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December 12, 2019, 19:30:26 pm


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Author Topic: More of Chuckeroo's insanity  (Read 1890 times)
dh42
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« Reply #30 on: October 15, 2019, 23:02:52 pm »

David,
Not for nothing, but he WROTE 'inches of mercury', when he noted '...25" hg...'.

Those are the English language conventions for inches ("), and (except for capitalization) mercury (Hg).

He wrote - in English - exactly and precisely-understandable information for a native English speaker/reader.

Just sayin'! (Ain't Engrich strange?)

<grin>

Lloyd

Hello

Yes, sorry, I don't paid attention to the " ... Embarrassed ... on the document I've quickly read they don't use the same symbol (inHg instead Hg") ...

Quote
International unit for measuring air pressure. Now a hectoPascal (hPa) is the standard unit for pressure."

On my pump (side channel blower) the manufacturer give the value in mbar (-330 mbar for mine) ....  and on some documents they don't give the depression produced by the pump but the pressure that remain when the pump is running (vane pump) ... and it's is given in Pa ...

++
David
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dave benson
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« Reply #31 on: October 16, 2019, 10:14:59 am »

Yes I avoid unit conversion between the various systems like the plague. spacecraft have been crashed like this. Roll Eyes
David, say in a few years that you would like to upgrade to a newer more powerful system and have selected a few pumps as likely candidates based on some criteria,physical size shape,capacity, and cost to run and are wondering how to objectively compare them apples to apples so that you can decide which pump is best suited to your application. Say your looking for Efficiency, notice in the table that all the power figures are 0.7 Kw even though Lloyds pump is 20 Hp. It's only comparing pump efficiency. This is the Apples to Apples  thing. Smiley

Well it's easy, the nice folks at the European and other standards organisations have laid out a series of tests so that you can do this and to meet this standard and to be able to put the sticker of compliance on the pump, manufacturers publish this data both the vacuum cleaner and your pump is the data I used from their websites not the info that would be on the pump.  Festool publish there specs in pascals not Mbar which is nice of them.

Have a look at this page if you are interested knowing more.
https://www.engineeringtoolbox.com/centrifugal-pumps-standards-d_1116.html
https://www.engineeringtoolbox.com/horsepower-d_472.html
The ISO standards look here  as an example https://www.iso.org/standard/17788.html

As to the spoil board I sat there in disbelief that CNCNutz threw the spoil board on the table and then threw a piece of al maybe 100mmx100mmx3mm on top of the spoilboard  at first it was reasonably easy to move and then after adding the newspaper had a moderately hard time to slide it across the table He's not big guy and hasn’t seen the Gym in a while so the 25 kg force I had guesstimated  acting on the plate seems not to far out of the realms of possibility.
At this stage Chuck I think you will have to keep the cutting forces fairly modest.
Maybe stick to 3 mm tools or less for the smaller pieces.

There will be a minimum size for the work piece to hold securely,  for milling Al I would guesstimate this would be in the range of 200 mm x 200 mm.

I found this from  Festool, the spec's for a vacuum table running at 0.150 Mbar  without a spoil plate, so multiplying up the figures to 250 Mbar multiplying by "the efficiency" of the spoil backing, I took a WAG here (0.6)  I figure the first piece you cut should start out at 200 mm x 200 mm  but to find  the minimum size, you're just going to have to experiment.

Dave


* Twin motor vac.PNG (17.25 KB, 833x234 - viewed 42 times.)

* festool.PNG (42.23 KB, 855x441 - viewed 40 times.)

* Vacuum Table expected holding force.PNG (39.83 KB, 362x313 - viewed 42 times.)
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