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View Full Version : Can't get 100% of smoke/smell to exhaust out



Todd Mueller
05-15-2016, 12:07 AM
i have a 600mmx400mm chinese laser cutter, with a lid

I cant keep all the smell going out, I have both a 273 cu feet a minute squirrel/furnace style fan and the fan that came with it which is similar style just a little smaller, and both of them running together and it still doesnt seem to be enough, which I absolutely cant have.
I have tried opening the top which visibly makes it look like all the smoke is rushing out,
keeping it half open,
putting tape around the seems of most of the doors,
taping the vents that are factory cut into the door and removing a long thin rectangular panel right below the top cover/door to try and draw air from a little below the table and keep smoke from being right by the vents in the door/top.
both fans have their own 4" duct that I mounted to a board in a window in that room and then closed the window against it and taped around the edge.

any tips, I have seen people online with a laser cutter in their office room in a house, and surely they are getting all of the smoke/smell out?

Tony Lenkic
05-15-2016, 10:40 AM
Todd,

Smoke and debris is what blower must remove. Smell is another matter.
Once you cut your substrate the pieces are still in laser cabinet that will produce smell for extended period and if left indoor you will produce that smell.
If you have place to remove end store them out of working area you will minimize lingering smell.

Note: Do not mask cabinet openings as they serve the purpose (intake air) .

Scott Marquez
05-15-2016, 10:49 AM
I would suggest opening a window on the other side of the room for new air to come in, which will allow your fans to work their best.
I vent my exhaust out the window in a similar fashion as you have described, you will also need to fill the small gap between the window panes that you created when you opened the window. I have a long slender piece of foam that I use to seal the gap.
Let me know if doing both of those things helps.
thanks, Scott

Al Launier
05-15-2016, 11:00 AM
You might consider this http://shop.naturalmagic.com/All-Products/Odor-Absorbers/Natural-Magic-Odor-Absorbing-Gel-Brushed-Cotton-14. I don't have a laser cutter, but have found this product to effectively absorb/eliminate odors from painting, etc. I prefer the "Brushed Cotton" as it leaves a nice clean scent, not perfumey. For more severe odors I use it in conjunction with an air filtration system to help remove "scented" air particles.

Bill George
05-15-2016, 12:52 PM
The smoke smell is telling you your system is not working. To remove air you need to bring in air in the front of the cabinet, and then out the rear port to a sealed opening in a outside wall or window. If the outside wall or window is not sealed you may get smell back inside. . Or you may have a negative in the room caused by another exhaust system running. If you put a lighted candle inside the cabinet with your exhaust fan on and close the lid the flame should bend toward the exhaust slot or port..

Todd Mueller
05-15-2016, 4:17 PM
Todd,

Smoke and debris is what blower must remove. Smell is another matter.
Once you cut your substrate the pieces are still in laser cabinet that will produce smell for extended period and if left indoor you will produce that smell.
If you have place to remove end store them out of working area you will minimize lingering smell.

Note: Do not mask cabinet openings as they serve the purpose (intake air) .

I have masked just some of the seems of doors on the sides of the cabinet as a test, there are many. But while i do this I am finding leaving the top/hood door open or cracked helps a ton, you can visually see the smoke rushing back and downward. i believe though that when the machine is making cuts near the very front of the machine, nearest the door, is when probably little bits are escaping. I have just under 500 cu ft/min of air, and am starting to think that somewhere around 800 cu ft/min would be much better. Could help to clear the front edge while cutting better

Todd Mueller
05-15-2016, 4:20 PM
I would suggest opening a window on the other side of the room for new air to come in, which will allow your fans to work their best.
I vent my exhaust out the window in a similar fashion as you have described, you will also need to fill the small gap between the window panes that you created when you opened the window. I have a long slender piece of foam that I use to seal the gap.
Let me know if doing both of those things helps.
thanks, Scott

I have actually worked with this today. this is in an unfinished basement, and the room with the laser is on the opposite side of the basement from a walkout slider door. i have opened the slider door and then also taped around the board and the area where the two windows meet but are partially open, effectively sealing all of the areas around the window, it has helped a ton, so i dont believe anything is coming in through the window area, during this time i also shut off the furnace/blower for the house so that nothing from that system was pulling anywhere... just one slider door open and the two exhaust hoses going out the board in the window.

