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HORIZONTAL FLASHING OR FINNING?
1. Incorrect powder/water ratio (too much water). Use correct
amount of water ( Important with vacuum investing machines).
2. Work time of investment not used up. Ensuring the work time is used up and slurry
temperature is of 20°- 22°C.
3. Casting the metal at too high a pressure ( centrifugal casting). Use the correct
spin speed to suit the weight and metal and type of work.
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OTHER FLASHING OR FINNING
1. Work cycle too long. Investment beginning to set while still
under vacuum. Ensure the work cycle is not too long and slurry temperature is 20°-22°C.
2. Disturbing the flasks too soon. Leave the flasks for at least one hour.
3. Heating too quickly during de-wax. Do not exceed 160°C during de-waxing.
4. Moulds allowed to dry out before burnout. If not burning out the same day, keep
moulds wet by covering with wet sacking or plastic sheets.
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BUBBLES,
COMPLETE SPHERES
1. Investment too thick. Too little water. Use correct powder/water
ratio.
2. Vacuum pump/tank faulty. Ensure equipment is regularly serviced and adequate
for the task.
3. Work cycle too long. Investment beginning to set while still under vacuum. Ensure
the work cycle is not too long and slurry temperature is 20°-22°C..
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BUBBLES, INCOMPLETE SPHERES
1. Static electricity or waxes. Use a product to deionise the
wax. The wax must be completely dry before investing.
2. Grease or dirt on waxes. Use a wax wash.
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WATER
MARKING
1. Incorrect powder/water ratio ( too much water). Using correct
amount of water. (Important with vacuum investing machines).
2. Work time of investment not used up. Ensuring the work time is used up and slurry
temperature is 20°- 22°C.
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ROUGH
SURFACES
1. Rough waxes. Use less release agents on the rubbers. Can be
caused by excess talc.
2. De-wax temperature too hot. Do not exceed 160°C during de-wax.
3. Steam de-waxed for too long. Steam de-wax for a maximum of an hour. Steam will
erode surface of the investment.
4. De-waxed too quickly. Leave flask at 160° for 2/4 hours before achieving
maximum strength.
5. Flasks overheated during burnout. Ensure maximum burnout temperature does not
exceed 750°C.
6. Metal too hot. Reduce casting temperature.
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INCLUSIONS
1. Canales d’alimentation pas corrects. Eliminer les angles
et les courbes trop droits dans le système.
2. Creuset brisé.Remplacer creuset.Ne pas utiliser des creusets vieux que
s’effritent facillement.
3. Metal sale. Ne pas utiliser plus de 50% d'alliage et faites assurer qu’il
soit propre.
4. Cylindres trop surchauffés pendant la cuisson. Faites assurer que la température
de la cuisson ne dépasse pas 750°C.
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INCOMPLETE
CASTINGS
1. Metal or flask too cold. Increase casting temperatures. If
the metal or mould are too cold, the metal will freeze before completely filling
the mould.
2. Improperly sprued. The sprue system should be designed to allow metal enter easily
and without restriction.
3. Incomplete burnout. Increase the burn out time at 760°C. If the flask is
not properly burnt out it will be impermeable and not allow gases to escape when
the metal enters the mould.
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SHRINKAGE
POROSITY
1. Incorrect spruing. Sprues should be attached to the heaviest
piece of the casting. There should be sufficient sprues to ensure the casting is
adequately fed.
2. Flask temperature too hot. The flask temperature should be just hot enough to
achieve complete fill.
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GAS
POROSITY
1. Overheating the metal. Reduce metal casting temperature.
2. Inadequate burn out. Increase the time at 760°C.
3. Flask overheated during burn out. Ensure maximum burn out temperature does not
exceed 760°C.
4. Impurities in the metal. Do not use more than 50% recycled alloy and ensure it
is clean.
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BLISTERS / SPALLING
1. Flask being heated too rapidly during de-wax. Do not exceed
160°C during de-wax. Wax will boil and erode investment surface.
2. Flasks overheated during burnout. Ensure maximum burnout temperature does not
exceed 760°C
3. Flasks put in furnace too soon after investing. Leave flasks undisturbed for
a minimum of one hour before de-wax.
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