Papers by Keyword: Quality

Abstract: The complex nature of metal casting process brings about a need to simulate it before undertaken in a foundry. Casting simulations provide insights on flow of molten metal within the mold, solidification sequence, nature and location of defects etc. Moreover, mold design can be optimized to minimize defects without undergoing physical trials-and-errors as previously practiced in traditional metal casting. This study is based on casting an ASTM A216 WCB steel spring flap for automotive suspension system using a simulation based optimized mold design. The initial and optimized mold designs are simulated in MAGMASoft for mold filling, solidification, stress distribution and defects prediction. The results of simulations and actual castings are found to be in good agreement. It is concluded that simulations are accurate in modeling casting process and in predicting defects followed by their minimization through mold design optimization. The use of auxiliary components in a carefully designed mold can lead to a nearly defect-free and high quality cast product.

Abstract: Sleman Regency, Yogyakarta Province, Indonesia has around 1,056.87 tons of unmanaged waste per day, with 74.22% of its composition is food waste. This phenomenon can be reduced by using an efficient composting method using modified aerobic reactors. The purpose of this research is to identify the quality and quantity of compost as well as larvae (maggots) produced. The research was done for 30 days using two reactors that have different feedstock composition, i.e., the comparison of food waste: vegetable waste of 1:3 (first reactor) and 3:1 (second reactor). The initial mass of each feedstock was 8 kg. The result of composting showed that the compost weight was shrinking by 92.5% in reactor one and 89% in reactor two. The results of the analysis also showed that the second compost reactor had better qualities than reactor one, but the maggot protein content of the first reactor is better than the second reactor. The moisture content in the first reactor did not meet the standards (Indonesian National Standard/SNI of compost), whereas in the second reactor, the standards were achieved with the moisture content being 20.63%; P 1.55%; K 1.45% and C/N 14.03%. The content of NPK in liquid compost produced from the first reactor was 0.18% N; 0.05% P and 0.76% K, while the liquid compost in the second reactor contained 0.30% N; 0.04% P and 0.58% K.

Abstract: The effect of super-chilling at -2°C compared with ice storage at 0°C on flavor quality changes of turbot (Psetta maxima) was investigated. Changes in total volatile basic nitrogen (TVB-N), sensory attributes and volatile compounds were periodically examined for 20 days. Results demonstrated that super-chilling retarded the increases of TVB-N values and maintained better sensory quality compared to the ice storage. Additionally, GC-MS analysis showed super-chilling could more effectively maintain the characteristic volatiles responsible for fresh fish flavor and reduce the contents of putrid compounds such as TMA and acetic acid.

Abstract: The process of formation of pores, cavities and similar defects in welded joints of stainless steels and aluminum alloys, affecting their quality, directly depends on spatial weld position in laser welding. Reducing the angle of inclination from 90° to 0° during downhill and uphill welding of AISI 321 stainless steel in the pulse mode of laser generation leads to an increase in both the number of pores and their size. At the same time, defects in the form of pores are not observed in the continuous mode of laser generation. In laser welding of butt joints of AISI 321 steel, the flat and vertical weld positions are the most promising, as they provide the highest level of quality. In order to provide a stable formation of a high-quality butt joint of aluminum AMg6M alloy and to prevent the failure of laser equipment, the welding process should be carried out in a vertical uphill weld position.

Abstract: Selective laser melting (SLM) is a manufacturing technology of metal parts of any shapes with target mechanical properties by means of laser melting. This paper discusses the effect of SLM parameters: laser output power, laser movement velocity, scanning pitch and preheating temperature of a powdered material on surface formation mechanism, namely, its physical configuration when melting cobalt-chromium-molybdenum powdered material Со28Cr3Mo. The study points at structural differences of melted surfaces even under identical process parameters. Several types of surface formation are identified, e.g. homogenous melt, coagulated particles, and shapeless particles. Vapor pressure, Marangoni effect, and heat effect of a melted powder are stated to be key reasons for rough surface. This research is of high importance for understanding the effect of SLM parameters on formation of a target quality surface, positive stability and repeatable accuracy of the process.

