Lasercutter fume exhaust - filters and cleaning them

[Henri Sallinen]

I ran into a problem: I run my lasercutters fume exhaust through a cleaning unit that consists of a active carbon filter, a HEPA filter and on top of those few filter more to take out the rougher fumes. Today I ran alot of cellulose acetate (material that's used on eyeglass frames) on my machine and the burning fumes clogged my HEPA filter and the filters on top of it. Fortunately it didn't get the active carbon. I've clogged a few HEPA filters by now, the earlier were because of a stupid mistake I myself made, but this newest one broke the camels back. The smoke coming from the acetate seems to be quite greasy since the filters can't be cleaned with compressed air blowers.

Now to the questions: How do you pre-filter your laser exhausts before the smoke hits the more expensive filters? Do you clean your filters regularly and how you do it? Today I had a crazy idea: Use a steam cleaner to clean my old HEPA filters. There isn't anything to lose anymore since they are all ready done for. Any comments on the steam cleaner idea? A doomed idea from the beginning or perhaps something that might actually work? I'll probably have to find a warm place to dry the filter as quick as possible.

I had to come up with a few very bizzarre ideas of pre-filtering the sticky smoke and one thing that came in to my mind was installing a sort of self made pre-filter that consists of rock/wood rubble. Something loose enough to catch most of the sticky smoke and save my HEPA etc. filters. The wood might be a bad idea since a spark from the laser could travel through the exhaust tube and set the wood on fire.

So heres just something that's been on my mind and just wanted to share a few ideas I got in a desperate situation. Hope this sparks off some kind of a conversation! All ideas and comments are quite welcome.

Sincerely, Henri from Finland

[Joe Hillmann]

Is your bed of charcoal deep enough? I really can't offer you much advice but could you vent the exhaust outside when you are working on material that you know clogs the filters?

[Walt Langhans]

I had a similar issue, all I work with is MDF and it was constantly making a mess of things very quickly. The easiest solution I came up with was to ditch the filter system and vent outside.

[Joe De Medeiros]

One way to eliminate some but not all, is to use a water fall stage in your filtration system, the idea is that the air coming in hits the running water fall first and carries the particulates with it. I have seen this used in Industrial cutting settings, I'm not sure how you would implement it on a small scale, but there are a lot of cleaver guys on here that may come up with a concept.

[Dan Hintz]

If you plan on continuing to do work with such particulate-filled smoke, I'd suggest a basic furnace filter (or two) in front of the airflow. You'll fill them up fast, but at <$1 each, it's a cheap/easy throw-away item.

[Charl Lourens]

Hi there.

New to the forum, so not sure if there have been a post on this one.

I have done the water filter concept with my laser machine. I was running to DIY home build water filters on it. Was cutting mostly MDF and a few other of those nasty ones.
The water tends to absorb a lot of the chemical. Non or a small portion of the smoke.
What i can tell is the water becomes very acidic, so make sure you use plastic for everything. I built the two scrubber towers from acrylic to see what the effect of the water is on the air coming in.

Medium used in the towers to increase the wetted area was the fish pond filters used to prevent algae and things clog the pump.
Fine enough to get some good water spread but course enough not to strain the fans too much.
Using a 100W Co2 laser.
Sucking off about 1600 CFM from the laser unit.
Cutting 9mm MDF leaves a BIG BIG smoke cloud.

Busy bring in a activated carbon filter system now. Still having some teething problems with this one.
But found some good ideas on this forum.

Thanks for sharing your ideas.

[Henri Sallinen]

Thank you all for the tips and suggestions! The biggest problem is that I can't vent outside without getting rid of the bad smell. The only thing that has "worked" so far was to remove the HEPA filter and use cheap media, like the furnace filters, carfilters etc. to get most of the grease off the smoke. Then I got a separate active charcoal filterbox just for the sellulose acetate. Current setups works for now, but still looking better ways to get it filtered. I will up this thread if I come up with an ultimate solution for my problem.

[Marius Nel]

Hi Charl,

Can you share more about your water filter concept? We are also using mdf and the neighbours are starting to complain about the smell..

Ps: Looking at your first name/surname it seems like you moved to Australia from RSA?

Thxs

[Nick Mauer]

This works=

If you plan on continuing to do work with such particulate-filled smoke, I'd suggest a basic furnace filter (or two) in front of the airflow. You'll fill them up fast, but at <$1 each, it's a cheap/easy throw-away item.

We use a BOFA AD4000 fume extractor with our laser, equipped with 2 each of pre-filters, HEPA filters, and carbon filters. Have had to change the pre-filters 3 times now (in 18 months), they are NOT cheap to replace. The others are more expensive.

We regularly cut 3/4" MDF, plywood, solid wood, acrylic, tectum, masonite, and more. Most of those materials, especially tectum, produce a lot of smoke and debris that gets caught in those expensive pre-filters. So we made a pre-pre-filter box.

It's a steel box with an exhaust "in" at the top, and exhaust "out" at the bottom, with a simple furnace filter in between the ports. Those furnace filters fill up quickly (3 days max usually), but you can pick up a 10-pack for $20 or less. They catch the bigger particles and sticky stuff and save your extractor's pre-filters from getting plugged as often.

[Henri Sallinen]

Nice that this thread popped back up! I've made some great improvements on the prefiltering.

I've changed the prefilter + furnace filters to the kinds of filter that they use in car industry to filter the intake of the cars AC-air. Here's a link to the kind of filter that I use (could not get the upload to work): http://images.biltema.com/PAXToImage...rge/2000030011 . I just seal the other end of the filter and plug the other end in my extractors inlet. These filters cost 12€ a piece and I have gained massive improvements on my HEPA filter clogging issue!

To take the prefiltering even further, I wrap the outer side of the tube shaped filter with approximately 2mm thick synthetic felt. The kind that are used in calligraphy art for something I'm told. The reason I'm using this kind of felt is because I have like 200 of those sheets laying around because of my fathers frame shop. This felt could be easily replaced with some other media. I wrap the felt around the car filter 2 times and secure it in place with rubber bands.

I'd post pictures of my setup, but for some reason I just get error messages when trying to upload them..

[Gale Smith]

Hi,
What is the construction of your original filtration system? Did you build it yourself? What is it made out of? Metal? Wood? Etc..
I'm needing a filtration box to remove odor because the neighbors are complaining. I have a good idea of what filters to use and what order they go in, but I don't know how to build the box.
Thanks!

[Dan Hintz]

Hi,
What is the construction of your original filtration system? Did you build it yourself? What is it made out of? Metal? Wood? Etc..
I'm needing a filtration box to remove odor because the neighbors are complaining. I have a good idea of what filters to use and what order they go in, but I don't know how to build the box.
Thanks!

Gale, see my one and only blog post on the subject (far right of my name)...

[Adam Swan]

Gale, see my one and only blog post on the subject (far right of my name)...

Thanks for the plans on the DIY fume extractor. I was thinking about building one, but I am concerned about the possibility of it catching fire if a spark ever passed through the exhaust. I currently vent outside, but I seem to blow all my conditioned air (hot or cold) right out of the shop. Makes for an expensive MN winter.

Any thoughts on the matter?

Thanks again,
Adam