Mirror Finish Research Articles

Development of Multi-Axis Cutting Method Using Non-Rotational Tool with Ultrasonic Vibration

In recent years, rotary tools such as ball and flat end mills are widely used to produce dies and parts. Machining using rotary tools shortens cutting time, raising efficiency and discharging cutting chips cleanly, but leaves the machined face rough due to arc-shaped rotation marks. The radius of rotation for the location of the cutting edge from the tool's center axis is non-consistent, varying tool edge cutting speed and direction, making it difficult to leave surface roughness uniform. Removing unfinished areas and reducing final machined face surface roughness to the submicron level thus requires secondary finishing, which conventionally relies on hand polishing by a skilled worker. We developed extremely small cut-in machining using a non-rotational tool to establish final die machine finishing. We discuss machining tests with ultrasonic vibration added to machine prehardened steel, used mainly as a die material, to a mirror finish using a nonrotational diamond tool, and evaluate its usefulness.

ブリキ材の調質圧延における表面性状と潤滑油挙動

On the temper rolling especially importance of surface quality such as tin sheet, it is considered as the tribological study to obtain the homogeneous surface quality of the strip. The aims of this study are to examine systematically the effect of tribological factors on the surface qualities in the temper rolling for tin plate and to estimate the surface quality by the analysis of inlet oil film thickness. The temper rolling experiments were carried out, changing the rolling speed, the viscosity of lubricant and the surface roughness of tin plate. The oil film thickness in the inlet zone of contact region is calculated analytically based on Reynolds equation considering the surface roughness of the roll and the tin plate. From these experiment data, the qualitative relationship is found between the calculated oil film thickness and the surface qualities such as the brightness and the roughness. But it is difficult to interpret this relationship quantitatively. However, the surface brightness and the surface roughness are expressed as a function of the oil film thickness. To obtain the high brightness after temper rolling by the roll with mirror finish, it is required that rolling is carried out under the condition of minimum thickness of the inlet oil film as possible.

Study of mirror finishing of PCD by constant-pressure dry grinding

Study of mirror finishing of PCD by constant-pressure dry grinding

Corrosion protection of carbon steel by thin films of poly(3-alkyl thiophenes) in 0.5 M H 2SO 4

Poly(3-octyl thiophene) (P3OT) and poly(3-hexylthiophene) (P3HT) dissolved in toluene were deposited onto 1018 carbon steel and corroded in 0.5 M H 2SO 4. P3OT and P3HT films were chemically deposited by drop casting onto 1018-type carbon steel with two surface finishing, i.e. abraded with 600-emery paper and with alumina (Al 2O 3) particles of 1.0 μm in diameter (mirror finish). Their corrosion resistance was estimated by using potentiodynamic polarization curves, linear polarization resistance (LPR), and electrochemical impedance spectroscopy, EIS, techniques. In all cases, polymeric films protected the substrate against corrosion, but the protection was improved if the surface was polished with Al 2O 3 particles of 1.0 μm in diameter. The polymer which gave the best protection was P3HT because the amount of defects was much lower than that for the P3OT films. The polymers did not act only as a barrier layer against aggressive environment, but they improved the passive film properties by decreasing the critical current necessary to passivate the substrate, increasing the pitting potential and broadening the passive interval.

Development of a virtual machining and inspection system for ultra-precision diamond turning

The conventional approach to establish optimal processing conditions in ultraprecision diamond turning is empirical in nature. The achievement of a super mirror finish and submicrometre form accuracy in many current industrial applications still depends much on the experience and skills of the machine operators through trial cutting tests when new materials or new machine tools are used. In this paper, a virtual machining and inspection system (VMIS) is presented for ultra-precision diamond turning. The development of the VMIS aims at creating a virtual manufacturing environment for the optimization of process parameters and evaluating the quality of machined surface through various modelbased simulation modules. The VMIS is validated through a series of practical cutting tests conducted on a two-axis computer numerical control ultra-precision turning machine. The experimental results agree well with the simulated data.

