Experimental evaluation of machinability performance of CNT coated HSS tool during turning of titanium alloy

Journal of Mechanical Science and Technology - The present research deals with the deposition of carbon nanotubes (CNT) over the HSS tool, and to evaluate the machining performance of the coated...     

Analysis of Optimum Batch Size in Multistage,Multifacility and Multiproduct Manufacturing Systems

In any type of manufacturing environment the most common configuration will be a multistage, multiproduct, manufacturing inventory system. An in-process inventory is inherent in any multistage manufacturing system, when the product is manufactured through several operations and stages. To satisfy demand requirements in multistage, multiproduct manufacturing systems, it is important to specify feasible production quantities, as batch sizes for each end product, over a finite time period at every stage. This paper deals with different methods for determining batch sizes in a multiproduct, multistage situation in the presence of decision support systems for maximum capacity. The mathematical model suggested by Gunasekaren is considered as the basis for comparison. A fuzzy logic model of the above has been developed to calculate the economic batch sizes such that machine hour and labour productivity constraints are not violated. Using Promodel, a simulation technique, the model was subjected to variable analysis and cost analysis and the results were compared. Case studies were conducted for validating the models for their ability to produce reliable output. MATLAB software package is used for developing the program to solve the problem by fuzzy approximation.     

Workflow balancing strategies in parallel machine scheduling

Workflow balancing on a shop floor helps to remove bottlenecks present in the manufacturing system. Workflow refers to the total time during which the work centres are busy. Idle time is not taken into account when calculating workflow. Earlier researchers have not specified the method for jobs to be executed in parallel in order to balance the workflow to each machine. In many manufacturing environments, multiple processing stations are used in parallel to obtain adequate capacity. In parallel machine scheduling there are m machines to which n jobs are to be assigned based on different priority strategies. The procedure is based on the idea of workload balancing and on balancing the workload among machines. In this paper, workflow and workload are assumed to have the same meaning. A machine with the lowest workflow is selected for assignment of a new job from the list of unfinished jobs. Different priority strategies are followed for the selection of jobs. Three different strategies are considered, namely random (RANDOM), shortest processing time (SPT) and longest processing time (LPT) for the selection of jobs for workflow balancing. The relative percentage of imbalance (RPI) is adopted among the parallel machines to evaluate the performance of these strategies in a standard manufacturing environment. The LPT rule shows better performance for the combination of larger job sizes and higher number of work centres or machines. A computer program was coded for validation in a standard manufacturing environment on an IBM/PC compatible system in the C++ language.     

Mixed convection on jet impingement cooling of a constant heat flux horizontal porous layer

In the present study, numerical investigation of jet impingement cooling of a constant heat flux horizontal surface immersed in a confined porous channel is performed under mixed convection conditions, and the Darcian and non-Darcian effects are evaluated. The unsteady stream function-vorticity formulation is used to solve the governing equations. The results are presented in the mixed convection regime with wide ranges of the governing parameters: Reynolds number (1 ≤ Re ≤ 1000), modified Grashof number (10 ≤ Gr¹ ≤ 100), half jet width (0.1 ≤ D ≤ 1.0), Darcy number (1 × 10^?6 ≤ Da ≤ 1 × 10^?2), and the distance between the jet and the heated portion (0.1 ≤ H ≤ 1.0). It is found that the average Nusselt number (Nu_avg) increases with increase in either modified Grashof number or jet width for high values of Reynolds number. The average Nusselt number also increases with decrease in the distance between the jet and the heated portion. The average Nusselt number decreases with the increase in Da for the non-Darcy regime when Re is low whereas Nu_avg increases when Re is high. It is shown that mixed convection mode can cause minimum heat transfer unfavorably due to counteraction of jet flow against buoyancy driven flow. Minimum Nu_avg occurs more obviously at higher values of H. Hence the design of jet impingement cooling through porous medium should be carefully considered in the mixed convection regimes.     

REDUCTION OF MACHINING VIBRATION BY USE OF RUBBER LAYERED LAMINATES BETWEEN TOOL HOLDER AND INSERT

The aim of the present study is to investigate chatter when using carbide inserts by measuring surface roughness of the workpiece. Dimensional accuracy of the workpiece is affected by vibration. In order to suppress chatter, the tool was provided with an ultra thin metal rubber laminate between the tool holder and insert. An experimental investigation has been carried out in CNC lathe using a “design of experiments” approach. In this study, vibration of the tool and surface roughness of the workpiece were measured. It has been observed that the vibration of the tool, as well as the tool insert, has been reduced by using ultra thin rubber layered laminates, and the surface finish of the workpiece has been improved.     

Development of a computer simulator for dynamic scheduling of FMS to achieve optimal performance

This paper deals with the development of a simulation software using the features of visual interactive computer graphics for analysing the dynamic scheduling of a flexible manufacturing system (FMS) to cater to the need of fluctuating markets. While carrying out this work, the main concepts of dynamic modelling, computer simulation and visual interactive graphics have been used for studying the reduction in backlogs of workorders. In addition, queue length, waiting time and the capacity utilisation of the manufacturing system are also considered. The arrival pattern of components is fitted to a suitable distribution pattern based on the workorder position. The effects of despatching rules such as SPT, LPT, EDD, SIO, SLACK, SLACK/LRO on scheduling are analysed using the simulator to imitate the real life operation of FMS. Visual interactive computer graphics enables the user to find out machine utilisation levels, queue length of the components, throughput and comparison between the application of various despatching rules. Since dynamic queue records are maintained, it is possible to establish the various components waiting in the respective work centres and their attributes like lateness, slack, remaining operations etc. This software is very useful in enabling the user to select the appropriate despatching rule for the system. The software has been developed in the C language for IBM/PC compatible systems.     

ANN–GA approach for predictive modeling and optimization of NOx emission in a tangentially fired boiler

An artificial neural network (ANN) and genetic algorithm (GA) approach to predict NOx emission of a 210 MW capacity pulverized coal-fired boiler and combustion parameter optimization to reduce NOx emission in flue gas, is proposed. The effects of oxygen concentration in flue gas, coal properties, coal flow, boiler load, air distribution scheme, flue gas outlet temperature, and nozzle tilt were studied. The data collected from parametric field experiments was used to build a feed-forward back-propagation neural net. The coal combustion parameters were used as inputs and NOx emission as outputs of the model. The ANN model was developed for full load conditions and its predicted values were verified with the actual values. The algebraic equation containing weights and biases of the trained net was used as fitness function in GA. The genetic search was used to find the optimum level of input operating conditions corresponding to low NOx emission. The results proved that the proposed approach could be used for generating feasible operating conditions.     

Intracranial suppuration caused by Micrococcus luteus

A patient with mixed squamous/basal cell carcinoma of the skin presented with hypercalcaemia and elevated serum levels of parathyroid hormone-related protein (PTH-rP). The tumour was resected, PTH-rP levels declined and the patient became normocalcaemic. This is the first case to associate squamous cell carcinoma of the skin with hypercalcaemia and significant levels of PTH-rP.