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Introduction to the Lost Foam Casting Process

Process Steps

  1. Mold foam pattern sections.
  2. Age pattern to allow dimensional shrinkage.
  3. Assemble pattern if it is a multiple piece pattern.
  4. Build cluster (multiple patterns per cluster).
  5. Coat cluster.
  6. Dry coating.
  7. Compact cluster in flask.
  8. Pour metal.
  9. Extract cluster from flask.

1. Mold Foam Pattern Sections

2. Age Patterns

  • Age Patterns
  • The foam material used to create the pattern shrinks in much the same manner as a typical casting.
  • Patterns are “aged” by allowing them to rest at room temperature for a period of 5 to 7 days.
  • Patterns may also be force aged in a drying oven to allow for quicker use.

3. Assemble the Patterns

  • Production patterns are assembled using a precision, automated gluing machine.
  • Glue is printed to one section of the foam and then pressed against the adjoining piece.
  • Multiple piece parts can be built up in this way and produce very complex geometry.

4. Clustering

  • Glue individual patterns to sprue.
  • Number of patterns per sprue is dependent on part size and/or part configuration.
  • Molded sprue is manufactured similar to foam pattern

5. Coating

  • Coating parameters are verified before coating cluster.
  • Coating is mixed continuously to maintain properties.
  • Cluster may be hand dipped or by automated robot station.

6. Drying

Coating is dried in an oven at 120oven at 120 - 140°F (49 - 60°C) for 3 to 5 hours.

7. Compaction

  • Cluster is delivered to the pouring line by conveyor.
  • Cluster is placed into flask and held in positionby a fixture
  • Fixture is timed to release the cluster during compaction cycle.
  • Sand is rained into flask from overhead bin.
  • Compaction tables can be either vertical or horizontal in orientation and vibrate during filling.
  • Sand is compacted from approximately 90lb/ft³ to 100 lb/ft³ by the compaction table

8. Metal Pour

  • Metal is poured to to displace the polystyrene.
  • Metal may be poured by hand or with an hand or with an automatic ladle

9. Extraction

  • Casting is allowed to cool in sand for a predetermined period.
  • Flask is then dumped on to a shakeout conveyor.
  • Loose sand around the casting cluster helps protect the parts from damage.
  • Castings proceed through shakeout to remove loose sand and coating.

Final Casting

 
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