A.N. Mustafizul Karim

Surface Integrity in Hot Machining of AISI D2 Hardened Steel

This study presents experimental results of machined surface integrity of die material (AISI D2 hardened steel) when hot machining (induction heating) assisted end milling using coated carbide is applied. The aim of this work was to study the influence of induction heating temperature, cutting speed, and feed on the effects induced by hard milling on surface integrity (microhardness and work-hardening). Microhardness was measured to observe the distribution of the hardness beneath the surface and to determine the effect of induction heating on the micro-hardness distribution and work-hardening phenomena. The behaviour of microhardness induced in the subsurface region when end milling under room and induction heating cutting conditions using coated carbide inserts was also investigated. The surface integrity and subsurface alteration have been investigated by employing scanning electron microscope (SEM) and Vickers microhardness tester.

Managing risk in production scheduling under uncertain disruption

Abstract The job scheduling problem (JSP) is considered as one of the most complex combinatorial optimization problems. JSP is not an independent task, but is rather a part of a company business case. In this paper, we have studied JSPs under sudden machine breakdown scenarios that introduce a risk of not completing the jobs on time. We have first solved JSPs using an improved memetic algorithm and extended the algorithm to deal with the disruption situations, and then developed a simulation model to analyze the risk of using a job order and delivery scenario. This paper deals with job scheduling under ideal conditions and rescheduling under machine breakdown, and provides a risk analysis for a production business case. The extended algorithm provides better understanding and results than existing algorithms, the rescheduling shows a good way of recovering from disruptions, and the risk analysis shows an effective way of maximizing return under such situations.

Performance Evaluation of PCBN in End Milling of AISI D2 Hardened Steel under Room and Preheated Machining Conditions

In this paper, the tool life and tool wear performance of PCBN tool in end milling of AISI D2 hardened steel under room and preheated machining conditions is presented. The tool life and tool wear patterns were examined through tool maker microscope and scanning electron microscope. The results show that the dominant modes of tool wear observed were flank wear, chipping, and notch wear. The main wear mechanisms were abrasion, adhesion, and diffusion promoted by high stress and cutting temperature. It was also observed that longer tool life and higher volume metal removed could be achieved when employing higher preheating temperature.

Assembly line productivity improvement as re-engineered by MOST

Purpose The purpose of this paper is to address and solve operational problems of an automotive industry in reaching production target by adopting Maynard Operation Sequence Technique (MOST) as lean and productivity improvement strategies. Design/methodology/approach In the undertaken case of auto-car rear window assembly line, a recurring production shortfall in fulfilling the daily demand is seemingly due to inappropriate work method. Initial observation of the operations led to suspect certain lapses in initiatives to adopt the time standards, to reduce or eliminate non-value added motions, to design suitable aisle and to assign tasks among workstations in a balanced manner. Subsequently an attempt is made to pinpoint the causes of poor performance and the bottlenecks through process flow analysis and time study by applying MOST. The elemental tasks are closely examined for possible reduction of workstation times by choosing efficient work methods with ergonomic features. Thus appropriate hand tools, jigs and fixture with nominal investment are prescribed to incorporate in the assembly works. The operational changes as steered by the MOST application have enhanced the workflow with a shorter cycle time which led to a substantial increase in productivity. Findings The productivity of the assembly line is increased by more than 29 percent from the earlier capacity through the MOST application which is deemed to meet the current level of demand. Originality/value The adopted framework for recognizing the effectiveness of MOST to expose and rectify the flaws in work methods without much investment is expected to be beneficial for a manufacturer in securing the competitiveness.

Investigation on Wall Thinning and Creep Damage in Boiler Tube due to Scale Formation

Boiler is a closed vessel in which the water is heated up to convert it from the liquid phase to superheat steam at specified pressure by addition of heat. The tubes are operated continuously at high temperature due to the formation of scale which has lower conductivity than that of steel. The scale can be formed for various reasons of which tube geometries, flue gas and steam temperature are prominent. The remaining wall thickness decreases due to the formation of scale which eventually causes failure of the boiler tubes. In this investigation an iterative technique was used to determine the temperature distribution across the tube with the increase of operating time. The operating time was considered up to 160,000 hours. The remaining life of the steam generator tube was found by finding hoop stress and Larson Miller Parameter from the Larson Miller Parameter curve for SA213-T22 material. The remaining life of the steam generator tube was used to find cumulative creep damage. By utilizing finite element modelling software, ANSYS 9/ ANSYS 11 the temperature distribution across the steam generator tube was evaluated. The temperature distribution along with Larson Miller Parameter predicted the oxide scale thickness. It was also observed that different input parameters have pronounced affect on the formation of oxide scale inside the steam generator tube. By increasing the heat transfer rate across the wall, the oxide scale thickness was increased more rapidly than normal condition. It was also observed that due to formation of scale the thermal conductivity in the boiler tubes was affected and the remaining life of boiler tubes was decreased and accelerated creep damage.

