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PET Preform Testing using Polariscope

Polariscope is an optical device used to check the defect in the PET preforms, glasses, gems and anything that passes light. A basic polariscope comprises of two polaroid lenses and an incident light. One is called polarizer and the other which is near the eye is called analyzer. This light will pass through the lenses. As soon, something comes in between the light and lenses, the light will either get reflected or refracted. The samples which are tested in this device does not refract the light. Any defect in the sample tends to refract the light doubly, thus creating a different pattern. In a standards device, you can see the sample from different viewing angles, usually 45° and 90°. You can refer the defect chart that comes with the device to identify the defect.


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How is it helpful in PET industry?

Internal stress caused by an external force creates the defect in the final product made out of preforms. Defects in the neck, bottle wall, bottle bottom can cause instability in the bottle. A bit of impact on the defected area can lead to product failure. And it can cost huge if something reactive is stored in the bottle, it can cause mishap or spoiling of complete lot stacked together or transported together. PET packaging is considered as very strong and reliable packaging and often mishandled. It would be dangerous if a bottle or jar having a defect is being mishandled. So, a vendor takes appropriate care not to produce defective preforms.


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Polariscope is used in the preform assembly to check the possible defect in the preforms. Take the precautions at the early stage would help a lot in cost cutting and time-saving. Moreover, after the preforms are blown, the defects tend to expand and becomes quite difficult to judge from naked eyes. Hence, the vulnerability of bottle to get deformed increases.

Presto offers specifically 2 models; one for glass and one for PET industry. The glass model is an upgraded version of PET defect identification model. Glass model can identify errors in the glass as well as PET. Both models are table top models and not very bulky. With easy to use functionality, designed ergonomically to minimize the fatigue.

What are different features of Polariscope?

  • The device gives you 2 slots for different light orientation; one is for 90° and other is for 45°
  • The weight of the device is not more than 20kgs
  • The viewing field size is 260X260mm
  • The device requires the standard power supply i.e. 220/240V
  • The testing device can be clamped at any angle
  • The diameter of the field view is 120mm

For more information regarding Polariscope models, you can drop a query.


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