Virtual design of a machine tools ball-screw feed drive.

Parpala, Radu ; Predincea, Nicolae

Abstract: Today machine tools manufacturers can no longer afford to consume time and money building and testing real prototypes of the machine tools model, instead they use virtual prototypes. This paper is focused on the virtual prototyping of a machine tools feed drive system. In the virtual prototype approach engineers are able to simulate the static, dynamic and kinematic behavior of the model before they build the real machine. The design model can be further improved in order to satisfy the required conditions before being produced.

Key words: Virtual machine tools, feed drive, simulation.

1. INTRODUCTION

In the virtual prototype approach it is possible to simulate the kinematic, static and dynamic behavior of the machine tools including all aspects of real life exploitation. Using different software packets one is able to simulate even the cutting process. This complex design concept was enabled by the use of high performance computer technology.

This paper presents the design and dynamic analyses of a ball-screw feed drive, this mechanism are used to realize translational movement of machine axes and play an essential role in machine tools performance. Because of the impact that feed drives imply over the finite piece quality the design demands are very high so accurate analyses must be performed in order to assure a very good behavior of the whole machine tools. (Altintas et al., 2005)

2. VIRTUAL PROTOTYPING

Because the fact that now days machine tools are very complex mecatronical system is essential to ensure that all design steeps are evaluated and simulated in order to obtain a physical prototype of the machine tools that will meets the requirements (Weck, 2001).

2.1 Computer aided design

One of the first steps in virtual prototyping is building the CAD model. The 3D model of the feed drive must be designed in order to be accepted as input by various software suits that will be used for further analyses. Because it's hard to find an integrated environment in which to perform all analyses engineers must take into consideration software's compatibilities.

The 3D model of the feed drive was designed by using the CATIA V5 CAD software mainly because of it's good integration with the ANSYS software which was used for statically and dynamical FEM analyses. All 3D part where fully parameterized in order to optimize needed parameters in FEM analyzes

A simulation of a manufacturing process was also perform using the CATIA V5 manufacturing module this was performed prior to the kinematics simulation in order to correctly consider input parameters as acceleration and velocities.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

2.2 Multi body motion simulation

During the initial design phase simplified models are used in order to analyze the cinematic behavior of the mechanism.

Using motion simulation engineers are not only able to determine speed and acceleration but also to get forces and moments for all the part involve in mechanism this way further individual static analyses can be performed.

For the multi body simulation, the feed drive mechanism consists of rigid bodies that have mass and inertia moment properties but cannot deform. The interactions between parts are modeled by using joints (revolute and translational), flexible connectors (spring-dampers), contact forces and motion generators.

The kinematic simulation analyzes the position of all the bodies of the mechanism depending on the time parameter. The movements of one or more parts are described by a low of motion. By using as input velocities and forces from the CAM simulation we can determinate inertia forces and moments. (Gross & Hamann, 2001)

2.3 FEM dynamic analysis

In the dynamic analysis the position of all bodies are determinate as a result of time dependent forces applied to the mechanism.

The finite element method is used to determinate dynamic characteristics of the feed drive system, e.g. natural-frequencies and mode shapes. (Zaeh & Oertli, 2004)

The meshed structural components are connected using spring elements with corresponding stiffness and damping values.

Load and boundary condition are also needed for FEM analysis, for machine tools elements loads can be obtained from cutting process simulation or from multi body motion simulation. (Golz, 1990).

By using ANSYS Workbench one is able to optimize the design process by changing one or more of the initial parameters; those parameters are automatically updated into the CATIA 3D CAD model.

By analyzing the calculation result in the post-processing program the designers can evaluate the machine properties during the design stage.

3. CONCLUSION

Using a set of dedicated softwares engineers are able to analyze and optimized all aspects of real life usage of machine tools elements without spending money on real prototypes this could bring important time and money savings.

Initiated mainly by the automotive and aircraft industry, the development of modern software tools for integrated simulation of products has been enchanted lately. Unfortunate at the moment there are no integrated software platform for the virtual design and analyze of the machines tools.

4. REFERENCES

Altintas, Y.; Brecher C.; Weck M. & Witt S. (2005). Virtual machine tool, Annals of the CIRP, 54/2: 651-669.

Zaeh, M. & Oertli, Th. (2004) Finite Element Modeling of Ball Screw Feed Drive Systems, Annals of the CIRP, 53/1: 289-292.

Gross, H. & Hamann, J. (2001) Electrical Feed Drives in Automation. Basics, Computation, Dimensioning. Siemens, Publicis MCD Corporate Publishing, Erlangen and Munich

Weck, M., (2001) Werkzeugmaschinen. Mechatronishce Systeme, Vorschube, Prozessdiagnose., Springer-Verlag, Berlin, Heidelberg, ISBN 3-540-67614-7

Golz, H.U.,(1990), Analyse, Modellbildung und Optimierung des Betriebsverhaltens von Kugelgewindetrieben, Universitat Karlsruhe, ISBN 0724-4967