Wyniki wyszukiwania - Biblioteka Nauki

1

Towards safe service ecosystems for production for value networks and manufacturing monitoring

100%

Lemme G. , Lemme D. , Nölscher K. A. , Ihlenfeldt S.

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tom Vol. 20, No. 1

117--126

EN

In a global sales market with networked production steps and increasing complex machine tools, scaling service ecosystems for production provide an adequate solution for handling the generated data. The existing sensor equipment at current and the extension possibility by the System-of-Systems approach for existing machine tools can offer value-added services by the smart handling of production-related data. It is important to make these data validatable and exchangeable, taking into account to different protection goals. The trust of the individual actors in such a volatile value chain and the different (partly cross-border) value creation partners play an important role. The participation of a large number of these actors creates an attractive overall system (ecosystem) with lots of services and network effects. Concerning data security there are numerous aspects, which have not been adequately answered or taken into account in the use of a service ecosystem in the production environment. The paper discusses a distributed ecosystem for production on a distributed ledger-based service ecosystem, in which services can be mapped in the machine tool environment (e.g. calibration). This technology can be used for secure data exchange in order to discuss traceability and unchangeability of data while maintaining data sovereignty.

2

Effects of variation in measurement chain on temperature measurement calibration with resistant temperature sensors

100%

Deutsch J. , Riedel M. , Müller J. , Ihlenfeldt S.

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tom Vol. 19, No. 3

56--65

EN

Temperature is one of the most important key parameter to consider in measurement and mechanical engineering, because every measurement has to be conducted with reference to standard temperature conditions (20°C, ISO 1). Strictly speaking, almost every measurement depends on the accuracy of the temperature measurement, which requires proper calibration. Therefore, standards list detailed criteria to fulfil temperature calibration with high precision. In fact, any calibration is only valid, if the whole measurement chain is taken into account. This would make recalibration necessary with each variation of the components in the measuring set-up (varying cable length, different measurement channel etc.), which is time-consuming or even impossible in practice. For that reason, this paper presents a practicable calibration strategy, which specifies each component individually and later combines the calibration results according to the composition of the measurement chain. This provides a fast and useful way to achieve the required accuracy of temperature measurement. The examined, exemplary measurement chain consists of an industrial platinum resistance thermometer (IPRT), cables with different lengths, an electrical amplifier and a reference temperature calibrator.

3

Stiffness evaluation of a hexapod machine tool with integrated force sensors

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Friedrich C. , Kauschinger B. , Ihlenfeldt S.

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tom Vol. 20, No. 1

58--69

EN

Today, in-process force measurement is required by many manufacturing applications, such as process monitoring, quality assurance, or adaptive process control. A very promising force measurement approach bases on sensor-integration into the machine structure and is particularly suitable for hexapod structures and kinematics, where it allows a measurement in 6 degrees of freedom. On the other hand, a sensor integration also affects the machine. Especially for strain-gauge-based force sensors, a stiffness reduction is predicted, as their measuring principle requires a deformation. The practical consequences of these influences are investigated in this contribution. In particular, this work presents extensive experimental studies of the stiffness change caused by sensor integration for a single hexapod strut as well as for the complete hexapod machine tool. The results are evaluated in comparison to compliances of other components, such as the kinematic joints, and to stiffness changes resulting from sensor-integration into the end-effector or the application of a commercial force/torque sensor at the end-effector. In conclusion, the studies support the approach of structure-integrated force measurement for parallel kinematics, as the stiffness loss is rather small in many cases.

4

Design approach for high-dynamic planar motion systems based on the principle of Kinematically Coupled Force Compensation

100%

Ihlenfeldt S. , Müller J. , Merx M. , Peukert C.