A physical vapor deposition method for controlled evaluation of biological response to biomaterial chemistry and topography

The purpose of this study was to characterize a technique to effectively mask surface chemistry without modifying surface topography. A thin layer of titanium was deposited by physical vapor deposition (PVD) onto different biomaterial surfaces. Commercially pure titanium disks were equally divided into three groups. Disks were either polished to a mirror finish, grit blasted with alumina particles, or grit blasted and subsequently plasma sprayed with a commercial grade of hydroxyapatite (HA). A subgroup of each of these treatment types was further treated by masking the entire disk surface with a thin layer of commercially pure titanium deposited by PVD. A comparison of surface topography and chemical composition was carried out between disks within each treatment group. Canine marrow cells were seeded on all disk surfaces to determine the stability of the PVD Ti mask under culture conditions. The PVD process did not significantly alter the surface topography of any samples. The thin titanium layer completely masked the underlying chemistry of the plasma sprayed HA surface and the chemistry of the plasma vapor deposited titanium layer did not differ from that of the commercially pure titanium disks. Aliquots obtained from the media during culture did not indicate any significant differences in Ti concentration amongst the Ti and Ti-masked surfaces. The PVD application of a Ti layer on HA coatings formed a stable, durable, and homogenous layer that effectively masked the underlying surface chemistry without altering the surface topography.

A Framework of a Model-Based Simulation System for Prediction of Surface Generation in Fast Tool Servo Machining of Optical Microstructures

The fabrication of high-quality optical microstructural surfaces is based on fast tool servo (FTS) machining. It makes use of auxiliary piezo-electric driven servos to rapidly actuate the diamond tool with a fine resolution and a sufficiently high bandwidth for machining optical microstructures with submicrometer form accuracy and a nanometric surface finish without the need for any subsequent post processing. However, the achievement of a superior mirror finish and form accuracy still depends largely on the experience and skills of the machine operators, acquired through an expensive trial-and-error approach to using new materials, new mircostructural surface designs, or new machine tools. As a result, this paper, a model-based simulation system is presented for the optimization of surface quality in the FTS machining of optical microstructures. Preliminary experimental work and the results are also presented.

Laser induced damage studies in mercury cadmium telluride

We have investigated laser induced damage at 1.06 μ m laser wavelength in diamond paste polished (mirror finish) and carborundum polished Hg 0.8 Cd 0.2 Te (MCT) samples with increasing fluence as well as number of pulses. Evolution of damage morphology in two types of samples is quite different. In case of diamond paste polished samples, evolution of damage morphological features is consistent with Hg evaporation with transport of Cd/Te globules towards the periphery of the molten region. Cd/Te globules get accumulated with successive laser pulses at the periphery indicating an accumulation effect. Real time reflectivity (RTR) measurement has been done to understand melt pool dynamics. RTR measurements along with the thermal profile of the melt pool are in good agreement with thermal melting model of laser irradiated MCT samples. In case of carborundum polished samples, laser damage threshold is significantly reduced. Damage morphological features are significantly influenced by surface microstructural condition. From comparison of the morphological features in the two cases, it can be inferred that laser processing of MCT for device applications depends significantly on surface preparation conditions.

Development of Silica Polyvinyl Alcohol Wheels for Wet Mirror Grinding of Silicon Wafer

It is strongly desired to develop a cup grinding wheel which enables mirror finishing of a device wafer on the same machine after back grinding. Silica wheels have the capability of mirror finish in a dry condition but there remain serious problems in flatness and thermal damage to a dicing tape. A new silica wheel which can be used in a wet condition has been developed. The PVA (polyvinyl alcohol) was adopted as the bonding agent, by which the absorbent swell resulted in disturbance of water infiltration to the inside in cup grinding. A series of experiments show that mirror finishing will be achieved within 2 min. This could not be accomplished utilizing phenol wheels.

Hardide™: advanced nano-structured CVD coating

Hardide™ is a family of new low-temperature Chemical Vapour Deposition (CVD) Tungsten/Tungsten Carbide coatings. Coating consists of Tungsten Carbide nano-particles dispersed in metal Tungsten matrix, that give the material enhanced hardness of between 1100 Hv and 1800 Hv, and abrasion resistance up to 12 times better than Hard Chrome. Nano-structured materials show unique toughness, crack and impact-resistance. The coating is resistant to acids and aggressive media, can be produced on steel, including stainless steel and some tool steels, with coating thickness varied from 5 microns to 100 microns. Gas-phase CVD process allows coating internal surfaces and items of complex shape like dies, moulds, pump cylinders. Homogeneous pore-free structure facilitates finishing by honing, polishing, mirror finish can be achieved with suitable substrate. Use of Hardide with cutting tools for paper and plastics makes them self-sharpening. Application of Hardide increases life of tools and critical components and reduces down-time.

