Laser Venting and Noise Concerns

[Chris Wright]

Hello all!

I have just purchased a 80w Trotec Speedy 400 and am in the process of figuring out the best way to vent the exhaust from the machine. We rented an office space that will allow us to blow it outside the building but have read about concerns with noise to neighboring businesses and filtering the exhaust because of the smell.

I was recommended a Penn State 2hp blower and was wondering if anyone else could shed light on if a noise suppressing box for the blower might be needed or how you vent your exhaust out. I read that aluminum or galvanized metal is recommended for hosing and was also wondering where you guys might have purchased any other accessories needed.

Thanks so much for your help. Excited to join the laser engraving community!

[Bruce Clumpner]

I run a muffler made for hydroponic farming, it just clamps on to my 4" flex tubing exhaust out under my garage door. It cut down the fan noise considerably, and is fairly cheap. My neighbors certainly appreciate it too...

[Bert Kemp]

My neighbors put an electric fence 40 feet from their house to keep their 3 horse's down on my property line 15 feet from my back door. they poop everywhere and the flys will pick you up and carry you off, never had flys till they moved in and the stink they never clean it up just leave it there, so I really don't care about the noise as if they could hear it anyway.Wish I could get the wind to blow towards their house when I'm cutting leather.

[Tim Bateson]

I have mine in another room to help me - it's up against the outside wall. Until I told a neighbor last year he thought it was just our cloths dryer. However I rarely do much that smells bad. It's been 7.5 years, so far no complaints & I live in a very strict HOA community (subdivision).

[Mark Sipes]

The requirment of the Trotec 400 for exhaust is 177 cfm minimum the 2hp blower you are looking at is rated at 1360 cfm the 1 hp is 660 cfm . more than enough unless you are pushing the air a fair distance noise factors are 72 and 62 db.... the noise created when 2 people are talking. The smell of the material is your major factor as I see it. You did not mention the items you would be cutting/rastering. Rubber stamps (worst) ----- aluminum (least)


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[Scott Shepherd]

The requirment of the Trotec 400 for exhaust is 177 cfm minimum the 2hp blower you are looking at is rated at 1360 cfm the 1 hp is 660 cfm . more than enough unless you are pushing the air a fair distance noise factors are 72 and 62 db.... the noise created when 2 people are talking. The smell of the material is your major factor as I see it. You did not mention the items you would be cutting/rastering. Rubber stamps (worst) ----- aluminum (least)


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I don't think that number is accurate. My belief, from extensive testing with some very high dollar equipment, is that when laser manufacturers spec something in CFM, they mean INSIDE their cabinet, meaning you want 177 cfm INSIDE the cabinet. That's VERY different than 177 CFM. If I owned a Speedy 400, I'd be looking at a 1200 CFM blower, which, in my testing, gives about the right amount of suction inside the cabinet.

[Keith Colson]

Scott is right 177cfm in the vent pipe would do nothing.

I have a 3 phase 1.1kw blower and it is perfect for me. With a VSD I can dial in the amount of air flow and noise I want to make. Typically I run it at 80% power but for those smokey jobs I can crank it up to 120%. The noise is not the motor but the air going through. I found that rigid ducting is so much quieter. Flexible plastic ducting lets a lot of the noise out.

Running at 80% speed I get less than 70db but if I crank it up to 120% i can make a terrible racket around 90+db. This is where the VSD is awesome, you can tune it to be quiet so you don't bother people around you.

Cheers
Keith

[Mark Sipes]

Maybe Trotec Corp. will add to the comments for their system... they state 300 m3/hr is a minimum

Scott..Please explain how 177 cfm going in and 177 CFM going out is different in volume calculations. If your statement is correct in the abstract.... then 3000-4000 cfm in should get you 1300 CFM out ?



My table is 17" x 29" x 6" for plastic that is 1.4' x 2.4' x .5' = 1.68 ft3 . at 177 cfm I should get 105.4 air exchanges/min or 1.75 x/per sec. at 1300 I am vent the room/house.

