profile("rtPWM");
global LaserAxis = p.GetInt("Axis",8);
global LaserMaxPower = 100;  //max power = 100%
global LaserPWMPeriod = p.GetFloat("Period",.0002); //for 5khz tickle 
global LaserPWMChannel = p.GetInt("Channel",4);

That's enough for tonight.

Mark
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ArtF
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Re: Couple of funnies - revisited

Post by ArtF »

Hi Mark:

I will do a check to see what might be going on..

As I recall, the lines below were necessary just to initialize the scripting.
The second part as in the line LaserAxis = p.GetInt("Axis",8); translates to
LaserAxis is ( Get the value stored under "Axis" and if there isnt one, use 8.)
So the setting for something like PWM tickle..should override the default when its set.
Ill check to see why it may be giving you a minimum instead of zero..


p = Profile("rtPWM");
global LaserAxis = p.GetInt("Axis",8);
global LaserMaxP ower = 100;  //max power = 100%
global LaserPWMP eriod = p.GetFloa t("Period",.0002); //for 5khz tickle
global LaserPWMC hannel = p.GetInt("Channel",4);

l
MarkW
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Re: Couple of funnies - revisited

Post by MarkW »

Thanks Art.  This morning I edited the script and changed those values. I noticed no difference in my observations.  So I changed then back to original.

Mark
MarkW
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Re: Couple of funnies - revisited

Post by MarkW »

Any news on this front?  Any way I can help?
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ArtF
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Re: Couple of funnies - revisited

Post by ArtF »

Sorry Mark:

Life intervened and I neglected this. I will test rigth now and see what I see. Ill post shortly to tell you what I find.

Thx
Art
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Re: Couple of funnies - revisited

Post by ArtF »

Mark:

  I just tested on my laser and I see your correct. The PWM minimum was being set to 1 no matter what.
I just uploaded a fixed file. The configuration setting will now work including zero.

Thx
Art
MarkW
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Re: Couple of funnies - revisited

Post by MarkW »

No worries Art.  I understand completely.  I live it too.

I'll go figure out how to get the fix just as soon as I can get to it. 

Hopefully tomorrow.

Mark
MarkW
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Re: Couple of funnies - revisited

Post by MarkW »

Art,  I downloaded the most recent Coninstall.exe file 4.3.0.347 Ver 3.7b this morning from gearotic.com/downloads.html.  I selected Auggie CNC Addon.  Ran the executable and took the defaults for file location and allowed it to overwrite the current files.  Successfully I think...

Now for the bad news.  I ran Auggie and had the same results.  PWM set to 500Hz, Tickle 0.  Issued M3 and observed Axis 8 went to 1 (some bouncing around) immediately and my diode emitted light. 

The only things I can think of is that I need to download your current development version of Gearotic or maybe I should have selected the patch and release notes.  I didn't want to just shotgun this and mess up my system before I checked with you.  What have I done wrong? 

Thanks,
Mark
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Re: Couple of funnies - revisited

Post by ArtF »

Mark:


Sorry abou tthat, the update is proper on the site but for some reason hasnt propogated. Use this link to get it while its sorted out..

http://gearotic.com/ConInstall.zip , the version you should get is 3.7d , not b..

Art
MarkW
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Re: Couple of funnies - revisited

Post by MarkW »

Thank you Art.  Problem solved. No 1% PWM output when M3 is called.

Another question comes to mind now regarding the min and max power settings in the engine config. I notice they  have no effect when I use the FIRE button.  Do they only apply when the laser is controlled through a program vs the fire button?  I'm hoping to set the control such that min power just marks the material being engraved.

Right now my light grays turn out white.  When I up the power to the point I get noticable engraving, it results in to much darkness overall.

Thanks for the hand holding.
Mark
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ArtF
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Re: Couple of funnies - revisited

Post by ArtF »

Mark:

Yes, the max power and MinPowerRad are used in doign photo's and such. Max power is usually set to 90% or
something just to make sure you dont overdrive your laser, some do not like 100%, its hurts them over time.
By setting to 90% or so you may lengthen the life of the laser.

  Now, as to the range of grey scale in a photo, this is really particular to the laser as to how
this is set. This is how I do it.

