Stipo Buljan

Optimization of machining parameters for turning operation with multiple quality characteristics using Grey relational analysis

Optimizacija parametara obrade tokarenja s vise kriterija kvalitete uporabom Grey relacijske analize Izvorni znanstveni clanak Optimizacija procesa obrade je neophodna za postizanje vece produktivnosti i visoke kvalitete proizvoda kako bi ostali tržisno konkurentni. Ovaj rad istražuje vise-kriterijsku optimizaciju procesa tokarenja s optimalnom kombinacijom parametara obrade koji osiguravaju minimalnu hrapavost povrsine (Ra) s maksimalnim ucinkom uklanjanja materijala (MRR) uporabom Grey-based Taguchi metode. Razmatrani parametri obrade tokarenjem su brzina rezanja, posmak i dubina rezanja. Primjenom Taguchijevog L9 (3 4 ) ortogonalnog plana provedeno je devet eksperimenata te je koristena Grey relacijska analiza kako bi se rijesio visekriterijski problem optimizacije. Temeljem vrijednosti Grey relacijskog stupnja utvrđene su optimalne razine parametara. Signifikantnost parametara na sveukupne kriterije kvalitete procesa tokarenja ocijenjena je analizom varijance (ANOVA). Optimalne vrijednosti parametara dobivene tijekom istraživanja potvrđene su verifikacijskim eksperimentom. Kljucne rijeci: ANOVA; Grey relacijska analiza; Taguchijeva metoda; tokarenje; visekriterijska optimizacija

Application of Explosives in Metal Forming

The use of explosives in deformation process is one of the most interesting and still insufficiently explored areas. This unconventional technology has an increasing use because of being much cheaper and not requiring expensive tools, machines. Explosive as a source of energy has a low price as well. This paper involves deep-drawing explosion technology as well as one of the tools which is used for this technology. High-alloy steels are used to make dies strength, concrete, plastics and others. Also types of media that can be used in processes of explosion are mentioned. Because the calculated mass of required explosives can differ up to 200%, three distinct expressions are suggested, as well as expression for calculating of detonation rate by Dautriche method.

An experimental and modelling approach for improving utilization rate of the cold roll forming production line

This paper presents theoretical approach and complex experimental research which was conducted within the real production conditions of cold roll forming channel sections. The experimental investigation was focused on forming forces measuring on the rolls and the deflections of roll stands due to the forming loads. The comparison and analysis of the obtained experimental results was performed for the majority roll stands. Based on the experimental results mathematical modelling of the forming a force‐roll load was performed by response surface methodology for different values of the input parameters of the process: material properties, sheet thickness, and sheet width. The defined force model and experimental research show insufficient energetic and technological utilization of the existing production line. After the conducted research in the production process a sheet thickness of up to 1.40 mm is used instead of 0.70 mm, and the utilization of the installed energy has increased from 20 % to 75 %. This is confirmed by the measured deformations of the roll stands and the energy consumption of the powered electric motor. Through realized modernization of the cold roll forming production line, 30 % higher productivity is achieved, which is a result of optimal number planning of roll forming stations and approximately the same load of all roll stands, as well as the higher flow rate of the profile sheet.

An Investigation of the Force and Torque at Profile Sheet Metal Rolling – Input Data for the Production System Reengineering

The fundamental basis for implementation of reengineering is: experimental measurement of forces and torques on the rollers-tools production line for profile sheet metal forming. The paper presents the experiments of measuring forces and torques, modeling and simulation in the aim of redesigning the process of sheet metal forming, selecting of the optimal process of sheet metal forming for each forming module and totally for the production line and increasing productivity on production lines. In the experimental research forces and torques were measured on the rollers of forming modules for profile forming of sheets for different values of the input parameters of the process: material type σm, sheet thickness s and sheet width b. Based on the experimental results mathematical models were defined, which enabled the analysis and implementation of reengineering the production system.