Young People's Page


| May/June 1971



Dimension of the flask

Torque Power Live Steam Models Hyattstown, Box 144-D R. F. D., Ijamsville, Maryland 21 754

Hi There Young Engineers:

I am going to discuss three types of molding processes sand molding, investment molding and permanent molding. You may end up using all three as each has its own advantages.

To do sand molding you must find a supply of molding sand. Hopefully you may have a nearby foundry from which you can get the sand and some firsthand knowledge about sand molding. The size, shape and material you wish to cast in, as individual factors which vary in combination, make it impossible to give one set of rules which will work all the time. So, this is something with which you are going to have to experiment. All I can do is give you some tips. Since aluminum is excellent to work with, I will mainly describe the molding of it.

The molding sand comes in several grades of coarseness; use the fine or medium. The fine can reproduce extreme details to the extent of being able to reproduce a fingerprint and it is the best for small castings. Be sure to get used sand as green sand is very hard with which to work. In regular foundry practice green and used sand are mixed fifty-fifty. The high temperature of iron or brass would eventually burn the green sand to the point where it would become workable. But with the low temperature of aluminum and with such little use as the sand would receive making small castings, it would take too long for green sand to get into good condition.

You will also need parting dust. The foundries use an industrial type of flour. So, any low grade flour would be good. The flour should be put in a small cloth bag that is porous enough to allow the flour to sift through it when shaken in an up and down motion over the open mold.