Filtering systems for laser cutting

[Rony Nemi]

Hi everybody,

I have a laser cutting shop working 8hs a day cutting a lot of MDF, some acryllic and other materials.
Actually I have an exhaust that goes outdoors but I would like to change this using a filtration system that at least give me a chance to put an exhaust in the window avoiding a long 4" duct.

I read lot of nice ideas with pre filters, HEPA filters and activated charcoal but as I work with sticky fumes (such as the MDF fumes), I guess prefilters and HEPA filters will not live for a long time, so I think that it is not a good solution for my needings. I thought about a water bubbler, but I don´t know if putting the exhaust in a water tank could filter odors and particles...odors are my main concern. In the past I did some test but my 0,75HP blower has not power enough to put the tube in the bottom of the 200 liters tank.

And last...how much power would be better to develop any of those ideas (filtration system or water) keeping a good flow to work with the laser? (MDF generates lot of fumes).

Thanks for your help!! :)

[Chris DeGerolamo]

*Cue Dan Hintz*

There's a thread and blog showing a DIY filter system.

http://www.sawmillcreek.org/showthread.php?143725-DIY-air-filtration-unit-for-lt-200

[Rony Nemi]

*Cue Dan Hintz*

There's a thread and blog showing a DIY filter system.

http://www.sawmillcreek.org/showthread.php?143725-DIY-air-filtration-unit-for-lt-200

Thanks Chris,
I have seen it, but I think all those filters will be dead in few work hours of MDF fumes. Because of that I am thinking in other option for heavy fumes...
Besides that I don´t know how much power I need to work with that filters or the water tank...

[Joe Hillmann]

When filtering through water you need something to break the air up into tiny bubbles. You also need a blower that draws enough extra suction to make up for the depth of the water.

[Rony Nemi]

When filtering through water you need something to break the air up into tiny bubbles. You also need a blower that draws enough extra suction to make up for the depth of the water.

Hi Joe, thank you for yor reply. I thought to put a grid at the end of the exhaust to do some turbulence.
At this time I don´t know how much blowing power I´ll need to do this work. In the past I used my 0,75HP blower and could only put the tube less than 20cm depth in the water. The tank I have is near 40cm diameter and 80cm depth.
The othere doubt is if the air goes out alone or if it is mandatory to put another blower to take out the air from the tank...hope not!

[Dave Sheldrake]

I've spent thousands trying to find a cost effective long term way of trying to deal with MDF smoke and got basically nowhere. The best I managed so far was a high pressure atomised jet of very light detergent mix being cross fired across the air extraction stream then recycled when it dropped into the collector.

On my industrial machines I have a proper fume / particulate system to deal with it but I didn't really want to spend $22,000 on an extractor for each machine.

I've been told electrostatics may be a possible method but I've yet to investigate it.

cheers

Dave

[Dan Hintz]

A water filter is nice if you can get enough water surface area on the airstream... this means tiny bubbles, which means either a very fast airflow rate or a huge bubble area. Not feasible in an indoor unit at the flowrates we'll typically want. Unfortunately, electrostatic filters run into the same issues... you need a large surface area to slow down the airflow enough to actually catch particles (and you'll be cleaning the panels every hour). Though it is refreshable without cost, except time.

For heavy particulate matter, you have two options... eat the cost of the filter, or exhaust outside. You don't want the latter, so you're stuck with the former.

[Henri Sallinen]

I myself have struggled with sticky exhaust fumes and have destroyed a couple of HEPA-filters with because of this.

Currently the HEPA filters that I use cost around 130€ (with tax & shipping). I then send an email straight to a distributor in Hong Kong that made HEPA filters and got a quote that priced a single filter to 30€ (inc. shipping & tax + customs). The "downside" is that I'd have to order the minimum of 12 filters. Which isn't that many since they are so cheap. If you would be going through many filters because of the sticky fumes, they should be as cheap as possible. On top of that I am currently testing out that as a pre-filter you could use the same air filters that the car industry uses. They are cheap and when combined with a prefiltering mat etc. you might get the costs down a bit. The downside is that the mats have to be changed quite regularly so that the sticky smoke gets caught in the pre-filters as much as possible.

