FP5/GROWTH-IMPRESS

Title: Improvement of Precision in Forming by Simultaneous Modelling of Deflections in Workpiece-Die-Press Systems

Partners: IPU, Technical University of Denmark (DK), CEMEF(FR), DIMEG (IT), C3M (SI), B&L Maskinfabrik (DK), SMETEK (DK), VACCARI (IT), ISKRA-AVTOELEKTRIKA (SI)

Summary: This project is about press stiffness and modelling of its impact on the precision of parts and service life of tooling systems which is not fully understood to-date. Imagine a conversation between two forging experts.

Herr Schmidt: "A good press must be stiff."

Signor Stampi: "Well, if it is too stiff then deterioration of dies due to fatigue damage and wear can increase. In some cases I would prefer to use somewhat softer press, if only I could predict deflections in the forming system and make appropriate compensations in the die design."

Herr Schmidt: "But softer presses usually have high energy dissipation and produce bigger scatter in product dimensions which make processes unreliable with respect to precision."

Signor Stampi: "This depends on the part, required tolerances and process as well. There are some processes that are very sensitive to deviations of billet dimensions, its initial positions, material imperfections, tribological non-homogenities, etc. while others are not. For a given product one should make optimal compromises to achieve the required precision at minimum production cost."

This conversation indicates that press stiffness can have controversial effects on the economy of forming production. This has been recognised a long time ago and many classical books on material forming address this problem. However, in spite of these facts the European forging industry at present neither has an adequate technique to measure and characterise press stiffness nor efficient and reliable methods to predict interactions that simultaneously occur in a combined workpiece-die-press system. In this project sustainable steps forward will be made in both aspects.

Two key problems related to modelling of deflections in forming systems will be approached:

(a) How to measure and characterise press stiffness under complex loading conditions
(b) How to efficiently compute deflections that simultaneously interact in a combined workpiece-die-press system and    to optimise precision of parts and service life of tooling systems by taking into account press stiffness