good coating for a beam dump?

[anselm]

Bending a tube, especially a copper tube, and keep it in tube shape, it's hard to do, without the right tool

Here's a quick trick my grandfather taught me once to bend a tube without it going
out of shape:
Fill the tube with sand and close up both ends, so the sand cannot "escape".
Gently heat (don't melt it, obviously) the section to be bent.
Now you can bend the tube, and it will stay (more or less) in shape.
The sand inside the tube will prevent it from folding up.

 

[HIMNL9]

Our shops have these ones, til 28mm dia, i suppose they can be found also in other countries

 

[Cyparagon]

On how it's made, sometimes they'll curve pipes by filling the length with water, then freezing it. During the bending, the ice helps keep the tube from collapsing. Similar to what anselm suggested, but without the need to enclose the ends (as long as the pipe is long enough).

 

[jib77]

On how it's made, sometimes they'll curve pipes by filling the length with water, then freezing it. During the bending, the ice helps keep the tube from collapsing. Similar to what anselm suggested, but without the need to enclose the ends (as long as the pipe is long enough).

I think I saw that, they were making a trombone.

 

[scopeguy20]

Bent pipe is a good idea, so w/b a sliver oxidized candle stick interior, the blackest common surface is oxidized silver and like copper in heat transfer but better! -Glenn

 

[Wolfman29]

How would I get a silver oxidized candle stick interior from around the home? Haha.

 

[scopeguy20]

If you have the candle stick, liver of sulfur does a great job of making the silver black...

 

[donprado]

I had a bending machine available, but it's no problem to use a 90 degree tubing. Even in the bending machine we had sand in the tube, this is very useful.
I'm glad you like this simple beam dump:beer:

 

[ndrew2505]

so what kind of heat is generated by a 5W laser? i dont have one to test with but this small piece of info might help.

 

[HIMNL9]

^ 5W of heat .....

No, seriously, it depend from how much the beam is adsorbed and/or reflected from the beamdump, ofcourse, but assuming that you are shooting a 5W of laser beam and your beamdump does adsorb it totally, your beamdump will adsorb 5W/s of energy and turn it in heat.

The problem is the diameter of the beam ..... if your 5W of laser is defocused over, say, 10 or 15mm dia, it does not cause any problem (assuming that your beamdump can dissipate the heat), where instead, if your laser beam is focused in an 1/10 of mm burning spot where it hit the beamdump, then the coating and the metal under it can be ruined very easily.

For this reason, the most part of the beamdumps have a cone, as impact point ..... being a circular section surface, it always spread around the beam, diffusing it, and also in the case that the cone does become damaged, it's usually an interchangeable part.

 

[BShanahan14rulz]

"Hey, I dare you to stick your finger in my beam dump..."

 

[Seoul_lasers]

what kind of coating would make for a good beam dump for a laser <5W? im thinking of trying to get some made as cheap as possible for hobbyists b/c the professional beam dumps are usually made for 50+W and cost anywhere from 150-500$ anodizing, powder coat, composite coating? whats your ideas?

Think simple. A Large piece of anodized Aluminum plate painted flat black should do the trick. I have used a copper plate painted with high temp enamel to work exceptionally well on my 2W labbies. I can't imagine 5 watts is going to be more of a problem. You aren't exactly using a CO2 or 808nm cutting laser here.

You do want to make sure that the surface is totally non reflective. flat black is such an animal.

 

[HIMNL9]

Beam-dump purpose is not just to block the beam, is also to reduce as possible all the reflected / scattered light from it ..... a flat surface will work good for block the beam, but not too much for take away reflections and scattering, especially from high power ones.

 

[NetGod3Com]

+1 for flat black grill paint sprayed into a 1/2" or 3/4" copper elbow with a cap on the end.

 

[chipdouglas]

i would make a small box out of sand blasted aluminum. then an aluminum insert that is facing the entrace hole at 45 degrees. then get the matte enclosure anodized black.

anodizing aluminum is cheap because you get charged a batch price. so if you have 100 pounds of these enclosures which is a lot of them, it is like less than 100 bucks.