Advanced Materials Research Vol. 1018

Abstract: Increasing demands concerning the performance of tribological systems for metal forming due to ecological restrictions or technologically increased process loads require the development of innovative tribological systems, especially in forming of stainless steel. It could be shown in preliminary work that surface structures on deep drawing tools manufactured by the incremental forming process machine hammer peening have the potential to reduce friction in strip drawing test by about 58 % in comparison with a ground reference surface. This is explained by the effect of lubricant pockets and a reduced true contact area in the interacting zone. However, due to the effect of a reduced contact area, the wear resistance of these surface structures is of main concern for the effectiveness of their application in deep drawing. Therefore, in this work strip drawing tests are performed over a minimum of 500 repetitions for the evaluation of friction characteristics. Additionally, the coating of the surface structures is investigated to improve the wear resistance of the structures.

Abstract: Many parts of today´s world are manufactured by cold forming operations or more precisely by mechanical upsetting such as wheelmounts or bevel gears because cold forming has several advantages compared to other machining operations. Due to size effects, the maximum achievable upset ratio in mechanical upsetting decreases with decreasing size of the work piece, so that upsetting becomes inefficient in micro range. Here, one promising approach is the laser rod end melting process generating a so called preform which allows upset ratios of several hundred within one stage. This preform is subsequently calibrated by a mechanical upsetting process. A numerical simulation showing the open die upsetting process of preforms, modeled with Abaqus, is presented in this work. Results of numerically determined natural strain are compared with an analytical model showing that the analytical model is a reasonable approximation. The maximum achievable average natural strain of preforms in upsetting is experimentally determined to be at least φ*=2.75.

Abstract: To make the advantages of electromagnetic forming applicable for industrial manufacturing, a three step tool design strategy is suggested. At first, simplified decoupled electromagnetic and structural mechanical simulations are used for creating a preliminary design via a systematic iterative optimization process. The selected design is verified in more accurate coupled simulations. A prototypic realization serves for further optimization, if necessary. The applicability of the approach is proved on the basis of an inductor system for magnetic pulse welding of tubes.

Abstract: Hot forging dies are exposed to a combination of high mechanical and thermal load in each forging cycle leading to abrasive wear that is one of the most frequent causes of die failure. Due to the high difference in temperature between the dies and the workpiece the surface layer material of forging dies undergoes very high thermal shock loads. High temperatures, which occur in each cycle lead to material annealing and to a softening of the material in the surface layer. However, there are die regions, like convex radiuses, where the surface temperatures exceed the austenitizing temperature. In combination with high cooling rates martensitic structures with a high hardness are generated in these regions. Both, softening as well as hardening of the tool material have a great influence on the wear resistance of dies. Nowadays a prediction of the wear amount is possible by using Finite Element Method (FEM) in combination with wear models. The approach for hot forging processes provides an input of die hardness curves under cyclic thermal load. Only by calculating die wear using this hardness curve a good accuracy of the FE result with experimental investigations is possible. Therefore relevant tests of hot forging material under typical forging load should be designed, conducted and afterwards used in the FE based wear prediction for hot forging dies.

Abstract: The motion quality of high precision feed drives is often limited by nonlinear friction effects. This paper presents an approach of using ultrasonic vibrations integrated into the linear bearings of the feed drive in order to control the friction. Measurement results of an ultrasonic excited prototype are shown and a control strategy for stick-slip reduction is proposed.

Abstract: Different causes lead to unforeseen contact situations between moving components in the working space of machine tools. These collisions can result in damage of the machine components. High cost and machine downtime are the consequences. This article presents a solution for the reduction of contact forces in case of collision. The damages of the machine structure and the main components like the motor spindle can be successfully avoided. Further a modified mechanism with higher stiffness and better process properties of the protection system will be described and compared to the current status.

Abstract: Besides the energy efficiency approach to reduce energy demands of production systems there are also other possibilities to decrease the energy related operating costs. Amongst others avoiding long-term peak loads represents a common measure. In possible future cases a flexible energy demand of factories can also be refunded by the energy provider within new tariff structures. This paper shows the potentials of production systems to alternate their energy demand within productive state, which is also referred to as technical energy flexibility. The focus is on machines of sensitive main processes, where an influence on the energy demand could induce distinct negative effects on the product quality. It is shown how and to which extent the energy demand of production systems can be controlled without negative effects.

Abstract: Mobile machining solutions use autonomous machining units that can be transported to different part locations, making possible easy maintenance and repair of large industrial equipment. Every new part and location results in different boundary conditions for the mobile machine tool-part system; influencing the dynamics of the combined system and necessitating different strategies for part/machine referencing and clamping. To facilitate efficient mutability and modularity in mobile machining solutions, this paper presents a dynamic substructuring strategy that combines the response characteristics of the mobile machine unit with that of two different simulated base models under varying levels of contact stiffness and damping to obtain the synthesized mobile machine tool dynamic response. Numerical verification of the approach is provided. Framework presented can also combine measured response of parts for which models may not be available a priori. Methods presented provide experimental guidelines for establishing strategies for part/machine referencing, and planning of machining strategies based on the evaluated dynamics.

Abstract: The current standards on the safety of machine tools are reliable sources for designers who need to know which materials and thicknesses are appropriate for safety guards on a certain type of machine tool. However, due to various possible designs of safety guards, information about requirements on their fixation is only provided for isolated cases. In this publication, a broad series of FE simulations and impact tests has been accomplished in order to provide quantitative values to machine tool guard designers. In addition, a method to validate FE simulation results and to determine their reliability is presented. This allows an integration of FE simulations in the dimensioning process of machine tool guards and significantly reduces required experimental impact tests.

Abstract: Classical lightweight construction in the field of machine tools is reaching its limits. New materials like fibre reinforced plastics are not widely used yet. The main reasons are the high material and production costs. This paper presents an approach for substituting a conventional component of the machine tool’s periphery by a structure made of fibre reinforced plastics. An easy and economic production process was used to enable quick fabrication.