4' x 8' table, how much CFM do I need for exhaust fan?

[blackhollowmfg]

I'm considering my options: a water table or an exhaust fan. If I do a fan, what would I need for CFM in order to be effective?

Thanks,
Bob

[jcc3inc]

Sir,

While I can't answer the CFM question, there are a couple of comments:
1.) You should cover ALL the openings on the topside so that the exhauster has to suck out the cut slot area only, and doesn't have to contend with massive air leaks.
2.) Some of our customers also had a hood of sorts above the cutting area with exhausting there. There is always some smoke/fumes coming off the top.
3.) Some customers used a water table; one who did thin SS had a table only about 2" deep, and his water depth was so that it just barely covered the top of the sheet. That arrangement was excellent in that it both minimized the smoke/fumes, and kept warping due to heat at a very minimum.

Regards,
Jack C.

[ironarbor]

I had a 5 hp paddle on mine(5 x 10),

bad news- sounded like jet
good news- nothing escaped

We are in the middle of refitting our table and building another, we plan to split the table into 2 sections with 10" duct and dampers. This will allow for a much smaller blower, Ive found we do 90 percent of our cutting on less than half the table. We used to leave a 5 x 5 chunk of sheet metal on the half we didnt use and it realy helped.

[mlaws1172]

You need 50 to 100cfm per sq ft of table
mike

[blackhollowmfg]

You need 50 to 100cfm per sq ft of table
mike

Thank you!

Bob

[CNCadmin]

You need 50 to 100cfm per sq ft of table
mike

What is that based on? Based on that I need a 7000cfm blower for my laser. I'm I figuering this right?

I have a total of 96 cubic feet I need to get sucked out, it's a enclosed laser table.

[xjdubber]

You need 50 to 100cfm per sq ft of table
mike

HAHHAHAHAHA


Really, there is no way of saying what you need, what you should ask yourself is what kind of budget do you have?

[mlaws1172]

A 4x10 table = 40 sq ft, that would take between 2000 and 4000 cfm. It is
best to use a bakward incline fan that is non-overloading. If it is enclosed or enclosed on 3 sides then you can figure what the intake opening is and use that for the size.
mike

[AKLance]

We put a 8000cfm kitchen exhaust fan on the outside wall of the building and piped with about 18 in sheetmetal pipe to it (I say about because part is rectangle , transitions, ect) Our table 5x10 has two suction ports out the bottom that we piped together. Here's the kicker-- use disposable welding blanket to cover the table were you are not cutting, we have pieces of various sizes and shapes that live on the table, when we set our material we adjust the blankets for maximum coverage. This system works very well for us.