Strange Dots outside of engraving area

[Dan Ashlin]

Hey Everyone. Over the past few days I've noticed some strange small dots outside of the engraving area on all of my projects. They seem to be random, but are becoming more frequent. Not sure if anyone can shed any light on the issue. I've tried all the normal stuff, checking belts, cleaning the lens, backlash compensation etc. to no avail.
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[Dave Sheldrake]

Loose trigger wire or a cap is breaking down, the fact they are random rules out drawing issues so I'd be checking the control card wires to make sure there are no loose connections first.

cheers

Dave

[Dan Ashlin]

Loose trigger wire or a cap is breaking down, the fact they are random rules out drawing issues so I'd be checking the control card wires to make sure there are no loose connections first.

cheers

Dave

Thanks for the info dave. I'm assuming by cap you mean capacitor? Also, I'm running a chinese engraver, similar to rabbit models. Would the rigger wire be on the tube itself?

[Dave Sheldrake]

Nope, trigger wire connects to the High Voltage PSU usually via a small screwed fitting at both ends, if one wire has come lose then I'd suspect others may well do too, probably a good idea to check all of them while you are inside the cabinet.

Cap = Capacitor, possible cause but unlikely

cheers

Dave

[Dan Ashlin]

Thanks,
I'll give it a look see and report back later today

[Dan Ashlin]

I checked everything and there don't seem to be any loose wires. I tightened everything just to make sure though and the problem is still there

[Dave Sheldrake]

On to the next possibles then :)

Take the lens tube out and clean BOTH sides of the final lens.

If that doesnt work we can work through the list of cheap free possible problems first ;)

cheers

Dave

[Ed Maloney]

How old is the tube?

[Kev Williams]

Does that Chinese thing have anything resembling a tickle setting?

[Dave Sheldrake]

No they don't Kev, while RECI and EFR tubes do have a 4mA tickle current function available it's turned off in the software

cheers

Dave

[Dan Ashlin]

It's an 80 watt reci tube. It's got about 3 years on it

[Dan Ashlin]

On to the next possibles then :)

Take the lens tube out and clean BOTH sides of the final lens.

If that doesnt work we can work through the list of cheap free possible problems first ;)

cheers

Dave

Just thoroughly cleaned the lens, Still making the dots

[Dave Sheldrake]

Lemme have a look through my notes Dan and I'll see what else pops up :) have some other free possibilities in mind but will PM them to you as it involves fiddling with the electrical side of things and not always the best thing to post on a public forum (end user technical knowledge etc etc)

cheers

Dave

[Rich Harman]

I have had the same problem, to a lesser extent, when engraving at high power and higher speeds. Slowing down and using lower power was the cure.

[Rich Harman]

... RECI and EFR tubes do have a 4mA tickle current function available it's turned off in the software

Could you elaborate a bit?

[Alexa Ristow]

If your machine has a test button that allows you to hold it in and trigger a burn while the head is not moving, then place a piece of thick card or MDF about 6 inches below the nozzle. Hold the test button for at least 5 seconds. You should end up burning a largish hole through the material but, if the small dots were caused by any form of optical scatter, then these spots would also be visible. This is a way of differentiating between spots caused by optics and spots caused by random or badly times firing. Hope that it is optics because that is generally easier to fix than random firing. my previous issues with random firing were caused by static build up. My newer generation controller boards do seam to be more immune.

Regards,

[Dan Ashlin]

Still having the issue. Seemed to resolve itself for a bit, but pops up randomly

[Dan Hintz]

Just so we're chasing down the right tree... this is an electrical issue, not physical (i.e., don't worry about lens cleanliness, etc.). Something is making the tube fire. This is an ideal spot for someone with an oscilloscope... let you know if it's being commanded to fire (something in the control pathway) or if it's firing on its own (think more towards the tickle end of things... overexcited tube, etc.).

[Dan Ashlin]

Just so we're chasing down the right tree... this is an electrical issue, not physical (i.e., don't worry about lens cleanliness, etc.). Something is making the tube fire. This is an ideal spot for someone with an oscilloscope... let you know if it's being commanded to fire (something in the control pathway) or if it's firing on its own (think more towards the tickle end of things... overexcited tube, etc.).

Thanks dan. To my understanding though, Chinese laser systems do not have a tickle adjustment. I'm not sure where to look otherwise, the power supply looks fine. Could this be a sign of my tube going bad maybe? I had also thought to change out the fuse that's in the back where it plugs in?

[Dan Hintz]

Thanks dan. To my understanding though, Chinese laser systems do not have a tickle adjustment. I'm not sure where to look otherwise, the power supply looks fine. Could this be a sign of my tube going bad maybe? I had also thought to change out the fuse that's in the back where it plugs in?

I would suspect the power supply first if nothing else seems obvious... if internal regulation is going, it could be raising the output voltage enough to cause what amounts to an increased tickle (random lasing).

[Dan Ashlin]

If it helps narrow down the problem, running at lesser power seems to resolve the issue. The dots are also not at full power, as I was running some flasks with cermark at 100 power and the dots appeared, but washed off with the cermark while the rest of the design remained.