Process of moulding by injection:

The moulding by injection was one of the tools of manufacture for the more important plastic industry since the oscillating roscadora in 1956 was patented. It is almost impossible to make something without the use of parts molded by injection due to his use for pieces of the interior of electronic automobiles, frames, articles for the home, medical equipment, compact discs and until cuchas for dogs. Within the typical applications of no-packaging of polyethylene they are: pallets, toys, baskets and buckets. The applications of packaging include thin packages for foods, promotional cups, covers, and covers for milk bottles. The process of moulding by injection requires of the smelting of the plastic in a extrusora and the use of the screw of the extrusora to inject the plastic in a mold, where it is cooled. The speed and the consistency are factors fundamental to carry out a successful operation of moulding by injection, since the advantage margins are generally below 10%. Speed: A molder will maximize the production, diminishing the duration of the cycle, that is the time that is needed to melt the plastic, to inject it in the mold, to cool it and to obtain a finished piece. By means of the use of molds greater than they produce more than a piece per time, the machine develops a cycle that also can increase the production. These molds one knows them with the name molds multiple cavities, because the section of the mold where the piece forms denominates cavity. Consistency: The consistency, or the elimination of remainders and the saving of time, are as important as the production in a successful operation of moulding. A number of variables enters game in the process of moulding by injection, but the most consistent processing happens when it is included/understood and they control the temperature of the plastic, the pressure of the full plastic when the mold, the speed in which the plastic one fills to the mold and the conditions of cooling. These four primary variables of moulding are not independent, but they are possible to be used to include/understand the changes of the process and generally to solve problems. The four variables are applicable for almost all the processes of moulding by injection, but the process will be moderately different in each case, depending in the application, the used plastic and the preferences of the molder. Indice of filling: The polyethylene moulding by injection in applications of thin walls, requires that the material is injected as rapidly as possible to avoid that the plastic is congealed before the piece completely has been filled up. The new resins and the last technology in machineries for this field are concentrated almost always in filled up fast and easy. Besides to diminish the duration of the cycle by means of one better filled up capacity of, the molder can save resin through the filled up one of thinner molds either to obtain a greater production, using great molds the more and with the more cavities. The moulding of thin wall is made with machines that can inject the material in less than 1 second, and are quite great to support extensive molds of multiple cavity. Since the covers and the packages of thin wall tend to be small, some molds are used to mold more than 100 small covers of a single time. The HD polyethylenes with an index of fusion superior to 90 are used to mold cups and packages; and the linear polyethylenes of low density with an index of fusion superior to 150 also are used to produce covers.