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Manufacturing Processes > Casting Processes > Ceramic Mold Casting

 

Ceramic Mold casting

 

Process description

A precision pattern generates the mold which is coated with a ceramic slurry. The mold is dried and baked. The molten metal is then poured into the mold and allowed to solidify. The mold is broken to remove the part.

Materials

All metals, but to a lesser degree, aluminum, magnesium, zinc, tin and copper alloys.

Ceramic Mold Casting

Process variations

  • Variations on the composition of the ceramic slurry and curing mechanism.
  • Plaster, wood, metal or rubber are used for patterns.

Economic considerations

  • Production rates of up to 10/h typical.
  • Lead times can be several days. Material utilization high.
  • Low scrap losses.
  • Best suited to metals having high melting temperatures and/or that are difficult to machine.
  • Can be combined with investment casting to produce parts with increased complexity with reduced cost.
  • Suitable for small batches and medium-volume production.
  • Can be used for one-offs.
  • Tooling costs moderate.
  • Equipment costs moderate to high.
  • Direct labor costs moderate to high.
  • Finishing costs low. Usually no machining is required.

Typical applications

  • All types of dies and molds for other casting and forming processes
  • Cutting tool blanks
  • Components for food handling machines
  • Pump impellers
  • Aerospace and atomic reactor components

Design aspects

  • High complexity possible – almost any shape possible.
  • Use of cores increases complexity obtainable.
  • Inserts, bosses and undercuts possible.
  • Placing of parting line important, i.e. avoid placement across critical dimensions.
  • Cored holes greater than Ø0.5 mm.
  • Where machining required, allowances of up to 0.6mm should be observed.
  • Draft angle usually zero, but 0.1–1° preferred.
  • Minimum section ranging 0.6–1.2 mm, depending on material used.
  • Sizes ranging 100 g–3 t in weight, but less than 50 kg better.

Quality issues

  • Low porosity.
  • Mechanical properties are good.
  • Good surface detail possible.
  • Surface roughness ranging 0.8–6.3 µm Ra.
  • A process capability chart showing the achievable dimensional tolerances is provided . An allowance of ±0.25mm should be added for dimensions across the parting line.
  • Parting lines sometimes pronounced on finished casting.

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