Peter Šugár

Analysis of Dimensional Accuracy of Spun Parts by Taguchi Approach

The paper brings the results of wall thickness distribution analysis of formed part produced by CNC multi-pass conventional metal spinning. The thickness reduction was measured by optical 3D scanning method and the influence of the feed, workpiece geometry and planar anisotropy of the blank on the wall thickness reduction was studied. For experiment design, an orthogonal array L27 was used and ANOVA (Analysis of Variance) was carried out. Based on the results it is determined that the highest reduction of wall thickness is observed in the conical part of the experimental sample. Workpiece geometry is the most important factor which influences the wall thickness variation.

Laser Beam Milling of Alumina Ceramics - The Impact on Material Removal Efficiency and Machined Surface Morphology

Laser machining is one of the most widely used advanced noncontact machining processes used for creating new surfaces, structures, cavities and also complex electro-mechanical devices, usually with very small dimensions, by laser radiation. It is the process in which the material’s thermophysical properties rather than mechanical properties determine the machinability. Design of process parameters is highly critical for successful material removal and high machine surface quality. In the paper the laser beam milling is experimentally studied applying the nanosecond pulse fibre laser and alumina ceramic as working material. The influence of pulse energy, pulse repetition rate, scanning speed and tracks displacement on material removal efficiency and the quality of machined surface is reported.

Laser surface texturing of tool steel: textured surfaces quality evaluation

Abstract In this experimental investigation the laser surface texturing of tool steel of type 90MnCrV8 has been conducted. The 5-axis highly dynamic laser precision machining centre Lasertec 80 Shape equipped with the nano-second pulsed ytterbium fibre laser and CNC system Siemens 840 D was used. The planar and spherical surfaces first prepared by turning have been textured. The regular array of spherical and ellipsoidal dimples with a different dimensions and different surface density has been created. Laser surface texturing has been realized under different combinations of process parameters: pulse frequency, pulse energy and laser beam scanning speed. The morphological characterization of ablated surfaces has been performed using scanning electron microscopy (SEM) technique. The results show limited possibility of ns pulse fibre laser application to generate different surface structures for tribological modification of metallic materials. These structures were obtained by varying the processing conditions between surface ablation, to surface remelting. In all cases the areas of molten material and re-cast layers were observed on the bottom and walls of the dimples. Beside the influence of laser beam parameters on the machined surface quality during laser machining of regular hemispherical and elipsoidal dimple texture on parabolic and hemispherical surfaces has been studied.

TECHNOLOGY-BASED SHEET METAL CLASSIFICATION AND CODING SYSTEM

Technology-Based Sheet Metal Classification and Coding System Group technology (GT) concept uses design similarity measure to identify the most similar design and retrieve a useful process plan. One of the existing formal methods of machine parts classifying for the group technology applications is the coding and classification. The researchers have developed many different GT coding schemes, which very precisely describe the design characteristics of the parts, but many of them do not explicitly describe the process plan. The paper presents a new approach to the sheet metal part coding and classification with plan-based attributes implementation in accordance with the technical standard STN 226001. Klasifikacija i Sistem Kodiranja Tehnologije Obrade Lima Plastičnim Deformisanjem Koncept grupnih tehnologija koristi sličnosti u geometriji i obliku delova kako bi se unapredio proces proizvodnje, odnosno ona povećava efikasnost proizvodnje na usnovu grupisanja sličnih delova u familije. U grupnim tehnologijama, dva dela su slična samo ako su njihove geometrije, ali i procesi obrade slični. Jedne od formalnih metoda grupnih tehnologija su i kodiranje i klasifikacija. Pored geometrije i oblika, kriterijumi za klasifikaciju mogu biti i drugi parametri, kao što su težina, tolerancije i sl. Istraživači su razvili različite kodne šeme, koje precizno opisuju geometrijske karakteristike delova, ali mnoge od njih ne opisuju plan procesa. Jedan od alata za sistematsku upotrebu dokumentacije u određenoj kompaniji je grupna tehnologija, koja po svom principu stvara spontani pritisak ka pojednostavljenu i standardizaciji konstrukcionog i tehnološkog dizajna proizvodnje. U literaturi se mogu naći brojni radovi na temu grupni tehnologija u oblasti tehnologije rezanja, ali ne i u oblasti obrade lima deformisanjem. Ovaj rad predstavlja nov pristup kodiranju i klasifikaciji tehnologije obrade lima koji je u skladu sa standardom STN226001. Prema tome, ovaj rad predstavlja doprinos razvoju preciznije klasifikacije obrade lima pogodne za različite planove procesa.

