December 2011


MM (Modern Machinery) Science Journal, December 2011
Jan Pavlik
Brno University of Technology, Faculty of Mechanical Engineering, Institute of Production Machines, Systems and Robotics, Brno, Czech Republic

The article is focused on the issue of the automatic tool change (ATC). The discussed topic can be onsidered at present to be the most relevant for the group of machines from the category of milling centres. The pressure for productivity, efficiency of the whole manufacturing process, reliability and, last but not least, safety, leads manufacturers to design and install modern equipment for the implementation of automatic tool change which fulfil the most strict requirements. Today, the most problematic area of used equipment for ATC is the manipulator ensuring the change of the tool between the spindle and the magazine. The kinematic arrangement and constructional solution of individual elements very significantly influence the dynamism of the whole process of change of the tool. Therefore, the work is focused just to the resolution of the issue of manipulators. The main results of the solution are the construction design of several types of manipulators, some of which were implemented within the project 1.2.4 in the Brno workplace RCMT (Research Centre of Manufacturing Technology) in the form of testing stands. Simulation models were created for selected types; for whose verification results of measurements from real equipment were used. On the basis of the solution of this issue, further key problem was identified related not only to the process of replacement, but also the complex problem of the service life of the spindle. It concerns the problem of the force originated during the process of the clamping of the tool. The article outlines possibilities for further research concerning the influences of these forces on the service life of the spindle (mainly service life of the bearing groups of the bedding of the spindle).

Keywords: automatic tool change, ATC, automation, tool interface, simulation model, LabView, Adams
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MM (Modern Machinery) Science Journal, December 2011
Jan Kmec, Lydia Sobotova and Peter Demec
The Department of Technologies and Materials, The Faculty of Mechanical Engineering, Technical University in Kosice, Kosice, The Slovak Republic

Water – jet cutting technology presents new accesses of shape cutting and various material separations at cold cut without heat influence to material on cutting edge.

Keywords: Water-jet cutting technology, cold cut, all materials
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MM (Modern Machinery) Science Journal, December 2011
Tomas Repak
CTU in Prague, Faculty of Electrical Engineering, Department of Control Engineering, Prague, Czech Republic

Presented contribution describes a seismically balanced machine tool axis with advantages and disadvantages of that kind of concept. After an introductory survey on the seismically balanced machine tool, a system simulation is presented. This system simulation includes a model of the mechanical parts, a model of a synchronous linear motor, and a model of the control circuits. The control algorithm of relative distance (with simulation of relative distance control of two masses) and centre of gravity movement control (absolutisation) is presented. The LQ control algorithm was compared to the heavily used PID control algorithm. The results are shown in the last section of this paper. With these results, optimal design of controller can be achieved.

Keywords: seismically balanced tool machine, simulation, model, control, LQ controller, PID controller
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The Analytical Formulations for Vehicle Motion Planning

MM (Modern Machinery) Science Journal, December 2011
Prof. D. Tesar,
The University of Texas at Austin, Austin, Texas, U.S.A.

We are now just entering the age of intelligent electro-mechanical systems. In this case, a multi-wheeled vehicle is to be modernized by opening up the architecture (it is fully modular and can be assembled on demand). In particular, the mobile platform can have any body geometry for N wheels (supported by articulated suspensions of 2 to 3 DOF), all acting in parallel. Given the motion specifications of each wheel/suspension leads to a programming and mathematical nightmare which rapidly loses all physical meaning. Here, we decide to specify the motion of the platform up to, say, the 4th order, algebraically compute the required input parameters at each of the N wheels (up to the 4th order) and then evaluate the actuator and traction resources to see if those input commands are satisfied and with what margins (positive means success, negative means failure). The ultimate goal is to balance all the margins in real time to ensure system success and how marginal that success is even in poor weather, rough terrain, emergency maneuvers, etc. This, then, leads to a 5 to10 milli-sec. decision making problem which must be made in terms of physically meaningful criteria, which is the basis for the formulation presented in this paper

Keywords: Vehicle Planning Motion, Instant Center
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