Showing papers on "Surface finishing published in 2007"

Finite Element Modeling of Hard Roller Burnishing: An Analysis on the Effects of Process Parameters Upon Surface Finish and Residual Stresses

Abstract: Hard roller burnishing is a cost-effective finishing and surface enhancement process where a ceramic ball rolls on the machined surface to flatten the roughness peaks The ball is supported and lubricated by hydrostatic fluid in a special tool holder The process not only improves surface finish but also imposes favorable compressive residual stresses in functional surfaces, which can lead to long fatigue life Most research in the past focused on experimental studies There is still a special need for a reliable finite element method (FEM) model that provides a fundamental understanding of the process mechanics In this study, two-dimensional (2D) and three-dimensional FEM models for hard roller burnishing were established The developed 2D FEM model was used to study the effects of process parameters (ie, burnishing pressure, feed rate) on surface finish and residual stresses The simulation results were evaluated and compared to the experimental data Results show that the established FEM model could predict the residual stresses and provided useful information for the effect of process parameters Both FEM and experiments show that burnishing pressure is the most influence, where high burnishing pressure produces less roughness and more compressive residual stress at the surface

Self-modulating abrasive medium and its application to abrasive flow machining for finishing micro channel surfaces

Abstract: This study developed a self-modulating abrasive medium whose viscosity and fluidity can be adjusted during the processing period. The complex micro channel was fabricated on the stainless steel (SUS304) by using wire electrical discharge machining (wire-EDM). An experiment of employing abrasive flow machining (AFM) was conducted to evaluate the characteristics of various levels of roughness and finishing of the micro channel surface. In the experiment, the parameters of affecting AFM machining including abrasive particle size, concentration, extrusion pressure and machining time were selected to verify the machining quality of the micro channel.

High-speed, ultra precision manufacturing station that combines direct metal deposition and EDM

Abstract: A direct-metal deposition (DMD) processing stage and a 5DOF (degree of freedom) dry micro-EDM (mEDM) stage are integrated to provide the submicron scale resolution necessary for the ultra-precision processing of work pieces. The DMD processing stage includes optical feedback for dimensional control utilizing a high-power, fiber-coupled diode laser with fast response time and small beam parameter product. The electrical discharge machining (EDM) stage is a dry EDM stage using an inert gas with appropriate dielectric properties to perform the surface finishing operations. The system further includes one or more surface treatment operations to obtain a desired level of surface hardness or wear resistance and/or to minimize the distortion induced in treating the surface.

Finishing effect of abrasive flow machining on micro slit fabricated by wire-EDM

Abstract: This experimental research use the method of abrasive flow machining (AFM) to evaluate the characteristics of various levels of roughness and finishing of the complex shaped micro slits fabricated by wire electrical discharge machining (Wire-EDM). An investigative methodology based on the Taguchi experimental method for the micro slits of biomedicine was developed to determine the parameters of AFM, including abrasive particle size, concentration, extrusion pressure and machining time. The parameters that influenced the machining quality of the micro slits were also analyzed. Furthermore, in the shape precision of the micro slit fabricated by wire-EDM and subsequently fine-finished by AFM was also elucidated using a scanning electron microscope (SEM). The significant machining parameters and the optimal combinations of the machining parameters were identified by ANOVA (analysis of variation) and the S/N (-to-noise) ratio response graph. ANOVA was proposed to obtain the surface finishing and the shape precision in this study.

