Polishing Technique Research Articles

Plasma-based isotropic etching polishing of synthetic quartz

Abstract To efficiently eliminate the surface defects and subsurface damage layer of synthetic quartz introduced by grinding, a plasma-based isotropic etching polishing (plasma-IEP) technique is proposed in this study. The smoothing of synthetic quartz by plasma-IEP is attributed to the formation, overlapping and merging of numerous and ultra-smooth etch pits formed by isotropic etching of SiO2 using inductively coupled plasma. Plasma diagnostics have revealed the existence of large amounts of etching radicals. The input radio frequency power and CF4 flow rate have been proved to be the two determinant factors of the material removal rate (MRR) of plasma-IEP. Under the optimized conditions, a maximum MRR of 5.62 μm/min of a 2-inch wafer has been achieved which is much higher than that of the conventional CMP process. After plasma-IEP for 30 min, the Sa roughness of the ground synthetic quartz decreases from 270.6 nm to 17.4 nm and the inner surface of the isotropic etch pits is smooth at the atomic level. The results presented in this paper demonstrate that plasma-IEP is a promising approach for the highly efficient and damage-free semi-finishing of synthetic quartz.

Experimental investigation and machine parameter optimization for nano finishing of fused silica using magnetorheological finishing process

Advanced optics design requires precise and super smooth finished glass surface. Most of the glasses that are used in the industries are Fused Silica, Bk7, Crown Glass and Boro-float glasses. Out of these, Fused Silica glass has a wide application in the field of optics. It has the capacity of withstanding and transmitting high energy laser pulses by limited absorption and having less deterioration to the material. It plays a major role, in the electromagnetic spectrum, specifically in the ultraviolet region. This paper describes about the non-conventional method of polishing technique. A sample of Fused silica glass has been considered and processed using Ball End Magneto rheological finishing method (BEMRF) with optimized machine and fluid parameters. This method has the capacity for polishing all sizes, shapes and types of materials. Advantage is that, subsurface damage can be minimized. This tool is being used for fabricating highly polished and precise optics. The increase in material removal with polishing time has resulted Fused silica glass sample with initial surface roughness of RMS 0.776 nm has been improved to RMS 0.257 nm by MRF polishing. Moreover, the surface roughness Ra has improved from the initial value of 0.594 nm to the final value of 0.165 nm. Further, the effect of polishing time on the volume of the material removal was also investigated. Based on the experimental results, the surface roughness and material removal are found as a function of the MR fluid condition and polishing time. Thus, angstrom level surface finishing on fused silica sample has been achieved by BEMRF technique.

Effects of Various Polishing Techniques on the Surface Characteristics of the Ti-6Al-4V Alloy and on Bacterial Adhesion

Ti-6Al-4V, although widely used in dental materials, causes peri-implant inflammation due to the long-term accumulation of bacteria around the implant, resulting in bone loss and eventual failure of the implant. This study aims to overcome the problem of dental implant infection by analyzing the influence of Ti-6Al-4V surface characteristics on the quantity of accumulated bacteria. Ti-6Al-4V specimens, each with different surface roughness are produced by mechanical, chemical, and electrolytic polishing. The surface roughness, surface contact angle, surface oxygen content, and surface structure were measured via atomic force microscopy (AFM), laser scanning confocal microscopy (LSCM), drop shape analysis (using sessile drop), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The micro and macro surface roughness are 10.33–120.05 nm and 0.68–2.34 μm, respectively. The surface X direction and Y direction contact angle are 21.38°–96.44° and 18.37°–92.72°, respectively. The surface oxygen content is 47.36–59.89 at.%. The number of colonies and the optical density (OD) are 7.87 × 106–17.73 × 106 CFU/mL and 0.189–0.245, respectively. The bacterial inhibition were the most effective under the electrolytic polishing of Ti-6Al-4V. The electrolytic polishing of Ti-6Al-4V exhibited the best surface characteristics: the surface roughness of 10 nm, surface contact angle of 92°, and surface oxygen content of 54 at.%, respectively. This provides the best surface treatment of Ti-6Al-4V in dental implants.

