Increasing the operating speed of a production machine

mksModell

The requirements on modern production machines in terms of productivity and efficiency are constantly increasing. Increasing the operating speed is one way to increase productivity. The quality of the product must not be impaired. Unwanted vibrations of the machine can significantly impair the quality of the final product. For this reason, when the operating speed is increased, it may be necessary to revise the machine with regard to vibration-related aspects. In the machine under investigation, a new drive motor was used to increase the operating speed. Due to this increase in speed, the undesired vibrations increased significantly. The procedure used to reduce machine vibration is described below.

 

Measurement

The measurement of the vibrations at the machine was carried out with a 3D coordinate measuring system. The movement of diodes mounted on the machine is recorded and evaluated in a special software. In addition, images were taken with a high-speed camera. In order to locate the vibration source (s), a machine ramp-up was recorded using the coordinate measuring system. Subsequently, different parts of the mechanism were uncoupled. Measurements were also taken for these arrangements across the entire speed spectrum. After filtering and processing the measured data, they were evaluated. A partial mechanism of the production machine could be identified as the main cause of the vibrations.

 

Simulation model

The partial mechanism identified in the course of the measurement data evaluation as the main cause of the vibrations was then constructed as a multi-body simulation model (MBS model). The mechanism under consideration is an unevenly geared transmission. Due to the uneven transmission, changing inertia forces and moments occur. These in turn lead to vibrations of the entire machine as well as a fluctuating demand torque at the drive. The torque of the drive motor must be continuously adapted to this torque requirement. The greater the relative torque fluctuations, the more difficult the motor control required for this purpose becomes. Under certain circumstances, new vibrations can be introduced into the drive train through this control system. In the course of modeling, a parameterized multi-body simulation model (MCS model) of the relevant partial mechanism was developed. By comparing the simulation results for different ramp-ups with the measurement results, a good correlation was found.

 

Vibration analysis

massInertia

Within the scope of the vibration analysis, various operating states and ramp-ups were simulated with the aid of the MBSmodel. A sensitivity analysis was then carried out to determine the influence of the various components on the overall vibration behaviour. The following steps followed

  • Mass reduction and
  • Optimization of kinematics.
In the simulation model, a significant reduction of the machines vertical vibrations became visible. It was also possible to reduce the fluctuation of the demand moment and its mean value. In order to further reduce the relative fluctuation, a compensation mass was added to the drive shaft in the next step (power compensation). Due to the lower demand torque, it could be installed without the need to increase the motor torque.

 

Vibration reduction

The final step was the implementation of the measures derived from the simulation model. The masses of various components were reduced by exchanging materials and revising the design, and the kinematics of the transmission were modified. Final measurements confirmed a quantitative reduction in vibration at higher operating speeds of the machine.

CONTACT


Institute of Mechanism Theory, Machine Dynamics and Robotics

RWTH Aachen University

Eilfschornsteinstraße 18

52062 Aachen

Germany

 

Phone: +49 241 80 95546

Fax:      +49 241 80 92263

Mail:     

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