A multi-criteria decision-making in relieving grinding process of surface of gear milling tooth based on the archimedean spiral using taguchi-ahp-topsis method

In this study, in order to optimize the quality criteria of the machined surface based on the Archimedean spiral, the relieving grinding process (RGP) was performed to machine the material of HSS P18 in a 1Б811 machine with four input parameters including graininess of grinding wheel (G), grinding wheel hardness (Hd), velocity of grinding wheel (V), and feed rate (s) and with three quality criteria including surface roughness (Ra), hardening of surface layer (∆HRC), and hardened layer thickness (∆L). Taguchi-AHP-Topsis method was successfully applied to solve the Multi-Criteria Decision Making (MCDM) problem in this case. The optimized results of the output parameters are surface roughness of 0.21 µm, surface hardening of 1.45 HRC, and hardened layer thickness of 34.18 µm. These results were determined at the set of the input parameters includes G, V, s with their values of 120, 24 m/s, 2.08 m/min, respectively, and Hd at level 1. The optimal results were verified through the comparison between the calculated and the experimental results using this set of optimal parameters. The differences between the calculated results and the experimental results were quite small (maximum different value was 4.8 %) Thus, the results of this study can be applied to solve the multi-objective optimization problems in RGP of the GMT surface based on the Archimedean spira

DEVELOPMENT OF A LOW COST PRECISION POLISHING MACHINE BASED ON PARALLEL KINEMATIC SYSTEM

The increasing demand on mass production of high precision parts, has pushed the precision manufacturing industry to develop reliable precision finishing processes such as Bonnet polishing to address market requirements. Indeed, the nature of the surface to be polished plays an important role in the design of a possible polishing machine. A gap within the research in polishing for precision industry needs has been identified. Small parts with <50mm x 50mm and possible freeform curvature containing small slopes cannot be polished with available bonnet polishing (BP) processes on market. This is caused by the tool head size and the tool holder being bigger than part curvature or the part itself. Although, the BP process has a huge potential for surface roughness improvement and form accuracy, it is generally seen in industry as an expensive solution for a non-deterministic finishing process. Therefore, this project has sought to develop a BP machine to cover the gap with an innovative and inexpensive design. In order to develop a machine which responded to the market expectations all possible requirements were listed from a customer point of view. Based on the requirement, a machine concept was produced. Market analysis helped to identify sub-systems of the machine. FEA analysis of the design was performed to check for stress distribution and displacement due to its own mass. Additional assembly parts are designed and a prototype of the machine was produced. The designed machine is tested for its ability as precision polishing machine. Flat surfaces of P20 tool steel were targets for polishing to nanometric surface finishes. Empirical experiments helped to identify parameters which influenced the surface roughness. Taguchi method were then used to optimise the parameters for better surface roughness. Optimum parameters conditions helped to reach less than 10 nm Ra systematically and repeatedly. The samples were also polished using re-circulating slurry techniques, and the obtained results were discussed. Further, pre polishing, Grolishing processes capable of improving surface roughness from ground finish to mirror like finish were developed for cost effective manufacturing procedures. The material removal was analysed to identify parameters capable of improving surface roughness over a step grolishing process. Two grolishing procedures were developed. Both processes produced nanometric range surface finishes. Other variations in results were compared and discussed. Although, machine axis has the ability to produce freeform movement, tool holders need to be improved to facilitate the identification of the distance between tool origin and workpiece origin. Therefore, a new spindle holder assembly is produced to hold the tool and an optical measurement device DRI used to evaluate accurately the distance separating the tool-workpiece origin and further align the workpiece inclination with respect to the machine axis. A CAD-CAM package is also developed to generate programme capable of performing freeform curvature

Design Process Control for Improved Surface Finish of Metal Additive Manufactured Parts of Complex Build Geometry

