Permanent Mold Casting or Gravity Die Casting utilizes metal molds, usually iron or steel. The mold is preheated, assembled and molten aluminum is introduced at the top of the mold. Steel cores, if used, are removed shortly thereafter. Upon solidification, the mold is opened and the casting ejected. The cycle repeated.
The process is not as quick or efficient as die casting over large product runs but offers significant advantages over sand casting in some situations. In limited production runs permanent mold casting has the lowest total per piece cost of any casting process.
Benefits & Advantages of Permanent Mold Casting
Reduced Weight and Dimensions from improved Mechanical Properties. A finer grain structure is achieved by rapid solidification caused by using a steel die, which acts like a heat sink. This characteristic allows for reduced section thickness and weight while maintaining the required physical strengths.
Design and Tolerance Control is achieved by casting using rigid steel dies. Parts can be cast to size with excellent dimensional repeatability.
Less Machining and Second Operations is due to tighter tolerances. This allows for holes and shapes to be cast ready for tapping or reaming. Also insert casting is easily accommodated.
Improved Surface Finish compared with a sand casting is again due to the steel die providing a superior surface texture. This results in a reduction in finishing operations or a more aesthetic appearance.