Troubleshooting

Problem Area

Symptom

Potential Problem

Solution

Pattern Issues

Softness in Patterns

Moisture Absorption

Dry pattern in a very low humidity environment

Return to pattern supplier for replacement

Holes in Cracks in Pattern

Damage to Pattern

Return to pattern supplier for repair or replacement

Patch with wax

Incomplete finishing

Return to pattern supplier for repair or replacement

Leak Test Failure

Surface holes or Cracks

Find leaks and repair or return to pattern supplier for repair or replacement

Has not proven to affect the performance of the pattern

Overexposure to UV light

Most likely will not affect performance of the pattern

 

Solid areas in pattern

Return pattern to pattern supplier for repair or replacement

Shelling Problems

Poor Shell Adhesion on QC Patterns

Contaminants on pattern

Wipe with etch solution or dip assembly in etch

Poor Shell Adhesion on Runners, Gates or Sprues

Contaminants on runners and sprues

Wipe with etch solution or dip assembly in etch

Autoclaving Problems

Shell Cracks in Autoclave Cycle

Vents not open to pattern interior

Make sure all vents are open at the ends and where they attach to the pattern – pattern skin is punctured, prior to placing he shell in the autoclave

Inadequate venting

Increase number and size of vents. There should be at least one vent per pattern

Burnout Problems

Incomplete combustion (material other than ash in the shell after burnout)

Inadequate venting

Increase number and size of vents. There should be at least one vent per pattern

Inadequate oven temperature

Increase furnace temperature to 1500F or higher

Inadequate burnout time

Increase time in furnace to 2 hour for small patterns, 3 hours or longer for large patterns

Inadequate oxygen to support combustion

Ensure that patterns are vented

Ensure that there is adequate oxygen in the furnace

Ensure that air can get into the shell easily

Casting Problems

Inclusions in the casting

Leakage of slurry into pattern

Ensure patterns are properly sealed

Hex pattern on castings

Leakage of slurry into pattern

Ensure patterns are properly sealed

Surface Pitting

Incomplete combustion of pattern

Increase airflow through pattern

Increase oxygen in furnace

Increase burnout temperature

Increase burnout time

Ash remaining in shells after combustion

Rinse shell prior to burnout

Blow out shell hot if unable to cool for rinse