구분마연 청동무기와 제작도구

구분마연 청동무기와 제작도구

Overview of advanced manufacturing technology of large-aperture aspheric mirror

The aspheric surface can correct the system aberration and improve the image quality in the optical imaging system, in addition to that it can simplify the system structure significantly; On the other hand, the resolution of imaging system can be increased by improving the system aperture. Therefore, in the domain of basic scientific research, astronomical cosmological exploration and military defense security the large-aperture aspheric mirrors are all highly required. The manufacturing of large-aperture aspheric mirrors plays a critical role in modern optical engineering. This paper focuses on the advanced manufacturing techniques of large-aperture aspheric mirrors. The optical manufacturing technologies, especially the grinding and polishing techniques of large-aperture aspheric mirrors in the past half century and the surface shape testing methods during the grinding and polishing process, are reviewed. In particular, it summarizes the technical characteristics of advanced (new generation) optical manufacturing, and looks forward to the future manufacturing strategy of large-diameter aspheric mirrors.

Comprehensive study of the rapid stressed mirror polishing method for off-axis aspheric SiC thin-plate mirrors.

In this study, the stressed mirror polishing technique is used to perform off-axis aspheric silicon carbide (SiC) mirror full-aperture polishing for the first time. Mechanical and optical parameter analysis methods have been proposed. A medium-diameter off-axis aspheric SiC thin-plate mirror is used as a scaling model for an optical system mirror. A full diameter polishing simulation was completed, and a conceptual design for stress loading equipment is presented. An initial aspheric surface method for stressed mirror polishing of an off-axis aspheric SiC thin-plate mirror, providing a reference for rapid stress mirror polishing of SiC mirrors, is also proposed.

Effect of Different Finishing and Polishing Techniques on Surface Roughness of Two Universal Nanohybrid Composite Resins

AIM: This study investigated the effect of different finishing and polishing systems on surface roughness of two types of universal nanohybrid composite resins.
 MATERIALS AND METHODS: A total number of 40 samples will be prepared to form two main equal groups of specimens (n = 20), according to the composite resin materials. Two universal nanohybrid resin composites were used in this study. First group (A1) is a universal nanohybrid composite resin (Mosaic) and the second group (A2) is a universal nanohybrid composite resin (Harmonize). Each group was subdivided equally into four equal subgroups (n = 5), according to the used finishing and polishing systems. Mold was made to prepare the specimens with a central hole of 4 mm in diameter and 4 mm in thickness. Light curing tip was placed touching the glass slab for 20 s then the cured specimens were removed from the mold and the specimens immediately and immersed in distilled water at 37°C for 24 h. Surface roughness (Ra) was measured using light sectioning vision system. SEM was done to support the results.
 RESULTS: The results showed that the lowest (Ra) values were recorded by the specimens under Myler strip followed by Polishing Discs treated specimens followed by Diacomp Plus specimens and the highest (Ra) values were recorded by white polishing stone specimens and regardless to finishing or polishing, it was found that mosaic resin composites group recorded statistically significant (p < 0.05) lower roughness mean value than Harmonize resin composites group. p ≤ 0.05 is statistically significant in all tests.
 CONCLUSION: Achieving long-lasting esthetics in resin composites restorations needs special attention for obtaining optimal resin polymerization and a perfect surface finish using the appropriate finishing and polishing system.

Surface Roughness of Milled Lithium Disilicate With and Without Reinforcement After Finishing and Polishing: An In Vitro Study.

To determine the efficacy of various finishing and polishing techniques on the surface roughness of two computer-aided design/computer-aided manufacturing (CAD/CAM) materials, lithium disilicate (IPS e.max), lithium disilicate reinforced with lithium aluminosilicate (Straumann® n!ce™), and a stackable low-fusing nanofluorapatite glass ceramic (Ceram). Flat specimens (n = 12) per treatment group were fabricated 2 mm thick, 15 mm in length, and 12mm in width. Samples were either glazed or polished. Glazing was accomplished with either Ivoclar IPS e.max CAD crystall glaze spray or IPS e.max Ceram glaze paste, according to manufacturer instructions. Three different polishing systems were tested: Brasseler Dialite HP, Ivoclar OptraFine, and Komet LD/ZR. Polishing was performed using a Kavo adjustable slow speed electric contra-angle handpiece mounted to an oscillating Toothbrush Dentifrice Assessment Instrument. Surface roughness data was collected using a benchtop stylus profilometer and analyzed for statistical significance using two-way ANOVA (α = 0.05). Representative scanning electron micrograph images were generated for all samples. Overall there was no significant difference in Ra when comparing types of ceramic (p = 0.9315, F = 0.071). However, there was a statistically significant difference when comparing groups of finishing treatments (p < 0.001, F = 113.5) and also when comparing finishing treatment with ceramic type (p < 0.001, F = 11.13). No significant difference was found with IPS e.max CAD crystall glaze spray on Straumann® n!ce™ versus IPS e.max Ceram glaze paste on IPS e.max Ceram (p = 0.8745) or IPS e.max CAD crystall glaze spray on IPS e.max versus IPS e.max Ceram glaze paste on IPS e.max Ceram (p = 0.3373). Significant differences in Ra of Straumann® n!ce™ were found when comparing Brasseler with Ivoclar (p = 0.0014) and Ivoclar with Komet (p = 0.047). No significant difference was observed between Brasseler and Komet (p = 0.8099). It appears that the degree of surface roughness depends upon the specific finishing system and ceramic combination used. Straumann® n!ce™ is more efficiently polished using Brasseler Dialite HP or Komet LD/ZR polishing systems. Ivoclar crystal glaze spray was found to be equally as effective on Straumann® n!ce™ and IPS e.max as IPS e.max Ceram glaze paste on IPS e.max Ceram.

