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| Glass production retrofitted with technology CPU | | Glass production retrofitted with technology CPU | The machine-blown drinking cups of the Essener RKL Ruhr Kristall Glas AG are on everyones lips. By modernizing a plant for pressed glass production with the Simatic technology CPU the company has not only solved its spare parts problems. It has also been possible to increase cup production by a third.
The most cost-effective way to manufacture drinking cups is by the press blowing method. Here, the glass drop falls into the preform through a gutter, where it is blown down by compressed air after closing the form. Then a metal die presses the glass mass into a preform which has roughly the shape of the end product. The preform opens and a swivel arm conveys the so-called parison into the finishing form where it is re-heated and blown into its final shape by compressed air. The glass container is then placed on a cooling plate by a gripper and transported for further processing after cooling down.
Future-oriented modernization
The RKL Ruhr Kristall Glas AG makes its well-known models "Köln", "Willy", "Alt" and various beer glasses by this method. The trademark of this company founded in 1923 is a wide assortment of all kinds of drinking glasses and customized products.
The existing plant for producing drinking cups no longer satisfied the company's high requirements in terms of reliability. The glass manufacturer therefore wanted to modernize the first plant section consisting of feeder, 12-station press blowing machine H28, edge cutting machine Eldred and gripper. Since all the plant elements are to be controlled by a new control system, they need new drives, switch cabinets and an operator panel. The second plant section for pressing stems for champagne or wine glasses is keeping the old components for the time being. The Essen company were looking for an automation provider to do the retrofit who combines good service and high quality and found what they were looking for in Siemens.
Optimum interaction of machines
The feeder serves as a master for the components and dictates the speed for all other drives. The speed is determined manually by entering it on the Simatic OP170 operator panel or is specified by a control signal from the second plant section. In a glass production system it is particularly important for all machines to be running synchronously. The heart of the automation is therefore a new plant controller with the Simatic S7-317T technology CPU. The integrated technology functions for the gear and cam synchronization in this PLC enable synchronized interaction of all axes. The position-synchronous operation is achieved by coupling all drives in current operation by gear synchronization with a virtual axis in the Simatic S7-317T. The operator can compensate the process-related rotary position offset between the individual machines by pressing buttons - the offset angle can be set on the Simatic OP170. The control panel is also used for parameters settings and monitoring the plant. The 1FK7 servo motors are used for feeder, belt, cap cutter and gripper, the 1FT6 servo motor for the press blowing machine on the drive side. A reliable speed control of the motors is guaranteed by the Simodrive 611U converter system. To prevent wear on the machines, Siemens has equipped all drives with torque reduction. The periphery is linked by Simatic ET 200M.
The products are passed on to the second plant section, which has not yet been modernized, for further processing. The product feed must therefore be adapted to the cycle of the old system. Siemens solved this problem by installing the analog drive interface ADI4: A squarewave control signal is read in from the control via the interface and the virtual axis is synchronized with this signal.
Cost saving conversion with a gain in productivity
RKL is convinced by the solution with the Simatic S7-317T technology CPU because all tasks from the drives to the PLC can be performed with Step 7 and no other engineering tools are necessary. The company can therefore exploit its existing Step 7 knowledge. No conversions are required either in terms of programming: Existing S7 programs can be transferred to the new system without any trouble, which helps save costs. Another cost advantage which is not to be underestimated is the use of standard products throughput the plant. The productivity of the plant could also be increased significantly: from 60 cups per minute to 80 cups per minute. This means 33% more drinking cups can be produced on the new plant. |  |
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