In the current economic scenario of global recession and high competitiveness in
the MSME sector, cost-effectiveness has a crucial role to play in determining the
edge of one over the other. In the foundry industry, casting rejection is a significant concern due to one or more defects noticed as a result of a single or multiple causes. Systematic analysis and identification of causes of product defects are important for casting quality improvement. A majority of the shrinkage-related defects in foundry are due to faulty gating system design rather than production issues. Optimization of gating system should invariably include developing a zero defect and sound casting with the optimized value of the feed ability index which represents yield of feeders and quality of casting at a lower cost. In the paper, “Defect Minimization in Motor Body Casing Using Analytical Calculation and Casting Simulation with Experimental Validation”, the authors, Shailee Acharya, Jeetendra A Vadher, M V Sheladiya and Mahesh Madhnani, have presented the results of a simulation study to identify the proper gating components, undertaken with e-foundry Internet resources. In their proposed gating design, the parameters such as pouring time, average filling rate, choke area, metal flow rate, velocity of molten metal, solidification time and freezing ratio are optimally selected. The results of simulating software indicate that the quality of the motor cover casting is affected by gating system parameters in a significant manner.

Fins are most commonly used in heat exchanging devices and staggered finned ducts are one of the widely used in compact heat exchangers for the enhancement of heat transfer. The heat transfer and pressure drop characteristics can change significantly with the change in their shape. In the paper, “The Effect of Major and Minor Axis of Elliptical Shape Pin Fins on Heat Transfer and Pressure Drop Characteristics”, the authors, Monoj Baruah, Manash Borah and H K Das, have investigated the heat transfer and pressure drop characteristics by changing the shape elliptical pin fins with constant surface area by using CFD software FLUENT 6.3.26. The major axis for the two types of fins is chosen as 1.3 mm and 1.4 mm respectively. Based on the pressure, temperature and velocity profiles at different locations within the computational domain for different Reynolds number, the heat transfer and pressure drop characteristics are assessed in the computational domain. Their analysis indicates that heat transfer can be increased by decreasing the pin major axis or by increasing the fin minor axis, which also is accompanied by high pressure drop, thereby indicating more pumping power. Overall, the study concludes that the overall performance of ellipse 1.4 pin fin heat exchanger is better than that of ellipse 1.3 pin fin heat exchanger.

Significant research effort has been directed towards developing vehicle transmissions that reduce the energy consumption of an automobile. Continuously Variable Transmission (CVT) systems offer many advantages to vehicle performance over traditional transmission technologies, in situations where frequent speed ratio changes are necessary to obtain more output power and to decrease fuel consumption. The cam-based CVT system offers advantages such as simplicity in design, reliability in operation and moderate efficiency. In the paper, “Design and Synthesis of Novel Cam-Based Continuously Variable Transmission”, the authors, Anup Sahebrao Borse and Nitin Vijay Satpute, have presented the details of the prototype designed, fabricated to validate the cam follower mechanism for speed control using eccentric fans. Camoids having profiles of constant velocity are mounted on input shaft and followers are mounted on output shaft. Oscillating followers are mounted on the shaft with the help of unidirectional clutches which convert the oscillating motion of followers into pure rotary motion. Speed control for the CVT is achieved by linearly traversing camoids. The results obtained using a three-dimensional cam/camoid are encouraging for stationary applications and in situations where there are fewer fluctuations in speed range. The model, however, may not be successful at higher RPMs due to probability of follower jump, and has limitations on the size of follower thickness.

S V Srirama Rao
Consulting Editor