Jerzy Józwik

IDENTIFICATION AND MONITORING OF NOISE SOURCES OF CNC MACHINE TOOLS BY ACOUSTIC HOLOGRAPHY METHODS

The paper presents the analysis of sound field emitted by selected CNC machine tools. The identification of noise sources and level was measured by acoustic holography for the 3-axis DMC 635eco machine tool and the 5-axis vertical machining centre DMU 65 monoBlock. The acoustic holography method allows precise identification and measurement of noise sources at different bandwidths of frequency. Detection of noise sources in tested objects allows diagnosis of their technical condition, as well as choice of effective means of noise reduction, which is highly significant from the perspective of minimising noise at the CNC machine operator workstation. Test results were presented as acoustic maps in various frequency ranges. Noise sources of the machine tool itself were identified, as well as the range of noise influence and the most frequent places of reflections and their span. The results of measurements were presented in figures and diagrams.

DIAGNOSTICS OF WORKPIECE SURFACE CONDITION BASED ON CUTTING TOOL VIBRATIONS DURING MACHINING

The paper presents functional relationships between surface geometry parameters, feedrate and vibrations level in the radial direction of the workpiece. Time characteristics of the acceleration of cutting tool vibration registered during C45 steel and stainless steel machining for separate axes (X, Y, Z) were presented as a function of feedrate f. During the tests surface geometric accuracy assessment was performed and 3D surface roughness parameters were determined. The Sz parameter was selected for the analysis, which was then collated with RMS vibration acceleration and feedrate f. The Sz parameter indirectly provides information on peak to valley height and is characterised by high generalising potential i.e. it is highly correlated to other surface and volume parameters of surface roughness. Test results presented in this paper may constitute a valuable source of information considering the influence of vibrations on geometric accuracy of elements for engineers designing technological processes.

NORMATIVE MEASUREMENTS OF NOISE AT CNC MACHINES WORK STATIONS

Minimisation of noise at a workstation is among fundamental tasks for maintaining safety at work, both in terms of health (the auditory system in particular) as well as work comfort. Thus, it is very important to systematically monitor noise levels by carrying out reliable measurements at a workstation. The method of performing noise measurements at workstations of specific machines is normalised so the results of such measurements for different machines is comparable. This paper presents noise measurements for DMC 635 numerically controlled milling machine, performed in accordance with PN ISO 230-5:2002 norm. The results showed that the level of noise at the operator’s workstation significantly exceeds the norm at certain machining parameters. The results of tests are concluded as detailed recommendation for the CNC machine tool operator to use hearing protection when at work.

ANALYSIS OF THE SURFACE PROFILE AND ITS MATERIAL SHARE DURING THE GRINDING INCONEL 718 ALLOY

Grinding is still an important method for surface finishing. At FPTM JEPU research, which deals with this issue is conducted. Experiments are carried out with grinding various materials under different conditions and then selected components of the surface integrity are evaluated. They include roughness Ra, Rm and Rz, Material ratio curve (Abbott Firestone curve) and also the obtained roundness. This article deals with grinding nickel Inconel 718 alloy, when selected cutting grinding conditions were used and subsequently the surface profile and the material ratio curve were mea sured and evaluated.

Monitoring of the Noise Emitted by Machine Tools in Industrial Conditions

The paper presents an analysis of noise emitted by selected machine tools in a production hall (under industrial conditions). Noise monitoring is a fundamental task for maintaining workplaces which are safe and healthy. This paper presents the noise measurements obtained for several machine tools, performed in accordance with the PN ISO 230–5:2002 standard. The identification of noise sources and levels was conducted by means of the UNIT 352 measurement system for DMU 50, BGO-CNC/RV/R, FU 251, FW 801, FWC 25/H. Detection of noise sources in the tested machine tools allows to maintain safety of workers and effective means of noise reduction, which are highly significant from the perspective of minimising noise at various workstations. The method of performing noise measurements at workstations using specific machines is normalised, so that the results of such measurements for different machines could be compared. The test results were presented in the form of diagrams and tables. The results of the tests are concluded by a detailed recommendation for the CNC machine tool operators to use hearing protection when at work. The results showed that the level of noise at the operator’s workstation significantly exceeds the standard at certain machining parameters.

