DIY Carbon Filter Fume Extraction Solutions

[quy.ngo]

2 Stage Filter
http://www.sawmillcreek.org/showthread.php?143725-DIY-air-filtration-unit-for-lt-200&p=1461106

 

 

3 Stage Filter

http://4volt.com/Blog/archive/2009/06/09/diy-3-stage-air-filter.aspx

4 Stage Filter

https://www.synthetos.com/diy-laser-fume-extractor-part-1/

[Steve Baker]

I'd love for this to work well for us...but I'm deeply skeptical.

I wonder how fast it gets clogged and whether it will absorb the smell of
cutting ABS?

Do we know what kind of laser cutter he's using? It makes a big difference.

He said it worked well for an hour etching 1/32" into maple - but that's
really not much information to go on. If you're using a 20 watt "hobby"
laser at 500m/min to do it then you won't be generating much smoke in the
first place.

But if you're cutting 1/4" plywood for an hour at 2000mm/min with a 120
watt lasersaur then you're removing thirty times as much material per
minute - so there would be around thirty times as much smoke...right?
That's the difference between it working or not - and between changing the
charcoal and cleaning the HEPA filter once a month and having to do it
every day!

Plus, with plywood there is the gunk generated from lasering the glue
layers that produces who-knows-what toxins. Burning wood also generates
carbon monoxide...which no amount of filtering is going to remove - and
which you really don't want in your workship. (Ever try putting a
carbon-monoxide detector in the outflow from your laser cutter?)

I also wonder whether it obstructs the airflow too much. You really need
to pull the smoke away from the laser path super-fast - and in our case
when the laser path could be 6 feet long - that's *way* more important
than with one of those tiny 12"x18" bed machines.

-- Steve

quy.ngo wrote:
> 2 Stage Filter
> http://www.sawmillcreek.org/showthread.php?143725-DIY-air-filtration-unit-for-lt-200&p=1461106
>

> <https://lh3.googleusercontent.com/-DVvwrGe3VDc/Ue5J_9uNG4I/AAAAAAAAI6g/fuBRQjvK9GM/s1600/Filter+HEPA.jpg>
> <https://lh6.googleusercontent.com/--MkcVz79_Gk/Ue5KEdVCG3I/AAAAAAAAI6o/MBxfTGew5Aw/s1600/Filter+outside.jpg>
>
> <https://lh3.googleusercontent.com/-b5Qh4MIXZXY/Ue5KI1Fl9SI/AAAAAAAAI6w/09Sxej_JxM4/s1600/Filter+inside.jpg>
> <https://lh5.googleusercontent.com/-RmXLrs8t4Nk/Ue5J5wYzukI/AAAAAAAAI6Y/mikmNZ-xdkk/s1600/Filter+furnace.jpg>

>
> 3 Stage Filter
> http://4volt.com/Blog/archive/2009/06/09/diy-3-stage-air-filter.aspx
>
> 4 Stage Filter
> https://www.synthetos.com/diy-laser-fume-extractor-part-1/
>

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-- Steve

[Dave Hrynkiw]

On 7/23/2013 3:21 AM, quy.ngo wrote:

4 Stage Filter

https://www.synthetos.com/diy-laser-fume-extractor-part-1/

I built one much like this last one. Construction images start here:
http://www.flickr.com/photos/solarbotics/8007526102/in/photostream/

Here's some post-usage filter images, starting here: http://www.flickr.com/photos/solarbotics/9019987304/in/set-72157623161564454/

Was surprised how thick the pre-filter stage got. Going to have to step up replacement to every 2 or 3 months.

Regards,
Dave

[quy.ngo]

I think he's got a Universal VersaLaser VLS4.60 which has a bed size of 24"x18". Price tag should be over $20k with taxes.

Your comment gave me a good laugh. No filtering system is going to work for your particular application where you are doing full bed lasering for hours at a time. 

A Trotec rep once told me a story about a University that had to change filters every week because the amount of wood they were cutting. I was told that if you're cutting a lot of wood it's best to vent it outside. 

I don't have a Lasersaur so I can only imagine the amount of smoke you're producing with your machine. I'm guessing the gunk doesn't affect the exhaust fan much if you've been running it for 2000+ hours.

