Laser power appears to be very low from LaserWeb, but manually firing laser works OK

[Peter Vieth]

Full Spectrum laser (just a rebadged K40) converted to using Smoothieboard v1 5X.  Ran fine for a year w/ Smoothie, but then I moved... and the laser power seems anemic-- it can cut paper but that's about it when I run it from LaserWeb.  However, when I test fire the laser using the front panel buttons, it'll burn a hole through 1/8" acrylic without much difficulty.  

I tried switching which channel the laser fires on, thinking maybe it had somehow died, but the results were the same.

Scratching my head as to where to go next.     Ideas?

[Arthur Wolf]

Use a voltmeter to check the board is sending the voltages you expect from it's control pins? Logic analyzer/scope even better here if you have access to one.

What does the "fire" command do ( see the wiki page about it ), does *that* fire normally?

Check your wiring, I expect something's loose, or you have a false contact somewhere.

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勇気とユーモア

[wolfmanjm]

Check the gcode laserweb produces specifically look to see what it passes in the S value. It is probably sending the wrong value for smoothie. Smoothie uses S0 to S1.0 (full power) laserweb maybe sending what some arduino controllers like which is S255.

[Peter Vieth]

I remember the power range settings from the initial setup.  

The test fire in the interface with power set at .5, works fine, same as the physical buttons.  Blows a hole through my test acrylic without much difficulty.

I tried to laser a circle via g-code and that barely works. Tried feed rate of 300mm/s and 100mm/s.  I viewed the g-code, and it sets S.8 

Something about motion while firing...?  I have not tried putting a volt meter on anything yet.

[wolfmanjm]

100mm/sec is incredibly fast, I run my K40 at around 5-10mm/sec to cut anything. also set S1.0  S0.8 is 80%

[Andy Evans]

If you have moved it, then the optics are probably out of alignment, unless you have checked that already. The K40 case is not that rigid and just picking it up can torsion it. It can have a sweet spot in one X-Y position, but then be unfocused at another position. So it might test ok at the homed position, but get weaker the further out it travels from there.

[Peter Vieth]

I rechecked it.  The first mirror, which I have never adjusted before, was out of alignment. The beam was right on the edge of the mirror.  

Thing is still lasering unevenly, but better than a few days ago!

Re speed, I need to load up some old laserweb files as I can't recall now what settings I used to use; I'm used to an IPS world.  Maybe it was a few hundred mm/sec for rastering... 

[Peter Vieth]

I've spent more time on this and there is something weird going on with the software.  I put down a strip of blue tape and then manually lasered a line across the X axis. Used the laser test button in the software then jogged over 3mm and fired again, repeated across the work area.  There's a dotted line across the strip of tape, looks totally even. The mirrors are dialed in.

If I generate gcode for a rounded corner box in the same area from an svg, the laser only fires for like the first 20% of the gcode, then it just turns off.  Sometimes the laser turns on again for a little bit.  I'm not sure why.  Looking at the g-code, S is used only once, so there is no command for the laser to turn itself off. 

G21 ; Set units to mm

G90 ; Absolute positioning

;

; Operation: 0

; Type: laser Cut

; Paths: 1

; Passes: 2

; Cut rate: 200 mm/min

;

; Pass 0 

; Pass 0 Path 0 

G0 X109.18 Y0.72

G1 X109.27 Y0.72 S1.00 F200

G1 X109.35 Y0.72

... so on ..

M5 ; Switch tool offEnd

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[Peter Vieth]

So I took the LaserWeb generated G-Code and added S1.00 F200 to every tenth line or so, in case the machine needs a reminder...

No go.  Same results as before.  

 So then I threw a multimeter onto the laser pin.  It goes from 0v to 24v when the laser fires.  It is on during the whole cut.  Guess it's not the software.  Not sure what to check next though.

[Andy Evans]

The laser tube uses high voltage that can arc to where it is not supposed to. You might need to clean inside where the tube is with the power removed. Dust and other debris can create a path of conduction for high voltage, especially if the connections are not sealed with high voltage rated material. Demineralized water on a lightly dampened cloth would probably be the best choice of cleaner. The tubes themselves do have a limited lifespan.

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[Peter Vieth]

Yes I will have to inspect it more closely. I checked the potentiometer (it works) and also pressed the safety switch on the tube cover so I could see if the tube glows while firing.  It does glow and stay glowing throughout the cut, though the laser intensity drops off after about 10 seconds.  Anyway, not a smoothie problem :) Thx for the help.

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[Arthur Wolf]

This sounds like very bad news for your PSU or tube...

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勇気とユーモア

[Peter Vieth]

Any suggestions on narrowing it down?  Although I'm tempted to buy a larger machine than deal with this one...

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[Andy Evans]

Make sure there are no large air bubbles trapped in the cooling water in the tube and that you have good flow. If the tube heats up, the power will drop significantly.

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[Arthur Wolf]

If you can test your tube with another psu, or your psu with another tube, that might help. You could also measure voltage ( caution, it's 40kV ) and current and see if those match expected values.

All in all, at this point in your position I'd just be looking at replacing hardware.

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勇気とユーモア

[Peter Vieth]

I had one last frustrated application of oscillatory repair... Surprise it worked for a bit after banging on it. Next time it dropped power I banged again til I found the problem spot. The potentiometer is intermittent. The water was also heating up, I went to two five gallon buckets and temp seems better. 

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