Build a Laser Cutter Fume Extractor

I built my first laser cutter in 1996 and learned right away that laser cutters "stink". Well, at least the fumes from cutting smell awful and are quite harmful to breath. After trying several fume extraction options, back in 2002 I found the ElectroCorp RSU filter. It was a bit expensive, I think I paid $1500, but it did a great job extracting even the worst fumes from cutting acrylic. Fast forward to 2013, I called up ElectroCorp to buy replacement filters for my unit and found out that the original company was sold and is now being run by another company. This new company claimed to supply the same replacement filters, but after almost three months of going back and forth with them, it turns out that their filters are no longer the same, cost way more and look to be much less robust. Going through this challenging and frustrating process with them got me thinking. After taking a close look at how my old unit worked, it was pretty clear that I could build a similar unit quite easily that would allow me to use off-the-shelf and readily available parts. I figured I would document the process so other people with laser cutters could try their hand at doing the same. Depending on the supplies you have laying around your workshop, you should be able to build one of these for somewhere between $400 and $450. Here's how...

Step 1: Gather Major Components and Supplies

Parts:

• Qty (1) Fantech Inline Exhaust Fan, 392 CFM, Centrifugal for 6" Duct
• Qty (1) 29500 Honeywell Air Cleaner Replacement Filter
• Qty (2) 3M Filtrete Air Conditioner Filter, 15-Inch by 24-Inc
• Qty (1) Duck Brand 1285234 24-Inch by 15-Inch by 1/4-Inch Foam Air Conditioner Filter
• Qty (1) 55lb bag of activated carbon (I called them and spoke to Karrie Gibbons. Just ask for "4 by 8 coconut shell carbon, for vapor filtration")
• Qty (1) Harbor Freight Router Speed Controlled
• Qty (1) Roll of squishy neoprene shelving liner (It's about 1/8" thick, soft, makes great gaskets)
• Qty (4) 2inch casters
• Qty (1) 3/8" Romex clamp or cord strain relief
• Qty (4) 3/8inch threaded rods
• Qty (8) 3/8inch nuts
• Qty (4) 3/8inch wing nuts
• Qty (8) 3/8inch washers
• Qty (1) 5' roll of window screen
• Qty (1) 5' roll of 1/4" wire cloth
• Qty (1) tube silicon caulking
• Qty (1) 3/8" dowel pin (for the router jig)
• An old extension cord (we only need the male end)
• 4'x4' piece (half a sheet) of 3/4" thick birch plywood smooth on both sides.
• Mat board
• Weather stripping (I had leftovers from other projects, but basically 1/4" thick, foam)
• Qty (1) Roll of post filter material (updated!)

Tools:

• Plunge router with a straight plunge bit
• Electric staple gun
• Drill (with Phillips tip and 3/8" drill bit)
• Jig saw
• Hot glue gun
• Hearing protection
• Face mask
• Dust mask
• Rubber gloves

Step 2: Cutting Disks and Rings

I started out making a jig for my router. If you have a circle cutting jig you can obviously skip this step. We need to cut two inner and two outer rings plus the top and bottom plate (note that the bottom plate doesn't have the 6inch hole in the center). I used the jig saw to cut out the top and bottom plate.

Remember to wear all your safety gear!

Step 3: Install the Casters

Figured it would be easiest to do this now. Just screw them to the base plate (the one without the hole).

Step 4: Staple the Screen and Mesh Into Place

iThe goal is to end up making two cylinders with the sets of inner and outer rings that are just a little taller than the hepa filter, which is 12" tall. I started by cutting strips of the 1/4" wire cloth 12" wide. I stapled this to the outside of the smaller inner rings and the inside of the larger outer rings so that the total height of each cylinder is 12-1/8". Then I lined the wire cloth with the fine window screen. I used a ton of staples since I wanted to be sure it didn't come apart and that there was no gaps between the wood and the mesh.

Step 5: Glue the Mesh Cylinders Down to the Base With Silicone

I drew a circle on the bottom plate so I would know where to position the inner cylinder. Then I ran a bead of caulking around the circle and squished the cylinder into place. I did the same with the outer cylinder.

Step 6: Filler' Up With Carbon

The carbon comes in something like a potato sack. I recommend you leave it in the box it's shipped in as there is fine carbon dust that seeps through the bag. I just used a cup and filled up the space between the two meshes. It is a bit messy so I would do it outside on a surface that you don't mind spilling a little carbon.

