P. V. M. Rao

Bio: P. V. M. Rao is an academic researcher from Indian Institute of Technology Delhi. The author has contributed to research in topics: Machining & Selective laser sintering. The author has an hindex of 23, co-authored 69 publications receiving 1417 citations. Previous affiliations of P. V. M. Rao include Banaras Hindu University & Indian Institute of Technology Kanpur.

Performance improvement of hard turning with solid lubricants

Abstract: Product quality is one of the most important criteria for the assessment of hard turning process. However, in view of the high temperatures developed in hard turning process, the surface quality deteriorates due to the tool wear. Because of the strict environmental restrictions on the use of cutting fluids, new cutting techniques are required to be investigated to reduce the tool wear. In the present work, the use of solid lubricants during hard turning has been explored while machining bearing steel with mixed ceramic inserts at different cutting conditions and tool geometry. Results show considerable improvement in the surface finish with the use of solid lubricants. Due to the presence of solid lubricants, there is a decrease of surface roughness values from 8 to 15% as compared to dry hard turning.

Effect of delay time on part strength in selective laser sintering

Abstract: Selective laser sintering (SLS) is one of the most popular layered manufacturing processes used for making functional prototypes of polymers and metals. It is a powder-based process in which layers of powder are spread and laser is used to sinter selected areas of preheated powder. In the present work, experimental investigations have been made to understand effect of delay time on SLS prototypes. Delay time is the time difference for laser exposure between any two adjacent points on successive scanning lines on a layer. Tensile specimens of polyamide material as per the ASTM standard are fabricated on SLS machine keeping delay time range constant for the entire specimen. Specimens are fabricated for different ranges of delay time and tested on universal testing machine for tensile strength. An optimum value of delay time range is obtained experimentally. As delay time depends on part build orientation, an algorithm has been developed and implemented to find out optimum part build orientation for improving tensile strength. The obtained results from developed code are validated experimentally for tensile specimen. Case study for a typical 3D part is also presented to demonstrate the capabilities of developed algorithm.

Tool deflection compensation in peripheral milling of curved geometries

Abstract: This paper presents compensation of surface error due to cutting force-induced tool deflections in a peripheral milling process. Previous research attempts on this topic deal with error compensation in machining of straight geometries only. This paper is concerned with peripheral milling of variable curvature geometries where the workpiece curvature changes continuously along the path of cut. In the case of curved geometries, both process geometry and the cutting forces have shown to have strong dependence on workpiece curvature and hence variation of surface error along the path of cut. This calls for a different error compensation strategy than the one which is normally used for machining straight geometries. The present work is an attempt to improve accuracy in machining of curved geometries by use of CNC tool path compensation. Mechanistic model for cutting force estimation and cantilever beam model for cutter deflection estimation are used. The results based on machining experiments performed on a variety of geometries show that the dimensional accuracy can be improved significantly in peripheral milling of curved geometries.

Experimental investigations for improving part strength in selective laser sintering

Abstract: Selective laser sintering (SLS) is a powder-based rapid prototyping process in which parts are built by sintering of selected areas of layers of powder using laser Nowadays, SLS is emerging as a rapid manufacturing technique, which produces functional parts in small batches, particularly in aerospace application and rapid tooling Therefore, SLS prototypes should have sufficient strength to satisfy functional requirements Apart from the energy density which is the combination of laser power, beam speed and hatch spacing, various other parameters like refresh rate, layer thickness and hatch pattern influence part strength In the present work, relationship between strength and the various process parameters namely layer thickness, refresh rate, part bed temperature and hatch pattern have been investigated Experiments are conducted based on Taguchi method using L16 modified orthogonal array Tensile specimens of polyamide (PA2200) material as per the standard ‘ASTM D638’ are fabricated on SLS machine wit

Polymers for 3D Printing and Customized Additive Manufacturing

Abstract: Additive manufacturing (AM) alias 3D printing translates computer-aided design (CAD) virtual 3D models into physical objects. By digital slicing of CAD, 3D scan, or tomography data, AM builds objects layer by layer without the need for molds or machining. AM enables decentralized fabrication of customized objects on demand by exploiting digital information storage and retrieval via the Internet. The ongoing transition from rapid prototyping to rapid manufacturing prompts new challenges for mechanical engineers and materials scientists alike. Because polymers are by far the most utilized class of materials for AM, this Review focuses on polymer processing and the development of polymers and advanced polymer systems specifically for AM. AM techniques covered include vat photopolymerization (stereolithography), powder bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D printing), sheet lamination (LOM), extrusion (FDM, 3D dispensing, 3D fiber deposition, and 3D plotting), and 3D bioprinting....

Evaluation of 3D printing and its potential impact on biotechnology and the chemical sciences.

Abstract: Nearing 30 years since its introduction, 3D printing technology is set to revolutionize research and teaching laboratories. This feature encompasses the history of 3D printing, reviews various printing methods, and presents current applications. The authors offer an appraisal of the future direction and impact this technology will have on laboratory settings as 3D printers become more accessible.