Drives & Controls April 2022

48 n MACHINE-BUILDING April 2022 www.drivesncontrols.com Robot machining cell produces kitchens in batches of one T he French kitchen manufacturer Schmidt has joined the trend towards personalisation by offering one-off kitchen systems to individual customers. The company has commissioned a robotic machining cell in Alsace, France, to produce the bespoke furniture. At the heart of the system are five ABB robots, connected by a flexible transport systemwithin which workpieces are clamped and moved, depending on their size, using four programmable shuttles. Operating with a cycle time of less than 2s, the robots machine holes and grooves in the components, and assemble fittings. A 2m-high side panel for a tall cabinet can be followed immediately by a small shelf, without any changeover or set-up time. “When we first discussed our plans for such a cell, we were told: don’t do it, it can’t be done with sufficient precision using robots,” recalls Achim Gauß, managing director of the German-based Zimmer Group, which designed and built the cell. “At first that was the case. We had to invest a lot in both hardware and software.” Individual furniture parts are clamped into the shuttles by a loading robot and then measured for their dimensions and position. The parts move through the various processing stations before finally being removed from the shuttles by an unloading robot. Because there is no need for un-clamping and re-clamping at different stations, there is no loss of accuracy. The drilling operations are performed by ABB robots to an accuracy of 0.2mm. “Schmidt wanted a system that had 100% availability if possible, where maintenance requirements did not have to lead to a complete machine shutdown,”Gauß continues. “This is only possible with a modular system. In addition, there was the desire for flexibility, accuracy, futureproofing, as well as a batch size of one production, without using predefined machining programs.” The high availability was achieved by ensuring easy accessibility to all parts. Individual shuttles can be removed and replaced without the system coming to a stop. In extreme cases, a“simple”exchange of a complete processing robot is also possible. To achieve the desired output, operations are assigned automatically between two machining robots and are combined in a single drilling stroke. To achieve this, each robot carries a multifunction head containing 41 tools. All machining operations can be performed without changing any tools. High levels of flexibility are achieved using optimising software that generates the machining program fromworkpiece descriptions held in a central database. This direct link between the control system and the higher-level MES provides full networking. In addition, HMIs allow intuitive operation and extended diagnostics for the entire cell. “To be able to reliably organise such a complex system during the design process, and also later when in operation, you need 100% real-time simulation,”Gauß explains. Digital twins allowed the cell to be built virtually to check its performance and functions before it was installed. The twins were also useful for preparing and scheduling the work.“We learned a lot in this project and have been able to transfer this know-how to all our components with the digital twin.” Zimmer used its own grippers and tool changers for the project, as well as a bespoke compensation algorithm that uses laser tracking measurement of the robots. Zimmer reports that Schmidt is delighted with the result, because the cell offers considerable economic advantages as well as high system availability. For example, by using robots instead of traditional machining techniques, combined with the simpler design, the investment costs were much lower than usual. The re-circulating shuttles in the transport system can be controlled individually in terms of speed, cycle time and positions, and can be operated individually or in combination. The flexible robot concept also offers a high level of investment security over the lifecycle of the system, because the modular design allows for future expansion. n A French kitchen manufacturer is producing bespoke kitchen furniture using an robotic machining cell to drill and assemble components. The cell is part of a line that produces kitchens in batches of one. One of the robots in the automated machining cell that Schmidt is using to produce bespoke kitchen furniture