Introduction:
Also known as no bake sand casting, the
no bake casting is the most sophisticated casting techniques of the modern times. In this process a strong chemical bond is created in the mold that is made from a mixture of sand, quick-setting resin and catalyst. Air set molding, which is a cold setting process, was developed in response to the increasing demand for castings by customers worldwide. Though is an expendable mold, this mold is largely favored because this strong molds, can stand on it own, without the used of mold boxes and therefore mold of any size can be made.
Process: Graded Kiln dried sand is manually mixed in a mixer with the chemical binder like urethane and catalyst. When the sand mix leaves the mixer it forms a strong mixture. The presence of resin in the mixture, helps to keep the sand to remain strongly bound at room temperature. This strong and hard non-reusable sand mixture is then packed around the pattern or multiple patterns made of wood, metal or plastic. This process is known as the compaction process. Now when the casting mold is set the pattern removed by the roll over process. In the mold cavity, molten metal in poured from the crucible guided by the sprure and the gating. Shrinkage during the solidification in compensated by the use of risers.
After casting , the molded sand is taken away from the casting. Sand can be reclaimed to some extend by thermal means. No bake sand mixture can be used not only to make mold but also to make cores for internal passages.
Reclamation of Sand: No bake sand casting is an expendable process where the mold cannot be reused. The Sand used for the mold cannot be reused as in other sand casting process. But some techniques are developed by which the sand can be broken down, cooled and filtered to be reused. The reclaimed sand is then mixed with a large amount of fresh sand in order to make a new no bake sand mold.
Application:
Widely favored for high precision casting in brass, bronze, aluminum and iron alloys, this process ensures accurate production of complicate designs. No bake process is an ideal process for high value, heavy and critical castings. Casting of large size can be done with perfection, since the mold can stand on it own without the need for flasks or other supports.
Advantages:
- A simple method that required less manual labour
- Reduced production cost
- More number of cast can be produced
- Complicated designs and excellent surface finish can be casted compared to other sand casting techniques
- Less time for mold setting
- Most efficient and advanced sand casting techniques currently available
- Big castings can be casted in a single mold.
- Large, heavy, intricate, castings can be produced
