Petr Blecha

Control Method for Elimination of Self–Excited Oscillations during Turning

The oscillations occurring between the tool and the machined area during the turning process lead to degradation of the machined surface, cause poor geometric accuracy, accelerate tool wear and generate noise. This paper deals with the possibility of elimination of these self-excited oscillations by changing the parameters of the turning process. On the basis of the regenerative principle of self-excited oscillation generation, a computer model of the machining process was developed. Furthermore, a PID controller was proposed to control the compensation of the vibrations and its suitability for elimination of the self-excited oscillations was verified experimentally.

Visualization of Energy Flows Using a Particle System

Nowadays simulation and visualization are used to a greater extent in real life. Needless to say, different kinds of visualization are widely applied in various spheres such as education, computer entertainment, economics and business, industrial sector, etc. New machine tools and industrial elements can be easily designed by means of visualization. Especially concerning research on energy efficiency, visualization is an important step for understanding. This paper describes a new method for energy visualization using a particle system.

Integration of Risk Management into the Machinery Design Process

Risk management is currently a key component of any design process. The designers are required to identify all hazards within the whole life cycle of the machine and, if necessary, to take appropriate measures in order to reduce the risk of these hazards to an acceptable level. Furthermore, the new machinery directive 2006/42/EC requires this process of assessment and minimization of risk to be documented, which is an essential prerequisite of placing the product on the market or into operation. As people generally tend to underestimate the risks, it is necessary to pay adequate attention also to elaboration of the instructions for use of the designed machine, and besides, to take into consideration any reasonably foreseeable misuse. This paper presents a concept of application and documentation of the technical risk management process during the design of machinery, with an emphasis on its transparency.

Device for Measuring of Active Power and Energy at Machine Tools

This article describes developing of device for measuring active power and energy at machine tools. Demands on measuring of electric energy flow in machine tools are more often with requirement to increasing of efficiency. This problematic is very complicated, because there are some types of electric power supply. Machine tools have main supply with harmonic supply with disturbance, direct current supply with high-frequency disturbance and power supply with PWM modulation. This device primary serves for measuring of AC power between inverter and motor, but also is able measure at other places. Developing consist from developing of electronics and algorithm. Both these part are describes in article.

Integration of Risk Management into the Process of PLC-Software Development in Machine Tools

Risk management is currently a key component of the design process. The designers are required to identify all hazards within the whole life cycle of a machine and, if necessary, to take appropriate measures in order to reduce the risk of these hazards to an acceptable level. To achieve overall safety of a machine, it is also very important to carry out risk management during the development of software to ensure correct function of the designed mechatronic system. The presented paper describes realization of risk management during development of PLC-software for the system of automatic tool change in a machine tool.

DELTA - Robot with Parallel Kinematics

A complex solution of a design of the DELTA type robot, i.e. the robot with parallel kinematics, is described in this paper. The project ensued from cooperation with the company Dyger, s.r.o., with the objective to develop a robotic device suitable for high-speed handling of small objects and applicable in many industrial configurations. The task was not only to design the mechanical part of the robot that would work together with the provided hardware and software, but also to develop our own algorithms for calculations of the target positions, singular positions of the mechanism etc.

Design of the Controller for Elimination of Self-excited Oscillations

The article deals with design of the controller for elimination of self-excited oscillations during machining. These oscillations are generated between a cutting tool and a work-piece surface and lead to decreased quality of the machined surface as well as decreased geometrical precision. The secondary effect is increased level of noise emissions. In general, the self-excited oscillations negatively affect the working productivity of metal cutting machines and inhibit its growth. The design of the controller is based on a model of the cutting process which works with so-called regenerative principle of the self-excited oscillations generation and is based on the variable chip thickness. The model itself serves to derivation of the controller gains. A piezoelectric compensator of the cutting force is controlled by the designed PSD controller. The compensator changes the position of the tool against the machined surface thereby changing the chip thickness.

ENVIRONMENTAL MANAGEMENT IN DESIGN PROCESS OF MACHINERY

e-mail: krbalova@fme.vutbr.cz Nowadays more and more intense discussions of professionals are carried out; they are focused on the issues of global warming. One of the latest documents in the fight against the climate change is the New Global Climate Agreement approved during the Climate Conference in Paris in December 2015. Although the signed agreement does not stipulate any timetable or particular targets for individual countries, it is nevertheless considered to have its impact on the individual spheres of economy, for which there are currently no mandatory environmental requirements. These results in the fact that the existing measures are not sufficient to achieve the objective of 40% reduction in greenhouse gas emissions by 2030 compared with 1990, to which the European Union has already committed itself [EC 2015]. Other measures thus may relate primarily to heavy industry, specifically to the area of machinery, which belongs among large energy consumers [Iskandirova et al. 2014]. The present article covers the assessment of environmental impact of greenhouse gas emissions on designing the machinery. The article describes a proposal of methodology for evaluation of emissions of greenhouse gases released in the production of engineering materials.

GEOMETRIC ERRORS COMPENSATION OF CNC MACHINE TOOL

This contribution assesses the possibilities of application of conventional compensation technology on a small three-axis vertical machining centre. Small CNC machine tools are intended for manufacture of small workpieces with dimensional accuracy of up to 0.001 mm. To achieve the required accuracy and reproducibility of manufacture, a variety of software compensations are deployed on machines. The aim of these compensations is to eliminate errors caused by deviations in the machine geometry, thermal expansion and dynamic compliance of the machine tool. In order to increase dimensional and geometric accuracy of workpieces, this study tested and evaluated methods to activate geometrical compensations such as approach to the desired position and volumetric compensations. Calibration and verification of set compensations were validated by testing geometric accuracy of machines using the devices Ballbar, Laser interferometer and LaserTRACER. Conclusions drawn from the performed study verified deployment of compensations on small CNC machine tools.

Assessing the impact of mechatronic systems on the environment

The ever-increasing power consumption and the associated consumption of non-renewable natural resources lead to an overall environmental degradation. Efforts to increase the energy efficiency, to reduce greenhouse gas emissions and the sustainable use of natural resources have a significant potential for improving the environment and its preservation for future generations. To realize this potential, it is however necessary to manage the assessment of the environmental impact of product design on the environment. Mechatronic systems (e.g. machinery, manipulators, actuators, and manufacturing machines ...) form significant industrial facilities and at the same time they also represent major appliances consuming the electrical energy, and during their entire life cycle they have a considerable impact on the environment. The most demanding industry sectors are: production of iron and steel, which are materials that are often used in the construction of mechatronic systems. The present article is devoted to the methodology of assessment of the effects of general mechatronic system on the environment. The environmental burden is presented in the form of carbon dioxide emissions caused by the production of selected construction materials.