Sand-based Moulding Methods:

Over the years, several processes have been proposed to overcome some of the restriction of the more traditional methods. While few have become commercially important, various are included here to shown the nature of these efforts.

In one method, called as the V-process or vacuum moulding, a vacuum is utilized in place of a sand binder. Then a vacuum flask is placed over the pattern, the flask is filled with sand, a sprue and pouring cup are created, and a second sheet of plastic is located over the mould. Then a second vacuum is drawn on the flask itself, compacting the sand and giving the essential strength and hardness. The pattern vacuum is free, the pattern is withdrawn, and the mould halves are assembled. The mould is poured when maintaining a vacuum in the cope and drags both segments of the flask.

Advantages of the vacuum procedure include the net absence of moisture-related defects. As no binder is utilized, binder cost is removed and the sand is totally reusable. No fumes (binders burning up) are produced during the pouring operation. Shakeout characteristics are exceptional; virtually the mould collapses while the vacuum is released. Unluckily, the procedure is relatively slow due to the additional steps and the time needed to pull an adequate vacuum.

In another procedure, sand with a small amount of clay and rather a bit of water is primary packed around a pattern. The pattern is eliminated and liquid nitrogen is sprayed onto the mould surface. The ice that make becomes the binder, and the mould is then poured when this is in its frozen condition. As with the V-procedure, binder cost is low and shakeout is outstanding.