Analysing the Properties of Surface Layers Generated by Sheet Metal Forming Operations

Analysing the Properties of Surface Layers Generated by Sheet Metal Forming Operations The paper brings results of the surface layers properties analysis of a thin wall hollow sheet metal parts, produced by metal spinning and deep drawing. The influence of mandrel (workpiece) frequency of rotation on the spun parts surface layer strainhardening is studied and compared with the quality of the formed part surface layer produced by deep drawing technology.

The Influence of the Tool Surface Texture on Friction and the Surface Layers Properties of Formed Component

The morphological texturing of forming tool surfaces has a high potential to reduce friction and tool wear and also has an impact on the surface layers properties of formed material. In order to understand the effect of different types of tool textures, produced by nanosecond fibre laser, on the tribological conditions at the interface tool-formed material and on the integrity of formed part surface layers, the series of experimental investigations have been carried out. The coefficient of friction for different texture parameters (individual feature shape, including the depth profile of the cavities and orientation of the features relative to the material flow) was evaluated via a Ring Test and the surface layers integrity of the formed material (surface roughness and subsurface micro hardness) was also experimentally analysed. The results showed a positive effect of surface texturing on the friction coefficients and the strain hardening of test samples material. Application of surface texture consisting of dimple-like depressions arranged in radial layout contributed to the most significant friction reduction of about 40%. On the other hand, this surface texture contributed to the increase of surface roughness parameters, Ra parameter increased from 0.49 μm to 2.19 μm and the Rz parameter increased from 0.99 μm to 16.79 μm.

Friction evaluation of laser textured tool steel surfaces

Abstract Surface textures can be defined as a regularly arranged micro-depressions or grooves with defined shape and dimensions. These textures, if they are manufactured by laser ablation process, contribute to a significant improvement of the tribological, optical or various biological properties. The aim of this paper is to analyze the influence of the surface textures prepared by laser surface texturing (LST) at the friction coefficient value measured on the tool (90MnCrV8 steel) – workpiece (S235JRG1 steel) interface. Planar frontal surfaces of compression platens have been covered by parabolic dimple-like depressions with different dimensions. The morphological analysis of such manufactured depressions has been performed by laser scanning microscopy. Influence of such created textures on the tribological properties of the contact pair has been analyzed by the ring compression test method in the terms of hydrodynamic lubrication regime. The experimental research shown that by applying of surface textures with defined shape and dimensions and using an appropriate liquid lubricant at the same time, the coefficient of contact friction can be reduced nearly to the half of its original value.

Strain Analysis of Parts Produced by Multi-Pass Conventional Metal Spinning

Sheet metal spinning is one of the forming processes based on gradual shaping of metal blank into an axisymetric part by a roller according to a mandrel. Very significant feature of spinning is ability to produce components with high mechanical properties and high quality of surface layers. The paper brings the results of major true strains analysis of mild steel parts produced by CNC multi-pass conventional metal spinning. The influence of the spindle speed, feed rate, workpiece geometry and planar anisotropy of the blank on the strain distribution of formed part is studied by method of grain size measurement. The design of experiment using the Taguchi approach and analysis of variance (ANOVA) is applied to find optimal process parameters.

Surface Integrity of Metal Spun Parts

Sheet metal spinning is one of the forming processes based on gradual shaping of metal blank into an axisymetric part by a roller according to a model (mandrel). Very significant feature of spinning is ability to produce components with high mechanical properties and high quality of surface layers. The paper brings the results of surface integrity analysis of mild steel parts produced by CNC multi-pass conventional metal spinning. The influence of the spindle speed, feed rate, workpiece geometry and planar anisotropy of the blank on the residual stresses distribution and microhardness of formed part surfaces is studied. For experiment design, an orthogonal array L27(313) was used and ANOVA (Analysis of Variance) was carried out. Based on the results it is determined that the geometry of the formed part (radius, conical area, cylindrical area) is the significant factor influencing both residual stresses and microhardness of the formed part surfaces.

Surface Roughness Analysis of Metal Spun Parts

The paper brings the results of roughness analysis of formed part produced by CNC multi-pass conventional metal spinning. The influence of the spindle speed, workpiece geometry and planar anisotropy of the blank on the formed part roughness was studied. For experiment design, an orthogonal array L27(313) was used and ANOVA (Analysis of Variance) was carried out. Based on the results it is determined that the higher spindle speed leads to rough surface finish. The surface roughness measured in different areas of experimental samples (corner R10, conical area, cylindrical area) indicates that the worst surface finish is in the conical area. Roughness in different directions refer to the sheet rolling direction shows minimal differences.