A study of die helical thread cavity surface finish made by Cu-W electrodes with planetary EDM

Abstract: An experimental research study intended for the application of a planetary electrical discharge machining (EDM) process with copper-tungsten (Cu-W) electrodes in the surface micro-finishing of die helical thread cavities made with AISI H13 tool steel full-hardened at 53 HRC is presented. To establish the EDM parameters’ effect on various surface finishing aspects and metallurgical transformations, three tool electrode Cu-W compositions are selected, and operating parameters such as the open-circuit voltage (U 0), the discharge voltage (u e), the peak discharge current (i e), the pulse-on duration (t i), the duty factor (τ) and the dielectric flushing pressure (p in), are correlated. The researched machining characteristics are the material removal rate (MRR—V w), the relative tool wear ratio (TWR—ϑ), the workpiece surface roughness (SR—Ra), the average white layer thickness (WLT—e wl) and the heat-affected zone (HAZ—Z ha). An empirical relation between the surface roughness (SR—Ra) and the energy per discharge (W e) has been determined. It is analysed that copper-tungsten electrodes with negative polarity are appropriate for planetary EDM die steel surface micro-finishing, allowing the attaining of good geometry accuracy and sharp details. For die steel precision EDM, the relative wear ratio optimum condition and minor surface roughness takes place at a gap voltage of 280 V, discharge current of 0.5–1.0 A, pulse-on duration of 0.8 μs, duty factor of 50%, dielectric flushing pressure of 40 kPa and copper tungsten (Cu20W80) as the tool electrode material with negative polarity. The copper-tungsten electrode’s low material removal rate and low tool-wear ratio allows the machining of EDM cavity surfaces with an accurate geometry and a “mirror-like” surface micro-finishing. A planetary EDM application to manufacture helical thread cavities in steel dies for polymer injection is presented. Conclusions are appointed for the planetary EDM of helical thread cavities with Cu-W electrodes validating the accomplishment as a novel technique for manufacturing processes.

An energy-based model for the wear of UHMWPE

Abstract: An energetic approach to model the wear of tribological systems in which one of the components of the pair is polymeric is presented in this work. Experimental data, obtained in ultra-high molecular weight polyethylene (UHMWPE) pin-on-disk tribological tests, showed that a linear correlation between the wear rate of the polymer and the dissipated energy exists, independently of the lubricant, of the material used as counterbody and of the surface finishing of both polymer and counterbody. This fact strongly suggests that, in UHMWPE-based tribological systems, energy dissipation is mainly caused by the elasto-plastic deformation and wear of the polymer. Based on this assumption, it is developed a mathematical model that yields for a physical interpretation of the parameters of the experimental wear vs. energy correlation. These parameters are intrinsic wear properties of the polymer and can be used for the optimization of polymer-based tribological systems.

Toward Magnetorheological Finishing of Magnetic Materials

Abstract: Magnetorheological finishing (MRF) is a precision optical finishing process traditionally limited to processing only nonmagnetic materials, e.g., optical glasses, ceramics, polymers, and metals. Here we demonstrate that MRF can be used for material removal from magnetic material surfaces. Our approach is to place an MRF spot on machined surfaces of magnetic WC-Co materials. The resulting surface roughness is comparable to that produced on nonmagnetic materials. This spotting technique may be used to evaluate the depth of subsurface damage, or deformed layer, induced by earlier manufacturing steps, such as grinding and lapping.

Sb-Te Base Alloy Sinter Sputtering Target

Abstract: An Sb-Te base alloy sintered sputtering target containing at least one of Sb and Te as a primary component, characterized in that it has a surface roughness Ra of 0.4 μm or less, a purity except a gas component of 4N or higher, a content of a gas component as an impurity of 1500 ppm or less and an average crystal grain diameter of 50 μm or less; and the above Sb-Te base alloy sintered sputtering target, characterized in that the density of defects having a maximum length of 10 μm or more due to the surface finishing by machine work is 80 pieces or less in an area of 800 μm square. The above sintered sputtering target has a Sb-Te base alloy sputtering target structure being improved in fineness and uniformity, is inhibited in the occurrence of clacks, can prevent the occurrence of arcing during sputtering, is reduced in concave and convex shapes in its surface due to sputter erosion, and is an Sb-Te base alloy sputtering target having good quality.