[Scott Shepherd]

Maybe Trotec Corp. will add to the comments for their system... they state 300 m3/hr is a minimum

Scott..Please explain how 177 cfm going in and 177 CFM going out is different in volume calculations. If your statement is correct in the abstract.... then 3000-4000 cfm in should get you 1300 CFM out ?



My table is 17" x 29" x 6" for plastic that is 1.4' x 2.4' x .5' = 1.68 ft3 . at 177 cfm I should get 105.4 air exchanges/min or 1.75 x/per sec. at 1300 I am vent the room/house.

Mark, you lost me on that calculation there. If I were to try and explain it, I would botch the technical terms horribly and confuse the issue even greater. I spoke at length with a number of higher ups at Trotec about it, I spoke to a number of people at other manufacturers as well. I came to the conclusion no one knows much about air flow and they don't want to.

We had an issue where we were helping someone with an airflow issue (lack of airflow in certain parts of the table). We brought in an airflow engineer that had measuring devices that costs $1000's of dollars. We started with a 1200 CFM blower, then went to 1,800, then to 2,300 CFM, even had a 300 CFM machine that had really high static pressure (18-19 if I recall correctly). While all that was going on, we were taking measurements inside the cabinet. The problem is, with all the changes, it didn't change the air speed coming through the cabinet.

We heard all the "you're pushing the exhaust too far" (it had to go up 2 stories) and "you have too many bends in it", "You need smooth pipe, not rippled". In the end, everything that all the experts said would solve the issue didn't move the needle. We were told things along the lines of smooth wall tubing would get you a 20-30% increase, when, in fact, measured, it got us less than 3%.

In the end, in my opinion, all that is non sense. It means nothing. Want to know what means something? Air speed. If you hit 180 fps (I think it's fps, not ips, I'd have to look at my notes from when it was happening), then the smoke cleared the cabinet really well. Didn't matter if it was a 45W single port laser or a 100 w double port laser. If you were down in the 150 fps range, you'd start seeing smoke drift up to the lens opening in the head, which was bad. Any time you got to 180 fps, then the smoke pulled through excellent.

It was in extensive talks with the air flow engineer where he said that the specs were not for the blower, they were from inside the cabinet. He explained why that would be the case, and it made sense at the time. Unfortunately, I'm not smart enough to recap what he told me

[Scott Shepherd]

That might be fpm, not fps. I'll see if I can dig out my reference material and find it to clarify.

[Bill George]

That might be fpm, not fps. I'll see if I can dig out my reference material and find it to clarify.

fpm feet per minute = air speed cfm cubic feet per minute = volume of air being moved
air has weight and it varies as to relative humidity.
I probably could find all my air flow books someplace, but I think we found out last time, as you pointed out none of the factory engineers really had a clue.

[Mark Sipes]

I pull my air 3 ft and push it 1ft. 4 foot run from table to outside.


Scott - "you're pushing the exhaust too far" (it had to go up 2 stories) and "you have too many bends in it", now we are talk resistance to air flow. that's a whole different issue. isp, fpm, fps is not a measue of volume but rather resistance to flow.


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[Scott Shepherd]

Scott - "you're pushing the exhaust too far" (it had to go up 2 stories) and "you have too many bends in it", now we are talk resistance to air flow. that's a whole different issue. isp, fpm, fps is not a measue of volume but rather resistance to flow.

Mark, I only mentioned those things to illustrate that all the things we were told would correct the issues didn't make any measurable difference. In the end, air speed was king and without it, no matter what the configuration, it wouldn't clear the cabinet.

[Mark Sipes]

How does this help Chris...... Chris... how far do you need to move the exhaust to vent to the out side?. how many turns will the pipes be making? what is the height difference from machine to vent?



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[Mike Lysov]

My blower makes up to 70db noise but it produces this level of noise when it is connected to a laser with plastic hoses.
It was much louder(about 80-85db) when I took it out brand new of its box and tested its noise level disconnected.