Drawbeads are commonly used to control material flow during the drawing operation in order to achieve the optimal forming of a part without cracks and wrinkles. Such control is often achieved by using drawbeads in combination with a binder force. Modifications to the position, length and strength of drawbeads are made during the process design phase to produce an optimal stamped part with minimum material usage. Drawbeads may also be manually modified during the tryout phase in order to obtain the desired process. The intensive usage of drawbeads as well as the need to carry out various modifications requires a structured approach to model drawbeads in a forming simulation.
With AutoForm Engineering’s latest release AutoFormplus R6, this issue is resolved. One of the major innovations in AutoFormplus R6 is the so-called drawbead reduction strategy used in combination with the adaptive line bead. The main idea behind this innovation is to support users with an easy-to-use and realistic model when determining and optimizing the drawbeads. The reduction strategy defines the order, the measures and the ranges in which both the drawbead parameters and the drawbead shape are simultaneously modified, including bead height, bead radius or groove radius. In this model, all of the defined measures are combined and made available to the user through one single parameter.
The basic principle of a simple reduction strategy is illustrated below. Starting with the initial profile geometry which corresponds to the highest restraining force, the reduction strategy is carried out by subsequently reducing the drawbead height. The ‘new’ profile results in a reduced restraining force. In the event that the restraining force is still too high, the bead height can be further reduced according to the defined reduction strategy.
In general, this corresponds to the real tryout in which reducing the bead by milling is preferred to increasing the bead by welding as it is much easier to reduce an existing drawbead if the deep drawn results are not satisfactory. Reduction of drawbead always leads to a reduction of drawbead restraining force, i.e. the influence of the drawbead on the deep drawn result is reduced.
Instead of having to deal with various measures and geometries, the user can now focus on one single parameter only, allowing for efficient process engineering even when complex parts are analyzed. With this model, drawbead handling in engineering is aligned with the real tryout and very easy to use.
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