Irregular metal formation; typically in slots, holes, passages or tight areas
Indicates that the metal broke out, or penetrated the ceramic shell
Usually due to the fact that the shell is typically too weak (due to structure or dryness) to adequately hold the metal in the desired shape
Often referred to as birdnesting when it appears in corners
Causes of this defect are evident in the shell and other portions of the process; to cure, R&R recommends taking the following actions:
Weak spots in the ceramic shell due to difficulty of buildup in details.
Improper shell build in the detail area.
Insufficient or poor shell drying.
Excess slurry and/or stucco left behind.
Rapid depressurization of autoclave.
Depressurize from maximum pressure to atmospheric gradually over about 2 minutes (evaluate autoclave operating parameters).