Applying Value Stream Mapping for Productivity Improvement of a Metal Stamping Industry

To sustain in business by meeting the customer expectations with limited resources under tight schedule is a great challenge for high volume manufacturing industry. In this respect Value Stream Mapping (VSM) plays an important role as a strategic tool in streamlining the processing operations and enhances capacity utilization. This study has been conducted on application of VSM in a make-to-order metal stamping company engaged in production of different stamped parts of which the LCD TV frame is a significant one. Based on the product flow analysis, a current state VSM has been constructed using pertinent data collected from the production floor. Analysis of recorded videos and time studies were performed in order to figure out the scope of improvements in framing the future state map (FSM) in the context of cycle time reduction and line balancing efficiency. As observed from the FSM, the efficiency of production line is possible to be significantly increased from about 48% to more than 93% vis-à-vis a reduced batch completion cycle time. Thus it is obvious that with minor adjustments in the system in line with the findings of the study, the industry can make a substantial improvement in their operational efficiency.

Analysis of End Crack in Boiler Tube

Boiler tube failures usually result in frequent forced outages, and ultimately in costly extended outages for major tubing replacement in a plant. There are several failure modes that may occur in a boiler tube, i.e. stress-corrosion cracking, pitting, water-side corrosion, fire-side corrosion, fatigue failure, overheating, dissimilar metal weld fatigue, mechanical fatigue and erosion. In this research the failure modes of boiler and its end cracks due to the dissimilar metal weld is analyzed. Hence data are collected and explored to determine the cause of failure and as a solution ceramic ferrule is suggested. The use of ceramic ferrule in boiler tube can eliminate the crack occurrence or delay the process due to thermal properties. The prevention of crack will reduce frequent maintenance and thus the cost of operation can be minimized.

Study of TiC Cutting Tool Insert Using Microwave Synthesis

Microwave processing ceramics is emerging fast as a new field of ceramic processing and material synthesis. The past year has witnessed significant progress in the aspects of commercialization and application of the technology to new areas. Further research states that Titanium Carbide (TiC) is the best cutting tool due to its high melting point and by that reason this project aims to show the difference between conventional sintering, microwave sintering and Hot Isostatic Pressing (HIP). Two different compositions consisting of 97TiC3Ni and 93TiC7Ni were sintered using conventional furnace, microwave furnace and HIP. Density, hardness and microstructure analysis were carried out on these TiC inserts. 97TiC3Ni produced higher density and hardness values compared to 93TiC7Ni for all three different methods. Microwave sintering produced the highest density and hardness values compared to conventional sintering and HIP. Microwave produced samples with improved density and hardness in a shorter processing time which is 93% faster than conventional sintering and 50% faster than HIP.

Preheating in end milling of AISI D2 hardened steel with coated carbide inserts

This study was conducted to investigate the effect of preheating through inductive heating mechanism in end milling of AISI D2 hardened steel (60-62 HRC) by using coated carbide tool inserts. Apart from preheating, two other machining parameters such as cutting speed and feed were varied while the depth of cut constant was kept constant. Tool wear phenomenon and machined surface finish were found to be significantly affected by preheating temperature and other two variables. End milling operation was performed on a Vertical Machining Centre (VMC). Preheating of the work material to a higher temperature range resulted in a noticeable reduction in tool wear rate leading to a longer tool life. In addition, improved surface finish was obtained with surface roughness values lower than 0.4 μm, leaving a possibility of skipping the grinding and polishing operations for certain applications.

Adoption of JMM practices – A key to performance improvement of a local automotive industry

It is imperative for a manufacturing company all over the world to constantly look for ways to increase productivity and at the same time to lower cost to secure a competitive position. It is recognized that practices associated with Japanese Manufacturing Management (JMM) can yield a superior competitive advantage in terms of productivity, quality and provide overall successful business performance. This paper discusses the transfer of the best practices of the JMM locally and analyses the impact of adoption and adaptation of the management system as an in-depth case study conducted in a Malaysian automotive company. This study is to identify what are the changes in terms of the philosophy and practices undertaken by the company and ascertain the impact of the JMM on its manufacturing and financial performances. The elements of business performance from the viewpoint of manufacturing are based on safety, Parts Per Million (PPM), in-line Defect per Unit (DPU), First Time Quality (FTQ), cycle time, productivity, efficiency and stock level. The results show a positive impact to the automotive plant manufacturing performance. For example, safety index has reduced to 0 major accident occurrences. The PPM and In-line DPU have improved by 98% and 91% respectively whereas the FTQ has improved by 167%. Cycle time has reduced from 20 to 6 minutes and productivity increased up to 43% whilst the efficiency reached at 99.9%. The stock level was reduced from half month to 3 days after the adoption of the JMM. The revenue has increased up to 92%, the percentage of expenses has reduced from 11.04% to 3.06% giving an improvement of 72% whilst the net profit has increased from 5.33% to 8.15%. The Return of Asset (RoA) and Return of Equity (RoE) also showed slight improvement despite the effects from the restructuring exercise, Tsunami calamity and fluctuation in Japanese exchange rate.