Analyse Stress and Strain Distribution of PET Material
Stress & strain analysis has a great relevance in quality inspection process that is used to determine the stress and strain in PET materials which are subjected to forces applied. The test is performed on a Polariscope-Strain Viewer. This method has a huge importance for quality PET bottle production.
During the manufacturing process, a PET bottle, at the very initial stage from which a PET material undergoes is the ‘injection stretch blow molding’ process.
This process is categorised into four stages:
1. Injection
Molten polymer flows into the injection gap through the hot runner block and makes the preform. After a specific set of time, the injection mold and the preform held in a neck carrier is rotated to a 90° angle.
2.Stretching
By adjusting to the appropriate temperature, the preform made ready for stretching. When the preform is within the blow mold area, the mold close, a stretch rod is commenced to elongate the preform longitudinally.
3.Blowing
After the stretching, using two levels of air pressure, the preform is blown circumferentially.
4.Discharge
After a specific set of time, when the mold is cooled off, it opens and the preform is removed through drop chutes or robotics
At the time of this process of stretch blow molding, the preform may incorporate different kind of stress distributions or strains on itself. This defect can disturb the required thickness distribution and properties of the final bottle. As the thickness dissemination is one of the most vital criteria in the production of bottles, the strain can be regarded as a major quality hampering factor for PET bottle manufacturers.
Stress & Strain analysis to detect PET preform defects
Stress analysis in PET preform works by observing the most obvious view of the mechanical characteristic of materials. It is supposed that the stresses which are observed are related to strain (deformation) of the material. This deformation can be identified using the photo elastic method on a Polariscope Strain Viewer.
The photo elastic process explains the changes in the optical properties of a preform having mechanical deformation. It identifies the strain in PET preform by giving a picture of stress distributions around gaps in the preform.
The accurate Polariscope from Pacorr can identify tiny stress or strain that occurs in the product and can help the manufacturer in testing the quality and transparency of PET preforms before the final production.
To learn more about the quality and best prices of Pacorr’s Polariscope Strain Viewer, please contact our technical team.