Improving production systems of thin sheet metal
The continuous expansion of the manufacturing industry imposes higher productivity in the supply of parts at the lowest cost. Nevertheless, compliance to high standards of quality for the results in terms of geometry and materials remains the key factor. Simultaneously, the variety in the parts that need to be provided is greater than ever, and this affects the complexity of parts. In order to address all these issues, the focus should be placed on the design and the development of the production means (presses, tools and feeding systems). The PROTOOL system is a new approach that implements new technologies into sheet metal forming production systems, for the monitoring of some relevant parameters of the stamping process, (such as sheet formability, component strength, drawability and cycle time). It comprises: an in-depth documentation of user requirements for the analysis of specifications aimed at improving the stamping process; a measurement and data collection system for the most important parameters, including the drawing force, blank holding force and blank holder travel; a computerised detector for the defects in a zone, with sorting out techniques and a neural network along with fuzzy logic that revaluate process parameters for improving the new part zone production. The system also comprises a set of three devices incorporated in the standard press- namely a pin-adjustment device, a ram parallelism device and a device for the deceleration of the slide. The pin-adjustment device redistributes the blank holder pins force according to the needs of the part. The ram parallelism device regulates the load distribution and maintains the parallelism of the ram during the press stroke to prevent faults from unbalanced loads and to increase tool life. The deceleration of the slide device slows down the slide at the time of impact, resulting in a significant reduction in the size of impact force, the tool wear, the machine vibrations and the noise produced. Ultimately, this positively affects drawability and cycle time. Generally, the system can be used as a predictor of splitting and wrinkling which are the two most important factors of defects production with small limitations in the size of splits and the height of wrinkles. There are also improvements been done to the system itself. For example, it was found that a slight reduction of the blank size would still give an acceptable part, and this modification has been included into production yielding savings of £0.12 per part or £69,000 per annum. The PROTOOL can be used in all small, medium and large die stampers. The standardisation of the technique leads to efficient and effective process control. Thus, there is a 10% decrease in cycle time, a 30% reduction of idle time and a 20% augmentation of part quality from diminishing scraps and faults. Initiating an automatic process control for the formation and part processes will lead to an improvement of output quality with concurrent cost and time savings affecting a very wide range of European industries.