[quy.ngo]

Pretty sweet looking unit and it's good to know that you'll need a bigger exhaust unit if you plan to use a filtering system.

[Steve Baker]

quy.ngo wrote:

> I think he's got a Universal VersaLaser VLS4.60 which has a bed size of
> 24"x18". Price tag should be over $20k with taxes.

Nice...but half the power of most lasersaurs - so probably significantly
less than half the volume of smoke - and a much lower airflow demands
because the beam path is only half as long.

> Your comment gave me a good laugh. No filtering system is going to work
> for your particular application where you are doing full bed lasering
> for hours at a time.

Well, that's what I thought. Since this *is* the "Lasersaur" mailing list
where people have larger/high-powered laser cutters - I felt it was worth
being a little skeptical of the value of that blog to the readership here.

We certainly vent outdoors without much filtering (but we don't cut
plastic). We have a 700 cfm "pancake" fan - which certainly does the job.

Getting good airflow has a dramatic effect on laser power when the laser
path is at it's longest - so I'm fairly fanatical about keeping the
airflow ducting as straight as possible - to the extent that I'm building
our second lasersaur as a mirror-image of the standard design in order to
keep my venting paths as short and simple as possible.

> A Trotec rep once told me a story about a University that had to change
> filters every week because the amount of wood they were cutting. I was
> told that if you're cutting a lot of wood it's best to vent it outside.

That's what I thought. When you think about it - with the kerf being
about a third of a millimeter wide and 5mm deep - and at 2000 mm/min,
you're making about 3 cubic centimeters of plywood "disappear" every
minute. Admittedly a lot of that will turn into CO, CO2 and water - but
there has to be a good chunk of that mass that's coming off as smoke - I'm
not sure what fraction of the total...but let's say it's a third. If the
filter is trapping most of it, you're probably getting around 1cc/minute
of more or less solid carbon being deposited on the filter.

(Wow! Over 2000 hours of operation, I've turned about a third of a cubic
meter of wood into smoke and exhaust gasses!)

> I don't have a Lasersaur so I can only imagine the amount of smoke you're
> producing with your machine. I'm guessing the gunk doesn't affect the
> exhaust fan much if you've been running it for 2000+ hours.

We clean the exhaust fan blades about once every couple of months because
they get pretty heavily coated with "gunk". Our original 400 cfm fan
lasted well over 2000 hours without a glitch. When we moved to a new
workshop and decided to add the second lasersaur, I needed to rebuild the
vent system and we decided to "retire" the 400 cfm fan and buy a couple of
the 700 cfm variety - one for each lasersaur. The improvement in smoke
clearance is really noticable and the machine stays cleaner for longer.

The additional volume of air as we went from 400 cfm to 700 cfm seems to
disperse the exhaust smoke better after it leaves the building - and aside
from a faint, unobjectionable barbeque-like smell right up close to the
building - you can't really tell that we're there.

-- Steve

[quy.ngo]

The value in these DIY solutions goes beyond whether the end user has a small or large bed size. 

The solarbotics video, on flickr, best illustrates why you'd want to build one of these units. For Dave (Solarbotics) it was about respecting your neighbours and any possible by-laws/regulations in the area. Some of the posts here have been about smells/fumes as a result of operating a laser cnc in a residential area. While fume extraction/filtering, in some use cases, may not resolve the issues of smells completely. It may be enough to keep you under the radar of some investigative neighbours who have the cops on speed dial.

The appeal to me was how it is inline with the Lasersaur design philosophy of "demystifying" technology to the end user. Enabling the user to understand how it works and empower them to maintain the unit themselves. The cost factor is also important to point out as you won't be vendor locked in where you have to buy a specific brand of filters or fans. Scalability, you can build it big or small to best suit your application. 

[Steve Baker]

quy.ngo wrote:

> The value in these DIY solutions goes beyond whether the end user has a
> small or large bed size.

Sure. In general, any kind of development that increases our level of
understanding is very useful - even if it's not directly applicable here.

