Duct muffling

[Robert Silvers]

I had a job running and went out to walk my dog, and when I was coming back to the house I stopped at my neighbor's mailbox to listen (160 feet away), and the sound was very noticeable and unusual coming from a residence. It sounded like a Shop Vac was in my front yard - quite metallic sounding. I was horrified at how loud the blower sounded outside of the house. I have it go to a 4 inch dryer vent with no filter.


Well it turns out that the pot growing industry does not like pesky neighbors calling the Man on their grow house - so there are all sorts of products to deal with this. I ordered this:


Amazon.com: Lighthouse Hydro Duct Muffler Inline Fan Hydroponics Noise Reducer Silencer, 6-Inch: Patio, Lawn & Garden (http://www.amazon.com/dp/B00C5RRG4Y/ref=pe_385040_30332190_TE_tr_M3T1_ST1_dp_1)


There are also others, but never tried them:


Suncourt 6 in. In-Line Duct Muffler-DM106 at The Home Depot (http://www.homedepot.com/p/Suncourt-6-in-In-Line-Duct-Muffler-DM106/202803671#.UmHB25RATHI)


Shop DuctMuffler 6-in x 24-in Galvanized Duct at Lowes.com (http://www.lowes.com/pd_223430-1061-DM106_0__?Ntt=duct+muffler&UserSearch=ductmuffler&productId=3199253&rpp=32)


When it arrived, it was just a 10 inch tube with Sonix(R)-like foam in it and step downs. You could make one for maybe $20 less.


I had to use that metallic tape to connect it, as it did not naturally fit the duct work and elbows that I ordered - though you need that tape anyway to seal it. I turned the blower on and walked back to the neighbor's house. I could not hear it at all. Nothing. I walked closer and closer, and I had to get to about 25 feet away before it sounded about as loud as I remember it did from the 160 feet away before. I actually own a B&K professional sound level meter, but I loaned it to someone, so no dB results. Better yet, it was not just quieter, but the metallic/industrial sound was gone and now it sounded just like a common dryer venting. The air was still rushing out as a powerful blast.


Amazon's listing says "reduces noise by up to 25dB." If my guess is correct and what used to be 160 feet now is at about 25 feet, then that is more like 16 dB. Even so, depending on the frequency, 6dB sounds about 1/2 as loud, so it resulted in a sound level that is almost 1/8 as loud. It worked way better than I expected given that it is only 24 inches long.


You may have to replace the foam periodically if tons of wood dust is building up in it.

[Mike Lassiter]

If I understand you correctly, you had your laser running and left it going to gowalk your dog? If cocorrect you are playing a very dangerous game.
Several have posted pictures of their lasers catching fire while they only briefly left it like 2 minutes or 5 minutes to go to another room or quick bathroom break. I don't always stand over mine watching it; but most of the time I am either watching it or on the computer beside it working that is running it. After seeing a burnt up laser that was left alone less than 5 minutes I am unwilling to risk that happening to mine. I have $45k approximately invested and just not comfortable leaving it unsupervised.
Mine is not in my home, but shop beside it. You risk burning your home if your laser should catch fire and you aren't there to do something. Are you comfortable with that?

[Mike Null]

A good and proper warning!

[Gary Hair]

If I understand you correctly, you had your laser running and left it going to gowalk your dog? If cocorrect you are playing a very dangerous game.

That really depends on what you are lasering. I laser thousands of anodized aluminum parts and almost as many Cermarked stainless parts, I have no problem leaving the laser with those jobs running. Now, put in a piece of wood or acrylic and I'm literally hovering over the laser to ensure it doesn't catch fire.

[Robert Silvers]

Has anyone mounted an automatic engine fire suppression system that uses a heat sensor?

Where are these photos?

How does the fire escape the metal enclosure? Through the acrylic window? What about replacing that with tempered glass?

[Dave Sheldrake]

That really depends on what you are lasering. I laser thousands of anodized aluminum parts and almost as many Cermarked stainless parts, I have no problem leaving the laser with those jobs running.

Fires don't always start at the material level, if a tube fails the HV side (on a DC tube) will arc even through the wiring silicone covers usually setting them on fire, if the hose ruptures it can dump water over the electrics leading to the same end result. You may be surprised by just how fast a fire supported by an extractor fan will propagate.

