strips straightening and feeding technology for auto parts stamping

Straightening and feeding technology for lighter vehicle components

The steady expansion of e-mobility and the legal regulations relating to conventional combustion engines are subjecting the traffic and transport sectors to comprehensive change. To reduce emissions, for example, lighter car bodies and vehicle components are needed. In addition, crash safety also plays a role, because the accommodation of heavy batteries in a vehicle requires appropriately designed body structures that take an accident scenario into account. While fiber composites are sometimes used in small series in this context, materials such as high-strength steel and aluminum are asserting themselves in large series construction with continuous refinement. In addition to the comparatively low costs, the excellent recyclability is a significant advantage of metallic materials. However, their further development often poses new challenges for the processing procedures and the machines used.

In particular, the residual stress state, the flatness and the cutting quality are very important quality characteristics that must be considered for the materials in the straightening and feeding technology. Remarkably, these criteria play a decisive role in the quality of the final product even before the final molding. In production, for reasons of cost and time, the aim is to achieve an ever-higher degree of automation, which can only be achieved if the semi-finished products have perfect flatness, a low level of residual stress. If these requirements are not met, this can have a negative effect on handling and further processing or even make it impossible.

Wide range of applications for aluminum and high-strength steels

Modern and sophisticated materials are used in automotive engineering not only for the outer skin and structure of the actual car bodies but are also used in vehicle components such as the chassis, drive train, seats or trim parts. Aluminum and steel are used for many components in the form of strips, sheets or plates, which are processed and formed in various manufacturing processes from semi-finished products to finished components. Even during these process steps, special demands are placed on the components. Due to the automated handling, good flatness and the lowest possible degree of cut are very important for a machining process without complications. If these quality criteria do not correspond to the defined specifications, there is no process reliability.

The companies of the world machinery have already supported their customers with appropriate solutions for demanding tasks in the past. Thanks to the experience gained from many different projects in this area, the world machinery continuously optimizes their competencies in terms of residual stress state, flatness level and cut quality of strips and sheets to meet the highest requirements. In addition, speed and surface protection play an important role in machining and must be taken into account in all approaches to process improvement.  An important prerequisite for these processes is a perfectly aligned. The world machinery has made it its business to react to these challenges and problems with the help of its decades of experience and to offer technologically mature solutions in the field of straightening and decoiling technology, strip feeding systems and automation.

Numerical simulation allows for more flexible straightening machines

Aluminum and high-strength steels, for example, place special demands on the individual processing steps. One factor that has a major influence on the quality of the end product is the straightening of the respective metal. In a straightening machine consisting of several staggered straightening rolls, the coil curvature of the starting material is eliminated. In addition, any edge or centre waves in the strip material can be compensated for, using suitable machines. The aim here is to achieve the lowest possible and most homogeneous residual stress state in order to maintain the flatness of the material during subsequent cutting processes. An elementary measure for the efficiency of a straightening process is the degree of plastification of the respective metal, which describes the proportion of the material cross-section that is plastically deformed during straightening. With the same yield strength and material thickness, aluminum requires significantly greater degrees of deformation than steel to achieve comparable plastification.

The reason for this is the significantly lower modulus of elasticity of aluminum compared to steel. However, in order to realise greater degrees of deformation, smaller straightening rolls must be used. With high-strength steels, on the other hand, a conflict of objectives arises. On the one hand, their high yield strengths require enormous forming forces and torques; on the other hand, small straightening roll diameters are also needed here to achieve a sufficient degree of plastification. The straightening of both aluminum and high-strength steels therefore requires a forming geometry adapted to the respective product. This is essentially determined by the number, diameter and spacing of the straightening rolls.

The experts of the world machinery have been dealing with the numerical simulation of forming processes in straightening machines for many years. For this reason, powerful simulation programmes are available today with which optimal configurations can be determined for the respective applications. The software has been validated by means of extensive experimental investigations so that the optimum straightening roll diameters can be determined for a specific area of application.