I need help! We have a problem with our castings (silver) not coming
out at the outer edges of the tree. We use a vacume caster, but the
vacume seems to be working properly…
Dop you have any advise?
Please?
Thank you
Reinette
Reinette
A few questions to ask.
How thick is your main flask “tree stem”? Are the ‘sprues’ thick
enough to allow for the flow of metal to extend into the far reach’s
of the ring.
Do you have enough sprues for the hot metal to traverse to the
different parts of the ring? I might be able to overcome some of these
questions by having you go to my “Gerry’s Blog” and look at the
multitude of photo’s listed under “Wax ring, set-up”…Keep me posted
off-line! regards. Gerry!
Reinette, your casting problem could be several things. Is the main
sprue adequate to act as a button for the pieces being cast, what is
your casting temperature, how are you melting the metal, are the
patterns all the same, are the lighter patterns at the top of the
tree or the bottom. I would be happy to help you figure out the
problem if you call me. Also there are good books out there that can
answer a lot of questions, I like the AJM guide to lost wax casting
for my students use.
Good luck!
Shannon Calloway
help! We have a problem with our castings (silver) not coming out at the outer edges of the tree. We use a vacume caster, but the vacume seems to be working properly.."
Hello Reinette,
You could supply a little more info as there may be different
issues.
Some failures may be due to melt not being hot enough or that of
inappropriate spruing technique. This often results in slightly
rounded ends of failed pieces.
Insufficient melt or poor spruing may result in sharp and/or
irregular ends of failed pieces.
Are the buttons/butts of usual/correct size?
Depending on your specific set-up, the vacuum gauge may not be
reading accurately due to a blockage in the line or of valve/pump
failure.
Are you using the same investment powder and mixing ratios that
worked well before?
Are you using perforated flasks? What is your casting set-up?
Are you at sea level or at a very much higher level?
How are you sure that all the wax is being burnt out?
Are you mixing light and heavy waxes on the same tree? Or are you
casting small single item flasks?
How do you measure the flask temps?
How do you know/judge/read melt temps?
Do you have a record of previously successful melt and flask temps?
How close to the flask wall do you build a wax tree?
Do you notice even a minor loss of vac during the pour?
What does your vac gauge read when you achieve the best possible
vacuum? Is it consistent?
These facts may assist others in helping to identify the problem.
This is just to start with. The problem could be one, some or none
of these issues.
Hope this gives you a starting point.
Phil.
We do have a cast defect chart.
Andy “The Tool Guy” Kroungold
This might help
helpful hints on investment casting: troubleshooting casting problems
Andy “The Tool Guy” Kroungold
Wow, it is awesome to get so many helpful responses! What happened
was that our castings were coming out great until a jeweller friend
gave us a batch of investment that was obviously too old, so it blew
the bottom of the flask into the casting machine, we then bought
fresh investment and since then have been having issues. We changed
the oil of the vacume caster, but it still happened. Today we took
the whole thing apart and found that inside the little glass-jar
where a small pipe goes in there was a bit of fluff and things
blocking the pipe, hopefully clearing that out has now sorted the
issue.
However my partner Zak has also decreased the size of the sprues we
were using so it could be the problem also. We will look at that!
We are running a burnout tonight again to see if it works better! I
will let you all know how it goes.
Thanks soooo much for the helpful responses!
Btw, we are in the Garden Route of South Africa!
Reinette
Wow, it is awesome to get so many helpful responses!
This is the true spirit of this forum!
What happened was that our castings were coming out great until a jeweller friend gave us a batch of investment that was obviously too old
Not too old but wrongly stored.
Regards
As an aside I’ve found that storing my investment with plastic
container half filled with calcium chloride- also known as"damp
rid"or"drierite" willprolong its life by up to a few years. I use a
1 liter yogurt container with lots of holes poked in the lid and
just push it slightly down into the investment to keep it from
spilling before I close the bag. This stuff has ahigh affinity for
water and soaks up moisture from the air around it. It will
eventually turn into a gooey mess if left out in the open but when
keptin the bag of investment it prevents the investment from going
bad due to moisture in the air.
I hope this is useful to you in the future. 