One of the most challenging tasks in the field of quality control in the plastic packaging industry is the inspection of preforms. While bottles and containers are finished products and can be inspected in their final form, preforms have to be inspected thoroughly to detect any defect and therefore avoid problems during the further processing. The challenge for an inspection system is to provide detailed data about the object yet being suitable to inspect in a comprehensive and objective way without disturbing the production.
Fig. 1: The Sample-PreWatcher from Intravis with periphery
The Sample-PreWatcher
The Sample-PreWatcher from Intravis is capable to do this and has many other features. The system inspects all kinds of preforms in detail and precisely – clear, colored or translucent preforms of different shapes and sizes. It inspects for all aspects and defect types like geometrical characteristics, material defects, color and contamination. Objects are inspected all around, from injection gate and dome over body and thread area to the top sealing surface. Up to nine measuring phases and different measuring technologies are used to inspect the preforms thoroughly. For sidewall inspection, for instance, several pictures of one preform are made. The color measurement is done with a color spectrometer.
The Sample-PreWatcher is also capable of cavity number reading, identifying the presence and correctness of each single cavity number. It detects problems with single cavities very early, helping to prevent recurring production errors. This enables a creation of cavity related statistics and the sorting of preforms according to previously specified cavity numbers.
Fig. 2: The Sample-PreWatcher itself requires
a floor space of only 1.5 square meters
Precise laboratory system
The system can be used for offline inspection as a laboratory system with optional setups. The basic system requires a manual filling, while a more elaborated solution is the use of an Intravis sorter: A shot of preforms is filled into a bunker, where the preforms are elevated from and fed into the system one by one. Also, the Sample-PreWatcher can be used as an inline solution, being installed behind an injection molding machine and fed with sample shots of preforms via T-belt. With this setup, the complete inspection results of the preforms of a 96 cavity mold are provided within less than eight minutes. This enables the user to intervene early in the production process to carry out the startup of a newly installed mold in a short time.
Fig. 3: Detailed information on different object
characteristics like thread measurement or body geometry and material faults are displayed
Optimized reports
As a summary of the inspection result, reports for each batch, shift and day or even whole months can be created. They give detailed and objective quality data on the screen, in reports or database entries. The reports are optimized for the process control, providing minimum, maximum, average and standard deviations and also providing the process capability indices Cp and Cpk.
The software is easy to use thanks to its clearly structured interface. All collected data can be transmitted into a SQL Server to be used for further evaluation. A long and short term quality analysis can be created with the data.
As the operators are in charge for more and more production lines, it is essential for their work to have a quick overview on the entire production development. They need an ideal connection between high precision quality control on the one hand and an overview at a glance on the other hand to see where the product characteristics develop and where it might be time to intervene.
Fig. 4: For the measured parameters meaningful
distribution diagrams are available
(here: histogram of the ovality distribution)
Production at a glance
A tool to meet these needs is the IntraVisualizer, a software that edits and visualizes the performance data of the entire production. To use it, the user only needs to connect his inspection system to a SQL server. With an easy-to-use interface it does not require long trainings and turns all relevant characteristic production numbers into significant visual diagrams. The software is also usable with a touchscreen and any standard internet-browser. It can therefore be used on a portable tablet device. The user can set up the display according to his needs by adding or changing system results. With just one click he can choose the value to be monitored – such as ovality, surface, diameter and others. It is also possible to track single measurement readings. When the IntraVisualizer accesses the data base, it can visualize different time periods and batches. The user receives instant answers to his questions: What is the ejection rate, what are the cavity related defects and what are the main reasons for the ejections?
Fig. 6: The IntraVisualizer provides trend statistics, displaying the estimated time before defective products are produced
As a result, there are several economical advantages for the customer. First of all, he saves material by preventing waste. Supporting the quality inspection, the Sample-PreWatcher also saves a certain amount of working hours. As the inspections are carried out exactly the same way, inaccuracies caused by manual measurings are eliminated. The non-destructively inspected objects can be used as retained samples. Moreover, it makes sense from an economical point of view to inspect preforms before they are finished bottles. With the Sample-PreWatcher and the IntraVisualizer supporting the quality control, the user has optimal tools to control and even forecast the product quality development and thus prevent waste – he can solve problems before they occur.
Fig. 5: Clear overview of the current statuses of the production lines
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