Controlled Unrolling

Food and beverage packings must be of top quality but must cost practically nothing. Very few consumers are aware of the technical effort behind the production of such articles.
The product and service program of Ball Packaging Europe covers two-part drink cans of tin and aluminum for beer, fizzy drinks, mineral water, fruit juices, milk and yoghurt drinks, coffee and alcoholic mixed drinks. The subsidiary of the Ball Corporation, the world's number one on the drink can market, produces at twelve sites close to its customers in Western Europe and in the growth regions of Eastern and Southern Europe. Just one of the punches in the lid production factory in Braunschweig runs off 11 million lids per day!

 

Constant speed as a control task

 

The production process begins with the provision of the sheet for the forming process. For this, aluminum sheet is rolled off a coil bobbin and fed into the punch. Ten circular blanks are punched out of the 1.8 m wide aluminum sheet at 350 strokes/min. Together with a seal and the ring pull, these produce the finished lid in further processing steps. The coil is delivered with a diameter of approx. one meter. The speed at which the material is fed to the punch must be absolutely constant up to the last meter - any delays reduce the availability of the whole plant. This means: the bobbin must increase its speed as the diameter of the coil diminishes. The drive control for this must respond at the appropriate speed and ensure absolutely stable running.

 

Retrofit for increased availability

 

The plant has been in operation for years. The punching speed has been increased continuously to meet the growing international demand for drink cans. It was no longer possible to maintain a constant drive speed for the coiler's bobbin drive with the hardware controller connected to the Simatic S5. The belt stopped increasingly with the diminishing coil diameter, with considerable effects on the availability. To counteract this, Ball decided to retrofit the drive control. From the start, they were looking for a solution which could be transposed to the material feeders of other punches.

 

Tight timeframe for the conversion

 

The contract was awarded to BMA Schaltanlagen GmbH, also based in Braunschweig, a subsidiary of Braunschweigische Maschinenbauanstalt AG, who specializes particularly in equipment for the sugar and starch industry. The timeframe for the conversion was extremely tight. The three-shift operation of the plant is only interrupted once a year for specific maintenance work. The new automation had to be commissioned during this time. The specialists from BMA achieved this goal and are proud to have accomplished the task in just four days even. In this time the control was changed, converters were set up, motors were replaced, sensors were installed and a control unit was mounted.

 

Stable control with integrated solution

 

The S7-315T was chosen as a drive control. The actual values for the controlling are provided by three Siemens sensors: the sheet hangs down in a loop before and after the driver stage; how far it hangs down is detected by one light curtain respectively. The reduction in the coil diameter is measured by a Bero sonar sensor which is mounted above the coil. The two axes for the bobbin and the driver stage which precedes the punch are driven by Sinamics 120 converters. Bernd Brennecke, Head of Engineering at BMA, sees this combination as the ideal solution: “The fact that we were able to configure both the control and the drives with Step 7 made our work much easier and allowed us to keep the narrow time schedule for commissioning.” The control has been running trouble-free for six months, the aluminum belt has not stuttered since. Ball is so pleased with the increased availability that they are firmly planning the appropriate retrofits for other systems.

 

Universally applicable technology

 

BMA are also happy with the positive experiences with the T-CPU and Sinamics in this plant. Rolling is a universal technology. It is used in many industries in different contexts. Solutions which have been implemented once can be varied and transferred to other applications. The appropriate projects are already being planned. T-CPU and Sinamics will definitely be on the team again.