Most lasers come with shiny "Do not run unattended" stickers all over them, the insurance company may not look kindly on a machine left running alone if there is a fire.

cheers

Dave

[Kev Williams]

If I had to stand next to my lasers (or any other machine) while they were running, I'd go bankrupt in a month for not getting any other work done. I made a video just yesterday of running jobs on 10 different machines at the same time. It's how I work. I check the machines when I can, but I got no time to babysit any of 'em. Anything attached to an electric circuit can catch fire while it's running. Does anyone stand over their 1500w coffee maker while its making your morning brew? We had a new coffee maker catch fire on about its 3rd pot of coffee, and that was in our boat. Lost a lot of respect for Black & Decker stuff over that one...

That said, noisy blowers-- I'm using Harbor Freight blowers, the small one on the 2 lasers, a the larger one I have plumbed to every engraving machine to suck up engraving chips. The 2 small ones are in the basement stairwell, with dryer vents exiting into the holly bush next to the porch steps. The motors make a slight whine, but 50 feet away they can't be heard. The actual air noise coming from the vents is almost silent. The big blower (and our big air compressor) are housed inside a 6x8 Rubbermaid storage shed. That shed really muffles the noise. The compressor can be heard 50 feet away, but just barely. The blower can barely be heard at all. The neighbor next door says they can't hear it inside their bedrooms closest to the shed even late at night. Got nothing but good to say about the blowers too, they're probably a big part of the reason for my high light bill as they run probably 5 hours a day (trying to learn to turn 'em off when I'm not using 'em!) The one is 13 years old, the other is 10, the big one is 8 years old. ONLY trouble I've had is the switch burning up on the big one. I thought that was odd since I never used that switch, but it does take a lot of juice to start up. Aside from that, they're a good, quiet blower...

[Dave Sheldrake]

I agree Kev, I don't stand over mine but I don't leave the room they are in either if none of my staff are in there.

Lasers have the ability to generate a HUGE mount of heat in whatever they hit :(

cheers

Dave

[Mike Null]

http://www.sawmillcreek.org/showthread.php?197834-Laser-Fire

http://www.sawmillcreek.org/showthread.php?177362-Laser-Fire-Incident

[Robert Silvers]

I searched around and have seen some examples of fires. Adafruit says they have heard of five fires.

Someone said their fire started, the best they can tell, when someone shut off their air assist. It does raise the possibility of a compressor going dead or tripping a fuse. Two of my compressors over the years have stopped working for whatever reason - like worn out piston rings.

The websites that mention it say that vector cutting is much more risk than engraving.

[Dave Sheldrake]

273304

Dan walked away from this incident unscathed.

273305

3 guys didn't from this one and one more chap was left crippled for life.

cheers

Dave

[Mike Null]

Little, invisible things like mistakes in a drawing can cause the beam to dwell in one spot and cause a fire. That happened to me; fortunately I was at the machine.

[Ronald Erickson]

I don't leave my house (or even go to sleep) with the dishwasher running, the microwave running, the oven baking, the clothes washer or dryer running, the toaster toasting, or the griddle frying. I don't leave the room with the laser lasing.

[Chris J Anderson]

Little, invisible things like mistakes in a drawing can cause the beam to dwell in one spot and cause a fire. That happened to me; fortunately I was at the machine.

Hi Mike,
This happens in one of my drawings, that I cut 2mm acrylic. What sort of mistake could it be ?

Cheers,
Chris

[Dave Sheldrake]

A legacy item Chris (such as an invisible but present dot) or an unpurged item that your software reads but does not show. If you are using a cad program on a DXF file type "Purge" on the input line, then select Y when it asks "Purge entire drawing" (it will also remove any unusual layers or non useful items like X-refs that serve no purpose as well as making your drawing a lot smaller)

cheers

Dave

[Jonathan Bowen]

I had a fire a while back. It was caused by a dirty machine and a failing air compressor. My compressor isn't putting out as much air as it used to and causing flame when cutting acrylic. I cut a lot of flight bases with small holes and the pieces fall through the honey comb. Some of the debris caught on fire. I wasn't lording over the machine but I did catch the odd color of light out of the corner of my eye and was able to take care of it. No machine damage but it wasn't a fun night. I'm replacing the compressor after arguing with the manufacturer who decided that they wouldn't replace it because my warranty was out a few weeks ago. Even if the fire was 2 months ago and the cause wasn't apparent till now.

That said. I have had a lot of luck muffling my exhaust noise with nothing but a dryer vent cover. I got a slatted one. It breaks up the exhaust enough to drastically reduce the noise output. You can't even hear it in my front yard.

[Mike Null]

In my case it turned out that the small circle being cut was actually several layers in the drawing and the laser cut them continuously until all layers had been cut. By this time the piece was on fire.