DIY Laser Fume Extraction System

[John Hutchinson]

Built a fume extraction system for my Trotec Speedy 400 120 Watt C02 Laser that is due to be delivered tomorrow. I am thinking the system may be redundant by using pairs of MERV 11 and MERV 16. It should easily meet the CFM and static pressure requirements as stated on the Trotec site prep document. What do you guys think?

I tested the system with a cigarette to see if I could get any traces of smell and there is zero scent being emitted from the charcoal canister. Not shown in the photos will be a 10 Gallon Oneida Dust Deputy that will be responsible for acting as my pre-filter to collect any large matter / particulates.

We have a ton of vector cutting ahead of us so I wanted to build a fairly robust system that can run for a while without needing filter replacement.

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Unrelated to the filter system... Can someone help me understand the attached snippet from my Trotec "Site Prep" document. I am scratching my head on this as to if the document is stating that the laser will have a power output range from 100 - 120 watts or if this document is intended for 100 watt and 120 watt systems. I paid for a 120 watt laser so I sure as hell am hoping this is what the laser is producing at the cut point since I am doing a lot of vector cutting with 1/4", 1/2" and hopefully 3/4" (not so much) ply. I visited a regional sales rep in LA County area and had him test his Trotec 80 watt setup on our 1/4" ply and it was crawling through the material leaving significant charring on the end grain - we need as much power as we can get to combat this and we can't afford a Kern unit yet.

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Cheers,

Hutch

[Glen Monaghan]

I'd be surprised if the hydroponics cannister was sufficient to remove the smells when cutting. I found that I needed a large bed of 8" deep charcoal to manage the smell of cut acrylic. What size is that fan, 8", 10", ??? Most hydroponic fans don't do well with filters, quickly losing CFMs as the static pressure goes up. In addition to 8" of activated charcoal, I also have two 4" deep whole-house filters (MERV 13) before the AC and a 4" deep HEPA filter after the AC. With all that, a 10" version of that fan was marginal for clearing the smoke from the laser quickly enough not to foul the lens when cutting baltic birch.

What are you doing to prevent air leaking through, between the filters and your box/frame/door? And do you have to remove 28 screws to take the door off every time you check/replace the filters?

[Rich Harman]

...had him test his Trotec 80 watt setup on our 1/4" ply and it was crawling through the material leaving significant charring on the end grain...

This is one thing I definitely dislike about mainstream lasers, they way they specify cutting speed in %. The speed of "crawling" could be anything. Without quantifying it, there is no way to know if it is normal. And even if you did specify the speed setting, it would not be useful for comparison. It could be that the speed was perfectly fine for the material (what was the material?) or it could be that the setup wasn't as good as it should be. I can tell you that I cut 1/4" lite ply at about 25mm/sec. Maybe I could cut faster but then I get jiggles where the laser head changes direction. Regular interior ply quite a bit slower, and marine ply slower yet. I don't remember the speed for those since I do them infrequently.

Also, while there is no argument that Trotec is a great machine, if vector cutting is all you are doing I would have seriously considered importing a Chinese machine (or a few of them) - hopefully you gave that option due consideration.

[John Hutchinson]

Great response Glen, thanks for your thoughts and consideration. An 8 inch bed of charcoal is significant. The hydroponic canister has roughly 25 lbs of activated carbon in it so only time will tell how long it effectively cleans the air but for now I feel confident it will work well for my application. I love buying tools so I look forward to getting an air flow meter to actually measure this data. Fortunately for us we have no intentions of cutting acrylic as we bought the machine purely for cutting wood and then engraving the decks with logos / after effects.

I have window gasket on the front and rear sections of each filter that are effectively sandwiched between the ply once the door is closed shut. I designed this cabinet to be 1/16th longer than the filters to accommodate this gasket and it works well. The rail sections offer zero clearance and have a slight bow (facing down) which sandwiches the filters so no air is to escape from the sides.

Glen, I would love to see your setup. Do you have a link to your build on this forum?

Rich,

I mean crawling in the sense that it was moving so slow that significant charring was occuring on the end grain to the point where you could scrape chuncks of black charcoal off the edges with your finger as opposed to a stronger laser doing the pass at a faster speed and using the laser to cut the material versus burn it's way through. We will be doing custom engravings on our decks so I wanted a machine that did this well.

I looked at a few Chinese machines and decided I didn't want to deal with them. I believe that you get what you pay for and that applies to not only the quality of the product but the quality of the support as well. Trotec units seem very well put together and the support seems top notch. Sure I could have saved $20+ thousand dollars but hopefully if this machine delivers as promised I should have no issues recouping my principle investment. And when the time comes that we can justify the expense for a Kern unit, this machine will sell like a hot cake compared to the Chinese variants.

[Glen Monaghan]

http://www.sawmillcreek.org/showthread.php?143725-DIY-air-filtration-unit-for-lt-200&p=2204306#post2204306
http://www.sawmillcreek.org/showthread.php?143725-DIY-air-filtration-unit-for-lt-200&p=2542909#post2542909

[John Hutchinson]

Nice, thanks for sharing these links. I would be suspect if those clamps provide enough tension on the door to create a complete seal? Even with the window gasket. I indeed plan on removing all of the screws when ever I need to access the inside of the box, it takes all of 2 minutes to do and I have the peace of mind that I have an air tight seal. You have to do a new tape job every time you need to replace a filter / change out the carbon I assume?

I think the biggest difference I see in our designs is the charcoal canister vs your charcoal trap setup. My charcoal canister has 25 - 30 lbs of activated carbon inside it and it's design maximizes surface area due to it's cylindrical shape. The increased surface area and sheer amount of activated carbon should be able to combat odors and fumes much more effectively as well as permit greater airflow due to less resistance through the membrane. This filter is rated at 970 CFM which is greater than the max setting of my exhaust fan... Air flow meter on the way!