Ultrasonically Assisted Grinding for Mirror Surface Finishing of Dies with Electroplated Diamond Tools

Abstract: This paper describes ultrasonically assisted grinding used to obtain a glossy surface quickly and precisely. High-quality surfaces are required for plastic injection molding dies used in the production of plastic parts such as dials for cellular phones. Traditionally, in order to finish the dies, manual polishing by a skilled worker has been required after the machining processes, such as electro discharge machining (EDM), which leaves an affected layer, and milling, which leaves tooling marks. However, manual polishing causes detrimental geometrical deviations of the die and consumes several days to finish a die surface. Therefore, a machining process for finishing dies without manual polishing to improve the surface roughness and form accuracy would be extremely valuable. In this study, a 3D positioning machine equipped with an ultrasonic spindle was used to conduct grinding experiments. An electroplated diamond tool was used for these experiments. Generally, diamond tools cannot grind steel because of excessive wear as a result of carbon atoms diffusing into bulk steel and chips. However, ultrasonically assisted grinding can achieve a fine surface (roughness Rz of 0.4 ㎛) on die steel without severe tool wear. The final aim of this study is to realize mirror surface grinding for injection molding dies without manual polishing. To do this, it is necessary to fabricate an electroplated diamond tool with high form accuracy and low run-out. This paper describes a tool-making method for high precision grinding and the grinding performance of a self-electroplated tool. The ground surface textures, tool performance and tool life were investigated. A ground surface roughness Rz of 0.14 ㎛ was achieved. Our results show that the spindle speed, feed rate and cross feed affected the surface texture. One tool could finish 5000㎟ of die steel surface without any deterioration of the ground surface roughness.

Process for producing highly anticorrosive rare earth permanent magnet and method of using the same

Abstract: A process for producing a highly anticorrosive rare earth permanent magnet, characterized by sequentially subjecting an R-Fe-B sintered magnet to surface finishing involving cutting and/or polishing, plating pretreatment, nickel electroplating to a given plating thickness, immersion in an aqueous solution containing a phosphoric salt, washing with water and heat treatment at 150° to 400°C for 1 to 24 hr in an atmosphere of 1.3×103 Pa or higher oxygen partial pressure so as to form a thin nickel oxide layer at the surface layer portion.

Research on machining mechanics and experiment of ultrasonic-magnetorheological compound finishing

Abstract: In this paper, Ultrasonic-Magnetorheological Compound finishing (UMC finishing), which is a new kind of polishing method, is first presented for the ultraprecision machining of concave optical surface with small radius. The principle of UMC finishing is studied and experimental set-up is developed based on the foregoing study. Experiments are carried out to verify the mechanics of UMC finishing. The results show that the surface roughness of the polished optical glass by UMC finishing is on nano-scale, which can satisfy the optical surface quality requirement. Furthermore, UMC finishing can also have higher machining efficiency than magnetorheological finishing under the same experiment conditions.

Low-Loss Thin Film Microstrip Lines and Filters Based on Magnetorheological Finishing

Abstract: This paper presents a surface finishing method based on magnetorheological fluid to obtain low-loss high-frequency transmission lines and filters on CMOS-grade silicon. As specimens for the magnetorheological finishing, high- and low- thin film microstrip lines with a 20 m-thick polyimide interface above the ground plane that is patterned on the silicon substrate are evaluated. In all cases, thin film microstrip lines treated with the magnetorheological finishing scheme reveal much lower losses compared to original lines owing to reduced conductor roughness. In addition, low-pass filters with 0.5 dB Chebyshev responses based on high-Z0 and low-Z0 thin film microstrip lines are designed and characterized before and after applying the magnetorheological finishing treatment, exhibiting a roughly 1.0-dB insertion loss improvement for the entire pass band range. The proposed magnetorheological finishing scheme can be applied to smoothen any 3-D high-frequency structures, and it can significantly improve conductor roughness.

Surface polishing-finishing processing method based on fluid-field restriction type hydraulic grinding-particle flow

Abstract: The invention relates to based on flow field bound type liquid operated abrasive particle flow finishing method. It includes the following steps: allocating bound module by clamp on work piece structuring surface to form liquid solid two phase abrasive particle flow passage; connecting the passage with the abrasive particle flow circulating system; starting up abrasive particle flow circulating system; forming flow field bound type liquid operated abrasive particle flow in passage to process erosion micro cutting for the work piece structuring surface. The invention can effectively process the structuring surface finishing with small size and special structure.

