WWW.07MET.TK Casting & Working of Metals Lab Manuals
PRACTICAL # 2 PRACTICE FOR MAKING SAND MOLDS USING DIFFERENT PATTERNS
Overview: Silica sand (SiO2) is used more commonly for making castings than any other molding materials. It is relatively cheap, and has sufficiently refractoriness even for steel foundry use. A suitable bonding agent (clay or molasses) is mixed with the sand; mixture is moistened with water to develop strength and plasticity and to make the aggregate suitable for molding. The resulting sand mixture is easily prepared and molded around various shapes to give satisfactory casting of almost any metal. The fundamentals of mold making are simple, but expert hand molding requires much skill and practice. Production line work is done today by machine molding, in which nearly all operations are automatic. The skilled molder is replaced by a relatively untrained machine operator.
Equipment: A. Flask or Molding Box B. Rammer C. Riddle D. Wooden or Steel Board E. Different Patterns F. Draw spikes
Chemicals / Materials: Molding Sand, Graphite Powder, Molasses
WWW.07MET.TK Casting & Working of Metals Lab Manuals
Procedure: 1. First of all place the wooden or steel board (bottom board) on the table or floor. 2. Place the draghalf of the flask on the bottom board and position draghalf of the pattern in it. 3. Sprinkle some amount of graphite powder in the flask and over the pattern to produce smooth surface finish. It also acts as a parting agent. 4. Now, fill the draghalf of the flask with molding sand keeping the pattern in position. 5. Ram the molding sand in the flask with the help of a rammer. 6. Continue adding and ramming the sand until it is densely packed in the flask. 7. When the flask is properly rammed, then use a metal strip to remove excess sand from the upper surface. 8. Now, place a second flat board upside down on the mold and flask, clamp it and over turn the whole. 9. Remove the first bottom board which is now on top and sprinkle some amount of graphite powder (parting powder) on the surface of mold to finish it. 10. Now, position the copehalf of the flask over drag and also the copehalf of the pattern. 11. Place two rods vertically on either sides of the pattern, at a suitable distance, to produce pouring basin and risering system. 12. Fill the copehalf with molding sand keeping the pattern and rods in position. 13. Ram the molding sand in the flask with the help of a rammer. 14. Continue adding and ramming the sand until it is densely packed in the cope. 15. When the flask is properly rammed, then use a metal strip to remove excess sand. 16. Now, remove the rods from the copehalf and as a result holes for spruce and riser will be produced. 17. Separate cope and drag portions of the flasks from each other, use draw spikes to remove the pattern from the mold. 18. Cut the ingates in the mold and again sprinkle some amount or graphite powder over the surface of mold to finally finish it. 19. If necessary, position the cores in the cavity of the mold and close the mold again by placing cope again atop the drag.
WWW.07MET.TK Casting & Working of Metals Lab Manuals
20. The mold is ready for pouring.