Can a bubble really cause the tube to overheat?

We have all heard that a bubble in the water jacket can cause an overheat condition.

After giving that advice today I started to wonder if that has ever been proven or is this just a logical expectation?

Can a bubble in the coolant overheat the output mirror or surrounding areas even though the surrounding coolant is the correct temperature?

Inquiring minds and all …

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I’m like you and I’ve never seen any evidence of this, just heard that you should avoid bubbles. I can’t really imagine a tiny bubble being an issue, but a large bubble would probably be more problematic.

So how could we test this?
Put a temp sensor at:

  • Tube jacket at the bubble
  • Output mirror
  • Coolant input
  • Coolant output

An measure rise in temp with and without bubbles?

I had a problem last week when raster engraving aluminum signs. The laser is supposed to burn away the black dye in the anodized stock and leave a white area. 10mA at 100 mm/s is ample.

Suddenly long strokes with the laser on started to fade at the end. Long runs with short strokes were OK.

I tried moving the print area on the bed, thinking it was a mirror alignment problem. No difference.

At the output end in the tube there was a large bubble. Purging the bubble fixed the problem.

Wild guess: could the uneven cooling bend the tube so the mirrors didn’t align?

Welcome to the forum!

Interesting. I suspect that could be what happened. With a large bubble is certainly conceivable that you could get some distortion due to localized over heating. The other concern you might run into is how overheating near the mirror might effect the seal on the tube end mirror.

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