Laser tube - should I hear anything when tapping it?

[tdiaz]

... long story short.

After ordering a tube that was quoted with a week lead time, that turned into 5-6 weeks, and the vendor even shipped me a loaner tube which arrived busted, and FedEx said tough shjt... so the waiting for the actual continued...

..and it arrived today. It's making a vibrating noise at the far end of the tube. I can't see anything shaking free. Thats the same noise I heard on the first one that came, except it was very visually busted. The inner most tube was broken at both ends where it has supports in the cooling jacket.

This one makes the same kinda noise but not as bad. Thumping or tapping on the glass over the coiled area results in a vibrating noise. Just like if it were a loose metal panel.

The original tube does not make any such noises at all. It just quit working due to electrolysis buildup blocking the water flow.

So, should I hear any kind of noise at all with tapping on the thing?

It's an RECI tube, purportedly not "Chinese" (even though it came from .. China.. )

[paulC]

Dosen't sound good. All I can sugest is hooking up the water and watching to see if the inner glass tube takes on any water. You sould be using de-mineralised water. Paul

[FlyGuy007]

I have bought 5-6 tubes in the the last two years. I have had the most luck with JW Weike in China. 5-6 weeks is not uncommon if everything goes wrong. I think I have it down to a science now.

I pay with Western Union online using VISA which costs about $15 more than a wire but they have the money in hours not days or weeks which has happened. The last tube arrived 5 days after I paid for it!!! A big improvement over the last few times I ordered. The first one took 6 weeks by the time I decided I needed it, could make an apt to get a wire transfer done, it was sent then returned due to insufficient info then sent again etc..... Spend the extra $15

I have them ship using DHL. They always double pack the tube. The tube is suspended in foam in a double walled box, then the box is suspended in foam in another bigger box. The bigger box always shows wear or damage but the tubes seem to survive. I haven't had one broken yet.

Here's a weird one, I was told by JW Weike rep that the tubes have a shelf life of only two years at most before the CO2 leaks out, maybe not all gone but they definitely said a fresh tube is better. I tried ordering two at once so I'd have a spare, by the time I tried the spare it was as dead as the broken one. The odd thing is ordering tubes individually is exactly the same price with shipping as ordering two at once so it made no sense at all to buy two.

Hmmmm... ways to ruin tubes..... and all from experience.
1. Used chlorinated water to stop algae from forming. It does stop the algae BUT it reacts with and corrodes the aluminum in the tube. The cooling jacket on the beam end eventually corroded so bad that coolant would not flow. I was able to snake it clear a few times but with the reduced flow it eventually self destructed.
2. Run the tube hot, at 30C the tube efficiency is way down compared to say 15C water. I have taken alot of life out of tubes by running them hot, often it's by not immediately turning on the coolant.
3. Forget to turn on the coolant at all..... Boom! The coolant will boil and the tube WILL explode with a bang! Opps. that was costly.
4. Tubes wear out, in my experience you will get about 700-1000 hrs before you have to reduce your cutting speed so much that it's just time to get a new one. My last one took 38 minutes to finish a project and I was able to knock that down to 12 minutes with fresh tube.

Mike

[DaveDoesIT]

Hi Mike, Some good information ion the tube purchasing and shipping stuff. I have built many lasers over the years. You need to use some interlocks. A Normally Open (NO) flow switch, wired in series with the laser power switch will prevent the laser starting unless the water is running. A Normally Closed (NC) temp cut off switch set for whatever temp you want to max at, wired in series with the flow and the start switch will take care of over heating problems. You should be able to get both switches for under 30-bucks total. Cheap insurance. I mount my flow and temp switches at the output side of the water flow. If it ain't coming out of the laser at the right temp and flow then it ain't lasering. Dave

[zax15uk]

Originally Posted by DaveDoesIT If it ain't coming out of the laser at the right temp and flow then it ain't lasering. Dave

Absolutely.

These should be on EVERY water cooled laser.

You can use one of the larger PC cooler flow switches and temp meters with digital output (just make sure it can handle your flow) or buy something like a Malema flow sensor and wire it to the laser interlock circuit. I used an aquarium temp gauge with digital output as it also has a warning beeper when the temp is getting close to shutdown, this allows you to stop cutting rather than have the laser cut off in the middle of a job.

Zax.

[FlyGuy007]

The cooler I use has a temp alarm but if you forget to turn it on like I have so many times then of course it doesn't warn you of the overheat problem.

I like the idea of the flow sensor with power cutoff in series with the safety lid interlock. As soon as I can find a sensor/switch with the proper ratings I am going to hook one up.

Mike

PS. My tubes do kind of make a rattling noise when you flick them with a finger. I also have had a tube with a bit ( 1 sq cm or so ) of glass loose inside but it still worked fine. I'd just hook it up and try it. The company I deal with are great as they will replace the tube within 90 days if it's defective, they only ask I ensure that the damage was not the result of abuse in transit as then they can make a claim against the shipper and not have to swallow the amount of the tube themselves.