Sand mould making procedure

Sand mould making procedure:-
The first step in making mould is to place the pattern on the moulding board. The drag is placed on the board . Dry facing sand is sprinkled over the board and pattern to provide a non sticky
layer. Moulding sand is then riddled in to cover the pattern with the fingers; then the drag is
completely filled. 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. After the ramming is over, the excess
sand is levelled off with a straight bar known as a strike rod. 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. The finished drag flask is now rolled over to the bottom board
exposing the pattern. 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 . The dry parting sand is sprinkled all over the drag and on the pattern. 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. The operation of filling, ramming and venting of the cope proceed in the same
manner as performed in the drag. The sprue and riser pins are removed first and a pouring basin is
scooped out at the top to pour the liquid metal. Then pattern from the cope and drag is removed and
facing sand in the form of paste is applied all over the mould cavity and runners which would give the
finished casting a good surface finish. The mould is now assembled. The mould now is ready for
pouring