Identifying Strains and Defects Using Polariscope

Identifying Strains and Defects Using Polariscope

Having good quality PET preforms is very important for packaging industry to deliver products safely. As PET packings are primary packings and it is very important that they should withstand the environmental and operation based stress throughout the lifetime. For such a performance, the preforms should be of best quality. Due to defective preforms, the production line will produce defective components. There could be 2 reasons for defects in preforms; 1. Design induced, 2. Process induces.
 
Design Induced Defects – It is possible that due to ignorance or lack of knowledge, some crucial factors of got ignored. This ignorance may lead to the development of defects which needs to be highlighted. Using a strain viewer like polariscope, to identify such defects before starting the mass production. 
 
Process-Induced Defects – These defects usually occur due to the faulty production process. When preforms are manufactured, they must be tested for any strain and other defects before starting the mass production. The defects can be matched with the preform defect chart to identify the root cause. 
Polariscope is an optical device that uses incident light to highlight the strain induced defects under polarised lenses. Under the effect of polarized lenses, the incident light creates birefringence when encountering a defect. These birefringence patterns can be easily recognised and matched with the defect chart. Based on the observation and chart comparison, the root cause of defects can be identified. 
 
A Polariscope is an optical device and works on the principle of the refractive index of light. Usually, a PET preform allows the light to pass completely without deviating its path. When this incident light encounters a defect, it creates birefringence due to double refraction of light. Strain identification is not only about the highlighting the defects. After understanding the defects, the regression in the production process can be considered and subsequent changes can be incorporated. 
Presto is the leading manufacturer of defect testing machine for preforms. Offering two models for defect identification, one is suitable for PET products and other is for glass products. The instrument comes in a very compact benchtop size.
 
How to Maintain Your Polariscope?
There are certain measures that are needed to be taken. This definitely helps in increasing the shelf life of the product.
Turn off the power device when not in use.
Try avoiding touching the lenses, this causes finger impressions. To wipe off the prints and dust, use a lint-free cloth.
Always cover the device when not in use.
Try to accommodate it in ideal laboratory conditions