vacuum pump

[pdrake]

anyone know stuff about vacuum pumps? mine froze up. i took it apart to clean it, it got investment dust in it. just got a few questions.

[random axe]

I know very little about vacuum pumps, but, more to the point, I don't think I understood your post in the first place.  Is this "investment" in the sense of surrounding something with something else?  Something from a mold you were making?

If a vacuum, motor, blower, etc, gets clogged with fine dust, sometimes you can clear it with compressed air.  Sometimes you can clear it using a vacuum (another one, if that's the case) that has an appropriate filter.  Wear a breathing mask if you're going to use compressed air or try anything else that will put the dust in the air.  If the dust is really fine, you're going to need a really good filter, but the industrial kind commonly used for drywall dust is pretty decent, as are most of the HEPA ones also easily found.  And you can use a vacuum and compressed air in tandem, to loosen dust and then keep it out of the air.

If you have a vacuum pump that's well and truly seized up, it's probably going to have to be taken apart.  But you might just be able to compressed-air-and-thump it clean.  It's worth a shot.

[pdrake]

i was casting and the bottom of a flask blew out. investment particulate and molten bronze went into the line. the filter stopped the metal, but a lot of the investment went into the pump. i took it all apart and am going to clean off all the pieces which, surprisingly quite few. it was like there was sand inside of it. investment is the plaster like substance used in lost wax casting.

i was wondering most about putting it back together and if i could use compressor oil instead of vacuum pump oil.

(seriously, like 4 moving parts and 8 static parts minus screws.)

[random axe]

I would try vacuuming the sandy crap out, is all.  I wouldn't try changing the oil without doing some research.

I totally don't understand how your casting process works -- which doesn't surprise me, since papier-mache and Permastone are more my speed.  You're doing a lost-wax casting with vacuum-forming?  Or does the pump pull the molten metal in to make sure there aren't any voids?  Something like that?

[mybabysmomma]

My SO says he doesn't really know enough to tell you for sure but he thinks it's a no for using any other kind of oil.

[pdrake]

this is the unit i'm using:



you put the flask on it (minus the neoprene pad and dome, that's for investing.) and turn on the vacuum. sucks the metal down so there are no voids. some investment broke off the bottom and it sucked that and metal into it.

i'm going to use a solvent to clean all the old oil and particles off of the parts. had to buy all new hoses, but all the places that sell the oil are closed today and close before i get off work all week. i'm kind of on a deadline. i don't want to ruin it, so i guess i'll make sure i get the right stuff.

thanks, ruthie. sorry, your piece was in that pour. gotta make a new wax piece for you.

[pdrake]

i'll have to post some pics of the parts apart. (need to take "put back together pics" anyway.  )

i was really surprised how simple it was inside. i'm sure the functions are more complicated, but the parts are very basic.

[random axe]

OK, so . . . if the investment is supposed to hang together and not crumble into the vacuum line, then how do you get low pressure inside the piece?  Is the investment porous?

I'm probably just not visualizing this correctly.  If it's too hard to explain, I can live with it being a mystery.

[pdrake]

process with illustrations:

http://www.shorinternational.com/vacuumprocraftinstr.htm

i guess the investment on my flask was just too thin and when i set it on the table it broke and i didn't know.

[random axe]

:googly:

I think I'd have to see it done right in front of me.  With the bell jar off, the vacuum could hold the flask firmly in place, but I can't see how it could induce low pressure inside the flask.  I mean, the top of the flask is open, and the bottom of the flask (where it contacts the pad) is closed.  Right?  If the bottom of the flask were open, you'd just suck metal down into the pump, like you accidentally did.

[mybabysmomma]

That's ok Perry, I'm not in a rush.  Wish I could help you out with the oil. 

[pdrake]

does this help?



there's a valve that switches the vacuum draw from the valve poking up inside the bell to a hole in the plate that the flask sits over. you can't see the hole because that pad is on the plate. you only use that when you're vacuuming the air from the investment during the mixing. when you cast metal you take all that off, put on a silicone pad and place the flask on that.

[pdrake]

this is a machine that has the two tables separate.

[random axe]

OK, so . . . the "flask" in this case is more of a tube, and the investment is porous.

OK, yeah, that makes sense.

[pdrake]

yep . . .

casting flask har