2036 SUS316L環状切欠き材の長寿命高サイクル疲労特性に及ぼす鏡面仕上げの影響(S11-3 表面処理・応力比等の影響,S11 金属材料の超高サイクル疲労特性の解明)

In order to investigate the effect of stress concentration and mirror finishing of austenitic stainless steel on very high cycle fatigue property, rotating bending fatigue tests were carried out on both circular notched and smooth specimens of SUS316L. It is shown that as a consequence of work-hardening caused by mirror finishing, the fatigue limit of mechanical polished specimens were about 6〜20% higher than that of electrochemical polished specimens. In the electrochemical polished specimens which did not break up to 10^8 cycles, a lot of slip bands were observed on the notch roots, but in the mechanical polished specimens, slip bands were not observed.

高性能超硬工具の開発

WC-Co cemented carbide with grain size less than 1μm is a very important tool material because it has high hardness and strength, and easily yields mirror finish and a sharp edge. On manufacturing the alloy, grain growth control is necessary. This report introduces effects of duplex addition of VC and Cr3C2 as a grain growth inhibitor.For investigating basic characteristics, submicro-grained WC-12mass%Co alloys with various amount of VC and Cr3C2 and with medium carbon content were used as a specimen which were heated up in vacuum to certain temperatures and immediately cooled. Some of them were fully sintered at 1380°C for 1 hr. They were examined by density measurement, TG-DTA, SEM, HRTEM, etc. Coarse-grained alloys were also used for analyzing binder composition by EPMA. Mechanical properties were measured using two series of submicro-grained specimens as above. One has fixed Cr3C2 content and varied VC content. The other is vice versa. They were vacuum-sintered at 1380°C for 1hr and HIP treated.Major results are as follows. (1) Similar to the alloy mono-doped with VC, duplex addition of VC and Cr3C2 (a) lowered liquidus temperature, (b) retarded densification from solid stage of sintering and abruptly increased density later, (c) remarkably controlled grain growth from solid stage, (d) formed micro-facets on WC grains composed of WC(1010) and WC(0001), and segregation of V mainly on WC(0001), and (e) decreased W content in the binder phase.(2) In the alloy series with fixed Cr3C2 content, grain size decreased with increasing VC addition to 0.5mass% and then was saturated, resulting in the corresponding change in hardness and fracture toughness. Bending strength and compressive strength had a peak at 0.2mass% and 0.5mass% addition of VC, respectively.(3) In the alloy series with fixed VC content, change in grain size was similar to that of the other alloy series though the critical value was 0.6mass%Cr3C2, and hardness and fracture toughness showed the same tendency as above. Bending strength was almost constant, and compressive strength increased up to 0.6mass%Cr3C2, then was saturated in the scope of this experiment. These changes in strength could be understood by considering the change in grain size, the fracture mechanism and the (V,W)C phase which precipitates in the binder phase over 0.5mass% addition of VC.

Ultrasonically Assisted Machining for Mirror Finishing of Die (2nd report)

Dies for injection molding parts such as cellular phones and light conductive parts require a high quality surface finish in terms of both appearance and integrity. Manual finishing is an important die manufacturing process, which decides the surface roughness of a die and influence the accuracy of its shape. However, manual polishing consumes several days to finish the die surface. Therefore, high precision die milling or grinding are required that improve surface roughness, in order to minimize polishing operation. In the previous report, ultrasonically diamond grinding experiments were carried out to confirm ultrasonically oscillation effect for die steel face grinding. And mirror surface was obtained. However, tool form error and run-out prevent 3D form mirror grinding. Because high shape accuracy tools are essential for high precision 3D form grinding. This paper provides results of toolmaking and performances of electroplated tools in ultrasonically assisted grinding. Electroplated tools can perform ultrasonically assisted face grinding and ground surface has roughness 0.24μmRz.

