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De-Airing Pugmill Conversion


docweathers

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I have an old bluebird pugmill that I would like to convert to de-airing. What I don't understand about de-airing pugmills is is how you keep lumps of clay from being sucked up with the air and filling the vacuum line or reservoir. I would think the pressure of the clay being twisted and compressed would push clay out any opening, but obviously this has been solved. Please explain to me how the air is pulled out without clay.

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not a problem.  yes, tiny bits of clay are sucked out of my bailey pugmill.  they collect in a sealed compartment with a removable clear plastic cover. there are only tiny amounts and since i can see them, if i pug for a long time i am able to remove them.  the power has to be off or i cannot remove the flat cover because of the strength of the vacuum.  there might be as much as a tablespoon of clay after pugging several buckets of clay.

 

since these reservoirs are built into the body of the pugmill, i wonder how you will be able to add one.  

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From looking at the manual, it appears that they are putting the vacuum chamber after the auger and doing nothing special to keep clay from getting into the vacuum chamber. It only little bits of clay are collecting in the vacuum chamber, it's not a problem.

 

 Does your bailey have a shredder screen before the vacuum chamber?

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The vacuum connection is likely at the top of the vacuum chamber. The clay at either end of the chamber creates the seal, and as the clay moves through the chamber the air is sucked out. It would have to be very tiny particles for the vacuum to be able to suck them up.

 

Large industrial pugmills, like those used by the clay body manufacturers, have two augers- one upper that moves the clay into the vacuum chamber, and one lower that moves the clay out of the vacuum chamber and extrudes it out the end nozzle. As the clay enters the chamber it goes through a screen of sorts that cuts it into pellets so the vacuum can really penetrate into the clay and get all the air out. For those, the vacuum pump itself is as big as a Bluebird pugger. Industrial puggers are 9-10 feet long. THIS is the system I installed when I was production manager for a clay supplier. The pugger is rated for over 6000 pounds per hour.

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The answer is really that because the clay is sticky, when it comes out of the main barrel through a little port hole into the little vacuum chamber that oldlady is describing, it kind of just pfffts* (*technical pottery term) in just past the port hole and sits there and builds up slowly.  It does not travel the extra three or four inches across that little chamber to get all the way into the tube hole on the far side where the vacuum from the pump REALLY is coming from, because the sucking force in the chamber is not that directionally specific.  However, if you do not clear that chamber for a long time or forget to do it and too much clay builds up in there, you will certainly plug up the vaccum hose and then you will no longer be de-airing.

 

If you are converting, aside from the vacuum creating pump, you will need a little chamber like that mounted on the barrel of the pugger, and you will need a release valve to dump pressure from the vacuum chamber when you need to stop and clear it of clay.

 

How often you have to release the vacuum and clear the clay really depends on how wet the clay is.  The wetter the clay, the more often the little chamber will fill up. 

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Going back to an oft covered design, the Walker had a side exit for the clay. This when I first saw it seemed counter productive as the clay had to be forced against the end wall of the tube by that giant auger until it got forced out of the side exit. In retrospect over the years I concluded that this was very purposeful as it would compress the clay somewhat and force out some air that my might be left in the clay.

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I know on some designs the slotted hole that is going in to the vacuum box is cut on an angle. This prevents the vacuum air box from filling with clay.

If the hole was straight it would fill with clay easier. If the angle was going the wrong direction it would scoop up the clay filling the box quickly.

In every design as I recall, there was always a way to clean the vacuum box out, because it will, no matter what get some clay in it.

 

In some cases the shredder screen is not used. I'll look today to see where I have the information.

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Doc on a peter pugger vac suck  attacment is between motor and clay mixing/pugging chamber . On the top of a seperate chamber-air moves from one to the next via the shaft. Clay that is sucked into the vac chamber has a seperate door to clean it out.

Its about as far from the nozzel as you can get. I do not think where the suck attaches is that important except for clay getting into it. You could screen it well but I would put it at the top. You also need an airtight chamber which is done with o-rings on all parts.

Mark

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I think the vacuum chamber (where the suck contacts the clay) is should be as far away from the clay hopper as you can get it, ie much closer to the end of the barrel where the clay comes out.  On my Venco pugger it is just after the shredder.

 

I often notice when pugging that, the stiffer the clay is, the more difficulty I have keeping vacuum pressures up where they should be to the accomplish the de-airing.  Often times when  the clay is that bit too stiff, you can hear air being sucked in through the clay hopper from the vaccum and pressure on the guage goes right down.  Not sure if anyone else has this problem.   Similarly, because the pugged clay is being forced out of the barrel under some pressure in a densified (de-aried) state, no air is going to leak into the vacuum there.

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I have a first draft of my de airing conversion operational. I threaded a half inch nipple into the barrel immediately after the blades. It extends about 3/8 of an inch in the barrel. On the leeward side to the clay travel path it is carved back about a quarter of an inch. On top of the nipple is bolted the lid to a peanut butter jar. A second hole and fittings pass a quarter-inch plastic tube from my $50 harbor freight vacuum pump to the bottom of the jar. For a vacuum chamber, the peanut butter jar is screwed into the lid upside down. On initial tests, this all seems to work pretty well. I'm sure Rube would approve. Pictures are attached.

 

Suggestions please

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I have a 440 Bluebird with a de-airing system. I have never used the

de-airing part and don't plan to. I think it is noisy and over rated.

The bluebird 440 isn't for everyone, but it works for me if I add water

to the clay then pug. Its faster than risking too much water and have

the pugmill sit and spin for minutes on end....

See ya, Alabama

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