Wearing a dust mask and gloves is a great idea for this step.

Step 7: Clean Up and Add Some Weather Stripping

Clean all the carbon dust off of the top edges of the inner and outer rings. Vacuum out the center area. Apply weather stripping to both the inner and outer rings. I also added some weather stripping to the underside of the top plate.

Step 8: Cut the Bottom Gasket

I cut a circle out of the shelving liner that was approximately the same size as the outer diameter of the hepa filter. I then placed it in center area so the hepa filter would sit on top of it and no fumes would leak under it.

Step 9: Build the Pre-filter

To save you from replacing your hepa filter as often, there is a pre-filter that filters the "big" particles. To make it, I cut a 11-3/4" x 25" piece of the 1/4" wire cloth and rolled it into a cylinder overlapping the ends by about 2". Then I used some gaffers tape wrapped around the top and bottom edges to hold it together. I cut the 1/4" Duck Brand foam to fit inside the cylinder and both layers of the 3M Filtrete filters to fit on the outside of the cylinder. A piece of gaffers tape holds the 3M filters together.

Step 10: Build the Mat Board Air Baffle

Having a laser makes cutting cardboard a breeze, but you could probably do the same by hand. Take a look at the attached DXF file.The baffle needs to fit snugly inside the pre-filter. It should be pretty easy to tell how it goes together. I used a fair bit of hot-glue to make sure there were no leaks. You might need to adjust the dimensions a little if your pre-filter cylinder is slightly different dimensions.

Step 11: Bolt It All Together

I cut the threaded rods to 15" and bolted everything together. You will want to tighten all the bolts evenly to compress the weather stripping straight down.

Step 12: Wire Up the Fan

I cut the male end off an old extension cord and wired it into the fan's junction box. I used a Romex clamp to provide strain relief. Then I plugged the extension cord into the variable speed router controller (which is just a high current rheostat). You could just add an on/off switch, but I like to be able to turn the fan down when cutting thin material like paper, so that it doesn't get blown around.

Step 13: (Update!) Post Filter

My old unit had this blue fuzzy filter on the outside of the carbon filter (see the picture at the beginning of this Instructible). I never could figure out why it was there since the carbon did such a good job removing the fumes. What could be left to filter out? Fortunately, Soundgod06 posted a comment asking if I saw carbon dust blow out when I turned on the filter. The answer was no, I didn't see any dust, but it got me thinking... Just because I couldn't see it, doesn't mean it wasn't there. Ah ha! THAT'S why the blue fuzzy filter was there. It's there to grab any carbon dust pushed out by the blower. It was simple enough to add, I just ordered a roll from McMaster for $19, cut it to fit in between the top and bottom plates and pressed it into place. I just overlapped the filter material at the end, and tucked the free end behind one of the threaded rods. It holds there quite nicely.

Step 14: Test It Out!

Plug it and flip the switch! It should draw quite nicely when on high. Hard to say what the final CFM rating would be, but it seems to be plenty to evacuate my laser.

There is no guarantee that this filter is filtering out 100% of the bad fumes, so use it at your own risk. So far, it has worked pretty well for me.

Comments

[DIYPro0505]

Does anyone here sell a filter like this? I want to purchase a ready-made fume scruber. Thanks

[wentzele]

How many times can you replace the carbon with a 55lb bag?

I am planning on building one of these. Great project, I live with neighbors close by and still plan to exhaust outside by adding another other container which would then duct outside.

[Zach]

You can fill it twice with a 55lb bag.

[jeanniel1]

How often would you refill it then? I guess that might depend on how often the filter is used, and amount of particulate it's collecting. What about the HEPA filter - does that get cleaned out - how? Or is it replaced?

[Zach]

With acrylic it really only takes a tiny leak to let the fumes out. I found my motor housing leaked a little as well as between the top two pieces of wood. For me a combination of caulking and some extra foam tape sealed it.

[bratan]

Thanks, that's useful piece of information! I'm off to Lowes to get some 1/4" ply, going to laser cut brand new top (as per "bar2" comment) with tighter motor housing hole. Having thinner top will help motor housing to go deeper into the pre-filter (I might even add small piece of pipe on the inside). And definitely more weather stripping, thanks for the suggestion! Another idea I had is to add some gaffer tape on top 2-3 inches of the outer ring. Carbon seems to settle which leaves empty gap there... Not ready to give up on my $570 investment just yet :)

[bratan]

Just wanted to post an update. Duct tape on top of the inside of the outer ring stopped most of the leaks. I suspect it might have leaked thru holes in the plywood (layers had some gaps) as well as thru less dens layers of carbon. I get just hint of the smell now, so it's not totally gone, but lights years better :) I now realize the circular is probably not the best design idea mainly because carbon compacts toward the bottom, and layers do not saturate evenly... Once I use up HEPA filter I'm going to try and make a box type filter.

