Issue 9/2016

„Wenn man immer das macht, was man immer macht, entwickelt sich nichts weiter“Wie Kühnlein die Herausforderungen vom Prototyp bis zur Großserie meistert

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Advanced technology for an advanced product:Customized machine technology contributes to the success of the Thermomix TM 5

SPECIAL PRINT

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‹ TECHNOLOGY

Thomas Rüschenschmidt, Head of Enginee-ring at the romantically located Vorwerk plant in France, recalls, “Since September of 2014 we have been producing the Thermo-mix TM5 using the new injection molding machines from KraussMaffei, among other equipment. The response to the product af-ter its market launch has far exceeded our expectations.” Twenty-four injection mol-ding machines in Cloyes-sur-le-Loir come from KraussMaffei Technologies GmbH in Munich, Germany; eight more have already been ordered. The plant in France alone pro-duces one million units per year; the plant in Wuppertal, Germany, produces another 500,000—likewise on KraussMaffei machi-nes. In the year 2015 alone, the Thermomix TM5 has earned the company just under 1.4 billion euros in sales, out of a total of 3.5 billion euros. “The Thermomix has develo-ped from a mixer into a multifunctional kit-chen appliance,” explains Rüschenschmidt with satisfaction. The partners have already been working together for two decades. The machine operators at Vorwerk are familiar with the systems, so it wasn't hard for Rü-schenschmidt to choose the supplier: “Pro-duction using the new injection molding

Advanced technology for an advanced productCustomized machine technology contributes to the success of the Thermomix TM 5

Housings made of ABS hover like spaceships under the hall ceiling, bases made of polypropylene, covers for mixing bowls made of PA6T/6I-GF40, covers for the Varoma steamer attachment made of PA 12 and three-component covers glide on conveyor belts over serpentine paths to a common destination. All of the individual parts join together there, step by step, as if by magic to become the sales hit known as the Ther-momix TM5 from Vorwerk. At Vorwerk Semco S.A.S. from Cloyes-sur-le-Loir in France, 34 injection molding machines operate in three shifts to produce the plastic compo-nents of the in-demand kitchen appliance out of everything from simple polypropy-lene to advanced PMMA.

Text: Graduate Engineer (University of Applied Sciences) Gabriele Rzepka, editorial staff K-PROFI

The four machines of the MX series installed in late 2013 and May 2014—two pairs of twins, each with a clamping force of 11,500 kN—use the three-

component process to manufacture the cover for the new kitchen appliance.

The 3-cavity mold rotates 120° after each shot in a precisely timed cycle. When the mold opens,

an industrial robot uses a specially designed gripper to remove the manufactured cover.

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The Thermomix provides its users with various options: cooking using the Guided Cooking function, either manually with one of the cookbooks or in the near future using the Cook Key, with which you will be able to send your favorite recipes directly to the Thermomix's display.

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machines was a technological leap forward for us. KraussMaffei has excellent service and technology, and that is why we decided in fa-vor of it as general contractor this time, too. The machines have an availability of over 90%, and everything runs well.”

Close partnership

If you let your eyes wander through the production halls, they will stop on the KraussMaffei machines of the GX series with clamping forces between 450 and 650 tonnes, just as they will on a CX 200, which uses water injection technology to manufacture the grips for the mixing bowl of the Thermomix. However, the four machines of the MX series installed in late 2013 and May 2014 take over the lion's share. Two pairs of twins, each with a clamping force of 1150 tonnes, use the three-component process to manufacture the cover for the kitchen appliance.

The designer cover needs to satisfy high standards for visual appeal while providing resistance to scratches and every kind of corrosi-ve food and spice. The use of three types of plastic makes this team-work a success. The white area consists of a polycarbonate (PC) from Covestro; the light gray, recessed part consists of a PC/ABS cover from the same company. A PMMA coating from Evonik provides for the visual properties, scratch resistance and resistance to chemi-cals, spices and foods that stain.

Scratch-resistant, chemical-resistant and � awless—those are the requirements for the cover of the Thermomix TM5, where the end customer expects not only functionality, but also premium quality surface aesthetics.

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The MX machines from KraussMaffei produce the covers in the 3-component injection molding process with a 59-second cycle. Three injection units provide the mold with the three different plas-tic melts. Secondary injection unit 1 is in a piggyback arrangement (Z) and secondary injection unit 2 is arranged in a vertical position (V). In this design, the 3-component machine needs only the same installation area as a 1-component machine. Furthermore, the in-jection units carry out injection parallel to each other; it is also pos-sible to have parallel plasticizing adapted to the customer require-ments. This con� guration ensures fast cycle times.

The screw for the PMMA components has a special coating due to the stringent requirements for the plastic to look absolutely � awless. The material conveyor system, dryer and separator come from Mo-tan-Colortronic GmbH (Constance, Germany) and the heat-balan-cing technology has been supplied by HB Therm (St. Gallen, Swit-zerland). To ful� ll the special challenges of maintaining the purity of the PMMA, the conveyor system is transparent as well as equip-ped with a � lter system.

