A success casting product comes from many factors. The first a caster has to consider is the sprue design.

According to the rule of thumb, the main sprue needs to be larger than the feeds sprue and the cross sectional area of the feed sprue should be between 70 and 150% of the attachment point on the pattern and be attached to the pattern at its thickest section.

However, when we received some drawings from our customers with complicated shape and special functions, rules of thumb could not provide completed fill where the design of sprue size and shape did not do as well, experiments would carry out to give a research on system temperature.

As patterns with different sizes are casted, they will hold different amount of heat energy and release different amount of temperature. Thus the surface area to volume ratio needs much consideration. The thinner the pattern is, the more the flask temperature influences. Thick and thin patterns should not be casted on a same tree because thin patterns need higher flask temperature to be filled while the thick ones need lower flask temperature. And casting temperatures vary with different alloys. The casting temperature for a certain alloy is higher for thin section patterns and lower for thick section patterns. Any way, a good sprue system is supposed to provide lower casting temperature.

After sprue selected and improved in order to have every pattern casted perfectly, next experiment would be introduced. A pattern is attached in different locations with five-six different feed sprue configurations to a tree. This is help to find the attachment point between the feed sprue and the pattern and the position of patterns also influences the quality of casting.

Finally, the gate phenomenon would be considered to reduce possible porosity.

As you see, every success casting part is a delicate art and craft.

Lei Xian Feng