Fabrication of micro-end mill tool by EDM and its performance evaluation

Abstract

Micro-milling is a fast, cheap and controlled process compared to other micro-fabrication processes such as lithography, laser/electron/ion beam machining, etc. However, scarcity of cutting tools of very small dimensions often results in limited application of micro-milling. In the present study, electro discharge machining (EDM) is used for fabrication of micro-end mill tool. To ensure high dimensional accuracy of the tool, a parametric study is conducted by replicating the a tungsten carbide block to a tungsten carbide (WC) block. The relationships between the drilled cavities on the block and the features on the micro-tool are established. The influence of machining parameters (voltage, capacitance and spindle speed) on the response variables (entrance diameter, hole depth, material removal rate (MRR) and surface roughness) is reported. Capacitance is found more dominant as compared to other selected process parameters. Using optimized parameters from the parametric study, a WC micro-end mill tool of 100?µm diameter is fabricated. Channel of around 110 µm width, 40?µm depth and surface roughness of 70?nm is successfully fabricated on aluminum. The performance of the fabricated tool is compared with a commercial end mill tool by milling micro channels on stainless steel.     

Some aspects of modelling an atmospheric dispersion problem

This work deals with dispersion of pollutants emitted from a continuous point source at ground level in unsteady situations under three atmospheric conditions: neutral, stable and unstable atmospheres at low inversion heights. The ground level concentration (g.l.c.) profiles are obtained and allow interpretation when comparative studies are made.     

Simple Prefabrication Proves its Worth

Reporting a user-reaction study of low-income dwellings near Delhi, the author, who is an architect with the Central Building Research Institute, Roorkee, presents evidence to show the general superiority of the Holopan System dwellings over the traditionally-built dwellings with similar specification on the same site. This type of simple prefabrication is advocated as an appropriate technology for mass housing in developing countries.     

Telehealth and neuropsychological assessment: New opportunities for psychologists.

The advent of telehealth technology gives psychologists new opportunities to expand their practices in a cost-effective manner, but little is known about telehealth efficacy and costs. This study of 49 neuropsychology clients interviewed using videoconferencing and 49 matched in-person controls yielded no group differences in client ratings of interpersonal factors. Telehealth clients were more likely to want to repeat their experience, but psychologist satisfaction was lower for telehealth sessions. Telehealth costs were significantly lower than in-person costs. Concerns about ethical issues, billing, and licensure must be addressed to help practitioners capitalize on new telehealth opportunities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Valve Distribution and Impact Analysis in Water Distribution Systems

In water distribution systems, valves play a crucial role in system reliability and security by providing a shutoff function when it is necessary to isolate subsystems. In this paper failure of shutoff valves to close is considered. The failure impact is quantified in terms of the expanding subnetwork and the increased number of customers out of service. To evaluate a system-wide valve failure impact, three methods are suggested: segment–valve matrix, decision tree analysis, and simulation. The segment–valve matrix shows the propagation of failure through the network as valves fail to close. The decision tree enumerates all possible valve failure combinations and corresponding event probabilities. Because the complete enumeration can be unwieldy, simulation procedures are offered that approximate the enumeration results closely. The details of the methods are illustrated with the aid of an example.     

Annual variations of temperature in a sample of UK dwellings

The internal temperatures of 25 households in Northern Ireland were measured in each house at four locations: the bedrooms, living rooms, halls and kitchens, and analysed on seasonal, monthly and daily bases. In 80% of the homes the winter average daily temperature was between 15 °C and 20 °C and in summer between 20 °C and 23 °C, therefore maintaining a reasonably comfortable temperature throughout the year. In 14% of the homes, the daily average temperature was above 21 °C throughout the year, suggesting a higher household temperature than required for comfort, thus exhibiting wasteful energy behaviour. Three percent of the homes did not use their heating adequately and the winter average temperature was below 15 °C. For the majority of households, the highest indoor temperature was in August and the lowest in February. In general the peak temperatures of households occur in the evening after 8:00 pm. The peak bedroom temperatures occur between 10:00 pm and midnight and in the morning after 8:00 am. The peak living room temperature is generally in the evening while it is occupied. Correlations between the temperature difference between indoor and outdoor temperatures with outdoor temperature have been developed for each house and the four locations. The relationship between the fluctuations of average daily temperature with annual average temperature has been established.     

Synthesis of a novel imidazolium-based electrolytes and application for dye-sensitized solar cells

A series of new imidazolium-based oligomers with different length of a poly(ethylene glycol) moiety as a linker were synthesized and studied as electrolytes for dye-sensitized solar cell (DSSC). These oligomeric molecules are expected to have an intra- or inter-molecular hydrogen bonding interaction through its urethane and urea bonds. They can be used to prepare the liquid-type electrolytes for DSSC by dissolving them into conventional solvent system or to develop solvent-free electrolytes by incorporating an extra redox mediator and other functional materials together as additives. It was found that these oligomers could replace the cationic component of the conventional electrolytes and became the source of redox species when iodine is added. The photocurrent-voltage characteristics of DSSCs with the electrolytes containing these oligomers demonstrated that they can successfully replace the conventional ionic liquid-type electrolytes such as 1-methyl-3-propyl imidazolium iodide (PMII) in 3-methoxypropionitrile (MPN) if the length of the linker is optimized.     

An inorganic–organic hybrid material with a novel oxometallic framework: Hydrothermal synthesis and characterization of [Zn3O3(C13H14N2)3]V6O15

A new hybrid material [Zn₃O₃(C₁₃H₁₄N₂)₃]V₆O₁₅ (1) with extended framework structure has been synthesized hydrothermally and characterized by vibrational spectroscopy, thermogravimetry and complete single crystal X-ray diffraction analysis. The compound has a complex three-dimensional covalent framework structure. It exhibits a fully oxidized novel oxometallic framework containing 10-membered {V₄ZnO₅} oxometalate rings and 4,4′-trimethylene dipyridine ligands (C₁₃H₁₄N₂) that connect pairs of crystallographically equivalent zinc atoms. The extended structure of 1 may also be viewed as containing a framework of corner-sharing {VO₄} and {ZnO₂N₂} polyhedra together with 4,4’-trimethylene dipyridine ligands linking zinc centers. The hybrid material is thermally stable up to 323 °C. It contains metal centers and coordination geometry that make it a potentially attractive model compound for investigating the structures of metallo-organic biomolecules by use of solid state NMR spectroscopic techniques. Crystal data for C₃₉H₄₂N₆O₁₈V₆Zn₃: monoclinicic P2₁, a = 10.9894(9) Å, b = 18.1493 (15) Å, c = 13.0903 (11) Å, β = 109.8880(10)°, V = 2455.1(4) Å³, Z = 2, D_calc. = 1.873 Mg/m³.