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Author Topic: Physical buttons for plasma  (Read 84154 times)

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Re: Physical buttons for plasma
« Reply #270 on: March 10, 2016, 03:36:30 AM »
Dave & Hood, funny thing doing posts after midnight.... gives you time to think a little (note to self, do before opening keyboard... [or mouth])

Dave, 3200m³/hr = 889 l/sec, & yup that is an axial fan.

Problem with axial fans is they have very little pressure displacement across the fan as said above, and manufacturers like to quote airflow numbers with the fan tested without any ductwork on it / or induced pressure loss (free air displacement).... hence when looking at a fan curve such as the one below, you can see that some manufacturers will choose the point of most airflow at zero pascals of pressure displacement at the far right of the curves (in day job be very suspicious of any fan manufacturer not publishing a fan curve for a fan but just quoting one number without a corresponding pressure displacement).

http://www.cibsejournal.com/wp-content/themes/cibsejournal/images/2011-12/images/figure-1.png

If you are adding ductwork on to it (flexible / ridgid) you need to consider the pressure loss (even roughly), and also the termination (louve, or even free air discharge), and also the intake.

(I'll try to do this over a few posts, if anyone is interested)



Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”

Offline Davek0974

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Re: Physical buttons for plasma
« Reply #271 on: March 10, 2016, 04:04:09 AM »
Interesting, luckily i have kept my ductwork to 12" on either side of fan - as short as possible so i should be at near fan capacity for flow rates.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives
Re: Physical buttons for plasma
« Reply #272 on: March 10, 2016, 04:13:51 AM »
How big is your table Dave?

Sorry Hood, can't remember (and 29 pages is a bit so search through...), how big is your table?
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”

Offline Davek0974

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Re: Physical buttons for plasma
« Reply #273 on: March 10, 2016, 05:08:08 AM »
Mine is a massive 1250x1250 cut area ;)
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

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Re: Physical buttons for plasma
« Reply #274 on: March 10, 2016, 08:41:13 AM »
The cutting area will be about 2700 x 1700.
Was thinking maybe having 4 funnels like in drawing below, would give quite steep sides and could have a tray underneath with a fan in or maybe even 2 trays/fans, thoughts?

Hood

Offline Davek0974

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Re: Physical buttons for plasma
« Reply #275 on: March 10, 2016, 09:16:44 AM »
Is it at all possible to get the gantry on the short axis ??

Trouble with tip-up table and fans will be disconnecting the duct work each time.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives
Re: Physical buttons for plasma
« Reply #276 on: March 10, 2016, 09:18:16 AM »
The steep sides are good... It's called the angle of repose, although the metal is molten.

I've tried to find the angle of repose for iron filings, but can't find the link now or source, but 60 degrees seems to be a number from somewhere.

Also think about what you intend to cut... Stuff with coatings can give off toxic fumes (galv etc)... Hence better to use new plate than second hand... Which I know you are not but someone following this might)
Rob

Albert Einstein ― “If you can't explain it to a six year old, you don't understand it yourself.”

Offline Hood

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Re: Physical buttons for plasma
« Reply #277 on: March 10, 2016, 10:43:59 AM »
Dave,
it is going to be a fixed design now, well as long as my welds hold up that is :D
Don't have enough steel to have it the other way, could have got more but I have it done now.
Pic below.

Rob,
 One side of the cones is 58 degrees, the other 68, so should be close.
It will be all new stuff I am cutting and no coatings. Mainly 316 stainless and 5083 Alu.
 
« Last Edit: March 10, 2016, 10:46:56 AM by Hood »

Offline Davek0974

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Re: Physical buttons for plasma
« Reply #278 on: March 10, 2016, 02:00:41 PM »
Stainless fumes are very bad news when plasma cut, I thinks its called hexavalent chromium and is carcinogenic, also la is pretty rough too i think, this is why I went for as much ventilation as I could fit in and run with the window open, even in winter to allow for make-up air.

Good idea on going fixed bed ;)
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline Hood

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Re: Physical buttons for plasma
« Reply #279 on: March 11, 2016, 05:18:58 AM »
Aye, Alu is not too great, fume wise,  either.

Hood