A preform inspection solution for every application
In recent years, the requirements and challenges in the production of preforms have grown steadily due to needs for increasing material savings and the expanding use of recycled materials. The demands on inspection solutions for preforms have also risen to the same extent during this period. More and more inspection systems and concepts have entered the market. When do you need an offline system and when is a monitoring system the better choice? Or perhaps is it best to use both systems combined? What are the differences between 100% inline inspection and a laboratory system for sample inspection? And how can you get even more out of your existing inspection solutions with the appropriate software? You will know answers to all of these questions in this article.
Despite the current prevailing negative mood about plastic packaging in the media, the number of drinks that have been filled in PET bottles have continued to increase in recent years. Lower manufacturing costs, safer transportability, increased recyclability and low weight are just some of the positive characteristics that explain the rising share of PET packaging.
Due to these advantages, the usage of PET bottles has increased significantly. Let's take the developments in Germany as an example: The market share of PET bottles was still around 30% in 2003 when the deposit on non-refillable bottles was introduced. In the coming years, the share has increased to almost 72% by the end of 2017. In line with this development, which can also be observed in many other countries around the world, more and more companies start to produce PET preforms or expand their capacities in this area. Due to these changes, indispensable elements in modern production lines now include inspection systems. They guarantee consistently high product quality and offer clear competitive advantages.
Increasing requirements
With more and more preforms being produced, new requirements and expectations for inspection systems have arisen. Because the market requirements are very different and sometimes incompatible, various system types were developed over time. Whereas years ago, suppliers often only offered one "system for preform inspection", today, they usually offer several different solutions that are adapted to meet specific customer requirements.
As a result, an ever-increasing range of systems for different situations have been introduced. However, the customers rarely know what the appropriate solution is for their production.
Critical applications: 100 % inspection
Choosing which inspection system is the right solution depends first and foremost on the customer’s requirements. Thus, the following questions need to be asked: How challenging is my product? Which risk factors can influence product quality? How important is the job that I produce on this machine? Do I produce for a demanding customer or critical market to which I only want to deliver perfect quality for any price? If so, even one defective preform can lead to the rejection of a delivery or, in the worst case, the end of a partnership. Accordingly, a 100% inline inspection solution is the best choice for such cases.
Systems such as the PreWatcher Offline, which can be used inline or offline, inspect all preforms immediately after an injection molding machine and sort out the defective ones. The PreWatcher Offline inspects up to 100,000 preforms per hour with a precision that is pixel accurate for a total of more than 20 criteria – including the reading of cavity numbers and correlation of data to the specific cavity number.
In-house production: Monitoring may be sufficient
Imagine a machine downtime due to a bursting preforms in the blow molder: If this happens in-house, it may be better forgiven than if it happens at a customer’s plant leading to production stoppage and complains about an entire delivery.
Due to this lower risk, 100% inline inspection may not be required. In this case, many customers rely on the results of a budget-friendly monitoring system. When embedded in a production line, these type of system does not achieve 100% inspection, but it offers a good compromise in terms of up-front costs, space requirements and inspection performance. Moreover, a monitoring system can achieve the same accuracy as the more expensive inline and offline 100% inspection system which also require particluarly larger footprints.
One of the latest monitoring systems on the market is the PreMon. Due to its innovative transport technology, it inspects up to 70% of preform production and costs only one fifth of the price of a 100% inspection system. Therefore, it offers the perfect mix of a fast ROI, small space requirements and it still delivers the security of high product quality.
One of the PreMon’s special features includes an optional ejector that sorts out defective preforms and that makes the system unique from alternative solutions. It also offers statistics and diagrams which visualize real-time data as well as the most important information of the last 24 hours. All information are even assigned to the corresponding packaging units (octabins). Due to an indication of the error rate, the display of corresponding error images and comprehensive statistical functionalities, the PreMon provides a stable foundation for making the right decision on whether an octabin meets quality requirements with reasonable certainty. With this information, every producer can reliably decide how to proceed with an octabin: recycle the entire packaging unit, send the octabin into storage and re-sort it via offline inspection, or release it for sale or for further processing.
Offline re-sorting systems
When an octabin is rejected due to too many faulty preforms, it is time for an offline inspection system. On the one hand, these systems are characterized by higher inspection speeds. On the other hand, they are particular flexible so that they can be quickly converted from one preform design to another. Compared to 100% inline inspection systems, offline inspection systems often offer a similar scope of inspection capabilities. In the INTRAVIS portfolio, the PreWatcher Offline also covers this task.
Laboratory systems support analysis and reporting
For comprehensive quality audits, preform producers require an extensive reporting in terms of the quality of produced preforms. If a company would like to offer its customers the highest possible level of detail, a laboratory system is the best choice. It is common practice to sort out the first and the last complete shot of a shift and to carry out a precise inspection in the laboratory with them. The Sample-PreWatcher with its nearly 30 inspection criteria replaces the laboratory: It offers not only an additional weight check, but also higher precision during inspection and measurement compared to an inline or offline vision system or manual procedure. Other capabilities also include a polarization test with which stress points in the preform can be detected.
With regard to the inspection speed, a laboratory system is considerably slower compared to an inline, offline or monitoring system. The Sample-PreWatcher inspects up to 1,200 preforms per hour. However, compared to conventional inspection methods within a laboratory, the laboratory system offers not only a higher inspection performance with up to 30,000 individual quality data points collected per hour, but also the decisive advantage of an objective and reproducible inspection situation. The “human” influence factor is thus eliminated from quality control and has no impact on the accuracy of the measurement results. In addition, the measurements of the laboratory system can be directly issued as a report, providing comprehensive support for the laboratory personnel.
If you do not want to selectively sort out your preforms from the production line or the octabin: The Sample-PreWatcher is also available inline. In this configuration, it regularly collects data from quality shots during ongoing production - fully automatically.
Two other laboratory systems are the ColorWatcher Lab and LayerWatcher. Together with the Sample-PreWatcher, they form a complete package of high-precision laboratory inspections.
Due to the usage of more and more recycled material, color deviations occur more frequently. To analyze even small nuances of the color, the ColorWatcher Lab is specially developed for a reliable color inspection. It is the perfect add-on for a laboratory which already uses the Sample-PreWatcher. Moreover, it is particularly space-saving since it can be place on a normal worktable.
With the LayerWatcher, the inspection of barrier layers in PET preforms is highly simplified. In a non-destructive inspection process, the system inspects the whole barrier material. In about 45 seconds, the LayerWatcher inspects up to 100,000 measuring points and visualizes all results in a comprehensive 3D overall image of the preform.
Conclusion
Each of the different inspection solutions has its own advantages and could be the best choice for certain situations and requirements. For future production, which is increasingly controlled and optimized by data and information, a combination of different system types together with additional analysis software might be the best choice. Overall, an optimal quality inspection concept can be found for every producer. It supports you to identify production advantages and provides you a decisive competitive edge in the global preform market.
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