[buddydog]

Extraction is a funny thing, you may also need to consider local laws, it may actually be illegal in your area.

4" soil pipe make for nice cheap long runs, if you need to turn a corner used radiused bends, not short 90' elbows as they screw up the flow rate.

dual domestic hidden in the roof space type inline / axial extractor fans, each capable of 350 cfm, are quiet, low power, and do the job, but site them where you can just swap one out if one dies.

HOW you plumb / attach the suction side of this to your laser is a question in itself, in my set-up one draws air though the bottom of the Z table, and one draws air out from the back of the bed, and for me this works excellently.

May I share a cautionary tale........

video - https://vimeo.com/album/3052977/video/112489108
related blog post - How to avoid producing scrap. | Exeter Laser

TLDR version - basically a laser cabinet with extractor fans running can very quickly turn into a forced draught wood burning stove, and even if you have fire and smoke alarms in your workshop, they won't be triggered until the extractor fans burn out or die

Nota Bene this is just extraction, not filtering, filter stages add back pressure, so it gets even more complex... a friend of mine made a wonderfully efficient filter that was basically a big copper water tank filled with layers of foam pellets and auto air filter paper and so on, incredibly efficient as a filter, then one day the whole lot caught fire, so now he had added an intercooler stage, which also needs cleaning, his complete filtration setup is now twice the size of the laser, and about 30% of the cost, but he has no alternative, thanks to legislation applying where his laser is sited.

One of the best posts I have seen on here. Thank you. Added new knowledge about thickness/cut distance to my stack.
Because my machine is already low power I am forced to make multiple passes often and so does that figure in any way into the thickness/distance between cuts equation? I have not tried any deep cuts close together. This problem may materialize when attempting "laser hinges"? Also could "skipcuts" help in anyway? is the problem related to heat. The fact that it doesn't work and "don't do it" is good but any good explanation as to the "why"?

[ELaser]

One of the best posts I have seen on here. Thank you. Added new knowledge about thickness/cut distance to my stack.
Because my machine is already low power I am forced to make multiple passes often and so does that figure in any way into the thickness/distance between cuts equation? I have not tried any deep cuts close together. This problem may materialize when attempting "laser hinges"? Also could "skipcuts" help in anyway? is the problem related to heat. The fact that it doesn't work and "don't do it" is good but any good explanation as to the "why"?

I don't know mate, I'm far from a laser expert, and I'm finding by trial and error that many so called laser experts aren't...lol... fwiw my background is real engineering and I also have cnc mill and lathe etc in my shop.

One thing I have learned, optics (mirrors / lenses / alignment / quality / cleanliness) and air assist (15 psi straight down through the lens nozzle) are vastly under estimated, in a world where everyone talks about tube power, alleged... lol

That video linked is cutting 16 mm thick pine board at 40 watts, so either someone dropped a bollock at the reci factory and despite my tube being 100 watt length and 100 watt nominal rated with 131 peak rating (which is a goooood one, not a "friday" job) someone must have dropped a few grams of unobtanium into the gas mix to double the efficiency and output power, because I see other people saying you *must* have 120 watts to cut 18 mm wood... I also do beautiful (if slow) cuts in 25 mm thick acrylic at 48 watts.




See my latest two vids for more on this, first is 2.5" lens, second is 4" lens, vs 100 mm thick acrylic, top tip, the 4" lens punches all the way through 100 mm of acrylic at 75 watts.. I think the tube is a "good un" and not a friday job, but I think the bulk of the reason I am doing so well is USA and German optics, set up right and cleaned right.

2.5" lens vs 100 mm acrylic -
4" lens vs 100 mm acrylic -

[ELaser]

That's kinda why I linked to those videos

1/ if the material being lasered is combustible, the gases given off when lasering are *very* combustible.

