Material for the base of enclosure?

Extrusions/Tubing/Hinges/Etc.

Material for the base of enclosure?

Postby Greolt » Mon Jan 16, 2012 10:08 pm

I am interested to learn from the collective experience and knowledge of the forum re enclosure base material.

As it stands at present my enclosure (unfinished machine) has a ply wood base which I have coated with ordinary polyurethane.

I didn't use this for any particular reason, other than I had it on hand (offcut from some job or other) so it was free. Have no idea at this stage whether it will last five minutes.

So what material is good for this? Keep in mind that the base is about 300mm plus below the laser head. Moving Z axis / table.

Thanks for any advise,

Greolt
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Re: Material for the base of enclosure?

Postby r691175002 » Mon Jan 16, 2012 10:14 pm

I would recommend a tray or something, tonnes of small pieces of material fall through the table when you are cutting.
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Re: Material for the base of enclosure?

Postby iGull » Mon Jan 16, 2012 10:25 pm

I just commented on this in my buildlog this afternoon strangely!

I have formica laminated ply on the base of my machine - about 230mm below the nozzle. My laser is 60W and it has caused severe burning on the formica substrate.

I would recommend an aluminium 'crumb' tray underneath - kill two bird with one stone - stop burning and keep all the offcuts together. You need to keep the tray emptied - all the offcuts burn too !

Cheers

Neil
EMOs are a sign of weakness ...
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Re: Material for the base of enclosure?

Postby educa » Mon Jan 16, 2012 10:36 pm

And doesn't an aluminium or steel tray mirror the beam to make it go UP again ?

I can easily put a metal tray in my machine, but I wonder if that won't let the laser bounce back upwards and burn again at the bottom of your working material. Be it uncollimated of course.

Any thoughts?
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Re: Material for the base of enclosure?

Postby iGull » Mon Jan 16, 2012 10:54 pm

That would give you 600mm of space and the power will be lower on the return beam. Unless you installed a sacrificial base made of IR opaque material that wasn't flammable, you are low on options :D Maybe at 40w, it isn't too much of a problem.

I'll direct you to a comment on the safety part of this forum - my laser burned a hole in my workshop HP printer case at 2 metres !

Cheers

Neil
EMOs are a sign of weakness ...
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Re: Material for the base of enclosure?

Postby educa » Mon Jan 16, 2012 11:02 pm

I understand that somehow the bottom WILL get touched and shown burning, but I'm just wondering what to put at best down there.

your formica gets burnt marks, but I suppose that also means that it'll make smoke and all.


Also, if I make my machine without moveable Z table, could I make my machine lower then (in height) or still better try to get as much hight (depth) below the cutting material as possilble ?


Kind regards,

Bart
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Re: Material for the base of enclosure?

Postby canadianavenger » Mon Jan 16, 2012 11:07 pm

you could try one of those silicon rubber cooking mats, they do not cut/burn well with the laser. They will mark over time, so will need periodic replacement, but not often enough to be cost prohibitive.
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Re: Material for the base of enclosure?

Postby BenJackson » Mon Jan 16, 2012 11:09 pm

iGull wrote:I'll direct you to a comment on the safety part of this forum - my laser burned a hole in my workshop HP printer case at 2 metres


Before you go through the final lens the beam is highly collimated (I understand it actually has a slight convergence over 5m+) so it has the same power right in front of the tube and (in your case) 2m away. Once it goes through the lens it is focused to much greater intensity at the work but then it drops off. With a 50mm focal length lens the beam is back to original size 100mm below the table. So it's maybe 20W/mm2 at the laser, 1250W/mm2 at the focal point, and <1W/mm2 at the bottom of a buildlog laser.
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Re: Material for the base of enclosure?

Postby iGull » Mon Jan 16, 2012 11:19 pm

Good point Ben - I had forgotten that it had missed the lens and hit me :D

Only 1W? I'm not about to argue with the numbers, but I would have thought that 1W over 1 mm^2 wouldn't be enough to burn formica - the results at the bottom of my laser show otherwise (it is 60W granted).

Cheers

Neil
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Re: Material for the base of enclosure?

Postby educa » Mon Jan 16, 2012 11:33 pm

But would aluminium or steel at the bottom then reflect that power back upward or would it absorb it ?
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