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2019

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tom Vol. 19, No. 2

5--17

EN

Machine tools’ feed dynamics are usually limited in order to reduce excitation of machine structure oscillations. Consequently, the potential increase in productivity provided by direct drives, e.g. linear motors, cannot be exploited. The novel approach of the Kinematically Coupled Force Compensation (KCFC) applies a redundant axis configuration combined with the principle of force compensation and thus achieves an increase in feed dynamics while drive reaction forces cancel out each other in the machine base. In this paper, the principle of KCFC is introduced briefly. Subsequently, the basics for the realisation of a highly dynamic KCFC motion system with planar motion are derived and discussed. In order to achieve highest acceleration (> 100 m/s2) and jerk (> 100000 m/s3), a mechatronic system with specially designed components for the mechanical, electrical and control system is required. Thus, the design approach presented in this paper applies lightweight slides, a decoupled guide frame and voice coil motors operated at high frequencies for the pulse width modulation and control loops.

5

Simplification of the rolling contact-related lifetime calculation of profiled rail guides with a polynomial regression

100%

Staroszyk D. , Müller J. , Ihlenfeldt S.

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tom Vol. 24, No. 1

60--73

EN

The calculation of the lifespan of profile rail guides is an essential part in the design process of machines. Conventional lifespan models yield good results when calculating lifespan values under a homogeneous distribution of individual rolling contact forces on the raceways. In the case of an uneven load distribution, significantly too low lifespan values are calculated, resulting in a considerable loss of lifetime potential. The novel and experimentally validated rolling contact-based lifespan calculation (RCBL) takes the transferred force on each rolling element into account, resulting in more realistic lifespan values that can be up to 4 times higher than those obtained through the classical method. The disadvantage lies in the complex calculation of the necessary individual rolling contact forces, which until now has been done by using extensive finite element models, along with the computationally intensive optimization problem of the RCBL. To overcome these disadvantages, a method is introduced that efficiently calculates the individual rolling contact forces, taking into account all relevant system elasticities, and pre-solves the RCBL for a variety of potential superimposed load combinations. The results are subsequently approximated through an analytical multiparametric polynomial function and can be utilized with the conventional lifespan formula for rolling bearings.

6

Investigation of local and modal based active vibration control strategies on the example of an elastic system

88%

Peukert C. , Pöhlmann P. , Merx M. , Müller J. , Ihlenfeldt S.

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2019

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tom Vol. 19, No. 2

32--45

EN

Nowadays, feed axes are often equipped with multiple parallel-acting actuators in order to increase the dynamics of the machine tool. Also, additional actuators for active damping are widely used. Normally, the drives or actuators are controlled independently without consideration for the impact on each other. In contrast, by using the modal space control, the system can be decoupled and the modal control loops can be adjusted independently. This control approach is particularly suitable for motion systems, such as machine tools, which have more drives or actuators than degrees of freedom of movement. This paper deals with the pre-investigation of the modal-based vibration control for machine tools with additional actuators. The object of investigation is an elastic system with a movable saddle. The modal-based control is compared with a local control approach. The results obtained experimentally on the test rig are presented. The modal control is superior since, with the modal approach, each control loop corresponds to a specific vibration mode, and the control law for this loop is designed to provide the desired performance of the control system at the corresponding resonance frequency. The parameterisation of the control loops is simplified by modal control, since the modes can be controlled independently.

7

Potential of tool clamping surfaces in forming machines for cognitive production

75%

Alaluss M. , Kurth R. , Tehel R. , Wagner M. , Wagner N. , Ihlenfeldt S.

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tom Vol. 22, No. 3

116--131

EN

High reproducibility of forming processes along with high quality expectations of the resulting formed parts demand cognitive production systems. The prerequisite is process transparency, which can be improved by increased knowledge of interdependencies between forming tool and forming machine that affects the tool clamping interface behavior. Due to the arrangement as surfaces transmitting process forces, their closeness to the forming process, and yet machine inherent, tool clamping interface provide greater potential for intelligent monitoring. This paper presents a holistic analysis of the interdependencies at the tool clamping interface. Here, the elastic deflection behavior of the press table and slide with their related clamping surfaces, the frictional slip behavior between the interacting machine components and the used clamping devices are described on qualitative level and verified by simulative analysis. Based on the results, available sensor systems are assessed regarding the capability to monitor the identified phenomena inline.