exhaust system for small garage w/laser cutter

[shatterjack]

I am running a 2'x4' 100watt cabinet laser out of my small garage. I can vent to the outside but am trying to cut down the fumes as much as possible for the neighbors. I am also trying to minimize sound for the same reason (and to save my own ears).

I've made a box to house my air compressor and vacuum pump (grizzly industrial 450 cfm) with flexible hose to a second box containing a homemade carbon filter (activated charcoal laid on a metal mesh about 18"x18") and then to the table. The vacuum pump sucks the air in the box and then vents directly outside and in this way cools the inside of the box. The inside of the compressor/vacuum box is lined with 1/2" foam and then soundboard on top.

The problems are:
1 Trying to figure out how much carbon to lay out on the mesh to effectively filter the fumes and not cut the cfm too much.

2 The noise of the vacuum pump comes straight out the vent to the outside. I saw a muffler at mcmaster for a 4" pipe but it was like $370. I could make a baffle but I'm afraid it would cut the cfm down.

3 Is a 450 cfm vacuum pump enough to vent and pull material flat for a 2'x4' table?

4 Is it a good idea to go with rigid duct over the flexible spiral hose? (the inside is relatively smooth)

Thanks a lot you guys! I figured the hardest part would be setting up the laser but it's all the other stuff!

tony

[bpoulin]

My machine is 47"x31" so just about 4'x3' If my memory serves me right the air extractor is 2200+/- CFM I will have to go out and read the label another time. I mounted the extractor outside in a housing and ducted it above the roof with PVC pipe. The blower is almost silent, standing next to it I can have a conversation over it without a problem, and I have APD (form of a hearing disorder). So neighbor's noise isn't a problem. Fumes aren't too bad, they disperse rather quickly, especially if you get them up high enough. The only time I can ever smell what I'm engraving is when I engrave acrylic. Even then it's barely noticeable. If they don't mind your air compressor, an air extractor will barely even be noticed. As far as size goes, the 2200cfm is barely adequate for my machine, I'm considering buying a 2nd one to up the airflow.

[shatterjack]

thanks bpoulin,

Could you tell me more about the housing you put your blower in? I made a box for mine, from outside in: 3/4" mdf (unsealed) then 1/2" foam, then that sound board stuff they sell at home depot. I was thinking about getting some vibration absorber feet for the box. I was looking at getting another blower too but only another 450 cfm since I only have another 15 amps to spare on my second circuit...

[zax15uk]

shatterjack, it sounds like you are looking for 2 different applications.

To exhaust the fumes you need flow rate, in bpoulin's case his 2200cfm should be sufficient as it is capable of pulling 100X his chamber per minute but I suspect it isn't near that due to restrictions and insufficient makeup air (intake vents).

To pull the material flat, as in a vacuum table you need flow to initially pull it down (or you can just push it to create the hold and cover open areas with scrap material) and then it's based on the negative pressure to hold it there - flow rate is almost zero at that point.

The equipment for each application is different.

Regarding the extractor, using activated charcoal and a HEPA etc becomes a mixed application - a centrifugal fan "squirrel cage" is the ideal solution.

A vacuum pump (venturi or other design) is suitable for the table hold-down.

Zax.

[bpoulin]

Is your blower that noisy? Because mine is almost silent, I have no sides on the box, just a roof, I'll try to get pics up today.

[bpoulin]

Originally Posted by zax15uk I suspect it isn't near that due to restrictions and insufficient makeup air (intake vents).Zax.

It doesn't help that I have to use crinkle hose between my machine and wall because the machine is mobile, and can be rolled around my back wall.

[shatterjack]

yeah I've got the crinkle hose too, but the inside of it is relatively smoothed out so it's not too bad. I guess most people use rigid duct? I'm not sure. The connections are sure easier I think...

Yeah my vac pump is loud. I don't have a sound meter but it's this one.

I got one and am thinking of buying a second one to increase the pull on the table materials. Even when I have the table almost all covered up, the pull through the cracks is light.

bpoulin, please tell me what vac pump can pull at 2200 CFM and is almost silent!

[shatterjack]

I'm trying to understand whether it would make any difference in the system if I had the vac pump directly after the cutting table, or after the filter. I made a little sketch to show the two setups. Also if I'm going to add a second vac pump to the system, what would be the best place to put it in to maintain suction on the table material and air flow through the air filter?

[lrob]

Best to pull the air through the filter than push it through.

[bpoulin]

I'm sorry I haven't gone and looked at the plate, I've been working the past 3 days, and I can't see it well enough in the dark. I'll get all the info soon.

[zax15uk]

Originally Posted by lrob Best to pull the air through the filter than push it through.

Agreed. It will also keep your blower assembly clean.

Zax.

[Litografa]

I already post here this pictures, but can't find my post So will repeat - may be this information will be helpful. Customer use only one filter (air filter from trucks). After air is pushed to the roof.