The 3-cavity mold from the moldmaking company Hofmann GmbH from Lichtenfels, Germany, has a hot runner system from Incoe and rotates 120° after each shot in a precisely timed cycle. All of this takes place on an integrated servo-electrically driven rotary tab-le from KraussMaffei. This table works quickly and precisely with

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Thomas Rüschenschmidt, Head of Engineering at Vorwerk Semco S.A.S. says, “We launched global production of the new Thermomix TM5 in September of 2014 using new injection molding machines from KraussMaffei.”

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outstanding energy ef� ciency. Even large molds with a maximum weight of approximately 16 tonnes can be handled safely and easi-ly. An MX machine stood for several weeks in the halls of the mold maker for mold proving. “KraussMaffei has built the injection mol-ding machines for us, in principle, around the mold and has tailored the entire process design to our speci� c space conditions here in the plant. Our development department brought KraussMaffei and Hof-mann on board as early as the development stage for the compo-nents of the new Thermomix model,” Rüschenschmidt makes clear.

“Still warm when entering the assembly process”

The machines move right along with their work. Two injection mol-ding machines, which face each other and run synchronously, share one post-mold processing system positioned between them. When the mold opens, a KraussMaffei industrial robot from KUKA uses a specially designed gripper to remove the manufactured co-ver. The six-axis robot brings the � nished part to the � rst stati-on: the sprue-cutting station. The sprue from the PC components is removed by eight cutting pincers and led away by a funnel. What follows is the further processing by a laser cell. For this, the robot places the part onto an article-speci� c holder, and a laser (from Hans von der Heyde GmbH & Co.KG) separates the sprue from the PMMA. The focus here is on creating a smooth cut and high cut-ting edge quality. Since the cutting edge is also an exposed edge,

ensuring precise cut guidance is absolutely essential. Therefore a downstream hot-air nozzle rounds off the burr. There must be no dust created during this process, as that could contaminate the transparent PMMA coating. In short, this is a considerable effort, but Rüschenschmidt says there is no alternative. “We sell an inno-vative product and provide our customers with excellent quality as well as premium design.”

Following the post-processing steps, the robot puts the product on-to a conveyor system, which links together all four machines. One after the other, the covers � le out to the � rst quality assurance sta-tion. Here, the critical eyes of trained employees make a visual ins-pection to see if they can discover any unwanted inclusions, points, specks or other irregularities. If this is not the case, the cover ma-kes its way back onto the conveyor belt and from there into the hot embossing station. Depending on where the end customer lives, this is where the Thermomix gets its imprint—Thermomix or Bim-by, according to Rüschenschmidt. “The name Bimby became esta-blished for our kitchen appliance in Italy and Portugal years ago. That is why two different names are available after each pair of twins is produced. Entering the assembly process while still warm.” Con-veyor belts from every which way take the components of the kit-chen appliance to the right assembly station, so that new units are fully packaged in short intervals and waiting to be delivered to their end customers.

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Core competence: plastics technology

There are 420 people working for Vorwerk in France, 250 of whom are employed in production. The production lines for Thermomix in Wuppertal look just like they do in Cloyes-sur-le-Loir: identical technology, machines, molds and the same process sequence.

All complex, larger plastic parts are manufactured by the plant in-house, just like drives and motors. “Plastics technology is one of our core competences, just like reluctance motors and electric drives,” Rüschenschmidt says when describing the company's expertise. In-jection molding machines have been standing in the halls of Vor-werk since the 1960s. In 1961, a universal kitchen appliance from Vorwerk was � rst put on the market with the VKM5. The � rst hea-ted mixer, which could cook and mix at the same time, was called VM 2000 and was created in 1971. That universal kitchen appliance, however, still was not able to stew, steam, weigh or guide users through recipes.

Today, the former kitchen aid has become a jack-of-all-trades and enjoys a large group of fans. The Thermomix provides its users with various options: cooking using the Guided Cooking function, eit-her manually with one of the Thermomix cookbooks or in the ne-ar future using the Cook Key, the new accessory with which you will be able to send your favorite recipes directly to the Thermomix's

The laser separates the PMMA sprue. The laser cell is shared by the two pairs of twins of the injection molding machines.

The sprue from the PC components is mechanically removed by a funnel.

The conveyor system feeds the covers from all four KraussMaffei machines to the � nal assembly station.

Thomas Rüschenschmidt (right) demonstrates the coordinated production of the cover for his project partners from KraussMaffei, Mail Hölscher (front) and Daniel Schittko (left).

display—wirelessly via the Internet connection (Wi-Fi). Rüschen-schmidt is also very impressed by the development. “The excite-ment of our customers for the Thermomix TM5 is enormous. We have appropriately increased production to optimally meet the increased demand, and thus meet the needs and expectations of our custo-mers.” ‹

www.kraussmaffei.comwww.vorwerk.com