Grinding coffee to the exact gram

This article originally appeared in the March'24 magazine issue of Electronic Specifier Design – see ES's Magazine Archives for more featured publications.

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The Gronbach Group was originally founded in 1964 as a manufacturer of hinges. The business developed very quickly and today, the group of companies operates a total of five production sites in Europe, has a sales office in the USA, and employs around 1,200 staff. As an OEM, Gronbach has specialised in the development and production of technical assemblies and complete products which are delivered internationally to more than 500 different customers – from large corporations down to startups – predominantly in the household appliances sector, including coffee machines, induction hobs, steamers, and much more.

Quality has the highest priority. The production and R&D site in Niederndorf in Tyrol is very important to the Gronbach Group when it comes to general development of product solutions – all the threads come together here in terms of mechanics, electrics, electronics, software, etc. An in-house expert team is devoted to research and customer-specific development of devices and assemblies. What all the products have in common is the high-quality standard when it comes to technology, sustainability, and energy efficiency. For the intensive quality control of a new coffee grinder, the development engineers relied on the support of the LBR iisy cobot from KUKA in a test setup.

As a premium OEM, Gronbach has broad manufacturing expertise with comprehensive know-how in the field of R&D. The wealth of experience built up in hundreds of customer-specific and successfully completed projects has now resulted in in its own brand LIGRE. The company is now entering the market under this name as a manufacturer of high-end coffee machines. One of the first products to be launched on the market is the LIGRE siji coffee grinder, alongside an espresso machine.

A completely new feature for a coffee grinder in the consumer segment is the ability to preset the amount of coffee to be ground to the exact gram. To ensure that the proverbial high quality is not just empty words, the R&D experts at Gronbach decided to subject this new development to intensive quality control in a series of tests. The basic assumption was that the coffee grinder would grind or process around 500kg of coffee over a service life of around ten years. Determining the long-term correct weighing results under different operating conditions for the total quantity of half a metric tonne of coffee not only required radical acceleration but also extremely precise repeatability; after all, the results had to be reliable, and the findings incorporated into future developments and improvements.

“Our aim was to test the grinder's simulated service life in order to gain insights into wear and accuracy,” said Dipl.-Wirt.-Ing. (FH) Alexander Fahringer, Technical Development and Test Engineer at Gronbach.

Cost-effective quality control

The R&D experts at Gronbach all agreed that an automated robot solution was the only way to achieve cost-effective quality control. The leap to KUKA was a short one; multiple industrial robots are already in use at the company's site in Niederndorf near Kufstein.

It’s a good thing that KUKA has a robot in its range, the LBR iisy cobot, which is perfect for solutions like this.

With a maximum load of 3kg, the cobot's full capacity is not used in this case, but “it’s good to know that there is more scope for other possible applications and processes,” says Fahringer, who is positive that this initial project will demonstrate that collaborative robots have a firm place in development departments in the future. Higher loads are also not a problem as KUKA offers the LBR iisy cobots with maximum loads of up to 15kg and a reach of between 760 and 1,300mm.

Quality management: test in six steps

A period of two months was scheduled for the actual quality assurance test, during which the LBR iisy cobot would carry out 55,000 coffee grinding and weighing processes. Each process was carried out in six identical steps: taring the portafilter on the precision scale, gripping the portafilter and moving it to the coffee grinder, uncoupling the portafilter and waiting for the grinding process to end, picking up the filled portafilter and moving it to the scale, uncoupling and saving the scale value in the database, picking up the portafilter, emptying it and placing it on the scale again.

The huge benefit of the LBR iisy cobot is its simple programming through human-robot collaboration thanks to the Teach button: “You can guide the cobot manually and thus teach it the desired movements and waiting times, etc. very easily with the press of a button,” says Michael Reindl, Account Manager at KUKA. Thanks to its intuitive handling, the LBR iisy cobot offers flexible application options and can be commissioned and operated quickly and reliably by automation experts and robotics beginners alike. The robot meets all the safety requirements for collaborative operation.

“The cobot solution is an invaluable benefit for the necessary flexibility in a test laboratory. Other industrial robot solutions with complex safety structures were not an option owing to the high expense for test series like ours because the costs were entirely disproportionate to the relatively short period of use,” said Peter Kopfensteiner, Research and Development, Division Appliances, Gronbach.

Millions of cycles

“The small LBR iisy cobot in particular, that is the variant with a load of up to 3kg, as well as the larger models, are predestined for taking care of rather simple, monotonous, and repetitive handling tasks in the immediate vicinity of other employees,” says Reindl. The 11 and 15kg variants are even dust and splash-proof (protection class IP 54).

This eases the burden of work steps which are unpopular or even harmful to health which also offer real added value thanks to precision, repeatability, and easy handling. This was also the case for quality management. Each individual grinding and weighting process was carried out and logged in continuous operation with absolute reliability so that variances were detected quickly. “In this application, the robot controller acted as the master for all other components,” said Reindl. Openness to different systems makes it possible.

“The grinder worked so well that the it indicated practically no wear and tear after simulated use for ten years, so it would last for significantly longer,” says Fahringer.

Easy to get started

It is clear to the R&D team that this will not be the last time the LBR iisy cobot is used at Gronbach. “As automation engineers, we are already thinking about how the cobot will assist us with further quality controls and processes,” says Fahringer. The best of the contributing factors for this was the excellent collaboration with KUKA. The robotics experts deliberately make it easy for those who are interested to get started: “We are happy to provide customers with handy collaborative robots like the LBR iisy cobot to try out and test in their operation,” says Reindl.