Publications

Coordinate Measuring Machine (CMM) is widely used for the accurate profile deviation evaluation of free-form components. Sampling, measurement and evaluation of the measured data are the most important steps of the CMM measurement process. Though various sampling strategies were proposed to reduce CMM measurement time, few error evaluation techniques have been reported to date. Generally, the CMM measured points are either fitted or registered with the continuous reference profile. The profile deviation is estimated using the point-inversion technique with relatively high time complexity. Hence, an alternate method is needed for quick and accurate profile deviation estimation.

Nickel-based alloys (Nimonic 90) are one of the most used materials for aircraft parts, gas turbine components and fasteners due to their inherent properties such as high strength at elevated temperature, good corrosion resistance, high stability, high wear resistance and low thermal conductivity. Because of the above-mentioned properties, Nimonic 90 alloy is difficult to machine, and the roughness obtained by machining of nimonic alloy is comparatively rough. The existing theoretically developed mathematical equations for roughness measurement do not consist of all the machining parameters. It lacks some of the effective roughness parameters such as depth of cut, spindle speed and cutting-edge angle. This article proposes a novel mathematical/geometrical model for the prediction of surface roughness using fundamental geometrical properties of tool and workpiece. For developing the mathematical model

Coordinate Measuring Machines (CMM) are widely used in form inspection of free-form surfaces. Generally, the form error at each measured point is estimated using the widely known and accurate point-inversion method. This method has relatively high time complexity and cannot be preferred for fast inspection. Hence in this work, an alternative two-stage methodology based on the concept of the Voronoi diagram is proposed. In the first stage, the poles data is extracted from the Voronoi diagram of the discretized surface. In the second stage, the form-error-estimate algorithm executing in O(m log n) time estimates the errors using the poles data and the discretized surface. Numerical and experimental implementations are executed using NURBS surfaces. The proposed method’s accuracy is on par with the point-inversion method and is 94.97% faster than the latter. Hence this method can be used for fast and accurate CMM and CNC based (in-situ) free-form surface inspection.

Surface engineered components with micro/nano scale periodic surface structures are having a wide range of industrial applications, owing to their unique tribology enhancing characteristics. Generally, design and development of highly controlled sub micro-scale structures with intricate feature characteristics are highly challenging for the manufacturing industries, especially super alloys like titanium due to its inherent low thermal conductivity and higher chemical reactive property. This forms the major objective of the present research work emphasizing the methodology-hatching technique (dot and line) to create highly controlled micro/nano scale periodic surface structures. The recently widespread femtosecond pulsed laser processing can be an efficient alternative method for the usual industrial practice of generating periodic surface structures. Femtosecond pules hatch pitch was varied from 10 to 50 μm

Micro features play a vital role in microfluidic devices as they induce laminar or patterned flow. Laser micromachining is an evolving technique in the fabrication of such micro features with various complicated shapes and sizes on metallic and polymeric surfaces. A variety of shapes and sizes are utilized in biomedical applications, such as bio-implants, bioreactors and particle separation modules. In this research work, the authors have attempted to fabricate a passive device for particle separation that works on the principle of Deterministic Lateral Displacement (DLD). Displacement of the particles in the microfluidic regime separates the particles in a size range of 5–17 µm. This separation is accomplished using appropriately placed microposts which act as diversions for the flow lines, bifurcating them into primary and secondary branches. The authors have fabricated these features using a two-step process: fabrication of P20 die steel masters using 1030 nm Ultrashort Pulsed Laser (Yb) and transferring the features to poly dimethyl siloxane (PDMS)-based polymeric devices using soft fabrication. The circular posts of diameter 40 ± 2 µm and triangular features inscribed in a circle of diameter 40 ± 2 µm are arranged in three configurations with varying row shift fractions (ɛ), namely 0.45, 0.57 and 0.70, resulting in a tilt angle (α) of 25 ± 1°, 30 ± 1° and 35 ± 1°. The effect of the tilt angles on the pressure and velocity gradients on the fluid flow and the particle deformation is studied. The microscopy of the fabricated steel masters and PDMS devices is carried out to characterize the micro-features for their shape, size and the heat-affected zones. 3D profilometry is carried out to determine the quality of the micro-holes. Polymeric devices are further fabricated using die steel masters by soft fabrication.