Specifications of Molding Machines

Molding Machines specifications have many characteristics yet there are only two most frequently used in specifying and describing the machine. The first is the shot size and the second is the clamping tonnage.

Shot Size

The shot size is the amount of material that can be injected into a cavity within one shot cycle. Due to the differences in material density, a standard for comparison was developed. Thus the accepted material for shot size comparison is polystyrene.

For example, a small lab size injection machine would be capable of about .5 oz of material. Where a large production capacity machine can be sized to the equivalent of 20 lbs of polystyrene.

Clamp Tonnage

This is the maximum force that a machine can apply to a mold. One method is to categorize the machines based on this clamping force. A small machine will have less than 100 tons where a medium machine will be between 100 and 2000 tons. The very large machines will be up to and over 10,000 tons.

As a rule of thumb you would need approximately 786 pounds of force for each square centimeter of mold cavity surface area.

For example, if you had a mold with the cavity area of 1200 square centimeters you would need [1200*786] =943200 pounds, or 472 tons of clamping force, minimum,  to keep the mold closed.