Metal additive manufacturing (AM) is increasingly used to create complex 3D components at near net shape. However, the surface finish (SF) of the metal AM part is uneven, with surface roughness being variable over the facets of the design. Standard post-processing methods such as grinding and linishing often meet with major challenges in finishing parts of complex shape. This paper reports on research that demonstrated that mass finishing (MF) processes are able to deliver high-quality surface finishes (Ra and Sa) on AM-generated parts of a relatively complex geometry (both internal features and external facets) under select conditions. Four processes were studied in this work: stream finishing, high-energy (HE) centrifuge, drag finishing and disc finishing. Optimisation of the drag finishing process was then studied using a structured design of experiments (DOE). The effects of a range of finishing parameters were evaluated and optimal parameters and conditions were determined. The study established that the proposed method can be successfully applied in drag finishing to optimise the surface roughness in an industrial application and that it is an economical way of obtaining the maximum amount of information in a short period of time with a small number of tests. The study has also provided an important step in helping understand the requirements of MF to deliver AM-generated parts to a target quality finish and cycle time

An in-process, non-contact surface finish sensor for high quality components generated using diamond turning

The object of this Ph.D. project was to design and construct an in-process, non contact surface finish sensor for high quality components generated using diamond turning. For this application the instrument must have the following properties: i rapid acquisition of data. ii capability of measuring translating and or rotating surfaces. iii ruggedness for in-process use. iv insensitivity to moderate vibrations. v remoteness from the surfaces to be measured. The remoteness requirement virtually excludes the otherwise ubiquitous stylus instrument, while the rapid gathering of data from rotating surfaces excludes other profiling techniques. The above mentioned properties strongly suggest an optical method. An optical diffraction technique has been chosen, since it produces an optical Fourier Transform of the surface. This transform is produced at the speed of light, since the optical system has the property of parallel data processing, unlike a typical electronic computer. With the aid of a microprocessor various surface finish parameters can be extracted from the optical transform. These parameters are respectively the rms surface roughness, slope and wavelength. The actual sensor consists of a measuring head and a minicomputer. It fulfils the above mentioned requirements. Its only limitations are: i limited to surface finishes up to 100nm ii presence of cutting fluids has to be avoided, although certain modern lubricating fluids can be tolerated. The algorithms devised to extract the surface finish parameters from the optical transforms have initially been tested on optical spectra produced by Thwaite. Comparison of the optical roughness values and the values quoted by Thwaite show close agreement. Thwaite's values are obtained by a stylus instrument. Rqopt (um) Rqstylus (um) 0.16 0.156 0.38 0.37 0.44 0.40 In addition a computer program has been devised which simulates the optical sensor head. The input data can be obtained by a profiling instrument, or generated by a computer program. This last option enables the creation of surface profiles with "controllable" machining errors. This program can be utilised to create an atlas, which maps optical diffraction patterns versus machine-tool errors

Alternative cut-off and surface finishing of investment castings

The research investigates the capability of replacing the cut-off and gate-removal processes at DePuy Synthes (Ireland) with a single cutting operation. Abrasive WaterJet Cutting (AWJC), laser cutting, Electrical Discharge Machining (EDM) and plasma cutting were considered as alternatives to the current system. Custom investment castings were produced for use in A WJC experiments to determine the cutting speeds for a range of cut thickness (2 to 30 mm) for the Cobalt-Chrominum-Molybdenum (CoCrMo) alloy. Femoral and tray castings, each with different tree designs, were evaluated post knockout (vibratory shell removal). Femoral parts were undamaged by jet deflection or wear when utilising the correct set up of the A WJC nozzle. Using a traverse speed of 130 mm/min, the surface finish at the bottom of the 16 mm thick femoral gate was visually equivalent to the current surface finish obtained after gate removal (Ra of 9 μm). Thin femoral sections (3.2 mm) cut at 400 mm/min achieved an acceptable Ra of 7 μm with a cycle time of 6 minutes per tree, which was 70% lower than the current processing time of 23 minutes. Tray castings cut with a traverse speed of 60 mm/min achieved a surface roughness Ra of 10 μm. However, the process was unsuitable for trays because jet deflection below the cut caused excessive wear to the machined parts. The use of AWJC for femorals has the ergonomic benefit of eliminating all manual grinding in the foundry, as well as labour savings equivalent to a Return-On-Investment (ROI) of two years. Further development of a 3-dimensional (3-0) vision system however is required to automate the AWJC of femoral castings