Abstract: This paper analyzes the effect of SLM parameters on mechanical characteristics and surface roughness of a single-component copper powder. The study reports on appropriate SLM conditions for a single-component copper powder; to form a layer a technique within layer-by-layer selective laser melting is suggested and comprises roughing, semi-finishing and finishing modes. The work establishes a range to vary surface roughness, porosity and ultimate compressive strength of a single-component copper powder by means of laser processing conditions. Rz is variable 332 to 689 μm, porosity ranges approximately 13-39%, and ultimate compressive strength is 8 to 104 МPа.

Abstract: SPC (Statistical Process Control) is one of the Lean Manufacturing techniques, but especially Six Sigma, being a method of improving the quality of the manufacturing process, which allows the identification of errors before their production, with the help of which a process can be supervised and when needed, it is possible to carry out an intervention of regulation, respectively of correction of the process, before being nonconformities. The paper presents a study regarding the use of SPC at a company in the automotive field in order to improve the quality of the manufacturing process for a knuckle. Thus, a number of 25 samples were taken, each sample containing a number of 5 pieces. After sampling, a series of techniques and statistical data were used, respectively diagrams and control sheets, which allowed the determination of the process capability by using MiniTab software.

Abstract: Electrochemical techniques can be used in the various fields, such as anodization, deposition, etching, polishing, pitting, and corrosion applications. In this paper, we focus on the high quality coloring anodic film fabrication. In the prior technologies, anodization generally has the main purpose of surface decoration or corrosion resistance. However, in the high technologies, the characteristics of film thickness, anti-voltage value, surface roughness, surface color and hardness of the anodic film have been strict requirements. The key parameters of anodization such as, electrolyte composition, current-voltage curve pattern, temperature, current density, time, final voltage, efficiency, and electricity affect the quality of anodic film. In order to make a high quality anodic film, this paper provided a detail anodization process and discussed the quality of anodic film.

Abstract: This article presents the development of energy-saving induction heating technology to accelerate significantly the process of heat treatment of steel wire. The analysis of international trends and prospects of the use of induction heating shows a steady expansion of the applied induction technologies in metallurgy. The article considers the advantages of induction heating in comparison with other competitive technologies. Heat treatment in electro-technical induction units is determined by the interrelated electrical and thermal processes in them, the complex nature of the distribution of internal heat sources, the dependence of the nature of the power distribution of the induction unit on the temperature of the products processed. The features of the applicated in the induction method of heating in the hardware industry for objects previously unused: such as coils of wire and riots of calibrated steel. The results of the study show the influence of the induction method of heating on temperature-time factors to the formation of the structure, to increase the uniformity of heating and the quality of heat treatment of steel wire, calibrated steel in riots, taking into account the technological problem. The authors give the assessment of the effectiveness of medium and high-frequency induction heating of steel wire of various diameters. The evaluation of the increase in the efficiency of an induction heating unit with the simultaneous heat treatment of several filaments of steel wire of the same diameter, combined into a bundle, was made.

Abstract: Since the quality management systems have undergone a significant change by taking into account the concept of risk, for the shipyards, becomes necessary, an approach aimed at improving organizational performance by implementing a actions plan based on the risks which may adversely affect the achievement of the objectives identification and assessment. The purpose of the paper is to propose a series of measures for improving the shiprepairs shipyards organizational performance,based on identifying and assessing the risks. The contents of the paper address the following aspects: summarizes the main changes made by the quality management systems; presents some developments in view of the identification and results of the risk assessment, identifying key performance indicators specific to the ships maintenance works in shiprepairs shipyards, the use of the performance indicators related to the management systems processes (quality, environment, security and occupational health). Concluding, the authors bring some proposals on improving the quality of institutional relations of the shiprepair shipyards.