First of all, there is a feedrate override button on the screen, I use this always in photo 3d engraving or
photo burning. Youll notice on the image import screen when creating an augmentation for a photo
burn there is a ramp size, I always set this to about 20m or so on my synrad laser system it runs slower
than my galvo. This is because my slow system conceivably needs a ramp to get up to a speed where
linear corrections work best. During initial start of motion the speed can be too slow for this linear power
curve to smooth things out. So make sure there is a ramp if your system has acceleration that might
be considered low or it takes a bit to get up to speed. On my galvo I use no ramp, but its speed is immediate
and its accel is very high.

Second, I control power with my power slider, not with S words, in fact I keep S words out of my
engraving power to make it all manual power adjustment, every material is different so they all need
to be individually set for power.

  Now about grey scales. It is said that power and speed have a linear correlation. This is not true
in the context of greying or blackening wood in my experience. While it may be true that 10 watts
at 100mm'sec is the same in linear terms to 20 watts at 200m's per second in terms of radiation
produced, its my finding that time is the variable that affects these two from being the same. Wood
simply darkens at differing time rates based on actual power.

  My advice is to use, as in most cnc, as fast a motion as you can while burning. I most always set to
a high power and adjust speed for the best grey scale. My lasers though probably dont react the way
yours does, so experimention is in order. I set my power to 90% or 95% and then do a test burn at a very
high overridden feed rate. I adjust it down till I get my grey scale. This  usually works. With some
materials I lower the power as the grey scale is bad, I then start fast and slow down again.

  Its worth havign a very small grey csalke augment to use as a test, I usually keep a small 75 x 5mm
test pattern of a full grey scale to use on scrap material to try to get the best grey scale before a
cut I want to keep.

  Another technique to use, is to do 3d engraving runs with 0 as the step distance in height. This is essentially
a multi pass system , and they are better at times for a good grey scale..

Art


 

 

BobbyW
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Re: Couple of funnies - revisited

Post by BobbyW »

ArtF wrote: Mark:

  Now about grey scales. It is said that power and speed have a linear correlation. This is not true
in the context of greying or blackening wood in my experience.
Wood simply darkens at differing time rates based on actual power.

Art
Yes , is not true. I contered that problem on same material i used before and i got always different results .
Even i set the same speed , power , same material , same code after a while , i notice that depends to much
the moisture of material. So my solution was to keep the polywood for engrave at same moisture all time.
I store him in my chamber for keeping the tobaco , inside is controlled at 71% RH all time.
Even like that some parts of polywood have different black level on same job.
At least now the differences are to small.
Is a little hard for my laser because are 2 reasons . One ,my laser is pretty big for engrave "80W" so the
power at low level is hard to controll. And second , my source has from fabrication a stupid residual current at 0 input,
i deal with that but sum of all errors will change the final result .
Thanks
Bobby
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Re: Couple of funnies - revisited

Post by ArtF »

>> One ,my laser is pretty big for engrave "80W" so the
power at low level is hard to controll.

  For this problem I built an arduino PWM re-formatter.

I set Auggie to 99% at all times, and the PWM from the Pokeys
feeds into an arduino, which then resends it to the laser after processing it a
bit. I have an LCD screen with buttons on the arduino and I can tell it to change
99% to 50% for example, and then my laser sees 100 steps from 0 - 50% power.
  Or I can set it for 10% and get 100 steps from 0 - 10% power.

  I think I posted the arduino code for it if you'd like to build one, it takes only
an arduino DUE and a cheap keypad with lcd screen to make it. It increases
Auggies resolution quite a bit and fixes the problem of a laser being too powerful
for engraving.

Art
BobbyW
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Re: Couple of funnies - revisited

Post by BobbyW »

ArtF wrote:
  I think I posted the arduino code for it if you'd like to build one, it takes only
an arduino DUE and a cheap keypad with lcd screen to make it. It increases
Auggies resolution quite a bit and fixes the problem of a laser being too powerful
for engraving.

Art
I know Art , we talk about that some time ago .
I buld my self too , not on arduino , i found a dsPIC from my workshop in that moment and
i write a small code to do same job. But not that is the issue .
The laser itself , or source are so cheap and bad controll.
Doesn't matter if my resolution are 0.0001w as example , if the laser jump from
1 to 4w any controll is pointless . To modify the source is not possible
the driver are epoxy covered , im sure is a Sg3525 but the rest of pieces are covered by resin.
I think i will buy in the future a small 10-30w laser only for engrave .
Thanks
Bobby
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