Double-side polished fiber for generation of mode-locked fiber lasers

A double-side polished fiber (DSPF) is fabricated for the passive generation of mode-locked pulses in an optical fiber ring cavity. The DSPF is made using a modified wheel polishing technique and coated with a cobalt oxide (Co3O4) solution as a saturable absorber (SA) to induce mode-locked operation by evanescent field interaction. The laser uses a thulium-holmium-doped fiber (THDF) for lasing in the two-micron region, with a mode-locked output having a pulse width of 1.44 ps. The repetition rate of the pulses is 11.8 MHz with a relatively high optical-signal-to-noise ratio value of 56 dB. This work demonstrates the fabrication method of the DSPF that would have potential applications as a SA for generating high power ultrafast lasers.

Investigation into Rheological Properties of Magnetorheological Polishing Slurry Using α-Cellulose as an Additive Agent and Its Polishing Performance

Magnetorheological finishing (MRF), considered as a promising polishing technique that can finish a nano-level smooth surface and free of surface or subsurface damage, has been widely utilized in ultra-smooth polishing of hard-to-machine materials. MRF process is mainly rely on shear stress to remove material. In this study, α-cellulose used as an additive agent to improve the rheological properties of magnetorheological polishing slurry (MRPS). The rheometer measurement results and polishing results showed that: (1) α-cellulose can enhance the shear stress of MRPS, but increased the apparent viscosity of MRPS. (2) α-cellulose can effectively improve the stability of MRPS, when the weight fraction of α-cellulose was 0.6 wt%, both stability and internal uniform of MRPS can be obtained. (3) If the weight fraction of α-cellulose was bigger than 0.6 wt%, the machining ability of MPRS was stable and the smooth polished surface can be obtained.

Influence of global and local process gas shielding on surface topography in laser micro polishing (LμP) of stainless steel 410

Laser micro polishing (LμP) is a new laser-based material processing method that has a high potential to overcome common disadvantages of traditional polishing techniques. A special challenge in LμP is the processing of large areas since processing in a process gas atmosphere is deemed necessary to avoid undesired oxidation and minimize surface roughness. Therefore, a new process strategy for LμP on stainless steel AISI 410 was investigated in which a gas nozzle was used to create a local process gas shielding and therefore to significantly increase the field of maximal processing. Using a Nd:YAG high power Q-switch laser, we demonstrated that local process gas shielding is feasible for LμP in terms of avoidance of surface defects and achieved micro-roughness. In addition, a wide process window in terms of nozzle distances and gas flow exists for LμP. The resulting surfaces are highly reproducible in terms of surface roughness. Besides Argon, Nitrogen is another process gas that is highly suitable for LμP of AISI 410. The use of Nitrogen might therefore significantly lower future production costs in LμP. Finally, spatially resolved LμP was explicitly demonstrated on a textured press plate.

Double-Sided Polishing Simulation Based on the Gap Theory - Theory of Pressure Distribution Analysis and Conditions for High Flatness

The double sided polishing technique is often applied to achieve high total thickness variance (TTV) of large silicon wafers that are employed to manufacture integrated circuit (IC) cards and smartphones. However, the theoretical analysis of high TTV is not sufficiently studied for the double sided polishing. Whereas, a polishing simulation for single sided polishing based on the gap theory was already developed. This simulation results were compared to the experimental results and indicate good behavior characteristics. This study presents a description of the theory for analyzing pressure distribution for double sided polishing and the simulation results of the surface generation process. It was demonstrated that the average of total running distance is nearly equal for the upper and the lower plates. Improved flatness is obtained when the rotation speed differences of the upper and lower plate rotations for the carrier revolution are equal. Furthermore, it was shown that TTV of less than 0.04 μm with a flatness of less than 0.05 μm may be attained when the cone upper plate with the optimum slope and the flat lower plate are employed with lower carrier rotation.