Kinetics of the electrolytic coloring process on anodized aluminum

Abstract: The kinetics of tin electrodeposition during the electrolytic coloring of porous anodic oxide films on aluminum is studied as a function of the oxide properties, e.g., the thickness of the porous oxide layer, and the surface resistance offered by the barrier oxide layer. While the thickness of the porous oxide layer is controlled by the anodization time, the surface resistance is controlled by the anodization voltage, and the anodization bath temperature. Steady-state polarization measurements are employed to characterize the dependence of the coloring kinetics on the oxide properties. Measurements indicate that the kinetics of the electrolytic coloring process can be accelerated by: (i) reducing the surface resistance of the oxide film (primarily offered by the barrier oxide layer) by growing the oxide at a lower anodization voltage, and/or a higher bath temperature, or (ii) growing a thinner porous oxide layer by decreasing the anodization time. The electrochemical measurements are supported by gravimetric analysis of electrolytically colored alumina samples (using calibrated wavelength-dispersive X-ray fluorescence spectroscopy), and by optical spectrophotometry.

Influence of Surface Finishing and Binder Phase on Friction and Wear of WC Based Hardmetals

Abstract: At present, cobalt is the most commonly used binder material in tungsten carbide based hardmetals. Current research on sliding wear performance of these cemented carbides, however, reveals promising results for nickel binder as well. Test samples of WC-Co and WC-Ni hardmetals have been machined and surface finished by wire-EDM and grinding. From comparative dry sliding pin-on-plate experiments on wire-EDM’ed, ground and polished grades, correlations are derived between wear volume loss and friction on the one hand and contact pressure, sliding distance, binder phase and microstructure on the other hand. The lowest wear levels are encountered with polished cemented carbides. The EDM induced surface modification turns out to deteriorate wear resistance, especially during the running-in stage of sliding. These findings are in agreement with Xray diffraction measurements of the residual stress level in the WC phase.

Reciprocating Friction and Wear Behavior of WC-Co Based Cemented Carbides Manufactured by Electro-Discharge Machining

Abstract: Tungsten carbide based hardmetals with cobalt binder phase are widely used in engineering industries for their excellent mechanical properties and outstanding wear performance. Reciprocative sliding wear behaviour of a number of WC-Co based hardmetal grades was investigated using a small-scale pin-on-plate tribometer. Test samples were manufactured by electro-discharge machining (EDM) with various surface finishing regimes. SEM topographies and cross-section views of the cemented carbides were obtained both before and after dry friction tests, revealing distinctive wear mechanisms. The generated wear loss was quantified topographically using surface scanning equipment. Wear debris particles were collected and examined by EDX and TEM analysis. Based on experimental results, the execution of consecutive gradually finer EDM cutting steps was found to considerably enhance wear performance. Furthermore, a significant influence of contact load, sliding movement duration, application of lubricant and wear debris formation on wear rate and friction was established.

Influence of PCB Surface Finish and Thermal and Temperature/Humidity Aging on the Performance of a Novel Anisotropic Conductive Adhesive for Lead-free Surface Mount Assembly

Abstract: The electronics industry, in recent years, has been focusing primarily on product miniaturization and lead-free assembly. The need to eliminate lead-based materials as a means of interconnection has renewed the industry's interest in exploring other means of assembling surface mount devices reliably, especially using conductive adhesives. This paper will discuss the performance characteristics and research findings pertaining to a novel anisotropic conductive adhesive for lead-free electronics packaging applications. The applicability of the novel conductive adhesive in board level assembly has been demonstrated successfully. The IV characteristics and the breakdown current characteristics have shown the importance of achieving very low initial contact resistance after assembly, in order to enable longer life under thermal and temperature-humidity aging conditions. Thermal aging of the adhesive material has revealed improvement in contact resistance and temperature/humidity aging has shown deterioration in performance within the first 100 hours of aging. Area array packages with and without bumps have shown variations in performance and their has revealed the importance of placement pressure, placement speed and placement dwell in achieving low initial contact resistance. Preliminary experiment has shown that the HASL finish performs better than OSP. The experimental study presented in this paper examines the performance of the adhesive on various printed circuit board (PCB) surface finishes which include Sn/Pb (HASL), Organic Solderability Preservative (OSP), Immersion Silver (ImAg), Electroless Nickel Immersion Gold (ENIG) and Immersion Tin (ImSn). The findings and performances of the various finishes under thermal and temperature/humidity aging will be discussed in detail in this paper.

Magnesium alloy surface pre-treating process

Abstract: The magnesium alloy surface pre-treating process includes the following steps: surface finishing, sand blasting, acid pickling and post-treatment. The process has low cost, simple operation and less environment pollution and influence on the health of the operator, and the increased sand blasting step can alter the surface structure of the magnesium alloy, raise the adhesion of the coating to the magnesium alloy substrate and strengthen the protection on the magnesium alloy substrate.

Aspheric surface finishing by fixed abrasives

Abstract: This paper presents a method for the finishing of aspheric surfaces using fixed abrasives. The strategy is to remove a specified amount of material from the surface. The method assumes concentric tool paths perpendicular to the axis of the surface. The key parts of the method are: (1) efficient computation of the material removal profile for each tool path and (2) optimisation of the feed rate for the tool paths. Simulation results are included to illustrate the proposed method, which suggest that the method is potentially useful for aspheric surface finishing.

2F-5 Surface Preparation of 1-3 Piezocomposite Material for Microfabrication of High Frequency Transducer Arrays

Abstract: A key issue in the development of ultrasound imaging arrays to operate at frequencies above 30 MHz is the need for photolithographic patterning of array electrodes. To achieve this directly on a 1-3 piezocomposite requires planar, parallel and smooth surfaces. This paper reports an investigation of the surface finishing of 1-3 piezocomposite material by mechanical lapping and/polishing that has demonstrated that excellent surface flatness can be obtained. Subsequently, high frequency array elements have been fabricated on these surfaces using a low temperature lift-off photolithography process. A 50 MHz linear array with 30 mum element pitch has been patterned on the lapped and polished surface of a low frequency 1-3 piezocomposite. Good electrode edge definition and electrical contact to the composite were obtained. Additionally, patterning has been demonstrated on a fine-scale composite, itself suitable for operation above 30 MHz.

Concrete template and method of use

Abstract: A method of transferring a design to an uncured concrete surface of a poured concrete mixture is provided. The method comprises the steps of: (a) placing a releasable template onto the surface to define exposed and covered regions; (b) manipulating the exposed regions corresponding to the design; (c) removing the template to reveal the covered regions; and (d) finishing the surface. The template may be variously configured and may incorporate positive and negative portions, which may be alternatively utilized to transfer the design to respective positive and negative regions of the surface. The template may preferably be fabricated from visquene, craft paper, or other suitable material. In addition, implementations of the present invention may be utilized with surface seeded exposed aggregate, troweling, or other surface finishing processes.

Improvement of the surface finish obtained by laser ablation with a Nd: YAG laser on pre-ablated tool steel

Abstract: Surface finish is an important requirement for tool and die makers and remains a challenge with conventional machining technologies. Nd: YAG lasers have been utilised for many years in the area of laser marking, engraving and micro machining. In recent years, these lasers have been used in other fields, such as laser ablation of small tools for plastics injection moulding. Laser ablation is a technology that is investigated as a method to improve the surface finish in tool steel. Different proposed strategies and techniques that are uniquely inherent to the technology will be investigated. The focus of this study is to employ a second routine of laser ablation on samples of pre-ablated rough surfaces. These strategies are expected to add surface quality that will reduce the need for further surface finishing. Strategies that reduce surface quality will also be identified. We report on the influence of machining parameters on the improvement of the quality of the surface finish.