Study of mirror finishing process using magneto-rheological fluid

Study of mirror finishing process using magneto-rheological fluid

Development of a novel binderless diamond grinding wheel for machining IC chips for failure analysis

The objective of this research is to machine the silicon die of an IC chip and the surrounding chip packaging. The silicon die had to be reduced from a thickness of 85 μm to about 50 μm by a machining technique such that not a single transistor of the 40 million under the die is destroyed and at the same the die presents a mirror finish for examination on a back emission infra red microscope. The chip packaging had to be machined such that the six layers of power conduits in the form of copper traces and the dielectric (insulator) between them could be studied at low magnification for discontinuity. Initially electroplated diamond grinding pins were used for the die that was successful but it left undesirable tracks behind that remained even after polishing. These pins were not ideal for the soft but tough chip packaging. A new binderless diamond grinding wheel was developed that had a width equal to that of the IC chip die and also that of the width of the chip packaging with considerable success. This new wheel was also used to machine plano silicon and optical glass lenses successfully.

Study on Electrolytic-Abrasive Sphere Finishing

Based on the principle of sphere generating and Electrolytic-Abrasive Machining (EAM), a new EAM method —Electrolytic-Abrasive Sphere Finishing is developed. In the experiments, the tubular cathode is covered by unwoven nylon cloth, and the abrasive grains are provided together with electrolyte which flows through the tool electrode. This paper chiefly clarifies the features of this method, the selecting bases for the running specifications and the ways to control low current density. The experimental results show that the pulse current is conducive to paucity of metal removal, and mirror or quasi-mirror finish can be achieved conveniently.

Abrasive Characteristics on Mirror Finishing by Alumina Fiber Brush

This study aims to develop a novel mirror finishing method using an alumina fiber brush. This alumina fiber brush is used in the burr process and has high processing ability. This fiber brush generally can not be used for mirror finishing. However, authors have found a way to utilize these brushes in mirror finishing making use of peach powder slurry or WA grain slurry. This report describes the processing characteristics in the case of slurry mixed with peach powder or WA grains. The following results were obtained regarding the mirror finishing method using the alumina fiber brush: (1) Finishing with the alumina fiber brush improves the surface roughness and specular glossiness. (2) The filaments of the alumina fiber brush do not glaze with finishing debris. (3) The peach powder slurry decreases scratches on the processing surface and a mirror surface can be obtained. (4) A better mirror surface can be obtained using the mixed slurry of WA grains and peach powder.

Ultrasonically Assisted Machining for Mirror Finishing of Die (1st report)

Dies for injection molding parts such as cellular phones and light conductive parts require a high quality surface finish in terms of both appearance and integrity. In order to finish dies, manual polishing by a skilled worker has required after machining processes; such as EDM and milling. But the manual polishing causes poor flatness of dies and time consuming then expensive. So it is desired to establish a machining process to finish dies without manual polishing. In this study, a 3D positioning machine equipped with an ultrasonic spindle was used for grinding experiments. Electroplated diamond tools were equipped. Generally, diamond tool cannot grind steel because of the terrible wear due to chemical reaction between diamond and steel. However, ultrasonically assisted grinding can make fine surface (0.4∼0.84μmRz) of die steel, without observable tool wear. Effects of tool feed rate, radial depth of cut and axial depth of cut were investigated.

An Investigation into the Effect of Surface Roughness of Stainless Steel on Human Umbilical Vein Endothelial Cell Gene Expression

The surface properties of vascular devices dictate the initial postimplantation reactions that occur and thus the efficacy of the implantation procedure. Over the last number of years, a number of different stent designs have emerged and stents are generally polished to a mirror finish during the manufacturing procedure. This study sought to investigate the effect of stainless steel surface roughness on endothelial cell gene expression using an appropriate cell culture in vitro assay system. Stainless steel discs were roughened by shot blasting or polished by mechanical polishing. The surface roughness of the treated and untreated discs was determined by atomic force microscopy (AFM). Cells were seeded on collagen type 1 gels and left to attach for 24 h. Stainless steel discs of varying roughness were then placed in contact with the cells and incubated for 24 h. RNA extractions and quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR) was then performed to determine the expression levels of candidate genes in the treated cells compared to suitable control cells. E-selectin and vascular cellular adhesion molecule (VCAM-1) were found to be significantly up-regulated in cells incubated with polished and roughened samples, indicating endothelial cell activation and inflammation. This study indicates that the surface roughness of stainless steel is an important surface property in the development of vascular stents.

Abrasive Characteristics on Mirror Finishing by Alumina Fiber Brush

Abrasive Characteristics on Mirror Finishing by Alumina Fiber Brush