Shrink

ShrinkShrink presents as irregular crevices, fissures or voids (apparent or not); usually on the surface of the casting or in the gating. This defect indicates poor feeding during metal solidification in certain areas. Metal shrinks as it solidifies and the defect occurs if molten metal can’t feed the solidifying area.

The causes of this defect are evident in the metal and other portions of the process. To cure these causes, R&R recommends taking the following actions.

 

Area

Cause

Cure

Wax

 

 

Shell

 

 

Metal

  1. Metal temperature is uncontrolled.
  1. Determine optimum temperature and control.

Other

  1. Improper setup to feed casting.
  2. Pouring practice.
  3. Rapid or uncontrolled cooling.
  1. Increase gate size, increase runner size, increase heat pressure (improve the runner or gating system by enlarging in-gates to allow for metal to enter a part more quickly. Increase the cooling speed of the metal. Reduce the mold mass.).
  2. Fill mold quickly.
  3. Kaowool wrap molds or other external measures.

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