Hope this helps. Good luck!

[Dave Sheldrake]

For heavy particulate matter, you have two options... eat the cost of the filter, or exhaust outside. You don't want the latter, so you're stuck with the former.

Pretty much covers what I have found, it's one area of production that doesn't seem to have easy/cheap solutions. I had a case of HEPA filters from the Dyson series of cleaners, cleaned the air up great but each one lasted about 10 minutes. So far the fine mist does enough to reduce the bulk of the smoke but even so it doesn't remove it totally. I have a DanBin model for acrylic that works great it's just MDF that seems to be a problem.

cheers

Dave

[Rony Nemi]

A water filter is nice if you can get enough water surface area on the airstream... this means tiny bubbles, which means either a very fast airflow rate or a huge bubble area. Not feasible in an indoor unit at the flowrates we'll typically want. Unfortunately, electrostatic filters run into the same issues... you need a large surface area to slow down the airflow enough to actually catch particles (and you'll be cleaning the panels every hour). Though it is refreshable without cost, except time.

For heavy particulate matter, you have two options... eat the cost of the filter, or exhaust outside. You don't want the latter, so you're stuck with the former.


Thanks Henri, Dave and Dan!

Your comments and other information I am finding on the net show me that MDF or other sticky smoke are hard to "clean".
At this time I discard HEPA/activated carbon filters. Besides that in my country (at this moment) is hard to get parts and consumables from foreign countries.
I remain with the idea to try with a water bubbler and if it doesn´t work at all I´ll remain venting outdoors.

Regarding water, the tank I have to do testings is near 40 cm diameter and 80cm heigh. Anybody knows power needed to put the exhaust pipe at the bottom of the tank and to maintain the airflow acceptable to cut with the laser? My exhaust is a pvc 4" tube.

It could be great if I get a 60 or 70% better air to put the tank in open air in a garden...maybe the water helps?

Thanks! :)

[Joe Hillmann]

If you wanted to put the tube in the bottom of the tank you would need a blower that has suction rated at 35 inches of water. 28 inches just to deal with the depth of the tank and the other 7 inches is to keep the air moving through the laser. (blowers are rated in cfm and inches of water) I doubt you will find a blower that powerful at a reasonable price.

I don't think a tank that size will hold enough water to do much filtering.

Do a google search for "wood gasifier build" and see what they use for filters, they remove tar from an airstream so it is clean enough to run into an engine.

Why do you want to filter the air. Anything you do will be expensive or messy. And if you want to vent the air back inside the building how would you be sure you are getting the bad stuff out of the air. If you are running paying jobs 8 hours a day just add another few bucks an hour to what you charge to make up for your heating or air conditioning losses.

[Joe Hillmann]

If you want to clean up the air before venting it outside, you could run a vertical pipe, say 6 inches in diameter and 8 feet tall. The bottom of the pipe is capped off, the air from the laser come in about 12 inches from the bottom. On the top of the pipe mount a sprayer that is spraying a mist of water down the pipe. At the bottom of the pipe you could either have a drain or a pump that recirculates the water back up to the sprayer. That way when the air is pulled through the pipe the falling water will filter some of the smoke out of the air.

Of course by doing this you now have some tar filled water to git rid of and all you did was trade clean air for dirty water.

[Brian R Cain]

MDF and plywood can be very expensive on filters but it helps if you choose the correct pre-filter. I had a guy complain that his HEPA filter was blocked within a couple of weeks. It turned out that all he was using his machine almost exclusively for was cutting plywood. The standard pre-filter that comes with a filtration system uses F6 media. This captures particles larger than 1 micron then the smaller particles get captured by the HEPA filter. The issue he was having was that glue particles are smaller than 1 micron and ended up coating the surface of the HEPA filter so no air could get through. Changing to a pre-filter made with F8/F9 media captures the glue particles and extends the life of the HEPA filter enormously.

OK, you still have to replace filters but the pre-filters are a fraction of the cost of the HEPA filter.