P.S. I measured wind speed generated by the filter, and it's pretty good 210 CFM inside the laser cutter!

[jeanniel1]

What do you mean the circular shape is not a good design - how would a square or rectangular box be better? Did you do the box type filter yet?

[bratan]

Something else worth mentioning. There are apparently different compositions of acrylic which affect smell. I was blaming it on the filter, but last night I tried cutting some 1/8" white acrylic, and to my shock there was NO smell at all in the room! Even freshly cut piece had only faint odor when I smelled it directly!

[gtennefoss]

The Honeywell 29500 filters now come a 4 individual "cleanable" filters. They each come with a foam gasket that is used in some applications. There are aftermarket single filters on ebay and amazon. Prices are similar for both the single and stacked filters. I was concerned about loss of air flow because of the loss 3"of filter because of the stack seams but Honeywell must of compensated by adding more folds because their cleaners use pressure switches to test for if a filter needs replacing. They claim these are lifetime filters that never need replacing under normal use. There seems that there is no reduction do the this.

I put a bead of silicon between the filters just to be sure there is a good seal and to keep the stack straight. 2 of the foam gaskets can replace the weather stripping on the top and bottom and may provide a better seal.

I also painted my top and bottom with a couple of coats of gloss to seal the plywood itself to make a better seal and prevent leakage into the plywood itself. This should take care any issues with voids in the plywood layers.

Lastly, if you want a 90 degree inlet, just go to the hardware store and get a 6" adustable elbow in the ventilation section for a few dollars. You can acheive a bend from 0 to 90 degrees just by twisting. You will more than likely need to use silicon or duct tape on the connection points to prevent suction leaks.

[TimJ94]

Activated carbon holds static electricity quite well which means they will try to repel each other. Get it damp to prevent a static charge and thus avoiding a loose carbon bed when packing the filter to make sure the carbon isnt repelling each other while it has a charge. Yes I know its a redundant way of phrasing I just want to make it super clear about the electrostatic repulsion and the easiest way to deal with it.

[patternmusic]

I built this laser cutter ventilation filter and wrote up this Instructable for it.

https://www.instructables.com/id/Fume-Coffin-Laser...

It's based on some of the ideas in this Instructable, but it is intended to filter exhaust air for ventilation outside rather than act as an air scrubber filter like this project.

Thanks for the inspiration and great ideas.

[SebastianG142]

Hi all

Its great project and I'm planing to build one for my self as well.

As this is 3 years old project all of you have tested it well already hence I have a question regarding the activated carbon.

How long it lasts? How often are you replacing it?

Thanks

[Gerges2001]

dear is it prevent smoking that come out while cutting wood ??

[1stage]

Great build! I'm going to be building one for the small Chinese K40 laser cutter/engraver I just bought. I got this metal cart from Harbor Freight (http://www.harborfreight.com/24-inch-x-36-inch-steel-service-cart-5770.html), assembled with the top "shelf" upside down, and now I'm going to try to incorporate a fume extractor build into the bottom area of it.

[jack ruby]

Hows the smell? Seems like you made this filter a while ago, have you noticed any improvement/degradation over time? Does this filter take care of even stinky acrylic cutting fumes?

[mahsa301]

I wanted to know is your filter worked for fume and smell of wood laser cutting?

and

I wanted to know what is the kind of carbon you use to made the filter?

[MossdaleMakerspace]

This is an awesome build! If anyone out there doesn't want to go through the trouble of building one, you can check out hydroponics stores; they sell duct fans and carbon filter cylinders for pretty cheap. You can probably find one for cheaper than you could build one, unless you have a lot of the materials already laying around.

[DaveA12]

Those are made to filter smell only - the particulates from the smoke will still get through the carbon only filters.

[Zach]

There are a ton of filtration options out there, but I knew the configuration used by my old ElectroCorp did the job of filtering acrylic fumes. I did a little searching in the hydroponics realm, but didn't find something that would allow me to do the same pre-filter->HEPA->activated carbon with similar surface area. If you know of a source that does, please post a link.