the room still gets smelly, a fair amount, and just really am starting to think i need more like 800 cu feet/min of fan power

Todd Mueller
05-15-2016, 4:24 PM
The smoke smell is telling you your system is not working. To remove air you need to bring in air in the front of the cabinet, and then out the rear port to a sealed opening in a outside wall or window. If the outside wall or window is not sealed you may get smell back inside. . Or you may have a negative in the room caused by another exhaust system running. If you put a lighted candle inside the cabinet with your exhaust fan on and close the lid the flame should bend toward the exhaust slot or port..

yes, i havent put a candle in the machine but no doubt the flame would get pulled back, when i watch the thing, it appears that all of the smoke is quickly rushing down and back, but the smell is still there, i do understand about the residual smell, but that is not what im talking about, the smell increases pretty drastically while cutting. I suspect the smoke/smell is escaping from the top/hood and mostly only when cutting near the front.

Todd Mueller
05-15-2016, 4:31 PM
Lots of great tips/advice so far, here is what i am thinking for my next test since I am so bent on thinking the smell only escapes during cutting near the front of the machine

i will program some cuts that only happen near the rear, and see if the smell enters the room, that would at least confirm whether or not my theory is right, if it stays smelling clean, then i will know that i have no leaks from the exhaust or around the window area, which I really don't think that i do but anything is possible.

If i find that it works perfect for rear cuts but not for front cuts, it would seem to me that i probably near more exhaust power

any thoughts on this approach?

David Somers
05-15-2016, 4:47 PM
Todd,

An additional thought. Is your blower near the start of the hose/pip run pushing the air out through a length of hose that is in your room? Or is it at the far end of the run of hose/pipe pulling the air through that length? If you are pushing you are probably pushing air out through all the seams and imperfections in the hose/pipe. If you are pulling it you will have negative pressure in all those lengths and reduce the amount of seepage into the room. I rarely have problems with odors in my garage until i actually open the laser. My blower is outside of the room pulling air for all but about 2 feet of length of hose. It works very well.

Keith Winter
05-15-2016, 5:14 PM
That's not enough cfm. Chinese machines sold as a set tend to under power their chillers and exhaust fans. Do yourself a favor and buy a $100 Hf dust collector. Toss the bags and use it as your exhaust fan instead. Cheap solution and will help the issue dramatically. Also seal seams/Windows near the exhaust point outside. Seal all joints alomg your duct work with metal duct tape. Make sure you have no big kinks in your duct lines.

After all that is done. As others have said many materials produce a smell after being cut. All you can do is store them outside or elsewhere for a few days if the smell bothers you. One thing to consider if the smell bothers you, how close are your neighbors, and will smell coming out of your house bother them? What material in particular are you cutting that the smell is bothersome?


i have a 600mmx400mm chinese laser cutter, with a lid

I cant keep all the smell going out, I have both a 273 cu feet a minute squirrel/furnace style fan and the fan that came with it which is similar style just a little smaller, and both of them running together and it still doesnt seem to be enough, which I absolutely cant have.
I have tried opening the top which visibly makes it look like all the smoke is rushing out,
keeping it half open,
putting tape around the seems of most of the doors,
taping the vents that are factory cut into the door and removing a long thin rectangular panel right below the top cover/door to try and draw air from a little below the table and keep smoke from being right by the vents in the door/top.
both fans have their own 4" duct that I mounted to a board in a window in that room and then closed the window against it and taped around the edge.

any tips, I have seen people online with a laser cutter in their office room in a house, and surely they are getting all of the smoke/smell out?

Todd Mueller
05-15-2016, 10:06 PM
Todd,

An additional thought. Is your blower near the start of the hose/pip run pushing the air out through a length of hose that is in your room? Or is it at the far end of the run of hose/pipe pulling the air through that length? If you are pushing you are probably pushing air out through all the seams and imperfections in the hose/pipe. If you are pulling it you will have negative pressure in all those lengths and reduce the amount of seepage into the room. I rarely have problems with odors in my garage until i actually open the laser. My blower is outside of the room pulling air for all but about 2 feet of length of hose. It works very well.

the fans are at the far end of the hoses not at the machine end, they are literally mounted on the board that sits in the window, so they pull air the whole run, no pushing at all.

