Oldřich Šuba

Investigation of Surface Roughness while Ball Milling Process

Increasing urge to raise production rate and production quality in the industry brings new requests and challenges. One of them is demand for accuracy and precision of produced parts. Especially in the CNC machining, where the expectations are high, the companies face new issues. Therefore, it is very important to recognize, understand and cope with the technological factors influencing the production accuracy and surface quality of CNC machined parts.

Structural Changes in Metals during Laser Cutting

The presented paper deals with the problems associated with laser machining of metal materials. Specifically, it solves the question of structural changes that occur as a result of the transfer of heat to the material. Experimental machining of selected technical materials was carried out, and on the basis of the hardness measurement near the cutting point, the heat-affected zone was evaluated after passing the laser beam. To confirm the detection of the affected zone width the models of transient temperature field were arranged, to represent the distribution of temperature in the vicinity of the cutting edge.

The Influence of Laser Beam Technological Parameters on the Polymethyl Methacrylate Surface Quality

The paper is focused on the determination of the course and change of the surface quality parameters obtained by the laser engraving of the material known under commercial name polymethyl methacrylate. The paper aims to find mathematical relations based on regression analysis for amplitudes parameters Ra and Rz. For this purpose, a sample of variable technology parameters will be machined followed by the surface measuring and evaluation using the Talysurf CLI 500 3D Surface Scanner. Thus the data obtained will be subjected to the detailed statistical analysis to check homoscedasticity, the presence of outliers, and multidimensional normality testing.

On Flexural Stiffness of Polymer Sandwich Walls

This paper deals with the flexural stiffness of sandwich structures based on fiberglass and polymeric foams. The influence of geometrical and material parameters on the resulting effective flexural stiffness of the sandwich structure is being studied experimentally, analytically and using FEM models. The effective elasticity module of the sandwich-structured element is being studied and it’s theoretical and model dependencies on the stiffness of the foam core are being investigated. These dependencies are then compared with experimentally observed values. This study shows it is necessary to pay special attention to the issue of flexural stiffness of walls when designing sandwich shell products in order to prevent possible failures in the practical applications of these types of structures.

Simulation of the Transient Temperature Field when Laser Machining Polymeric Materials

The paper deals with possibilities of using the laser in technologies. The parametric temperature field analysis was realized by the finite element method. The analysis was run in COSMOS/M software solver. A thermal module HSTAR makes it possible to realize cases of the temperature dependences on the material properties. Material data can be entered as a function of a temperature. The thermal and physical characteristics of the polymeric materials change significantly. The output of the analysis was described by spectrograms with temperature field distribution of various materials.

PMMA Surface Structure within CO2 Laser Micro-Machining

This article presents some possibilities of laser micro-machining. Results of the laser micro-machining surface quality of product and his utility in specific application depend on the laser parameters and the polymer material type. From the obtained scientific knowledge it follows, that the character of surface machined by laser depends on thermal conductivity of polymer. The action of laser beam is best shown on specimens from PMMA, therefore tests were carried out with this material. Optimal parameters of CO2 laser for used material are presented in given study. Visual evaluation of action laser ray on surface of PMMA was made also.

Laser Micro-Machining and Temperature Field Simulation

The parametric thermal field analyses were realized by the finite element method. The analysis was run in the software solver COSMOS/DesignSTAR thermal. The thermal module makes possible to realize cases of the thermal dependences on the material properties. Material data can be entered as a function of the temperature. The thermal and physical characteristic of the polymeric materials are changed very expressively. The output of the analysis was temperature distribution described by various colors and assigned values in the spectrogram.

Stress Modelling in Curved Parts of Short Fibres Reinforced Plastic Products

An investigation was carried out through a study of the influence of material anisotropy of the rounded corners of thin-walled plastic injection molded products reinforced by short-fibres, on the state of stress. It has been shown that the result of such injection-moulded processes is an anisotropic and layered product, whose mechanical behaviour differs for that of isotropic and homogenous solids. Unlike unreinforced plastics, fibre composites exhibit secondary stress effects thus need to be careful consideration in the course in designing of short fibres reinforced plastic products.