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Impol Completes Rolling Mill Process Audit

Improves Quality of Aluminum Foil Products

Impol’s aluminum rolling plant in Slovenska Bistrica, Slovenia.

The Impol Group is a well known manufacturer of semi-finished products, with 165,000 tons of rolling capacity and 100,000 tons of extrusion capacity. In its rolling division, the company produces rolled products at three production sites located in Slovenia, Croatia, and Serbia, employing a total of 2,500 people across all three locations. The company’s Slovenska Bistrica plant is Slovenia’s largest producer of rolled aluminum, serving a diverse range of markets, including automotive, pharmacy, food and packaging, construction, and renewable energy—with thin and thick foil being among the site’s most important products.

Impol prides itself on supplying high quality aluminum products to its customers. In order to ensure the continued quality of its products and to keep up with industry trends, the company strategically invests in its operations and the know-how of its personnel. Over the last ten years, the company has invested more than €365 million in various projects aimed at modernizing its equipment and mastering the production process in order to improve quality and increase capacity.

Impol reached out to Innoval Technology, based in Banbury, U.K., for a consultation on the performance of its Slovenska Bistrica plant and the quality of its foil products. An assessment and audit of the facility was conducted, which resulted in the aluminum producer making process improvements within the plant.

Operational Assessment

Impol and Innoval have collaborated on various projects for over 12 years, including consultation, process audits, product development trials, and training. For the recent audit of the Slovenska Bistrica plant, Innoval worked closely with Impol to fully understand the challenges that the company was facing and its targets regarding improving the quality of its foil products. “In production process audits, the first step is always preparation for teamwork in the assessment,” noted Dr. Darja Volšak, technology and development director of Impol’s Rolling Division. “The Impol team carried out a comprehensive inventory of the current state of the process, from technological parameters to maintenance, after which Innoval prepared so that their time on location at our plant was concentrated toward a carefully highly intensive work plan from morning to evening.”

As part of the planning process Innoval went over the major concerns presented by Impol. The audit team then requested additional information, such as process data, and made its own indexes and calculations, considering the data from a perspective that is different from what the aluminum facility would normally do. In addition, the information helped Innoval to better understand what areas Impol’s personnel had already explored. “In order to know the origin of a problem it is also important to know what hasn’t worked,” said Vicente Martin, senior consultant, Innoval Technology. “On many occasions the history of a problem will help us understand where it comes from.”

Once Innoval had a good understanding of the major concerns presented by Impol, they put together a multidisciplinary team of consultants to further assess the issues. “Our team of consultants looked at all possible elements of the situation, from the metallurgical issues to the production/engineering side,” said Martin. “We normally include experts that are focused on particular areas of the operation, but we also include people who can look at the process from beginning to end. Together, they set up a program of work/road to discovery.”

With the preparation for the audit complete, the Innoval team was able to visit the Slovenska Bistrica plant and observe the production process, focusing on key areas of the operation where defects might originate. In addition to this, they reviewed the automation of the cold mills. “Analyzing issues such as surface quality require lots of hours of observation,” explained Martin. “We spent hours watching the metal going through the process and checking its behavior. At the same time, if we suspect issues with the control system, we will suggest small software modifications and check how the machine responds. This has to be done on-site, so that we can test many different configurations in subsequent coils.”

The on-site audit took about three days to complete. Innoval’s deep understanding of the manufacturing process helped them in recognizing what was and what was not normal. The audit team was able to identify potential quality problems that were reducing the recovery of the material as a result of issues with metal flow. Throughout the audit Impol personnel were able to discuss the findings with Innoval’s team, who provided recommendations for improvement along with a final report citing specific priorities.


Altogether, the preparation, audit, and implementation of the recommendations was a multi-month project that resulted in several improvements at the facility. This included changes to the software of the control system along with other technical modifications that resulted in a significant improvement in the quality of their foil products. “We implemented the priority suggestions for improvements given in the audit reports with the aim of improving the quality of the foils,” said Volšak. “We know that our process parameters are stable and will ensure stable product quality, which is reflected in the satisfaction of our customers.”

In addition, Innoval offered product development trials with the aim of providing new commercial opportunities. “Innoval played an important role by carrying out their study of the production capabilities of the rolling mill and searching for areas of improvement,” said Volšak. “Innoval identified a group of five possible new production programs in the Impol rolling division. Almost all of these programs have been implemented commercially. If nothing else, the individual products were presented to potential customers as prototypes.

Another important finding from the audit was the need to expand the knowledge of Impol’s key personnel to encourage them to implement good ideas in their day-to-day work. As a result, Innoval conducted a five-day training program at Impol (Figure 1), providing in-depth information about the rolling process to a group of technologists and experts from all three of Impol’s rolling plants. “We have increased the level of knowledge of our engineers who plan and use foil production technology, empowering them to enact good product planning,” said Volšak. “In recent years, we have ranked among the best manufacturers of aluminum foil in Europe, which has certainly been helped by the higher level of special know-how that we have acquired over the years through Innoval.”

Figure 1. One of the training sessions at Impol.

Editor’s Note: This article first appeared in the December 2022 issue of Light Metal Age. To receive the current issue, please subscribe.

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