2/ I know of *no* laser cutting or engraving process where the combustion is desired or an improvement over the same process without combustion.*****

***** laser cutting steel is of course done with oxygen so in many ways the same as a gas axe cutting steel, arguably this is combustion of a sort, but steel is a metal... and so outside the scope of what you were discussing.

getting back to that video I linked to, you can HEAR it when the gases ignite, it sounds like a blowtorch cut, and it totally screws up the work being cut.

Speaking personally, I do *NOT* want my gases combusted *anywhere*, as the un-combusted gases are a lot "cleaner" and safer than the combusted ones, because the free air combustion temperatures are way way way too low to break everything down.

You can *easily* create copious and lethal quantities of cyanide if you ignite the gases produced by laser cutting some materials.

There are no circumstances whatsoever where I want laser produced "smoke" being ignited anywhere in or near my laser or workshop.

[Retroplayer]

or... maybe it is only a matter of time before someone comes here reporting that their K40 laser with stock exhaust fan turned into a flamethrower in their workshop.

[buddydog]

or... maybe it is only a matter of time before someone comes here reporting that their K40 laser with stock exhaust fan turned into a flamethrower in their workshop.

Yes it's interesting to note that we don't hear a lot about lasers exploding so it is probably a lot like sawmills: takes a very special condition but I still think the danger is possible particularly since I have not seen any other thread explore/explain this theory we are maybe exposing here.

Your a better man than me to invest 100-200 hours into openscad programming and prototypes and not try to recoup a little of it on ebay. Maybe after I get costs back.

[ELaser]

centrifugal style blowers have a motor separate from the gas flow channel, and induction motors don't have brushes anyway, axial motors have flame arrestors in the cooling air flow for the armature same as an acetylene line, and are still induction motors with no brushes.



I could spray gasoline from a paint spray gun into my extractor inlet and it wouldn't ignite.

[buddydog]

centrifugal style blowers have a motor separate from the gas flow channel, and induction motors don't have brushes anyway, axial motors have flame arrestors in the cooling air flow for the armature same as an acetylene line, and are still induction motors with no brushes.



I could spray gasoline from a paint spray gun into my extractor inlet and it wouldn't ignite.

True but the scenario I was thinking of: exhaust fan quits during a cut unknown to you, fuel air mixture "passes"through" that needed for combustion, laser head is making some "fire" the whole time, and that is the ignition source? Boom? Worse yet you notice the build up of smoke in the cabinet and open the lid. As the firemen say:Backdraft?

I don't know if any of this is possible but the discussion is about putting things in line with the smoke and that made me think of a couple of possible problems I had not seen discussed before,only that "there is the possibility" of fire, not the mechanism. I am haunted by a picture I saw somewhere of a larger, completely burned up laser machine. I was impressed with the completely burned off paint on the outside and the gutted insides. The poster claimed it was a complete write off. No real cause was discussed as I remember and no time line. Is watching the machine (I always do) enough? In a back draft situation I don't think you would know until it's to late. Again I'm not saying, just discussing and open to why's or why not's. The one "why not"is you don't read about fires happening to much if normal installation.

Here is another thought: I am planning on using 100 feet of 4" plastic drain pipe for my future system with a "dust collector" extractor fan at the far end. Hmm. I just remembered you need to have a grounded bare wire running through your pipe to stop saw dust explosions so probably a good idea for laser smoke too!

[ELaser]

True but the scenario I was thinking of: exhaust fan quits during a cut unknown to you, fuel air mixture "passes"through" that needed for combustion, laser head is making some "fire" the whole time, and that is the ignition source? Boom? Worse yet you notice the build up of smoke in the cabinet and open the lid. As the firemen say:Backdraft?

That's why I have dual exhaust blowers, and they, chiller, and a bunch of other stuff are on the interlocks, it goes out the back of the machine and exits the workshop at ceiling / roof height many metres from the nearest door or window....

One of the reasons I did it this way is I am NOT a fan of the "only use the exhaust when making something really smoky" because the exhaust is a noisy 3,000 CFM centrifugal job that eats electrical power, in my setup fans and chiller fire up before the laser boots, and shut down after the laser, so I wanted quiet and efficient.