Increasingly stringent product liability legislation is forcing car manufacturers to ensure complete retraceability of individual components. Automobile producers and their vendors can no longer avoid proving the exact production data related to the components they cast, for example the production date, work shift, casting diagram, or metal temperature. This data is most reliably recorded by stamping it onto the castings.
In every die casting system supplied by Buhler, the dat@net process control system saves the quality-determining parameters of each casting cycle. The BuhlMark marking unit is capable of unmistakably allocating these parameters to the specific castings, for example by adding the cycle number on the casting by scores or dots. This closes the cycle of complete component retracing.
Scores or dots
Extensive tests have shown scoring and dot stamping to be the only labelling processes that are suitable for die casting, offering high efficiency and ensuring readability after surface finishing.
For the human eye, plain text is the type of marking easiest to read. It can be stamped onto the casting in the form of dots or be applied by scoring. Scoring produces the more elegant result and can be applied faster. If the labeling is to be machine-readable, the most widely used method today is the data matrix. This code, stamped in the form of dots onto the component, ensures high process reliability. If it is to be possible to read the text by machine and by the naked eye, the information is written twice onto the casting: as stamped data matrix dots and as scored plain text.
Overall system
It is not necessary to label the cast component right after extraction from the die casting machine. The extraction robot may first deposit the part in a cooling rack with up to 20 cooling places before labeling, or transfer it to a trimming press. This means it is crucial to ensure that the cycle number is always clearly allocated to the casting throughout the combination “die casting machine – extraction robot – marking unit…” The Buhler component marking solution therefore comprises the die casting machine with its dat@net control system, the BuhlRob extraction robot, and the BuhlMark marking unit. If no data bus link exists between these three system components, it will not be possible to guarantee complete retracing of castings.
Unified operating philosophy
The introduction of a new peripheral unit in a casting cell will typically require additional operator training. This is not so with the Buhler integration concept, which has been systematically implemented also with the BuhlMark. The marking unit is fully controlled through the screen of the machine control system (HMI – Human Machine Interface) of the die casting cell using the same operating philosophy. This eliminates the need for fresh training.
Beside the cycle number, other information can also be added to the labelling in any required format, for example the date and time, quality attributes, or free texts. The complete labeling text can be applied with high flexibility. Also the font size, font type, and position of the text on the casting can be programmed through the HMI of the die casting cell.
Buhler is a global leader in the supply of process engineering solutions, especially production technologies for making foods and engineering materials. Buhler is present in over 140 countries and employs some 6,600 people. In fiscal 2006, the Group generated sales of CHF 1,613 million.
For more information on the BuhlMark, please contact:
Christian Eisenegger, Head of Automation & Control System Engineering at Buhler Die Casting in Uzwil,
T +41 71 955 38 00, F +41 71 955 25 88,
E-mail christian.eisenegger(at)buhlergroup.com