[Rony Nemi]

If you want to clean up the air before venting it outside, you could run a vertical pipe, say 6 inches in diameter and 8 feet tall. The bottom of the pipe is capped off, the air from the laser come in about 12 inches from the bottom. On the top of the pipe mount a sprayer that is spraying a mist of water down the pipe. At the bottom of the pipe you could either have a drain or a pump that recirculates the water back up to the sprayer. That way when the air is pulled through the pipe the falling water will filter some of the smoke out of the air.

Of course by doing this you now have some tar filled water to git rid of and all you did was trade clean air for dirty water.

Joe,
The only reason I would like to vent "better air" is because I had in the past some complaints of some neighbours.
Now I need to rent other place for my shop (not for that reason) and my main concern is to select an industrial area or not...the industrial areas are not so accesible and "nice" to work...
If I could avoid the external vent I could select new places for my shop in better locations...

In the past when my problem were some neighbours, I have never get a good solution...the only thing I did was to put the exhaust pipe some meters away of those people direction...but when wind doesn´t help there is nothing to do...I must stop working with leather or some plastics cutting...

Readings all the comments I received, apparently I must try to find an industrial place and vent happily to the sky...

[Dan Hintz]

Readings all the comments I received, apparently I must try to find an industrial place and vent happily to the sky...

Well, you could go the electrostatic filter route. Put four of them in a square and run all of the air through them (or see what kind of restriction several in a row would create). That might be enough surface area to cut down on the amount of junk flying out of the pipe. They're really meant for a low airflow rate so they have time to charge the particles and let them get attracted to the plates, but with enough of them you might get lucky... don't know myself, you'd just have to try it and see. Electricity draw would be relatively minor.

[Dave Sheldrake]

If you want to clean up the air before venting it outside, you could run a vertical pipe, say 6 inches in diameter and 8 feet tall. The bottom of the pipe is capped off, the air from the laser come in about 12 inches from the bottom. On the top of the pipe mount a sprayer that is spraying a mist of water down the pipe. At the bottom of the pipe you could either have a drain or a pump that recirculates the water back up to the sprayer. That way when the air is pulled through the pipe the falling water will filter some of the smoke out of the air.

Of course by doing this you now have some tar filled water to git rid of and all you did was trade clean air for dirty water.

Pretty much what I did Joe, it works but is messy, it needed high water pressure to atomise the droplets to make it efficient and even then was far from perfect.

Afterburner filters also work well on sticky wood smoke but as was said, none of the good methods are cheap :(


Readings all the comments I received, apparently I must try to find an industrial place and vent happily to the sky...

pretty much so Rony, it's far easier so long as you don't have too many regulations on industrial discharges in your country.

cheers

Dave

[Larry Robinson]

If smell is your problem, perhaps you might consider injecting some type of fragrance in to the exhaust line to cover the odor. I experimented with this last year for cutting Baltic Birch. It work, however, it took a lot of the liquid solution I used. It was a very primitive setup to test and a lot of maintenance. Just have not taken the time to look for a different fragrance. Now I just check the wind direction and laser on the days where I know I will not get any complaints.

[Dan Hintz]

That would require a LOT of scent fluid, and without the proper makeup you'd end up with pine- or rose-scented burning wood ;)

[Rony Nemi]

pretty much so Rony, it's far easier so long as you don't have too many regulations on industrial discharges in your country.


As I have only one laser machine running, I think I could work without severe restrictions, so, apparently it would be the easy way...
But I still would like to test water in order to know what happen...:)
I´ll check with filtration systems using water...only to know options...but in accordance with lot of comments I´ll probably waste my time...


I am starting the high season in my country, so I guess I could only try near January...if I get the 1,5HP blower...

[Rony Nemi]

If smell is your problem, perhaps you might consider injecting some type of fragrance in to the exhaust line to cover the odor. I experimented with this last year for cutting Baltic Birch. It work, however, it took a lot of the liquid solution I used. It was a very primitive setup to test and a lot of maintenance. Just have not taken the time to look for a different fragrance. Now I just check the wind direction and laser on the days where I know I will not get any complaints.

Thanks for the idea Larry...
My friends gave me that idea as a joke...I never thought it could work! :)
When I have to cut some special materials (such as leather or some plastics) I use the same method...checking the wind...I love South East wind that keeps me working with all type of materials!