ZURICH, SWITZERLAND — When you’re the country’s largest wheat flour producer and don’t have another milling facility that can absorb production during an equipment upgrade, replacing old equipment with new machinery while still satisfying the needs of your customers can be a tremendous challenge.

Since the fall of 2021, Swissmill, the largest flour milling company in Switzerland, has been faced with this difficult challenge of producing about 25% and 40% of the country’s bread flour and pasta flour, respectively, while simultaneously installing the latest Bühler technology at its flour mill in Zurich.

The mill sits next to a river in an urban area and has limited space available within the plant, thus an expansion is not possible. And with no alternative milling facilities to transfer production during the installation, production interruptions have had to be kept to a minimum, said Simon Künzle, Swissmill’s technology manger.

“This means we have to renew the mills during ongoing production and on a step-by-step basis,” Künzle said. “Production, mechanics, electronics and automation must be in perfect harmony for this to work.”

The transition is nearly complete at the plant, which grinds more than 220,000 tonnes of wheat per year. 

A major part of the upgrade consisted of replacing Bühler’s MDDK generation roller mills, which were installed 36 years ago, with its newest line — the Diorit MDDY. The gradual modernization was carried out on milling lines A and B by Swissmill in collaboration with Bühler.

“The seasoned roller mills will be replaced to bring product safety, hygiene and occupational safety in line with the new state of the art,” said Antoine Bolay, production and technology manager at Swissmill.

Upgraded by Bühler in 2019 to focus on user-friendliness, the Diorit’s machine control was completely overhauled and the user interface was graphically redesigned. 

With the upgrade, Bühler describes the Diorit, which can be operated remotely, as facilitating “intuitive, simple monitoring and control of the roller mills.” Bühler also noted that modern sensor technology ensures that the rollers always operate in the right position and at the right speed.

Out with the old, in with the new

Prior to the most important step for modernizing the A and B milling lines — replacing the old roller mills with new ones — the 72 drives of both mills were upgraded with energy-efficient motors and specially designed motor suspensions. The new suspensions make it possible to replace defective motors in the shortest possible time and with minimum personnel.

“Many meters of pipelines, cables and quite a few machines had to be routed and set up. The relief was palpable when the mills were put back into operation and the first improvements could be felt.” - Simon Künzle, Swissmill’s technology manger

The electrical setup, such as the power distribution and supply lines, also was upgraded, he said.

During the last stage of the upgrade, the mill diagram was adapted and aligned with present-day conditions, Künzle said.

“It may sound simple, but this entailed a lot of work for the Swissmill crew,” he said. “Many meters of pipelines, cables and quite a few machines had to be routed and set up. The relief was palpable when the mills were put back into operation and the first improvements could be felt.”

The short period in which production went offline also was used to restore 12 drawer-type plansifters MPAD, also manufactured by Bühler. The 144 doors and 72 inlets were thoroughly restored and repaired through extensive manual labor involving both Bühler and Swissmill employees.

“As it was not feasible for Swissmill to exchange these important machines due to both time and technology constraints, another solution had to be found to extend their lifetime,” said Martin Ruckstuhl of Bühler’s sales department.

As for the swapping out of roller mills, both milling lines were retrofitted one after the other in six stages during ongoing production. 

Beginning in October 2021, Bühler delivered two to four roller mills to the Swissmill plant on a weekly basis. Each installation required only a 24-hour shutdown, Künzle said.

The A mill was finished at the end of 2021 and the B mill is scheduled to be completed this summer, Künzle said.

“The cooperation with Bühler went very well,” he said. “We were able to work hand in hand and keep well within the ambitious schedule.”

Künzle said the existing mill layout, the proven and reliable Bühler technology and the new control system that was installed were among the reasons Swissmill decided to proceed with the modernization project.

“It was important to us that the machine would be produced and assembled in Switzerland,” he said.

Other aspects of the modernization included replacing the existing Sortex color sorters in the two wheat cleaning lines with Sortex H, Bühler’s latest-generation optical sorter. 

Bolay said restorations and expansions also are planning for the remaining milling lines. 

“A mill is a structure that must constantly adapt to changing market conditions and the new possibilities technology affords,” Bolay said.

More than 100 types of flour

As Switzerland’s top flour and semolina producer, Swissmill is constantly monitoring the latest consumer trends to tailor its products to meet the evolving demand.

“Current trends are moving toward healthy eating (oat milk or gluten-free products),” Künzle said. “Of course, this has also had an influence on our production.”

Almost all of Swissmill’s customer base is located in Switzerland, with 80% of its end products going to industrial bakeries and restaurants, Künzle said, noting that all end products are transported by truck.

“For industrial bakeries, 80% is delivered in bulk, and the rest is packed in 500-gram to 25-kilogram bags and big bags,” he said.

In all, Swissmill produces more than 100 types of flour and semolina for its customers. Wheat flour for bread production accounts for the majority of its product line. Other products include grain flakes, mixtures and specialties.