David Somers
05-15-2016, 10:14 PM
Thanks Todd! In that case I agree with others, you are likely not getting enough CFM. Keith mentioned the Hf dust collector a few messages above? By Hf he means Harbor Freight. Just FYI.

Todd Mueller
05-15-2016, 10:35 PM
That's not enough cfm. Chinese machines sold as a set tend to under power their chillers and exhaust fans. Do yourself a favor and buy a $100 Hf dust collector. Toss the bags and use it as your exhaust fan instead. Cheap solution and will help the issue dramatically. Also seal seams/Windows near the exhaust point outside. Seal all joints alomg your duct work with metal duct tape. Make sure you have no big kinks in your duct lines.

After all that is done. As others have said many materials produce a smell after being cut. All you can do is store them outside or elsewhere for a few days if the smell bothers you. One thing to consider if the smell bothers you, how close are your neighbors, and will smell coming out of your house bother them? What material in particular are you cutting that the smell is bothersome?

Great tip on fans, i just looked at harbor freights website and they have 2, for $149 which is 660 cfm, and one for $229 which is 1550 cfm,
I have 2 fans right now, and would guess i have somewhere between 425 cfm and 500 cfm max. The one fan i have been thinking about, if I determine that is the best route is this one
http://www.amazon.com/Dayton-Model-1TDT8-Blower-2-speed/dp/B000TK3ZM6/ref=sr_1_18?ie=UTF8&qid=1463365772&sr=8-18&keywords=dayton+blower
Daytons are great fans, and this one is a 2 speed with the max speed handling 800 cfm for $208.00, which to me if i used 6" exhaust seems like it would handle anything i threw at it, but not sure. that one from harbor freight that does 1550 cfm would be a ton of air movement but I am thinking about if that might be overkill and also the amount of conditioned air it would remove from the house, but whatever the case i need to make sure all of the smell/odors are removed, whatever the solution... I would use short straight pipe 6" exhaust tube with whatever option i chose to go with.

Keith Winter
05-15-2016, 11:07 PM
Elaborate on the you have two fans comment. Do you have two lasers or what is the other hooked up to?


Great tip on fans, i just looked at harbor freights website and they have 2, for $149 which is 660 cfm, and one for $229 which is 1550 cfm,
I have 2 fans right now, and would guess i have somewhere between 425 cfm and 500 cfm max. The one fan i have been thinking about, if I determine that is the best route is this one
http://www.amazon.com/Dayton-Model-1TDT8-Blower-2-speed/dp/B000TK3ZM6/ref=sr_1_18?ie=UTF8&qid=1463365772&sr=8-18&keywords=dayton+blower
Daytons are great fans, and this one is a 2 speed with the max speed handling 800 cfm for $208.00, which to me if i used 6" exhaust seems like it would handle anything i threw at it, but not sure. that one from harbor freight that does 1550 cfm would be a ton of air movement but I am thinking about if that might be overkill and also the amount of conditioned air it would remove from the house, but whatever the case i need to make sure all of the smell/odors are removed, whatever the solution... I would use short straight pipe 6" exhaust tube with whatever option i chose to go with.

Kev Williams
05-15-2016, 11:32 PM
I can't quite tell from from what I've read, so I'll ask--

Are the blowers outside, or inside?

Because if they're INside whatsoever, you will have positive pressure inside the room, which will push smoke and smell into the room. No matter how well you think the blower or your vent piping is sealed, positive pressure from the blower will find a way out, thru the vent or the blower housing itself...

The only sure fix is to have the blower OUTSIDE. This way, ALL of the moving air within the vent tubing will be in a negative pressure/vacuum condition until it reaches the blower outside. Any leaks in the plumbing will draw room air INTO the vent, not push smoke OUT...

Todd Mueller
05-16-2016, 8:50 AM
I can't quite tell from from what I've read, so I'll ask--

Are the blowers outside, or inside?

Because if they're INside whatsoever, you will have positive pressure inside the room, which will push smoke and smell into the room. No matter how well you think the blower or your vent piping is sealed, positive pressure from the blower will find a way out, thru the vent or the blower housing itself...