[Scott A Evans]

Good Luck, I started out with DIY setup. MERV 11, 13 then 16 with hepa filtration and 8-10" of charcoal.(even tried charcoal mat ...Baltic birch ply killed me on Filter changes and cutting acrylic I needed a lot more CFM that was being restricted by the setup.....finally just dumped outside and eliminated the filtration. the carbon did good job on odors but I could tell it wasn't going to keep up with non stop speedy 300 use as I had to change it out after a short order.

Is that Trotec spec a general spec for the different wattages....it should arrive with the wattage you ordered or more. Either have the tech test it or buy a Mahoney tester so you can periodically test it.

[Glen Monaghan]

I've only had to change the carbon once in the last six months. I pulled the tape from the edges, removed the trays, replaced the granules, reinserted the trays, and put the tape back in place (which might take 10 seconds per strip?), so I'm pretty happy with that arrangement. With the 3 clamps on each long side of the door, it compresses the gasket all around and seals perfectly. It only takes about 10-15 seconds to pop the clamps and pull the door when you want to inspect/replace filters, which is handy if you don't have any sort of gauge or meter to determine when they need replacing. Even so, I purchased half a dozen manometers and, once I move into the new office/shop space, I'm going to install one across each filter and the fan to make it easier to monitor degrading performance over time and determine when to change which filter (especially the carbon and HEPA ones), as well as to objectively compare a couple of different fans in the system.

[John Hutchinson]

The manometer is a great idea. I may have to steal this idea off you!

[Robert Tepper]

I splurged and purchased the Atmos system. It works exceptionally well. I do a lot of vector cutting as well as raster engraving. One filter lasts about 2 months and they run $335.00 each. A little pricey but worth the investment.

Robert

[John Hutchinson]

I splurged and purchased the Atmos system. It works exceptionally well. I do a lot of vector cutting as well as raster engraving. One filter lasts about 2 months and they run $335.00 each. A little pricey but worth the investment.

Robert

That is awesome. Like anything Trotec that Atmos system was an impressive unit. We spent a solid 35 minutes cutting material in a relatively small space with the unit venting into that area and never once did I get even the slightest wiff of anything burning. I believe you get what you pay for hence why we decided to go the Trotec route. The machine purchase was already way more than our ideal proposed budget so we couldn't even consider getting the exhaust system at this point, maybe down the line if this custom application does not suffice.

Robert, are you using any type of catch can inline with your system before it reaches your filters? If not, take a look at the Oenida Dust Deputy. I have one rigged up in our system and am hoping it will prove to extend the life of the filters.

My business partner who flys f18's for the Navy (VFA 113) is coming down to San Diego to see the setup this weekend and catch up with some guys from other squadrons. He hasn't seen the machine yet and will be bringing over the rest of the gang to check it out. Brisket, beers and vector cutting our components... cant wait!

[Glen Monaghan]

[...]who flys f18's for the Navy[...]
We won't hold either of those facts against him... ;^)

[John Hutchinson]

We won't hold either of those facts against him... ;^)

What is funny is that our working partnership started over a "free" craigslist ad. Having the privilege to work with a guy of this caliber is hard to put in words honestly. Thought I would share a few photos he shared with me from when they took part of a large Naval operation called "Valiant Shield". My dream was always to be a fighter pilot so getting to work along side one is the next best thing. For building surfboards, it does not hurt that before he started flying he was an aerospace engineer.

He is actually designing a venturi scrubber / cyclonic collection system that will hopefully replace our current air filtration system. I'll be sure to share that when we have a functional prototype.

Photos below, pretty cool stuff!

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[Glen Monaghan]

I finally got around to installing manometers on my filter unit. Put one across each: HEPA, carbon, prefilter; and one from free air to the top of the prefilter to see how much restriction is in the laser and ductwork to the filter unit. Add up all four and you get the restriction of the entire system (alternatively, it's the SP seen by the fan). I figured the HEPA would have the most or second most significant restriction, but the 8" of carbon was far, far more. In fact, the restriction across the carbon was 3.3" while the restriction across the HEPA was not quite 0.1"!! I couldn't even measure the restriction across the prefilter (a 4" thick MERV 13 whole house filter) until I tilted the manometer 45 degrees, and then I could see about 0.05" change. The filters are old, purposely left in place longer than normal so I could get "worst case" readings before putting in new ones (which I haven't done yet, but it looks like I need to rethink how to detect clogging on the prefilter and HEPA, at minimum).

[Henri Sallinen]

A tip for the filters: Have a own filter setup for every material you use. We've found out our filters last so much longer when you don't mix different materials with each other. Some gasses are more sticky than others and if you add dry fumes with sticky fumes, you'll clog up the filter real fast.

If you only cut "sticky fume" materials with their own filter and "dry fumes" with their own, they will last a whole lot longer!

[Raphael Weil]

A tip for the filters: Have a own filter setup for every material you use. We've found out our filters last so much longer when you don't mix different materials with each other. Some gasses are more sticky than others and if you add dry fumes with sticky fumes, you'll clog up the filter real fast.

If you only cut "sticky fume" materials with their own filter and "dry fumes" with their own, they will last a whole lot longer!

That's quite interesting.

I discovered the Merv 13's end up being my biggest bottle neck because they clog fast. I tried protecting my carbon shelves with their own dedicated Merv 13's, and it was just too hard on the airflow. My setup's problem is keeping things airtight within my cabinet. Still haven't totally solved that, so my prefilter isn't prefiltering everything. I'm now pretty eager for winter for once, where I can be a lot more lax about how much of my fumes make it outside. Here in Canada the smell of burning hardwood in the winter isn't a big problem :)