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Understanding casting shrinkage


#1

Todd, I saw your comment relative to quenching and wish to caution
all.

When you quench have a deep enough bucket of water so that when
you plunge the flask into the water you go DEEP enough not to see
any vapors or bubbles come out of the water. All the bad particles
should stay under water, trapped and harmless to your lungs this
way. 

The fact is, the instant the flask is plunged through the surface of
the water, the seriously dangerous particles hit the air you will
breath. You must wear proper breathing protection when quenching, no
matter your theories about depth of water.

Regards,

Bill
Zero-D Products, Inc.
precision engineered materials solutions
http://www.zerodproducts.com


#2

WEAR A MASK! WEAR A MASK! WEAR A MASK! That from my instructor. I
HATE masks, but wear (one under threat of having my ears boxed by my
instructor and good friend).

Veronica


#3

Dear Bill,

I always leave something out. A mask is an absolute must. Everyone
in my casting classes get one. Mine is fit and tested while I am
wearing it by an OSHA certified technician. My technique about the
proper quenching process comes right from the Ultravest folks at
Ransom & Randolf. Their technical staff is always willing to help.

Here is another tip from my experience. Ultravest is the best
investment for both vacuum and spin casting. Satin Cast doesn’t spin
cast as well. They made it new and improved a few years ago and it
doesn’t breathe as well.

Best Regards,
Todd


#4

Thanks Todd,

Over the years, I’ve encountered countless casting folks who never
knew about the danger inherent in the quench step. Many assume that
the dust they see in handling the powder is the most dangerous. I’ve
even heard “I hold my breath” What?

I’ve posted on this topic before and find that it draws little or no
comment. Yawn!

Thanks Veronica for your input.

Masks and safety glasses. Don’t fail to use them and have huge
regrets later, when the damage in either case is irreversible.

Silicosis provides a slow, painful death. Blindness happens in an
instant and usually does not kill-happily. Or not!

In our mold rubber manufacturing process, there are no really
dangerous respirable ingredients, however, nobody enters or works in
our factory without masks and safety glasses.

Regards,

Bill
Zero-D Products, Inc.
http://www.zerodproducts.com


#5

Bill,

Just a few more thoughts. I always plunge my castings into the
bucket fast. There is really no chance for the material to vaporize.
The flask goes the eight or so inches immediately, rumbles to a stop
and is then removed and cleaned. I’ve never really seen anything rise
to breath with this procedure.

I’ve noted this step several times before also. Make sure before you
quench you take an old dental tool of some type of scraper and
scrape around the spru button. This material should be gathered and
sent to the refinery when enough has been gathered. You would be
surprised how much money I get back every other year or so with this
material.

Best Regards,
Todd


#6
Just a few more thoughts. I always plunge my castings into the
bucket fast. There is really no chance for the material to
vaporize. The flask goes the eight or so inches immediately,
rumbles to a stop and is then removed and cleaned. I've never really
seen anything rise to breath with this procedure. 

If you have an air sample run you will find that there is indeed
silica released into the air when you do this. Not as much as when
you go slowly but it is there. The sub micron dust is so fine it
will sty in the air for long periods of time. All quenching of flasks
should be done in a properly ventilated space. Better yet wait till
cold and use a water blast system to remove castings. Then there is
no sub micron silica dust released into the air.

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550