The only sure fix is to have the blower OUTSIDE. This way, ALL of the moving air within the vent tubing will be in a negative pressure/vacuum condition until it reaches the blower outside. Any leaks in the plumbing will draw room air INTO the vent, not push smoke OUT...

They are inside mounted directly to the board that have fixed into the window. I had never read anything about this yet. Keeping the fan outside in the elements and weathe proof could be a challenge from moisture, rusting, rain etc. How do most people handle this. It does make sense what you said. I'm sure it could find some small space somewhere to leak out

Todd Mueller
05-16-2016, 8:53 AM
Elaborate on the you have two fans comment. Do you have two lasers or what is the other hooked up to?

There are two 4 inch exhaust ports on my machine. One goes to a kind of enclosed area that sucks from the underside of my cutting area, the other is below that one and sucks from the main lower cabinet area. Both on the backside of machine and both are factory installed ports

Bill George
05-16-2016, 9:42 AM
There are two 4 inch exhaust ports on my machine. One goes to a kind of enclosed area that sucks from the underside of my cutting area, the other is below that one and sucks from the main lower cabinet area. Both on the backside of machine and both are factory installed ports

They both need to be on the same fan. Your blower is mounted correctly. Its inside out of the weather most or nearly all of the pipe is on the negative side of the fan and the exhaust goes directly to the outside.

Lee DeRaud
05-16-2016, 11:46 AM
The suggestions regarding using the HF dust-collector are probably the best.

One further consideration: is the smell only while you're actually cutting, or does it linger for some time afterward? I've noticed the room where my machine is located smells smoky for awhile after cutting MDF, but the smell is only noticeable after the fan is shut off. Eventually figured out it was from residue on the honeycomb cutting bed...not much the fans can do about that.

Lee DeRaud
05-16-2016, 11:48 AM
Your blower is mounted correctly. Its inside out of the weather most or nearly all of the pipe is on the negative side of the fan and the exhaust goes directly to the outside.What he said. They call them "blowers", but they're much more efficient as "suckers".

Todd Mueller
05-16-2016, 12:57 PM
The suggestions regarding using the HF dust-collector are probably the best.

One further consideration: is the smell only while you're actually cutting, or does it linger for some time afterward? I've noticed the room where my machine is located smells smoky for awhile after cutting MDF, but the smell is only noticeable after the fan is shut off. Eventually figured out it was from residue on the honeycomb cutting bed...not much the fans can do about that.

It increases while cutting so it's getting out. And yes it lingers afterwards too. I am ordering the big harbor freight dust collector today. 1550 cu feet per minute. I can't imagine anything escaping that power?

Bill George
05-16-2016, 1:30 PM
Way over kill, but the picture shows two 4 inch intakes.

Keith Winter
05-16-2016, 1:33 PM
It increases while cutting so it's getting out. And yes it lingers afterwards too. I am ordering the big harbor freight dust collector today. 1550 cu feet per minute. I can't imagine anything escaping that power?

Two different blowers pulling different amounts at different speeds...not good. Upgrading to a single more powerful blower will make a difference, you will like the bigger one fine. As for the lingering what are you cutting again that is smelling?

Keith Winter
05-16-2016, 1:37 PM
Way over kill, and I am assuming the big one is 220 volts?

A little overkill yes, he could make do with the smaller I would think, his two 4" ports though is a strange setup. I haven't seen two 4" ports before in such a small laser, he might need more power than the small HF just from the standpoint of him having to divide the output into two 4" ports. I think the output off the small HF is only one 4" port, and the output off the bigger HF is a 5" port.

Kev Williams
05-16-2016, 2:19 PM
About the HF 'green' -- or 'gray' blowers these days-- I've had 2 of them in my basement stairwell, once since 2002, the other since 2004. The 2004 model was literally out in the weather, on it's side, intake up, motor down, been rained and snowed on 24-7-365. I just barely replaced it maybe 6 weeks ago, because one of the motor bearings started seizing up and was tripping my power strip. The 2002 model had a bearing start to get noisy about a week later. '. It still works just fine, but the noise carries at night.