INDUSTRIAL ROBOT REPEATABILITY TESTING WITH HIGH SPEED CAMERA PHANTOM V2511

Apart from accuracy, one of the parameters describing industrial robots is positioning accuracy. The parameter in question, which is the subject of this paper, is often the decisive factor determining whether to apply a given robot to perform certain tasks or not. Articulated robots are predominantly used in such processes as: spot welding, transport of materials and other welding applications, where high positioning repeatability is required. It is therefore essential to recognise the parameter in question and to control it throughout the operation of the robot. This paper presents methodology for robot positioning accuracy measurements based on vision technique. The measurements were conducted with Phantom v2511 high-speed camera and TEMA Motion software, for motion analysis. The object of the measurements was a 6-axis Yaskawa Motoman HP20F industrial robot. The results of measurements obtained in tests provided data for the calculation of positioning accuracy of the robot, which was then juxtaposed against robot specifications. Also analysed was the impact of the direction of displacement on the value of attained pose errors. Test results are given in a graphic form.

MEASUREMENT UNCERTAINTY ANALYSIS OF DIFFERENT CNC MACHINE TOOLS MEASUREMENT SYSTEMS

In this paper the results of measurement uncertainty tests conducted with a Heidenhain TS 649 probe on CNC machine tools are presented. In addition, identification and analysis of random and systematic errors of measurement were presented. Analyses were performed on the basis of measurements taken on two different CNC machine tools with Heidenhain control system. The evaluated errors were discussed and compensation procedures were proposed. The obtained results were described in tables and figures.

DIAGNOSTIC OF CNC LATHE WITH QC 20 BALLBAR SYSTEM

This paper presents the evaluation of the influence of the feedmotion speed on the value of selected geometric errors of CNC lathe CTX 310 eco by DMG, indentified by QC 20 Ballbar system. Diagnostically evaluated were: the deviation of the axis squareness, reversal spike, and backlash. These errors determine the forming of the dimensional and shape accuracy of a machine tool. The article discusses the process of the CNC diagnostic test, the diagnostic evaluation and formulates guidelines on further CNC operation. The results of measurements were presented in tables and diagrams.

Advanced Time-Frequency Representation in Voice Signal Analysis

The most commonly used time-frequency representation of the analysis in voice signal is spectrogram. This representation belongs in general to Cohen’s class, the class of time-frequency energy distributions. From the standpoint of properties of the resolution, spectrogram representation is not optimal. In Cohen class representations are known which have a better resolution properties. All of them are created by smoothing the Wigner-Ville’a distribution characterized by the best resolution, however, the biggest harmful interference. The used smoothing functions decide about a compromise between the properties of resolution and eliminating harmful interference term. Another class of time-frequency energy distributions is the affine class of distributions. From the point of view of readability of analysis of the best properties are known so called Redistribution of energy caused by the use of a general methodology referred to as reassignment to any time-frequency representation. Reassigned distributions efficiently combine a reduction of the interference terms provided by a well adapted smoothing kernel and an increased concentration of the signal components.

Exposure to electromagnetic fields in the surrounding area of microtomograph for the frequency of 50Hz

Minimizing the level of harmful factors in the workplace is one of the basic tasks in maintaining industrial safety, including health care and work comfort. In this view systematic monitoring of harmful factors level by performing reliable measurements in the workplace is crucial. The method of measuring electromagnetic field (PEM) levels in the workplace of particular machines and devices is standardized so that the measurement results of different machines can be compared. This work presents the PEM around object measurements of microtomograph GE v|tome|xs.