Spray automated balancing of rotors: Methods and materials

The work described consists of two parts. In the first part, a survey is performed to assess the state of the art in rotor balancing technology as it applies to Army gas turbine engines and associated power transmission hardware. The second part evaluates thermal spray processes for balancing weight addition in an automated balancing procedure. The industry survey reveals that: (1) computerized balancing equipment is valuable to reduce errors, improve balance quality, and provide documentation; (2) slow-speed balancing is used exclusively, with no forseeable need for production high-speed balancing; (3) automated procedures are desired; and (4) thermal spray balancing is viewed with cautious optimism whereas laser balancing is viewed with concern for flight propulsion hardware. The FARE method (Fuel/Air Repetitive Explosion) was selected for experimental evaluation of bond strength and fatigue strength. Material combinations tested were tungsten carbide on stainless steel (17-4), Inconel 718 on Inconel 718, and Triballoy 800 on Inconel 718. Bond strengths were entirely adequate for use in balancing. Material combinations have been identified for use in hot and cold sections of an engine, with fatigue strengths equivalent to those for hand-ground materials

Abrasive machining with MQSL

Grinding and polishing of engineered components are critical aspects of the precision manufacturing of high performance, quality assured products. Elevated process temperatures, however, are a common and for the most part undesirable feature of the grinding process. High process temperatures increase the likelihood of microstructural change within the immediate subsurface layer and are detrimental to the strength and performance of the manufactured products. Increasing processing costs and tighter environmental legislation are encouraging industry to seek innovative fluid application techniques as significant savings in production can be achieved. In this context, and with sponsorship from three industrial partners, namely; Fives Cinetic, Fuchs Lubricants plc and Southside Thermal Sciences Ltd, and also from the Engineering and Physical Science Research Council (EPSRC), this research aimed to develop an understanding of Minimum Quantity Solid Lubrication (MQSL) as a method for abrasive machining, with particular reference to the control of surface temperatures. Improving the lubricity of Minimum Quantity Lubrication (MQL) fluids reduces the frictional source of process heat and controls the finish surface temperature. The application of effective solid lubricants is known as Minimum Quantity Solid Lubrication (MQSL). Molybdenum Disulphide (MoS2), Calcium Fluoride (CaF2), and hexagonal Boron Nitride (hBN) were compared against a semi-synthetic water soluble machining fluid (Fuchs EcoCool). A series of Taguchi factorial experimental trials assessed their performances through ANOVA (ANalysis Of VAriance) statistical method. The hBN produced the lowest grinding temperatures of the solid lubricants tested, although they still remained higher than those achieved using the EcoCool control. The reduction of the machining fluid enabled a Charged Coupled Device (CCD) sensor to be fitted into the grinding machine. The recorded movement in the emitted spectrum from the grinding chips was compared to experimental and modelled process temperatures. This showed that the wavelengths of the chip light correlated to the temperature of the finish grinding surface. This greatly contributed to determining the feasibility of constructing a non-destructive, non-invasive, thermally-adaptive control system for controlling grinding surface temperatures.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The Effects of Material and Configuration on the Acoustic Response of an Impact Stop

The noise levels on factory floors have been a historical concern with respect to worker health. The sponsor utilizes impact stops throughout their production facilities; each stop is hit hundreds of times per minute contributing to high decibel levels. The goal of this project was to identify alternative materials and configurations of the stop to minimize the noise output upon impact. This was accomplished by researching alternative materials, constructing a testing apparatus, and the construction and testing of prototype stops

Advances and Trends in Non-conventional, Abrasive and Precision Machining

The work included in this book pertains to advanced abrasive and nonconventional machining processes. These processes are at the forefront of modern technology, with significant practical significance. Their importance is also made clear by the case studies that are included in the research that is presented in the book, pertaining to important materials and high-end applications. However, the particularities of these manufacturing processes need to be further investigated and the processes themselves need to be optimized. This is conducted in the presented works with significant experimental and modeling work, incorporating modern tools of analysis and measurements