Vacuum Blower Over-heating issues

[JNathan09]

Hello Shopbotters,
Great forum! First time poster.

We recently replaced the plenum, spoil boards, and vacuum hold down system on our Shopbot.

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I used a 3/8" endmill to cut the large grooves in the plenum material. This material is a product called Richlite, a GREAT material for this application. The smaller grooves where cut using a 1/4" ball endmill. After machining, we installed new MDF spoil boards, and a new 6 zone plumbing system. Then we started up the vacuum blower...

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and then this happened to the exhaust tube...

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The blower is VERY hot to touch. With only one zone open, the vacuum gauge is reading 8.5 "hg. With all 6 ports open the reading is 6 "hg. Before replacing the plenum/MDF etc., there were no heating issues.

Could the problem be:
Not enough cfm of air to keep it cool? Which could be from using a 3/8" instead of a 1/2" endmill to cut the grooves? Could it be from using MDF instead of a low density board?

Thoughts?

Thanks in advance!

[Brady Watson]

8.5 Hg" is about right for that pump. My FPZ runs about 8.5-9 Hg" full tilt.

Note that performance will be greatly affected on this system without the use of ultralight MDF. Your effective vacuum will be 8.5 - 6 = 2 Hg", which is not much. That is your usable vacuum.

I would close off the table ports and open up the '5th valve' to atmosphere (assuming you have 5 risers w/valves and only 4 ported to the table) and let the pump run. It will (or should!) register 0 Hg" free flowing. Check it to make sure it is cool.

-B

[PNast]

I have a Becker VT 4.40 pump and I use 3/8 inch Polyethylene tubing with a gasket plenum system cut into Phenolic plastic. I have to run with a separate zone open to get enough airflow to keep the pump cool. Sometimes I get enough airflow moving through the Pine board but not always. I also had a problem with the voltage, the pump is a European model and runs on 220 +/- 6%. I had between 240 and 250 coming in from the service, this overheated the pump and shut it down. I had to purchase a transformer to regulate the voltage to 220.