Karl Kuzman

Optimization of sheet metal forming processes by the use of numerical simulations

Abstract If the final part is to be produced without any defects, the development process has to be supported by means of numerical simulations based on finite element method (FEM). The experiences gained with optimization of sheet metal forming processes are presented on the industrial examples. The presented examples are carefully selected in order to present all important issues concerning sheet metal forming: determination of optimal product shape and optimal initial blank geometry, prediction of fracture, prediction of final sheet thickness, prediction of wrinkling, prediction of loads acting on the active tool surfaces, prediction of springback and residual stresses in the product. The results of the numerical simulations were compared to the samples from the production processes. Reliability of the results, costs, benefits, and times required for performing numerical simulations are evaluated.

Problems of accuracy control in cold forming

Abstract Modern manufacturing technologies demand components produced to very narrow tolerances: the number of non-satisfying parts is nowadays limited to some tens per million, the final goal being “zero-defect production”. In order to fulfil these preconditions, the forming processes must be well understood and kept under permanent control. The geometrical accuracy of cold-formed components depends on many parameters, among which the most important are the incoming material, the machine, the tools, and the process itself. This paper first discusses some efforts in analysing the impacts of different process parameters where a combination of experiments and numerical evaluations was used. The research was oriented towards ranking of the parameters, according to their influence and studying their interrelated effects on the processes. In the final sections, an interesting phenomenon concerning the accuracy control were presented: it is possible to find such a combination of parameters where the process is stable, and not so sensitive to the fluctuations of parameters. The definition of such “stable technological windows” will be very valuable for practice, especially for technology planning.

Sensitivity and stability evaluation of the deep drawing process

Abstract In forming processes the final part is exactly defined. The allowable scatter of the input parameters, necessary to achieve the requested output properties and optimal setting of input parameters necessary for stability of the production process are not always well defined. Deep drawing of a rectangular box is studied here as an example. Firstly the stability of the production process is studied by experiments and by means of numerical simulations, based on the finite element method. Later the influence of the fluctuation of the input parameters on the output parameters is studied.

Numerical simulations in optimisation of product and forming process

Abstract Modern systems for the development and manufacturing of new products are strongly connected to market demand. To achieve fast and effective response to market needs, the concept and design phase must take place in a virtual CA-x environment. Once the approximate product geometry is known, a numerical simulation has to be performed to study the forming process and appropriate tool design. After some iterations, product geometry, with some variants, is known and the best of them is chosen for further development. The number of stamping steps and the exact tooling geometry are determined. The stamping processes which are widely used in the manufacturing of sheet metal parts are hard to control, since they depend on numerous parameters relating to geometry and material type. The purpose of this paper is to present the industrial application of 3D numerical simulations using the PAM-STAMP program in the product and process development cycle. The simulations were performed during product and process development including tool design and manufacturing. The issues theoretically discussed in the first part of the paper will be explained by example. The time, costs and benefits analysis of using the numerical simulation in the product and process development cycle will also be discussed.

Stabilisation of mechanical properties of the wire by roller straightening

Abstract One of the most important problems in the production engineering is assurance of geometrical stability of semiproducts, which is the basis for the further successful automatic assembling. In the field of cold forming, fluctuation of mechanical properties of the input material has a major contribution to the final product geometry. Thus a good knowledge about mechanical properties of the input material is essential for successful control over the production processes. Research work in the field of cold wire forming showed that it is possible to influence the process by appropriate corrections of the position of bending tools. Corrections depend upon mechanical properties of the wire, which fluctuates during the process run. It means that it is necessary to capture them on-line by an appropriate equipment and then act accordingly. The paper presents a numerical analytical model for the characterisation of the input material properties during the wire straightening process. Based on the assessed data an appropriate correction of the rollers intermeshing is made to stabilise mechanical properties of the wire material.

Control of material flow in a combined backward can - forward rod extrusion

Abstract The paper deals with an analysis of an extrusion process with a divided material flow. As we are forced to seek for optimal technological solutions with short testing times and low risks and costs, a reliable process evaluation is of the greatest importance. The paper discusses the influences of tool geometry, friction and lubrication as well as workpiece properties on balanced material flow in a combined extrusion process. The FEM analysis applying the DEFORM code has been used in order to predict the process parameters and to estimate its stability. The subsequent experimental verification has resulted in a conclusion that modern computer aided tools, tuned by proper experimental sets, can be used for fast and reliable cold metal forging process planning.

Backward Drawing of Necks Using Incremental Approach

The paper presents a modern manufacturing concept called the “backward incremental hole-flanging process”. It enables drawing necks on the final products that can be very complex or even closed with minimal expense. Special attention is dedicated to researching the most influential process parameters affecting the neck height and the thinning of the neck using empirical modelling. Results show that forming tool diameter, and horizontal and vertical step sizes have the greatest influence on the forming results.

Injection moulding simulation results as an input to the injection moulding process

Abstract In the presented research work the authors tried to develop the software which will suit all the needs of the injection moulding when optimising the part-mould-technology system. The simulation results consist of geometrical and technological data. Geometrical data are useful for both: the part as well as the mould designers, because technological data help the moulders to understand the process parameters. On the basis of the simulation results, the part designers can optimise the geometry of the part and the mould designers can optimise the running and the cooling system of the mould. In this way the optimal input values for the technology optimisation can be defined. The paper provides evidence that the program with its open structure suits the needs of the laboratory environment as well as of the real production.

The integration of rapid prototyping and CAE in mould manufacturing

Abstract In order to shorten the manufacturing time for new products and their moulds, the use and the development of modern techniques are critical. One of such technologies is the rapid prototyping method, which enables the designer and the customer to see the physical presentation of a new product which will be ready for marketing in the period of 3–6 months, already at the early stage of its development. During this period of 3–6 months, the mould must be manufactured and the product must be placed to the market. In this comprehensive R&D work, modern computer techniques must be applied. With the help of computer aided numerical simulations, solving of the greater part of the problems that can emerge during the product and/or mould manufacturing can be predicted. This paper is a result of the co-operation between three Slovenian companies in the development of new products. It starts with the rapid prototyping and computer simulations in the development phase of the product. The same CAE approach will be used in the implementation of modern mould manufacturing techniques, the whole development of the products being treated as an industrial implementation of concurrent engineering methods.

Genetic programming approach to determining of metal materials properties

The paper deals with determining metal material properties by the use of genetic programming (GP). As an example, the determination of the flow stress in bulk forming is presented. The flow stress can be calculated on the basis of known forming efficiency. The experimental data obtained during pressure test serve as an environment to which models for forming efficiency have to be adapted during simulated evolution as much as possible. By performing four experiments, several different models for forming efficiency are genetically developed. The models are not a result of the human intelligence but of intelligent evolutionary process. With regard to their precision, the successful models are more or less equivalent; they differ mainly in size, shape, and complexity of solutions. The influence of selection of different initial model components (genes) on the probability of successful solution is studied in detail. In one especially successful run of the GP system the Siebels expression was genetically developed. In addition, redundancy of the knowledge hidden in the experimental data was detected and eliminated without the influence of human intelligence. Researches showed excellent agreement between the experimental data, existing analytical solutions, and models obtained genetically.