Fluid-jet technique to polish the posterior capsule for phacoemulsification surgeries: efficacy and safety evaluation.

To compare the efficacy and safety of a fluid-jet technique with capsular polish in reducing residual lens fibers (RLFs) in phacoemulsification surgery. Single center. Prospective nonrandomized comparative study. Patients receiving phacoemulsification were included. Consecutive eligible patients alternately underwent either removal of RLFs on the posterior capsule using capsular polish after irrigation and aspiration, and before intraocular lens (IOL) implantation, or RLF removal using a fluid-jet technique after IOL implantation. Posterior capsular images were used to quantify RLFs. Visual parameters were evaluated at 1 day, 1 week, and 1 year postoperatively. The proportion of capsule occupied by posterior capsule opacification (PCO) (area %) and incidence of protocol-driven laser posterior capsulotomy were recorded at 1 year in masked fashion. Seven hundred forty eyes were allocated to polishing (n = 370) or fluid-jet technique (n = 370). Polishing required 70.4 ± 17.5 seconds and fluid-jet 32.2 ± 9.9 seconds (P ≤ 0.001). Compared with the polishing group, capsular area occupied by RLFs in the fluid-jet group was significantly smaller (3.5% vs 0.5%, P = .031) at the end of surgery. One day postoperatively, the fluid-jet group had more desirable corrected distance visual acuity, objective scattering index, and Strehl ratio (all P < .05). PCO area percentage did not differ between groups (6.5% vs 4.5%, P = .252) 1 year postoperatively, but incidence of posterior capsulotomy was lower in the fluid-jet group (3.2% vs 0.8%, P = .019). Fluid-jet removed RLFs effectively and had lower incidence of postoperative capsulotomy than capsular polishing.

Implications of using two low-power continuous-wave lasers for polishing

Laser polishing is widely employed to reduce the surface roughness of products with complex geometries. Traditional laser polishing techniques use a single high-power Gaussian beam to melt and smooth a thin layer of surface material. However, the reliance on high power lasers can present practical challenges such as minimizing surface evaporation or reducing overall cost. In this work, we combined two identical low-power laser beams with a spatial offset in between them to construct an elliptical beam. By changing the spatial offset, combined beams with different lengths along the major axis can be created. We observe over 20% improvement in line roughness reduction using this approach compared to a single Gaussian laser beam with the same total power. Additionally, both experiment and simulation results suggest such improvement is because this dual-laser set-up can create a longer molten pool compared to a single laser.

Dry mechanical-electrochemical polishing of selective laser melted 316L stainless steel

This paper aims to improve the surface quality of 316L stainless steel parts manufactured by selective laser melting (SLM) using dry mechanical-electrochemical polishing (DMECP). DMECP is an advanced surface finishing method combining the advantages of both mechanical and electrochemical polishing techniques in a more environmentally friendly manner. In this paper, the SLM process-related defects causing poor surface quality are analysed first. The material removal mechanism of DMECP is investigated to continuously remove the oxide layers formed during polishing. Surface morphology and roughness evolution under different polishing conditions are characterised. The top surface roughness can be reduced by over 91% from 8.72 μm to 0.75 μm compared to side surface by over 93% from 12.10 to 0.80 μm. The material removal on the top surface is more efficient than that on the side surface under the same polishing condition. The secondary defects formed during polishing can be removed using mechanical polishing mode. The chemical element composition of the polished surface exhibits almost identical content to the initial 316L powders. Compared with the initial dark and rough surfaces, the results validate the capability of DMECP as an effective tool to improve the SLM surface quality and achieve a mirror finish.

Use of extra-fine crosscut bur to produce horizontal texture in composite resin restorations

Reproducing the developmental lobes and perikymata of the anterior teeth of young patients with composite resin restorations is a clinical challenge.1-3 Different finishing and polishing systems and techniques are available, although a standard protocol is lacking. The selection of the correct instruments will depend on the position of the tooth and the type of surface to be reproduced. Multibladed and diamond rotary instruments and abrasive rubber points are commonly used for this procedure.4

Effect of the components of Magnetic Compound Fluid (MCF) slurry on polishing characteristics in aspheric-surface finishing with the doughnut-shaped MCF tool

