To prepare a mould for sand casting for given pattern

Objective

1. To prepare a mould for sand casting for given pattern.
2. To melt and pour iron metal into the mold.

Equipment and Materials

1. Split piece Pattern
2. Molding flasks
3. Molding tools
4. Melting furnace
5. Fluxes
6. Pouring ladle
7. Pyrometer.

Mould Making

1. The first step in making mold is to place the pattern on the molding board.
2. The drag is placed on the board Figure 3(a).
3. Dry facing sand is sprinkled over the board and pattern to provide a non sticky layer.
4. Molding sand is then riddled in to cover the pattern with the fingers; then the drag is completely filled.
5. The sand is then firmly packed in the drag by means of hand rammers. The ramming must be proper i.e. it must neither be too hard or soft.
6. After the ramming is over, the excess sand is leveled off with a straight bar known as a strike rod.
7. With the help of vent rod, vent holes are made in the drag to the full depth of the flask as well as to the pattern to facilitate the removal of gases during pouring and solidification.
8. The finished drag flask is now rolled over to the bottom board exposing the pattern.
9. Cope half of the pattern is then placed over the drag pattern with the help of locating pins. The cope flask on the drag is located aligning again with the help of pins (Figure 2 (b)).
10. The dry parting sand is sprinkled all over the drag and on the pattern.
11. A sprue pin for making the sprue passage is located at a small distance from the pattern. Also, riser pin, if required, is placed at an appropriate place.
12. The operation of filling, ramming and venting of the cope proceed in the same manner as performed in the drag.
13. The sprue and riser pins are removed first and a pouring basin is scooped out at the top to pour the liquid metal.
14. Then pattern from the cope and drag is removed and facing sand in the form of paste is applied all over the mold cavity and runners which would give the finished casting a good surface finish.
15. The mold is now assembled. The mold now is ready for pouring.

Melting and Pouring

1. Melt the metal in the furnace. Use appropriate fluxes at proper stages and measure metal temperature from time to time.
2. Pour the molten metal into the pouring ladle at a higher temperature (say 100o C higher) than the pouring temperature. (Fig. 3(c)). As soon as the desired pouring temperature is reached, pour the liquid metal into the mold in a steady stream with ladle close to the pouring basin of the mold. Do not allow any dross or slag to go in.
3. Allow sufficient time for the metal to solidify in the mold. Break the mold carefully and remove the casting.
4. Cut-off the riser and gating system from the casting and clean it for any sand etc.
5. Inspect the casting visually and record any surface and dimensional defects observed.

Sketch:

Precautions:

1. Ramming should be uniform to impart uniform strength to the mould.
2. Apply parting sand at the partitions for ease separation of boxes.
3. Locate the two halves of pattern properly to avoid mismatch.

Result: