Degussa Motorcast

Hi, I have a Degussa Motorcast casting machine that I have been using
to cast gold and platinum about 7-10 times per week for about two
years. Its been getting a bit tempermental lately. The problem is
its won’t always spin when the door shuts. I have been careful to
keep it clean, especially around the little button that pops up when
the door shuts to activate the motor. I have taken the door off,
removed the disc surrounding the pop-up button and cleaned it as
well as I can (removing and bits of gold or platinum). It will work
most of the time but sometimes (like today for intance) I melt the
gold, shut the door and nothing. The button seems unincumbered and
still no action. Is there something I am missing here? The owners
manual is of no help. Mark

    Is there something I am missing here? 

I don’t know the machine in question, but from that description, I’d
guess an electrical switch or relay isn’t switching. Might be a bad
switch, such as a sticking internal contact, or just as likely, it
might be just that the contacts have gotton dirty or slightly
corroded, or some such. If the button switch can be disassembled,
you can clean the contacts, which should help if it’s the culprit.
Take care not to remove any lubrication that may be on moving parts
of a switch. if it’s sealed, you can still try some spray contact
cleaner (from Radio shack). If that doesn’t work, then perhaps it’s
time to replace the switch, if it’s the faulty componant. The other
possibility is that the button switch drives a relay which drives
the motor. This is a common, and likely, situation if the motor
takes significant power, since many types of small switches don’t
like to switch large loads. Relays can go bad, or stick, and often
are just plugged into a socket, which makes them easy to replace. If
these two obvious possibilities aren’t the problem, then it may take
someone with a bit more experience in troubleshooting to find the
trouble. Actual failures are easier to find than the type of
intermittant problem you describe. they can be due to either the
switches, as discussed, sticking at times, or it can be loose
connections, perhaps from thermal stresses (you ARE, after all,
warming up at least parts of the machine with your torch, not to
mention the electrical heating that occurs in use.), or any of a
number of other, sometimes more difficult to find problems. One
other thing to check would be motor brushes. If they’ve worn down a
lot, it might be that at certain rotational positions of the motor
shaft, the brushes don’t quite make good contact any more, so if the
motor is at that position, it won’t start, while at others, it
would. Check the brushes if this is a motor type that uses them. (It
probably is).

Good luck.
Peter Rowe