Automated quality assurance

AI and optical quality inspection solution for rPET bottles

Doloop, a leading European PET packaging producer, has partnered with high-tech company Sprana to create a new quality inspection solution for beverage bottle preforms. The technology is claimed to allow the use of higher percentages of recycled material, while ensuring high product quality. This new system can inspect PET preforms at very early stages of production and provide information on quality before they are blown into bottles. Used inline, it allows detection of any defect that may have occurred during the production process. AI (artificial intelligence) driven technology enables automated, continuous quality assurance.

PET bottles and increasing interest in recycled PET

CO2 emissions created during production processes have a significant environmental impact; which can be reduced by greater use of recycled PET derived from collected post-consumer bottles. The EU Single-Use Plastic Directive requires PET bottles for beverages to include 25% of recycled materials by 2025, and 30% by 2030. These requirements create a need for methods and tools that can improve and guarantee high quality control and accurate analysis in the manufacturing process. The greatest challenges in increasing usage of recycled PET in preforms are: maintaining high product quality; guaranteed efficient production; and ensuring optimal performance of PET bottles in later phases. Quality control during manufacturing is thus becoming increasingly crucial in the plastics sector.

Quality inspection solution

Doloop has already invested € 7 million in the last seven years in quality assurance, including new inspection technologies. The use of recycled material increases colour variations. It can be difficult to ensure consistent production and product quality as recycled PET colour tends to differ from batch to batch. This is because of different sources of PET bottles, collected in different markets, being used as inputs in the recycling process. 

Doloop has been able to overcome this challenge by partnering with Sprana, an expert in visual inspection technologies and AI. This R&D project was supported by the EEA and Norway Grants Program for Business Development, Innovation and SMEs. During the project, the company carried out research and experimental activities to improve the control of PET preforms using artificial intelligence technologies, while increasing the use of recycled materials. Realtime monitoring and analysis allowed much faster and more efficiently inspection. Manual inspection of PET preforms is inefficient, time consuming and increases the possibility of defective production. Doloop maintains that, by optimising and improving quality control at preform stage, manufacturers are able to reduce human involvement in quality assurance and move personnel to more demanding production processes. The project aimed not only to increase the use of recycled PET in packaging products, but also to take another step towards the goal of a circular economy in the plastic packaging industry.

Image recognition systems and artificial intelligence-based quality control systems and inline colour analysers have been installed in nine Doloop injection lines. Finished preforms’ colour can now be analysed and evaluated continuously during the production process. Automating the quality inspection process with the new technology saved up to 89,760 manhours of labour per year, according to Doloop’s CEO.

Since introducing the technologies in 2019, the number of quality claims due to discolouration have been reduced by as much as 50 per cent, states the company, and add that clients have found that:

Inline quality control and PET preforms inspection technology
  • bottling lines could work with high efficiency and had few stoppages, due to better quality of preforms with rPET content;
  • almost one day per year is saved in hours spent administering discolouration claims;
  • clients develop and deliver to market new products with rPET easier and faster, as less time is spent optimising production and adjusting quality;
  • bottles on the shelf appear visually much more consistent, with less colour variation.

Future challenges

Doloop is aiming to become carbon-neutral. The company is achieving this by offsetting the CO2 emissions generated during production with renewable energy projects. It is also making all of its products recyclable or compostable. The automated quality inspection is now moving to the second stage of development to tackle another quality issue: black specs, which are small, dark fractions or particles found in blown bottles, resulting from increased use of recycled materials. They do not harm product itself but the appearance is affected when the bottle is blown. Doloop and Sprana plan to upgrade the existing base of the PET preform inspection system and adapt to detect black specs during in-line production.