[abbtech]

I need to add more exhaust capability to my 600mm X 900mm 60W laser cutter. The machine came with a large blower and I think the instructions said the exhaust should be 15 feet or less. I have to go about 45 feet... I purchased one of these duct boosters and placed it at the end of the run but I need more air flow.
http://www.smarthome.com/3011/6-In-1...n-DB200/p.aspx

What should I add to make this work well? I was thinking about something like this.
http://cgi.ebay.com/New-6-Inch-Inlin...item35ac6a9b77

The line is 6 inch all the way by the way.

[zax15uk]

abbtech,

It looks like you already have sufficient exhaust, so if the fumes are still not being extracted you may need to consider increasing the vents (allowing more air into the chamber to increase flow).

How to correctly do this depends on the setup. If you have a pin / honeycomb table and do mostly cutting the exhaust should be extracting from under the material so a top vent would be better. Alternatively if you mainly do engraving the exhaust is best mounted slightly above the material with vents below or to the side.

Zax.

[abbtech]

Hi Zax,

Thanks for the reply. The machine I have has a damper that allows you to select if you are pulling from above, below or from both areas. When I am cutting I place solid sheets of material on the table so that the smoke is trapped below and I set the exhaust to only pull from below.

If I am cutting acrylic I can see the smoke wafting around and not getting pulled back towards the exhaust like other people who have the same machine. There is a ton of intake louvers at the front of the machine so it can suck all the fresh air it wants.

When I engrave I have the machine pull from the top only and the smoke hangs around and is slowly migrated to the vent. Eventually the smoke clears into the exhaust and the cutting room remains smoke free so it is at least preventing the smoke from escaping.

[zax15uk]

Well it sounds like you have it configured correctly so there shouldn't be any 'dead' spots inside the chamber.

If you don't have any leaks, I would expect it to have enough capacity unless the hose length or some other factor is restricting flow too much.

Is it possibly to remove the fan near the machine and use only your booster to see if that improves things?

Zax.

[abbtech]

Compared to the main fan the booster is a joke. With just the booster running I would think a smokey chamber would clear in minutes instead of seconds. I always turn on the booster but I don't think it helps much.

[zax15uk]

The booster fan claims 160cfm (free air), so that should turn over the chamber in about 3 seconds.

It sounds like their claims are over rated or something else is going on to restrict the flow.

What I was trying to point out previously was that adding a more powerful fan in line may require removing the fan which is restricting the air flow, or you will be fighting against it's blades and trying to push it.

Zax.

[tdiaz]

If one of those fans is sucking through the other then I suspect you're just not getting the flow from it. Plus that thing on eBay looks dodgy too me.

OTOH, that inline fan is just a better deal. You can only move so much, and your 45 feet is a factor. I've got a similar issue, my exhaust consists of a 10 inch deep box over the 3x5 cutting (2x4 cut area) and the whole lid is hinged. Currently I have a 3" bathroom fan hidden in the ceiling and it's hooked up to the furnace riser that I've appropriated.

What I'm considering doing is putting a 4 inch inline fan into the furnace riser so I can suck from above and run 4 inch all the way to the pickup inside the laser cutter enclosure that sits near the home position.

My bed surface is a solid slab of wood. I really want to do a honeycomb setup and suck from underneath, but I've got to make a ton of bucks first ;-)

[abbtech]

Thanks for the feedback guys. I was probably not giving the booster fan the benefit of the doubt since it would have been trying to pull through the first big fan. I also have 4 or 5 90 degree bends in the length of 6 inch pipe so I am sure that adds to the air resistance.

I am using this type of ducting but it probably isn't very friendly to moving large volumes of air.
http://www.horticulturesource.com/c-...e59126e370c98b

[tdiaz]

I'd figure that flexible stuff as being an inch less diameter than it actually is when you do the math on air flow. Because it's actually measured at the wire and unless you stretch it fully, very taut, you are not getting the full benefit, and with air crashing into the the peaks and valleys especially going around corners, the flow is probably not optimal at all.

[abbtech]

I'd figure that flexible stuff as being an inch less diameter than it actually is when you do the math on air flow. Because it's actually measured at the wire and unless you stretch it fully, very taut, you are not getting the full benefit, and with air crashing into the the peaks and valleys especially going around corners, the flow is probably not optimal at all.

I was going to use the smooth round duct that comes in 6 foot lengths until I saw the price! My next thought was to use 8 inch flex ducting but there are a few places in the run where 8 inch ducting would not fit...