That's the longevity story, 14 and 12 years old, outside the whole time, one for at least 10 years in direct weather exposure. Not bad for a Chinese blower...

Now for the smell story-

The 2004 model, before it went outside, was inside right behind my LS900. No matter what I did, I could NOT keep the basement smoke and odor free. No amount of new hose, duct tape or clamps helped. Once I moved it outside, voila, my basement has been completely devoid of smoke & smells ever since. I've lasered leather in the ULS and deer horns in the LS900 at the same time, two of the worst smelling things you can burn. While you can smell faint odor from the machines while engraving, and for a minute or so afterward, you can stand 2' from either running machine and you can't tell they're lasering ANYthing.

However- in the garage is another HF blower, connected to my Triumph and GCC, which I've sealed up as best as I possibly can. From the output I'm running a 4" to 6" adapter and 6" plumbing out a window, about 6' worth. It's duct taped from Hades to breakfast, but it doesn't matter. If I engrave wood or leather in either garage machine, the garage smells for hours afterwards.

It's simply because the blower housing is under pressure and isn't perfectly sealed. There's no visible smoke, but plenty of smell.

The only reason THAT blower isn't outside is because I need to build a box for it to keep it quiet as it's much closer to neighbors than the other blowers. Just haven't found time, so I put up with the smells...

Gary Hair
05-16-2016, 2:42 PM
It's simply because the blower housing is under pressure and isn't perfectly sealed. There's no visible smoke, but plenty of smell.

And no matter how hard you try to seal it, and I've tried, you can't... I disassembled my first one and silicon sealed every possible leaking point, still leaks. Like Kev, moved it outside. I made a 2x6 framed pedestal and covered the blower with a large rectangular plastic tote. It's been in the weather for 6 or 7 years and still going strong.

Rich Harman
05-16-2016, 2:49 PM
It increases while cutting so it's getting out. And yes it lingers afterwards too. I am ordering the big harbor freight dust collector today. 1550 cu feet per minute. I can't imagine anything escaping that power?

No, stop! Don't get the big one. I have two of them, tried one on my laser and it really does no better than the cheaper (and quieter) one. The 13 gal 1 HP one is what you want.

Lee DeRaud
05-16-2016, 4:13 PM
No, stop! Don't get the big one. I have two of them, tried one on my laser and it really does no better than the cheaper (and quieter) one. The 13 gal 1 HP one is what you want.Second that. I'm using the smaller one (or the clone of it that Lowes used to sell), works fine.

I suspect the big one would work better if it had 6" ports and ducting, but yeah, if it's as loud as the big Jet dust collector I use with the bandsaw and planer, it would drive you crazy.

Bill George
05-16-2016, 4:41 PM
Funny my blower exhaust fan is smaller than the HF one, its about 1/2 Hp mounted inside with 4 ft of metal duct to the machine and vented to the outside with a flex metal duct 7 ft long rated for exhaust fan duty. No smell. It is in my shop/garage that is sealed pretty tight but far from air tight so it can draw makeup air without a problem.

Lee DeRaud
05-16-2016, 5:36 PM
Funny my blower exhaust fan is smaller than the HF one, its about 1/2 Hp...Advertised HP for this class of electric motor are mostly fiction. The "1HP" HF unit shows a current draw of 7 amps, which works out to maybe 5/8HP. As I recall, my identical unit from Lowes said 3/4HP on the box.

(Oddly enough, the big HP unit is spec'd at 20A, which really is ~2HP...go figure.)

Keith Winter
05-16-2016, 5:50 PM
As Lee said. I would agree, the HF stuff is all over-rated. Every tool they sell blowers included.

Lee DeRaud
05-16-2016, 5:55 PM
As Lee said. I would agree, the HF stuff is all over-rated. Every tool they sell blowers included.Hardly unique to HF, it's pretty much standard for all consumer-grade tools. Even "name-brand" stuff like Porter-Cable routers are fudged significantly.

Keith Winter
05-16-2016, 5:58 PM
Hardly unique to HF, it's pretty much standard for all consumer-grade tools. Even "name-brand" stuff like Porter-Cable routers are fudged significantly.

True, don't even get me started on crapsman tools, oops I mean craftsmen :rolleyes: