Experimental investigation of process parameters for roll-type linear chemical mechanical polishing (Roll-CMP) system

The fabrication processes for electronic components are now demanding a higher degree of planarity for integration and multistacking, with chemical mechanical polishing (CMP) processes replacing conventional etching or mechanical polishing owing to their ability to attain global planarization. As CMP has been applied to more and more fields, new types of CMP machines have been developed. This study introduces a novel roll-type linear CMP (Roll-CMP) process that uses a line-contact material removal mechanism to for the polish flexible substrates, and examines the effect of the process parameters on the material removal rate (MRR) and its nonuniformity (NU). The parameters affecting the Roll-CMP process include down force, roll speed, table feed rate, slurry flow rate, slurry temperature, and the table oscillation length. Increasing the down force, roll speed, slurry flow rate, and slurry temperature resulted in a high average MRR (MRR_avg). Further, the MRR_avg was found to decrease with an increase in the oscillation length because of the effect of the polishing area. A large down force, high roll speed, high table feed rate, and high slurry flow rate were effective for reducing the NU. These results will be helpful for understanding the newly developed Roll-CMP process.     

Experimental study on micro EDM-drilling of Ti6Al4V using helical electrode

There is a growing interest in the machining of micro-holes with high aspect-ratio in difficult-to-machine alloys for the aerospace industry. Processes based on electro discharge machining (EDM) and developed for the manufacture of both micro-electrode and micro-hole are actually used, but most of them involve micro-EDM machines. In this work, the influence of EDM parameters on material removal rate, electrode wear, machining time and micro-hole quality when machining Ti6Al4V is studied. Due to an inefficient removal of debris when increasing hole depth, a new strategy based on the use of helical-shaped electrodes has been proposed. The influence of helix angle and flute depth with respect to process performance has been addressed. Main results include 37% reduction in machining times (hole diameter 800 μm) when using electrode helix angle of 45° and flute-depth of 50 μm, and an additional 19% with flute-depth of 150 μm. Holes of 661 μm diameter and as much as 6.81 mm depth, which yields in aspect ratio of 10:1, have successfully been machined in Ti6Al4V.     

Finishing effects of spiral polishing method on micro lapping surface

This study presents a spiral polishing method and a device for micro-finishing purposes. This novel finishing process has wider application than traditional processes. This offers both automation and flexibility in final machining operations for deburring, polishing, and removing recast layers, thereby producing compressive residual stresses even in difficult to reach areas. Applying of this method can obtain a fine polished surface by removing tiny fragments via a micro lapping generated by transmission of an abrasive medium through a screw rod. The effect of the removal of the tiny fragments can be achieved due to the function of micro lapping. The method is not dependent on the size of the work-piece's application area in order to carry out the ultra precise process. The application of this research can be extended to various products of precision ball-bearing lead screw. The proposed method produces products with greater precision and more efficiently than traditional processes, in terms of processing precisions and the surface quality of products. These parameters used in achieving maximum material removal rate (MRR) and the lowest surface roughness (SR) are abrasive particle size, abrasive concentration, gap, revolution speed and machining time.     

FREE-FORM SURFACE MACHINING AND COMPARING FEEDRATE SCHEDULING STRATEGIES

This article presents mathematical models of cutting forces and surface-form errors for machining of free-form surfaces. Besides the predictive models of cutting forces and surface deflections, a newly developed force based feedrate scheduling (FFS) technique is compared with material removal rate (MRR) based feedrate scheduling method that was used in feedrate optimization packages. With the experimental validations in free-form surfaces, it is shown that the mechanic models predict the forces and surface-form errors quite well. Moreover, by modifying the CNC programs with the new FFS technique, cycle times of the free-form parts can be decreased significantly.     

Multi response optimization of wire EDM operations using robust design of experiments

In this present study a multi response optimization method using Taguchi’s robust design approach is proposed for wire electrical discharge machining (WEDM) operations. Experimentation was planned as per Taguchi’s L16 orthogonal array. Each experiment has been performed under different cutting conditions of pulse on time, wire tension, delay time, wire feed speed, and ignition current intensity. Three responses namely material removal rate, surface roughness, and wire wear ratio have been considered for each experiment. The machining parameters are optimized with the multi response characteristics of the material removal rate, surface roughness, and wire wear ratio. Multi response S/N (MRSN) ratio was applied to measure the performance characteristics deviating from the actual value. Analysis of variance (ANOVA) is employed to identify the level of importance of the machining parameters on the multiple performance characteristics considered. Finally experimental confirmation was carried out to identify the effectiveness of this proposed method. A good improvement was obtained.     

