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What is Injection Molding Process?

Technically, injection molding is the process of injecting head material in the mold. The granulated particles converted into molten state using some heaters. This molten plastic is fed into the molds using injection heads. This plastic is then cooled down to become a solid article. Using ejectors this harden plastic which has taken the shape of the cavity is taken out.

Testing is an important step of injection molding process. There are some tests which are performed before molding to check if the polymer would be able to take the shape without defects and faults. However, post molding tests are also very important to see if final products are as per standards.

Some of the commonly performed tests are;

Melt flow index test. This test determines the fluidity of the molten plastic. In this test, the fluid is sprayed from the nozzle of defined diameter. If the polymer has high melt flow index, it is easy for the manufacturer to mold it using different techniques. If the polymer has low MFI, it is considered as the stiff form and only dedicated techniques can be used for molding.

Tensile Strength test. As its name defines, the tensile strength test is performed to check the resistance to force when applied from opposite directions. This is actually a very important test to adjudge the suitability of polymer as per the application. For instance, the polymer used in beehive crates need to bear the load, thus tensile strength must be high. On the other hand, the external body of writing pen doesn’t have to be very strong. A Tensile strength tester can do this job very easily. And, if some high-end testers are installed, their output is in a graphical format which gives very minute details.


Impact strength tester. This test determines the ability of the plastic to bear the impact of free-falling object. In labs, a weight as per standards made to fall on the test sample. A Visual inspection would determine how the sample behaved to the impact.

Why testing in injection molding process is important?

In plastic industry, quality management is a difficult task. Because on one end, there is always a constant pressure to decrease the use of raw material. On the other, maintaining the quality as per standards is important. So, every fraction of a millimetre is important. Here, tensile strength tester plays an important role determine the threshold force that polymer can bear.

Research and development are another reason to perform testing on polymers. How can things be made better and cost effective for manufacturer and consumer? What are the new perspectives and opportunities? How can resources be exploited in the best possible manner? To answer some questions like these, it becomes imperative to conduct the testing.

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