SIAM CASTING POWDERS LTD.
HIGH QUALITY INVESTMENT POWDERS
AND CASTING EQUIPMENT

 

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Technical data
Siam Casting Powders Ltd
Jewellery Trouble Shooting
Casting problems
Mould Rubber problems
Wax Pattern problems
Mixing Guide
Burn Out
Casting Temperature Guide
Melting point and specific
gravity of jewellery alloys
Comparative Weights
and Measures
 
    TECHNICAL DATA Technical data
Jewellery Trouble Shooting Casting problems  
 

Problem Cause Remedy
Flashing or Finning    
Incorrect powder/water ratio
(too much water)
Use correct amount of water (especially
important with vacuum investing machines)
Work time of investment too long.
Slurry start to set while still under vacuum.
Ensure the work time is fully used.
Normally 8 minutes.
Casting the material with too much force. For centrifugal casting, use the correct
spin For vacuum casting, reduce pressure.
Moving flask too soon Leave the flasks for at least 1 hour.
Moulds allowed to dry out before
burn out.
If not burning out the same day, keep moulds wet by covering with wet sacking.
Flasks overheated during burn out. Ensure maximum burn out temperature
does not exceed 750 °C
Bubbles    
Investment too thick. Too little water. Use correct powder/water ratio.
Vacuum pump/tank faulty. Ensure equipment is regularly serviced
and adequate for the task.
   
Water marking    
Incorrect powder/water ratio
(too much water)
Use correct amount of water (especially important with vacuum investing machines)
Work time of investment not used up. Ensure the work time is used up and slurry temperature is 20 - 30 °C.
Investment powder expired(too old) Do not keep investment too long time.
Blister    
Dewax soak time not long enough. Extend time for dry dewax at least 3 hours
(temperatures between 150 to 250°C)
Flasks dewaxed at too high temperature. Do not exceed 250°C during dry de-wax.
Wax will boil and erode investment surface.
Flasks put in furnace too soon after investing. Leave flasks undisturbed for a minimum of
one hour before de-wax.
 

 
   
Problem Cause Remedy
Rough surfaces    
Rough waxes. Use too much powder on the rubbers.
Flasks dewaxed at too high temperature. Do not exceed 250°C during dry de-wax.
Wax will boil and erode investment surface.
Steam de-wax for too long. Steam, de-wax for a maximum of 1 hour.
Steam will erode surface of the casting.
Flasks overheated during burn out. Ensure maximum burn out temperature
does not exceed 750 °C
Metal temperature too hot. Reduce metal casting temperature.
Gas porosity    
Usage of low quality metal. Do not use more than 50% recycled alloy
and ensure it is clean.
Reaction with investment temperature.
(Flask temperature too hot)
Reduce flask temperature down, Specially
on big design.
Overheating the metal. Reduce metal casting temperature.
Temperature inside furnaces over. Ensure the quality of Thermocouple can control temperature.
Shrinkage porosity    
Incorrect spruing Sprues should be attached to the
heaviestpiece of the casting. There
should be sufficient sprues to ensure
the casting is adequately fed.
Flask temperature too cold. The flask temperature should be just hot enough to achieve complete fill.
   
Incomplete casting    
Metal or flask temperature too cold. Increase casting temperatures. If the
metal or flask is too cold, the metal will
freeze before completely filling the mould.
Improperly sprued. the sprue system should be designed
to allow the metal to enter easily and
without restriction.