In our facility there is a VST e-beam deposition machine.

As part of maintenance process we look after user usage data and among other things, how much gold was used.

The gold is added when about one quarter of gold is left in the cruicable and add just enough to fill the cruicable for about three quarters of the cruicable.

The problem is, that the amount of added gold is different each time and the VST machine does not keep track of gold usage of any kind, and we end up filling gold in the cruicable way too often yet we don't understand the reason.

Any insights will be appreciated.