Injection molding machine

Injection molding machine

Introduction:

This is one of the manufacturing processes through which raw form of plastic can be converted into parts or products. An injection molding machine produces parts or products by using thermo-set and thermoplastic polymers. In this process these polymers are melted, reshaped and cooled in the mold to get the desired shape of the product, as a pot maker molds mud to a pot. Injection molding machine is the cost effective method through which an organization can deliver number of quality, simple or complex products in less time with high precision. Typically the production time falls between 10 to 30 seconds.  On the other hand, to set up this machine an organization need to spend a lot of money and also operator need to follow strict guidelines to avoid incomplete filling, surface imperfections, burned parts and warped parts which results in the desired product.

Major parts of the molding machine:

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This machine comprises of two major units injection unit and the clamping unit which are discussed below.

Injection unit: There are two types of injection units available named as reciprocating- screw machine and another is crew- preplasticizer. In this unit all the polymers which are fed in hopper are driven by the rotation of the screw and at the same time heat applied to them which melt these polymers and these melted polymers are injected into the mold.

Mold: This is the customized unit depending on the customer’s final product requirements. Once the production is finished for one part then the mold is replaced by new mold for the next part. Mold contains more than one cavity, as the cavities increases the production rate also increases but it is expensive to buy the multi cavity mold. A typical 16 cavity mold is depicted below, this produces 16 parts in one production run.

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http://www.efunda.com/processes/plastic_molding/molding_injection.cfm

Clamping unit: This unit helps to open and close the mold which also helps to eject the parts. Ejection system and the cooling system are the two major parts of this unit which are discussed below.

Ejection system: The main function of this system is to eject the molded parts from the cavity by using the ejector pins which push these parts out of the cavity.

Cooling system: Two types of cooling systems are available which are direct and indirect. In direct method carob dioxide or pressured air used to cool down the mold and water supplied through pipes in indirect cooling method to cool down the mold.

References:

  1. German, R. M., & Bose, A. (1997). Injection molding of metals and ceramics. Metal Powder Industries Federation.
  2. Introduction to Injection Modeling. Retrieved from http://www.efunda.com/processes/plastic_molding/molding_injection.cfm
  3. Sayer, M. E. (1988). U.S. Patent No. 4,740,150. Washington, DC: U.S. Patent and Trademark Office.

 

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