The sheet metal forming process is becoming more and more complex due to the ever increasing number of different car models, the geometric complexity of stamped parts as well as the widespread applications of high-strength steels and aluminum. In light of increased global competition, car manufacturers aim to deliver high quality stamped parts using state-of-the-art technologies which allow for a lower lead time. To address these challenges, AutoForm Engineering has developed an innovative approach to the systematic improvement of the sheet metal forming process. This approach enables engineers to systematically improve the sheet metal forming process already in the early engineering stage.
Systematic Process Improvement (SPI) brings deeper insight and transparency to the forming process by identifying which design parameters influence part quality and to what extent. In SPI, multiple stamping simulations are carried out automatically. During these simulations, design parameters are varied while engineers maintain their focus on the quality targets set for the stamped part. The quality target can be specified with regard to one or more output variables from the simulation, e.g. no splits, no wrinkles or sufficient stretching. In this way, design parameters which have the most influence on the stamped part can be identified already during the early engineering stage. Engineers can then make the necessary adjustments to the design parameters and simultaneously follow the effects these changes have on the entire part by viewing them on the computer screen. This procedure results in the systematic improvement of the forming process.
By way of example, the simulation of an inner deck lid is carried out in order to present how Systematic Process Improvement instead of Trial and Error can be successfully applied in practice. After simulating the inner deck lid, the results show critical areas which indicate the risk of splits. The engineer’s main tasks at this stage are to examine where these critical areas are in the part, which measures will resolve these effectively and what will happen to the other areas as a result. In order to improve the forming process and obtain a part without splits, the binder force with a current value of 1800 kN has to be adjusted.
“Splits” and “Risk of Splits” areas in a deck lid.
When applying the traditional Trial and Error approach, the engineer modifies the binder force value and carries out the simulation again. The simulation results show whether the appropriate binder force value was selected to attain the required part quality without splits. If the required part quality is not reached, new single simulations with newly adapted binder force values are carried out until the required part quality without splits is attained. The first successful result is considered the best solution for this particular case. The Trial and Error approach is dependent on the experience of the engineer carrying out the simulations and is a time consuming process as it must allow for the time necessary for Trial and Error corrections. It is obvious that a faster and more reliable solution is required. By applying the SPI approach, reliable simulation results which are correctly evaluated, lead to a considerable reduction of the time necessary to reach the required part quality.
Systematic Process Improvement greatly enhances the forming process. Once the quality target has been selected, which is in this case a part without splits, the design variable is then selected, which is in this case the binder force. Its current value of 1800 kN is now considered as a variable with a range between 1000 kN (min) and 2000 kN (max). Multiple stamping simulations, each of them with a different binder force value within this range, are carried out automatically. AutoForm’s software enables the engineer to visualize the process window, e.g. green shading in the process window represents the binder force settings where all split issues are solved and in contrast, red shading represents the binder force settings where splits could appear. For the inner deck lid, the green process window is reached with a binder force ranging between 1000 kN and 1240 kN. The final result, with a binder force value of 1100 kN, identifies no more critical areas where splits could appear.
Systematic Process Improvement leads to “Safe” deck lid without critical areas.
In SPI, the best selected set of design variable values results in the most feasible process. It enables engineers to successfully deal with complex part geometry, high-strength materials and aluminum, tight deadline requirements as well as high quality demands. Through the better understanding of the forming process, shorter development times are achieved. By implementing SPI, engineers can address and solve key manufacturing problems before going into production.
Systematic Process Improvement can be easily carried out with AutoForm’s latest release AutoFormplus R7. This release enables users to benefit from all AutoForm-Sigmaplus capabilities as all Sigma pre and post processing functionalities are now integrated within AutoForm-ProcessExplorerplus. As a result, users can ensure a highly efficient engineering process while meeting desired quality requirements.
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