The domestication of Laser Cutters

I bought one of those Chinese blue box 50W laser Johnnies second hand for taking apart. I am a bench top explorer.

The software had some weird dongle, but sort of worked once you got the idea. The final lens had about 1/16" of gunge which I took to be glue residue from burning plywood. The aquarium pump designed to circulate cooling water soon demised and I melted one of the mirrors off the laser tube end. The fume extraction was totally ineffective. The high voltage power supply was an open PCB and looked frightfully dangerous.

However it sliced Perspex/Acryllic like there was nothing there. It just disappears where the laser light touches it. These things are God's gift to anyone wanting to cut acrylic.

I bought a new tube, a new PSU, I am choosing a new chiller pump frame and head.

Also the below workpiece table, a sort of frosted aluminium plate designed to scatter the beam. Could do with a bit of a raise lower mechanism. Maybe some of that honeycomb aluminium.

The laser head needs air blowing downwards to clear the fumes away.

I 3D printed new clamps to hold the tube. The originals were the wrong size and well packed below to raise them up. You get the picture.

Hi

There's some very good videos concerning Chinese laser engravers/cutters on this channel, very comprehensive and informative, well worth a look.

https://www.youtube.com/user/SarbarMultimedia

https://www.youtube.com/user/SarbarMultimedia

Nige

Edited By tractionengine42 on 05/09/2017 12:26:49

If you are cutting acrylic and not pulling the fumes away, this would explain the gunged up lens. Acrylic smoke has all manner of nasty stuff and resin vapours in it. Some sort of vacuum extraction system as near as possible to the beam, exhausting outdoors, would probably relieve a lot of the gunge and would improve the quality of the air for breathing greatly. Probably an inexpensive shop vac could be adapted. Look for a quiet model if finding one.

I like quiet, I have no less than 3 Bambi compressors, is this "quiet model" shop vac for real or just wishful thinking?

Edited By Robin Hewitt 1 on 05/09/2017 19:58:05

Hi Robin, I probably should have said quiet-er rather than quiet. Not sure about UK but in North America there are models available with sound insulation around the motor head, quieter air flow in the plumbing, and with exhaust muffling systems. See link to one such unit below. You can still hear them, but they make less noise than normal screaming 70 dB ish shop vacs. Have not seen any manufacturer state actual decibels though, despite the "Quiet Series" claim. If you could place one outdoors in a plywood box open on the side away from the workshop, with rock wool insulation on the inside, that would further reduce noise. Just be sure to leave lots of room around the vac unit in the box for cooling air to circulate.

https://www.amazon.ca/Shop-Vac-5940682-Quiet-Wet-Dry/dp/B0041HXXXO

If there was an off the shelf way to silent fume extraction I'd probably go for it. We just have to wait for technology to catch up with us

I might be wrong here (frequently the case!), but I would expect this task to be better suited to an air-con style high volume, low pressure extractor fan rather than something built around a shop vac geared up to pulling a significant vacuum.

Also, not sure about 'shop vacs' but I think most ordinary vacuums use the sucked air to help cool the motor, after the mechanical extraction of the dirt of course. However heavy vapours from acrylics etc. would presumably pass through the mechanical filters to be presented at the (often sparky-sparky brushed) motor - might reduce the need for breathing air but...

My 2c..

Simon

A

As an "off the wall" comment on fume extraction, how about using a remote air compressor to power a venturi pump, (like a water powered jet pump used in a chemistry lab) with the exhaust going to external atmosphere?

(and ignore the the local environment - before anyone else says it!)

No doubt a lot of experimentation to optimise sizes to balance fume extraction against duty factor of the air compressor. At 5 psi, a LOT of air will pass through a 1.5mm hole, believe me!

Howard

On the blue box the extraction "duct" doesn't seem to reach anywhere useful. I cut it out with an angle grinder.

The air inlets were accidental rather than carefully positioned to get any useful flow going.

What it really needs is air piped in to keep hot condensing solids off the final lens.

The fan that came with it was actually quite good, unfortunately it was designed for something completely different.

It is all very well looking for a big air flow but which parts of the case are you going to cut out and what are you going to do with the air once you have sucked it?

Someone I know used tumble drier ducting and a decent computer fan to take ABS fumes from a 3D printer outside.

Neil

Am I allowed to confess that I am not very concerned with Health and Safety,

I already know what is going to get me, I take pills for it

I did the same .... except the fan was an in-line duct-fan. Not that the fumes from a printer melting plastic compare with a burning a plastic in a laser printer.

In the real world you get a laser, you put the fan on the back, you put the ducting on the fan, you open the window and realise there is no easy way to connect duct to window so that the fumes wouldn't just blow straight back in to the room. You sort of wedge it in a half open window but it is so insubstantial it won't stay put. You resolve only to cut things that don't set off the smoke alarm. Problem solved.

I just found a new CW-3000DG chiller for £165 with free shipping from Germany on that auction site.

This is wonderful, arguing about fume extraction has got me back on to lasers.

What a wonderful forum this is, I totally approve of anything that comes with a shopping opportunity

www.trotec24.co.uk/machines/air-conditioning/air-conditioner-accessories/airlock-200-window-sealing.html?rc=5b89253657

Or:

Good try Neil but it ain't gonna happen

Don't you have laundry dryer vents (this kind of thing) with shutters that close if the wind overcomes the fan pressure?

My case wasn't a problem. The setup is in the basement which has small, sliding windows a little below ground level. On the outside of the house, there are window-wells around these windows and, except under extreme conditions they don't get much blow-back (in fact the wind blowing over the window-well tends to create a small pressure drop if anything). I blocked a window permanently open and screwed a sheet of acrylic to the inside frame. I mounted a dryer vent through that.

I admit that after a hard day bent over a hot soldering iron on Friday the jolly old Ersin Multicore left me feeling a bit chesty, but despite all the abuse my lungs are still in fine fettle. What I really need are some new teeth, wifelet has forbidden me from smiling in public until this is done.