For the aspheric optical surface finished with a doughnut-shaped MCF (magnetic compound fluid) polishing tool, the performance of the polishing tool depends mainly on the properties of the MCF slurry. Therefore, understanding the effect of each MCF slurry component on the polishing characteristics is crucial to developing novel polishing techniques. In this paper, the polishing principle was depicted and the corresponding polishing jig was constructed with a six-degree-of-freedom manipulator. The conical surfaces, which were considered as special aspheric surfaces, were experimentally polished under proper polishing conditions to examine the effects of the carbonyl iron particles (CIPs) concentration and the sizes of the abrasive particles (APs) on the polishing ability to remove material/tool marks and improve work surface qualities. Theoretical analyses were also performed to gain a more comprehensive understanding of the behaviors of CIPs and APs in the magnetic field. The results were shown as follows: (1) The CIPs concentration affected positively the magnetization of the MCF slurry, leading to better performance in the removal rate of material/tool marks when a higher CIPs concentration of was applied. The best surface quality was attained with a CIPs concentration of 45 wt%. (2) Larger APs were beneficial for obtaining higher removal rates of material/tool marks. The APs with 1 μm in diameter were preferred for achieving a better surface quality. (3) Ferric clusters were formed along the magnetic line of force and their orientations changed periodically to stir the APs with the magnet revolution. (4) The Aps, at a given working gap, can squeeze the work-surface. The squeezing action was much more intense when larger APs and the MCF slurry with a higher magnetization were employed. (5) The material removal model suggested that the material was removed due to the APs and the relative motion between the work-surface and APs.

D-shape Fiber Coated with Indium Tin Oxide for Temperature Sensor Application

We designed a temperature sensor by using a D-shape fiber coated with indium tin oxide as a sensing probe. D-shape fiber was fabricated out of conventional single mode fiber by a homemade setup using wheel polishing technique. Insertion loss of D-shape fiber was about 3.5 dB. ITO was deposited over the D-shape fiber by electron-beam deposition technique to have precise deposition of 60nm thin film over the D-shape region of fiber to be utilized as a sensor. It is observed that the transmitted power increased with the increase in temperature with a sensitivity of 0. 0013 dBm/°C. The proposed sensor also provides a good linearity and stability.

Experimental investigation of mid-spatial frequency surface textures on fused silica after computer numerical control bonnet polishing

Automated bonnet polishing is achieved using computer numerical control (CNC) technology. However, owing to specific toolpaths, CNC bonnet polishing is generally accompanied by the mid-spatial frequency (MSF) of surface textures on polished surfaces that could produce surface ripples or waviness and degrade image quality. In this study, the MSF surface textures on fused silica are investigated by developing a CNC bonnet polishing technique using a cerium oxide-filled polyurethane pad (LP66)—a cellular polyurethane material designed to handle high flatness and surface finishing requirements for optical glass materials. To minimize the MSF, optimal combinations of various polishing parameters, including tool offset, head speed, track spacing, and surface feed rate, are studied. Experimental results demonstrate that the head speed and feed rate significantly affect the surface texture during bonnet polishing. Although the tool offset does not cause surface textures, the material removal rate is affected. A series of optimization experiments is conducted, consequently leading to the effective removal of irregular surface ripples and a reduction of MSF errors. By optimizing the polishing parameters, extremely accurate surface quality is achieved, along with a root mean square error of 1.6 nm. These results demonstrate the potential applications of LP66 in CNC bonnet polishing for highly accurate freeform optical components.

Nonlinear Hydraulic Pressure Response of an Improved Fiber Tip Interferometric High-Pressure Sensor.

We demonstrate a silica diaphragm-based fiber tip Fabry–Perot interferometer (FPI) for high-pressure (40 MPa) sensing. By using a fiber tip polishing technique, the thickness of the silica diaphragm could be precisely controlled and the pressure sensitivity of the fabricated FPI sensor was enhanced significantly by reducing the diaphragm thickness; however, the relationship between the pressure sensitivity and diaphragm thickness is not linear. A high sensitivity of −1.436 nm/MPa and a linearity of 0.99124 in hydraulic pressure range of 0 to 40 MPa were demonstrated for a sensor with a diaphragm thickness of 4.63 μm. The achieved sensitivity was about one order of magnitude higher than the previous results reported on similar fiber tip FPI sensors in the same pressure measurement range. Sensors with a thinner silica diaphragm (i.e., 4.01 and 2.09 μm) rendered further increased hydraulic pressure sensitivity, but yield a significant nonlinear response. Two geometric models and a finite element method (FEM) were carried out to explain the nonlinear response. The simulation results indicated the formation of cambered internal silica surface during the arc discharge process in the fiber tip FPI sensor fabrication.