Pinholes or Gas

PinholesPinholes or gas present as bubble-shape cavities located on top side of parts when the tree is in casting position. This defect indicates that there was unburned wax pattern residue (soot or ash) in the shell; when molten metal was poured into the shell cavity and came into contact with the ash residue, gas was formed and trapped in the mold.

The causes of this defect are evident in the other portion of the process. To cure these causes, R&R recommends taking the following actions.


Area

Cause

Cure

Wax

 

 

Shell

 

 

Metal

 

 

Other

  1. Burnout cycle is too short, burnout temperature is too low or there is a lack of oxygen in the burnout oven; any of these can cause incomplete pattern burnout.
  1. Improve the burnout conditions in the burnout oven to allow for complete pattern burnout prior to pouring.

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