Multiobjective optimization and analysis of copper–titanium diboride electrode in EDM of monel 400™ alloy

Electrical discharge machining (EDM) is one of the most accepted machining processes in the precision manufacturing industry. In EDM process, finding an alternative tool material is the demand in modern manufacturing industry. Therefore, an attempt had been made to fabricate copper–titanium diboride powder metallurgy electrode to test in EDM on monel 400? material. The experiments are planned using center composite second-order rotatable design and the model is developed by response surface methodology. The machining characteristics have analyzed using the developed model. In this study, four input parameters such as titanium diboride percentage, pulse current, pulse on time, and flushing pressure are selected to evaluate the material removal rate (MRR) and tool wear rate (TWR). The adequacy of the developed regression model has tested through analysis of variance test. The desirability-based multiobjective optimization is used to find the optimal process parameter which has given maximum MRR and minimum TWR. The optimum process parameters obtained were titanium diboride of 16%, pulse current of 6 A, flushing pressure of 1 Mpa, and pulse on time of 35?µs. The validity of the response surface model is further verified by conducting confirmation experiments.     

WEDM of layered composite: analyzing material removal and cut quality issues

The use of cladded bimaterial composites has grown in the recent past as they offer a combination of properties at low cost. But the heterogeneity which is the inherent attribute of these composites makes it challenging to accurately cut via conventional means. Therefore, thermal cutting is commonly employed for their cutting which not only produce poor cut quality and deeper heat affected zones but also demand subsequent finishing operations. Wire electric discharge cutting (WEDM) is a proficient alternate but low material removal (MRR) and widen kerf slot (KW) due to sideways sparking limit its application. Moreover, both layers of material have different thermoelectric properties and are subjected to simultaneous cutting by a single moving wire electrode which lead to produce different spark strength against both layers. In this regard, the present study aims to investigate the cutting potential of WEDM for cladded bimaterial with a prior focus on both the aforesaid issues, i.e. MRR and KW. Considering the thermoelectric nature of the WEDM, workpiece-related parameters like orientation of work surface and layer thickness of each layer are taken as control variables in addition to the WEDM process parameters. Experimental results are thoroughly analyzed using statistical and SEM analysis.     

Optimization of photochemical machining process parameters for manufacturing microfluidic channel

In the present study, the investigation on photochemical machining (PCM) of stainless steel (SS-304) by ferric chloride as etchant is reported. SS-304 is machined by PCM process to obtain accurate dimensions and better geometrical features. Weighted grey relational analysis (WGRA) technique is used in optimization of PCM process parameters. DoE (L₂₇) orthogonal array is applied to evaluate machining parameters, such as concentration of etchant, etching time, and temperature of etchant. The multiobjective optimization technique is used to optimize material removal rate (MRR), surface roughness (R_a), undercut (U_c) and etch factor (EF). Weighted grey relational grade is calculated to minimize U_c and surface roughness and to maximize MRR and EF. The quality characteristics MRR, EF, U_c, and R_a are reporting the improvement after the confirmatory test. The optimum machining parameters are processed to manufacture the microfluidic channel used in biomedical applications. The microfluidic channels and its assembly with Y-type for mixing of fluid with a size of 100 µm, 200 µm, and 300 µm are developed and investigated.     

On effect of tool rotation on performance of rotary tool micro-ultrasonic machining

The present research paper is based on a comparative study of stationary tool micro-ultrasonic machining (STMUSM) and rotary tool micro-ultrasonic machining (RTMUSM). Microchannels were developed on glass work material by using both processes. The effect of tool rotation on the performance of micro-USM was investigated. The performance of both processes was compared on the basis of material removal rate (MRR) and depth of channel (DOC) as response characteristics. The power rating, work feed rate, concentration of abrasive slurry, and abrasive mesh size were chosen as variable input process parameters in this investigation. The form accuracy of the fabricated microchannels was analyzed with the help of imaging technique. Also, a qualitative analysis of tool wear was carried out with the help of microscopic images. The experimental results revealed that the tool rotation significantly improved the performance of micro-USM. The RTMUSM resulted in 155% and 147% higher MRR and DOC as compared to STMUSM. The tool wear was also found to be lesser in RTMUSM as compared to STMUSM and as a result of that form accuracy of machined microchannels improved.     

Investigation of machining characteristics in rotary ultrasonic machining of alumina ceramic

Alumina ceramic is well documented as a much-demanded advanced ceramic in the present competitive structure of manufacturing and industrial applications owing to its excellent and superior properties. The current article aimed to experimentally investigate the influence of several process variables, namely: spindle speed, feed rate, coolant pressure, and ultrasonic power, on considered machining characteristics of interest, i.e., chipping size and material removal rate in the rotary ultrasonic machining of alumina ceramic. Response surface methodology has been employed in the form of a central composite rotatable design to design the experiments. Variance analysis testing has also been performed with a view to observing the consequence of the considered parameters. The microstructure of machined rod samples was evaluated and analyzed using a scanning electron microscope. This analysis has revealed and confirmed the presence of plastic deformation that caused removal of material along with brittle fractures in rotary ultrasonic machining of alumina ceramic. The validity and competence of the developed mathematical model have been verified with test results. The multi-response optimization of machining responses (material removal rate and chipping size) has also been attempted by employing a desirability approach, and at an optimized parametric setting the obtained experimental values for material removal rate and chipping size were 0.4166?mm³/s and 0.5134?mm, respectively, with a combined desirability index value of 0.849.