> The solarbotics video, on flickr, best illustrates why you'd want to build
> one of these units. For Dave (Solarbotics) it was about respecting your
> neighbours and any possible by-laws/regulations in the area. Some of the
> posts here have been about smells/fumes as a result of operating a laser
> cnc in a residential area. While fume extraction/filtering, in some use
> cases, may not resolve the issues of smells completely. It may be enough
> to keep you under the radar of some investigative neighbours who have the
> cops on speed dial.

I completely understand that desire. We initially ran our (unfiltered)
lasersaur from the spare bedroom of a 2nd floor apartment!

People just need to be aware that this kind of filtering approach may not
be useful for larger machines like ours when they are used at the limits
of their capabilities.

It's not that it might maybe only somewhat reduce emissions...I agree that
in some cases, reducing emissions without completely eliminating them is a
valuable thing.

My concern is that it might maybe impede the airflow enough to make the
lasersaur dramatically less effective and might maybe wreck expensive
lenses and mirrors long before they'd normally need to be replaced. Just
one lens costs more than that entire filter box!

It might also be that at our higher cut speeds, the filter would clog up
so fast as to be effectively unusable at the normal range of the
lasersaur's capability.

You can't sugar-coat that with "Well, it might help" and blindly assume
that this thing is useful to us. We need to think rather carefully
through all of the issues so that people can choose whether they should
spend the resources to build one.

It seems to me that building one in a much larger container might well
work here. A larger filter area would take longer to clog up and would
impede the airflow far less...but the cylindrical hepa filter doesn't
scale well...so I'm not sure.

> The appeal to me was how it is inline with the Lasersaur design philosophy
> of "demystifying" technology to the end user. Enabling the user to
> understand how it works and empower them to maintain the unit themselves.
> The cost factor is also important to point out as you won't be vendor
> locked in where you have to buy a specific brand of filters or fans.
> Scalability, you can build it big or small to best suit your application.

Sure, it's a great approach to solving the problem for smaller machines.
No doubt about that.

It's classic "Maker-mentality" engineering...which is A Good Thing!

[Stefan Hechenberger]

We definitely want to have an open source design for the exhaust system.

The approach we take is to filter as well as you can and evacuate to the
outside. Indoor filtering is just not practically feasible, I think. Any
commercial indoor systems I had to do with didn't really work well
enough for my taste. It's may be doable for some materials but the
system would probably be huge if done well.

The main obstacle with creating a reference design is suppliers for
filters. The system has to be designed around filters that are available
and cheap.

Didn't you can just get activated carbon in a bag and poor it into
filter trays. that's good to know. I wonder how well a system would work
that is mostly a couple of trays activated carbon. That would be very
simple to design universally.

Maybe we can also find filter material and build z-filters ourselves.

Keep on sharing,

--
Stefan Hechenberger
studio: Nortd Labs - labs.nortd.com
work: Institut f�r Experimentelle Architektur, UIBK
resident: F.A.T. Lab - fffff.at
project: Lasersaur - labs.nortd.com/lasersaur

[Steve Baker]

My biggest concern with indoor filtering is the amount of carbon monoxide
build-up you'd get. Neither activated chacoal nor a hepa filter will
remove that...you'd need something like the palladium catalyst in a car
exhaust or a material called "Hopcalite" to remove it.

-- Steve

Stefan Hechenberger wrote:
>
> We definitely want to have an open source design for the exhaust system.
>
> The approach we take is to filter as well as you can and evacuate to the
> outside. Indoor filtering is just not practically feasible, I think. Any
> commercial indoor systems I had to do with didn't really work well
> enough for my taste. It's may be doable for some materials but the
> system would probably be huge if done well.
>
> The main obstacle with creating a reference design is suppliers for
> filters. The system has to be designed around filters that are available
> and cheap.
>
> Didn't you can just get activated carbon in a bag and poor it into
> filter trays. that's good to know. I wonder how well a system would work
> that is mostly a couple of trays activated carbon. That would be very
> simple to design universally.
>
> Maybe we can also find filter material and build z-filters ourselves.
>
> Keep on sharing,
>
> --
> Stefan Hechenberger
> studio: Nortd Labs - labs.nortd.com

> work: Institut für Experimentelle Architektur, UIBK