UNDERSTANDING THE PROCESS

 THE FIRST STEP is usually drying the plastic material. most plastics have to be heated to a certain temperature for a specific amount of time to pull moisture from the plastic prior to molding.  PLASTIC IS HEATED to a liquid form. that plastic is forced into a mold and cures. it sounds simple, but is a complex process.  THERE ARE THREE MAIN UNITS which make up an injection molding machine – the feed hopper, the heater barrel and the screw. the plastic in the hopper is in most cases in granular form.  THE PLASTIC from the hopper enters the heated barrel and is moved along with the screw. as it moves, it is heated and by the time it reaches the end of the barrel it has been heated to a liquid state and is injected from the end of the barrel through a heated nozzle into the tightly clamped mold filling all the cavities and then allowed to cool. thermoset plastics require a heated and temperature controlled mold to set the plastic.  ONCE THE PLASTIC has cooled or set for the necessary time the mold is opened and the part is ejected from the mold. the mold closes and the process starts over again.

 INJECTION MOLDING enables complex shapes to be manufactured, some of which might be near impossible to produce economically by any other means.  IN VOLUME it is a low cost process, arguably with minimal environmental impact. There is little scrap created in this process, and scrap that is produced, can be re-ground and re- used.

 THE INVESTMENT IN TOOLING Making the mold - typically requires high volume production to recover the investment, though this does depend on the particular part.  PRODUCING THE TOOLING Takes development time and some parts do not readily lend themselves to a practical mold design.

 A HIGH QUALITY MOLD Although of relatively high cost, will be capable of turning out hundreds of thousands of parts.  THE PLASTIC ITSELF is quite inexpensive and despite the energy required to heat the plastic and cycle the press (to remove each part) the process can be economical for even the most basic items.

 Making a mold often requires complex design, multiple machine operations and a high degree of skill. A mold is usually in two main assemblies clamped together in the molder press. CNC machines have enabled a high degree of the automation of the of mold manufacturing process.  ALUMINUM The most common molds are manufactured from aluminum when pressures and types of plastics allow. Aluminum is cheaper and easier to machine.  STEEL Steel is used when higher pressures are used for more complex shapes or more abrasive plastics such as glass filled products. Steel offers longer mold life than aluminum.

OPEN ALUMINUM MOLD CLOSED ALUMINUM MOLD

 120 Ton Machine  250 Ton Machine  390 Ton Machine  Shot sizes up to 29 oz.  2 core pulls  MOLD SIZE – Up to 29” x 29” tie bar spacing (max physical mold size)  Common materials processed – PVC, Ultem Polypropylene, ABS, Polycarbonate, Styrene, Acetal, Delrin, Nylon

BLACK POLYPROPYLENE CONTAINERSPOLYPROPYLENE POLYCARBONATE

ACETAL, HDPE, POLYURATHANE ABS