TROUBLESHOOTING

a good cast
A Good Cast

A good casting should be smooth with no blemishes and faults on any side of the casting. Follow the storing, mixing and burnout procedures of the powder will render perfect results every time

a good cast
Flashing
Incorrect water or powder ratio
  • Ensure Correct Ratio P:W
  • Conventional Mix 40:100
  • Vacuum Mix 38:100
Incorrect burnout cycle
  • Follow recommended burnout cycle
  • Ensure furnace ramp does NOT exceed 250ºC/Hr
  • Ensure 1st stage burnout does NOT exceed 220ºC and is held for 4.5 hours minimum.
  • If problem still occurs increase hold time.
Excessive casting forces
  • Centrifugal casting: Lower torque and RPM settings
  • Vacuum casting: Reduce over pressure
Disturbed flask during setting After investing bench set and do NOT move flask, strip base or remove tape for a minimum of 90 minutes.
Over working investment Ensure all flasks are poured and removed from vacuum tank and put on bench to set by max. 7.5 minutes from starting mixing
Waxes too close Waxes too close together creating a very thin wall of investment. Waxes too close to side or top of flask; ensure min. 5mm gap to top and sides of flask.
Slurry too hot Adjust slurry temperature to 21ºC +/- 1ºC by decreasing water temperature
Moulds dried out before burnout If flasks are left on bench for more than 4 hours before burnout place a damp towel over the tops of the flasks to stop them drying out. Do NOT leave flasks in furnace overnight before burnout.
Flask base leak during investing Ensure good seal between wax sprue and base.
It is suggested that it be sealed with molten wax.

a good cast
Rough Surfaces
Overheated flasks during burnout
  • Follow recommended burnout cycle
  • Ensure furnace ramp does NOT exceed 250ºC/Hr
  • Ensure 1st stage burnout does NOT exceed 220ºC and is held for 4.5 hours minimum.
  • If problem still occurs, increase hold time.
Dust on waxes or trees Ensure once waxes or wax trees are made, they are stored in a dry, clean and dust-free atmosphere. Do NOT store waxes or trees in a dusty environment or investing room.
Metal/Flask temperature incorrect Reduce or increase metal / flask temperature.
Rough waxes Ensure excessive talc or release agent is not used, as this will produce rough waxes and therefore rough castings
Flask burnt too quickly after mixing Do NOT burn out before minimum of 90 minutes after investment.
Under or over-worked Follow the recommended mixing
Steam de-waxed for too long Steam de-wax for a maximum of 60 minutes at atmospheric pressure. If steam de-waxed for longer than 60 minutes, the steam may start to erode the surface of the mould.

partial fill
Non/Partial Fill
Metal temperature incorrect Increase metal temperature first before increasing the flask temperature
Flask temperature incorrect Increase flask temperature
Incorrect feed/sprue system Feed or gate should be attached to the thickest part of the casting. It should be at least 25% of the thickness of the largest cross section of the casting
Insufficient centrifugal force Increase torque first and then RPM of the centrifugal casting machine. Only increase by small amounts each time (5%)
Low vacuum when vacuum casting
  • Change oil in pump on a regular basis
  • Check seals for blockages in the vacuum pipes
Not enough over pressure Only increase over pressure by small amounts each time (5%)

partial fill
Bubbles/Pins
Bad vacuum Change oil in vacuum pump. Pump should be serviced on a regular basis
Dust on waxes or trees Ensure once waxes or wax trees are made, they are stored in a dry, clean and dust-free atmosphere. Do NOT store waxes or trees in the same room that you weigh powder or invest in
Rough waxes Ensure excessive talc or release agent is not used, as this will produce rough waxes and therefore rough castings
Under or over worked Follow the recommended mixing instructions

partial fill
Blistering/Spauling
1st stage burnout hold too short
  • Ensure 1st stage burnout hold time at 220ºC is 4.5 hours.
  • If problem still occurs, increase hold to 5.5 hours
Flasks de-wax at toohigh a temperature Do NOT exceed 220ºC in the 1st-stage burnout
Flasks placed in furnace too soon after investing Do NOT burn out before min. 90 minutes after investing
Flask placed too close to or touching elements Leave a minimum of 50mm gap between flasks and elements.