STRAIN VIEWER FOR PET PREFORMS (Ref. S-400)
Check PET Preforms for CRYSTALLINITY and other defects.
Strain Viewer with special Alignment Stage removed. / This Sharples Strain Viewer is already in worldwide use for the quality control of PET preforms.
The advantages of our PET preform Strain Viewer are : -
1.Crystallinity is readily identified.
2.Not only can the molecular birefringent flow lines (fringes) be seen in colour but the black isoclinic lines are visible when the preform axis are parallel to the polarising axis of the viewer. The isoclinic lines indicate the directions of the molecular orientational strains.
3. A special and removable stage is provided to rapidly obtain the correct alignments of the preforms when viewing.
For observations of the fringes the preforms are aligned at 45 degrees to
the polarising axis and at 0 degrees to view the black isoclinics.
The stage allows for the rotation of the preforms whilst viewing.
Sodium light is also provided, in addition to white light, for the examination of coloured preforms or completed bottles. The lamphouse is fan cooled.
Data:
Viewing field:...... 260 x 260mm
Overall size:...... 445 x 280 x 280mm
Mains voltage:...... 220/240v or 110v /
Preform strain pattern
COMPACT POLARISED LIGHT STRAIN VIEWER FOR PET PREFORMS (Ref S-402)
160mm x 160mm Field of View
/ The advantages of our Strain Viewer for PET Preforms are as follows : -
1. Not only can the molecular birefringent flow lines (isochromatic pattern) be seen in colour but also the black isoclinic lines are visible when the preform axes are parallel to the polarising axis of the viewer. The isoclinic lines indicate the directions of the molecular orientational strains.
2. Crystallinity and other defects which are not easily seen in ordinary light can be readily identified.
3. The Strain Viewer is economical and can sit along side each injection moulding machine.
Data :
Light Source : Two compact cool white fluorescent lamps
Overall size :
Breadth : 200mm
Width :200mm
Height: 245mm
Viewing field : 160mm x 160mm
Voltage : 220/240V : 50Hz or 110V : 60Hz /
Sharples Stress Engineers Ltd
Unit 29 Old Mill Industrial Estate,School Lane,Bamber Bridge,Preston, PR5 6SY, UK
Tel : + 44 1772 323359/60 Fax : + 44 1772 316017
Bottle Pressure Tester
(Ref. S-401)
For Plastic Bottles and other containers.
/ The illustration shows a pressure tester designed for up to 3 litre PET plastic bottles which can be tested to a pressure of up to 14 bar. The tester uses compressed air or nitrogen gas to pressurise the sample bottle which is filled with water via the reservoir mounted on top of the test chamber.The compressed air, or nitrogen, is fed to the top of the reservoir and controlled by a main operating valve and a snubber valve which regulates the flow of gas into the reservoir.
The sample bottle is secured by its neck in the closed test chamber and may be observed during the test through a polycarbonate safety window.
The test pressure is read from a large dial pressure gauge and should the bottle burst during the test, a red following pointer on the gauge will remain at the bursting pressure. If the bottle reaches maximum test pressure without bursting then the the pressure in the system is relieved by a slide valve before removing the bottle. A drain pipe and sump is provided to run off surplus water.
The testers are of rugged construction and designed to ensure safety and convenience of operation. They are attractively finished to fit into a laboratory environment.
Products & Technologies 1.05
Even a good stretch blow molding machine can only produce perfect bottles when the preform quality is good. Preform and bottle quality detection systems help to increase the overall line efficiency.
Certainly the major focus of a manufacturer of machines for the production of PET bottles is directed towards high efficiency at high specific machine outputs, leading to an inherent high product quality and process capability. At the same time it has become evident that with the increasing pressure on packaging cost and with a highly competitive market, the material quality at the machine in-feed is increasingly variable, making it more desirable to check and verify the quality of the produced bottle. Indeed, any defect in a bottle sent into the filling line will have an immediate influence on the overall line efficiency and hence on the total cost of the packaging.
Preform inspection
Therefore, SIG Corpoplast has been working on developing a series of tools that can be integrated in, or added on to the BLOMAX Series III stretch blow molding machines in order to achieve highest possible product quality.
Although the characteristic mandrel conveying system used in the BLOMAX Series III blow molders ensures that pre-forms, once loaded in the machine, will not suffer any undue force or damage, and provides additional protection during the bottle blowing process, it cannot prevent poorly injection molded or bad preforms from being fed into the machine. Integration of an AgrTopWave preform inspection unit in the preform feeding chute, positioned between the preform ori-entation unit and machine in-feed, allows inspection of the sealing surface of the pre-forms, as well as checking for oval necks. Thus bad preforms can be ejected prior to reaching the machine in-feed section. Used in combination with the mandrel transport system in the blow molding machine, a perfect neck on the bottle is therefore guaranteed.
With the new BLOMAX 24 Series III, the loading section of the machine has been reengineered to allow for the integration of a camera inspection unit in the loading wheel, to detect such bad neck finishes, and subsequently eject the preforms prior to feeding into the oven section.
Sensor tests pressure loss
Bottle quality deficiencies that strongly interfere with the bottle filling / capping process are; bottles with pinholes, non-uniform material distribution (leading to local deformations or bursting bottles during filling) or deformed bases (causing bottles to fall over during handling).
Small holes can be detected during the bottle blowing cycle by means of a pressure differential sensor that can be installed in each blowing valve. This sensor will detect a pressure drop when a bottle is leaking during its inflation. Through carefully set limit values, this pressure drop is picked up by the machine control system and will eject the bottle before transferring it into the air conveyor.
Selection of eccentric bases (via camera surveillance)
Non-uniform material distribution caused by a non-uniform preform heating due to foreign particles or material in the preform, can be detected by different means: Detection of off-centre bases is one solution. In this case, the blown bottles are transferred into a conveyor section at the machine out-feed, which lines up the bott-les in front of a camera with light source, allowing comparison of the actual blown base with a reference base, using both positioning or grey tone values. A bottle that has an image that differs from a preset ideal image, with free programmable tolerances, is ejected before being transferred into the air conveyor.
In the BLOMAX 24 Series III this detection system is integrated in the bottle unloading wheel. Through a reengineered bottle transfer system, space has been created to allow room for a base off-centre detection camera.
This camera system can be extended with a second unit, which will detect if a base has had enough cooling to guarantee a free standing bottle.
Interface with wall thickness measurement
For critical applications, it is beneficial to measure the bottle wall thickness and material distribution at specific areas in the bottle, as it defines the bottle strength required for top load or creep performance. Other influence areas are shelf life performance or Pressure Resistance.
For this requirement, interfaces have been created to install AgrTopWave PETWall plusTM wall thickness measuring systems. By scanning the bottle wall at a predefined height, a measurement of the bottle wall thickness is obtained. The gathered information is correlated to the BlowStations and Mandrels and allows also a further process control. When this value is outside a preset tolerance, the bottle is ejected prior to reaching the air conveyor. The system has been further developed by AgrTopWave to allow the measurement of the wall thickness at up to 4 defined heights on the bottle.
Although these quality detection systems help in increasing the overall line efficiency, it remains the inherent process stability and capability provided by a unique preform reheat system, a highly repetitive mechanically driven stretching system and a blowing process with least dead air volume, quick reaction times, that are the best guarantee to high bottle quality obtained with BLOMAX Series III blow molders.
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