Incomplete Pressing:

• Amount of ceramic used is too small
• Pressing temperature is too low
• Diameter of wax sprues is too small
• Holding time at final tempature is too short
• Pressing time is too short
• Pressure is too low

Pre-Heating:

• Strictly follow stated burnout times
• Place rings in the burnout furnace to facilitate proper pressing rhythm. (max. 90 minutes at final tempature)
• Prolonged exposure at final temperature increases oxide formation on alloy structure
• Pressing rings must not contact each other or the sides of the furnance

Cracks in the pressing ring during pressing procedure:

• Check investment mixing ratio
• Sprued objects have been placed too close to the edge of the pressing ring
• Pressing temperature is too high
• Pressure is too high
• Aluminum oxide plungers are encrusted with ceramic material or out of the round (disposable plungers guarantee perfect geometry)

Cracks in the Ceramic:

• Shifting of opaque due to pressing temperature being too low/ high
• Check opening speed of furnace (especially for non-precious alloys)
• Alloy used has the wrong CTE (Alloy needs to be in the CTE range of 13.8 - 14.6 at 25-500°C)
• Forced cooling of pressing ring
• Inappropriate processing of opaque (insufficient bond between opaque and alloy)

Graying of the Ceramic

• Pressing temperature is too high
• Inappropriate ingot selection
• Inappropriate opaque selection
• Pressing time is too long

 

Bubbles/ inclusions:

• Pressing temperature is too high (boiling pores)
• Modeling wax is contaminated or not ash free
• Wax Sprues were contaminated
• Rough edges and connections have been created during the waxing process
• Funnel shaped transition from pressing channel to object