[Kiwi]

Looking for a material to use as a shield to prevent far side of tube being defaced.
Silver has been suggested but prefer a cheaper material.

[HuFlungDung]

Would it be possible to reflect the beam out of the tube with a mirror?

[Kiwi]

Will suggest this to the company doing the job.
I see problems holding a mirror in the tube as the mirror would need to be held directly under the beam while the laser head moves about.
Some how would like to absorb the energy.
Thanks for your help.

[laser3kw]

What size tube? depends on your rate of cut. If you are moving fast, you can use wet sand. If your are moving slow try fire brick

[under-dog]

Would it be possible to reflect the beam out of the tube with a mirror?

I would think that deflecting it with a mirror would be dangerous. You never know where that beam would go. Absorbtion would be better I think.

[HuFlungDung]

Yes, it could be dangerous. A dual mirror set in a tube similar to a periscope could accurately redirect the beam downwards as it exits. But I don't know what commercial laser tables use underneath to ultimately absorb the beam.

[LenMcC]

I would think that deflecting it with a mirror would be dangerous. You never know where that beam would go. Absorbtion would be better I think.

i've never used a laser myself, but i know i've read that lasers can be damaged when cutting high-reflectivity materials that bounce the laser back at the machine. reflecting was the first thought that came to mind, though.

[ImanCarrot]

When working with lasers a few years ago we had to use safety glasses, I'm sure that the beam was actualy absorbed by the material- vaguely recall that it contained platinum?

Your best bet would be to contact a laser safety glasses manufacturer and ask em for a free sample. I'm positive that the material will be wavelength specific, so You'll need to know what wavelength you're operating at.

Sorry if this sounds a bit vague.. been a while since I messed about with lasers but I can still remember the smell as I accidently burnt a hole in my thumbnail with a CO2 laser *ouch*.

[MonoNeuron]

Emission technologies use a fire retardant tile inside their box. Look them up and find out what it is.
Quote from their website (hope they don't mind)
quote " The Stainless Steel Vacuum Box under the honeycomb is 8" deep and is Ceramic Lined to absorb excess laser radiation. " end quote.

[Lotus14]

What you need is something that will not reflect the laser, but will absorb it. your laser cutting service should know all about this. Usually it is a container, coated or painted black, which is filled with an temperature absorbing material.

I assume by your note you are cutting metal tubing by rotating the tube rather than cutting the tube in one pass like a saw. Are you making stents?

I would think you just need to have a bar or rod, which has been blackened, and if this is really high power stuff, maybe a water cooling system within the rod...inserting the whole thing inside your rotating tube.

Years ago I worked at a linear accelerator research facility, and we used big blocks of copper with water passages cut into them to act as beam stops.

[MonoNeuron]

Kiwi,
How much power has you laser got?
If it's only 100 watt or so then maybe a polished piece of Aluminium inserted into the tube will help.
If you give us more info then I reckon someone here will have the answer.
Rich.

[Kiwi]

Hi Rich
This is not my machine. My son's Company gets rectangle (RHS) stainless cut by a local company. These are for gas fired heaters and the patterned cuts are for the gas to pass through and with fire resistant logs on top to create a log fire appearance. .
The machine is a 4KW Amada FO-4020 NT.
http://www.farra.co.nz/home.html
A present they slide a steel plate inside the tube to prevent the lower side from being damaged.
The steel plates need to be replaced often, unsure exactly.

[MonoNeuron]

Hey Kiwi,
Could you fabricate an aluminium trough and fill it with water and slide this into the tubing. Water absorbs the laser beam fairly well and the Aluminium is pretty reflective of the beam and the water would also catch the sparks. It could be topped up each time and would be very cheap to make. The laser could also be lowered to a point at which it just cuts through the tubing.
Hope this may help
Rich.

[fgeiser]

A chunk of graphite works very well for a beam stop.
It will absorb quite a lot of power without being damaged.

Another idea would be an aluminum heat sink; something with plenty of fins so it can absorb and disperse the heat.

Additionally, keep the stop as far away from the cut as possible, so the beam is more out of focus by the time it reaches the stop.

[laser3kw]

Say away from anything "shiny". The directing mirrors in a Trumf are polished copper! Shiny can reflect the beam back thru the focus lense and damage it or it can get back to the resonator and cause bigger problems.
Water? maybe - but watch out for steam. That will rise and fog up the focus lens and burn it out.
Look for something that will absorb the beam/heat (sand) and the rest fall into place.
Most of the beam energy will be used up in the initial cut, hot slag and gas will be doing 50% of the damage to the other wall. distance is also your friend (large distance between initial cut and parallel wall is better- beam diverges and loses it's focus intensity).

[coleong]

The steel are used to prevent damage to the bottom of the material.

Most large laser machine companies advise to use the same method to prevent damage on the workpiece. Some company advise to use stainless steel as it can last longer.

I hope that can answer your question.

[Kiwi]

A present the laser company is cutting 4mm thick stainless plate to place inside to protect opposite side but need a new plate every 5-6 parts.
Hoping to find a more cost effective way.
Thanks for all suggestions.

[bennett71]

I agree with everyone that says absorb it. If you dont you might catch a nasty reflection & get burned badly. Maybe some kind of ceramic would work.