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.."
You could supply a little more info as there may be different
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
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.