Polishing Disk Research Articles

Experiment on Chemical Magnetorheological Finishing of SiC Single Crystal Wafer

Experiment was performed to examine the plane polishing of SiC single crystal wafer by using the chemical magnetorheological finishing (CMRF) technique. The influence of some process parameters such as the concentration of diamond abrasive particles, the concentration of carbonyl iron powder and the machining gap in CMRF were studied comparing with the magnetorheological finishing (MRF) method. The results show that the surface roughness of polished SiC single crystal by the CMRF is slightly lower than that by the MRF. Polishing liquid with different components and processing parameters affects the coupling effect of mechanical removal and chemical removal in CMRF, and a better coupling effect can produce a better surface quality in CMRP. In the MRF, the surface roughness of SiC single crystal is lower for a higher concentration of carbonyl iron powder (CIP). However, in the CMRF, the CIP’s concentration may change the contact state between the catalyst and SiC, and the CIP’s concentration of about 20% can produce a better surface roughness of SiC. The machining gap between the polishing disk and the workpiece surface determines the processing effect, and the machining gap of 1.0 mm is suitable for the polishing of SiC in the MRF and CMRF.

A hydrodynamic suspension polishing method for ultrasmooth and low-damage surface

A novel polishing process was proposed based on the hydrodynamic phenomenon. The structure of the polishing disk was designed to form the optimal distribution of the hydrodynamic stress. Computational fluid dynamics (CFD) simulation was conducted to assist the structure design and discuss the relative mechanism. The influence of the rotating speed and suspension distance of the polishing disk on the hydrodynamic stress field were also investigated by CFD method, respectively. The microscale material removal mechanism was discussed. And then a novel polishing device was fabricated. The quality of the polishing samples were discussed. Results showed that the novel polishing disk with the wedge region, constraint boundary and flow storage tank can realize the stable hydrodynamic stress field in the workpiece region. The higher rotating speed and the shorter suspension distance both raised the magnitudes of the hydrodynamic stress. The kinetic energy of the polishing abrasive can destroy the bonding energy of the atom under the sufficient rotating speed. The stripping or moving of the raising atoms on the workpiece surface was the reason for the ultrasmooth surface. The experimental results showed that the ultrasmooth surface can be obtained by the present novel polishing process. And there were almost no machining deformation layer and micro damages.

Ingenious technique of smoothening costal cartilage graft by glass polishing disc.

Ingenious technique of smoothening costal cartilage graft by glass polishing disc.

Characterisation of asphalt pavement surfaces using torque measurements

Continuous increase in traffic volume in the recent years has resulted in greater surface friction loss of asphalt pavements. While the literature presents several ways of aggregate and asphalt mix screening to ensure that surface characteristics are at an acceptable level of friction to control skid-related accidents, the recommended polishing tests using different accelerated polishing devices are time-consuming and to some extent labour-intensive. Therefore, it is imperative that existing polishing devices be improved to shorten the test duration to a level desired by the industry as well as state and federal agencies. This paper aims at addressing this improvement that uses power unit (or motor) to generate energy enough to rotate the polishing disk at constant rotational speed while being pressed against the specimen surface, then read the power needed from the display screen for the following steps. Multiple verification techniques including comparison studies and statistical analyses were used to examine the validity of this improvement. It was found that data collected by the power unit was repeatable and able to precisely detect surface deterioration history for different asphalt mixes with different polish susceptibility in a manner similar to conventional friction and texture-measuring devices. Hence, aggregates and mixes were classified based on their surface frictional properties. Additionally, results from this study correlated well with results from other studies using conventional methods. Most importantly, it was found to be possible to cut down the polishing test time using torque values in lieu of conventional surface quantification methods.

Material removal mechanism of cluster magnetorheological effect in plane polishing

A cluster magnetorheological (MR) plane polishing based on a combination of magnetorheological finishing (MRF) and cluster mechanism (arrange in a regular array) has been developed for large planar optical workpiece. In this paper, the polishing pressure of an individual MR micro-grinding head on workpieces was investigated, and the mathematical model for cluster MR plane polishing was established based on the Preston equation and the properties of the workpiece material. An arc-shaped polishing belt was processed on monocrystalline 6H-SiC and Si wafer by the cluster MR polishing apparatus which polishing disk inlaid with cylindrical flat bottom magnetic pole arrange in the same direction regularly and monocyclically. The profile of arc polishing belt’s cross section and the surface morphology were observed and analysed to verify the obtained model. The abrasives with different size were found to have an equal effect on the processed surface because of the accommodated-sinking effect of the polishing pad constituted by the cluster MR micro-grinding head. It was found that the monocrystalline 6H-SiC and Si wafer were polished in a plastic mode with a smooth, damage-free surface.

Study on the influence of the rotational speed of polishing disk on material removal in aspheric surface compliant polishing

When a soft polishing tool is compressed on a stiff workpiece of curved surface, the contact area is a piece of the curved surface. In the process of aspheric surface polishing, the machining speed is always provided by the rotational speed of the spindle of a computer numerical control lathe. Yet, the polishing tool is usually made rotating to remove cutting scraps and broken abrasives from the contact area. The rotational speed of the polishing tool would change the distribution state of the relative speed in the whole contact area, and it would definitely change the volume of material removal in the surface of the workpiece. This article studies how the rotational speed of the polishing tool changes the distribution state of the relative speed in the whole contact area and material removal in the volume of the surface of the workpiece. The computing results show that the volume of material removal increases with the increase in both the rotational speed of polishing disk and the rotational speed of lathe spindle, but the polishing quality is totally not in this case.

Research on a processing model of CMP 6H-SiC (0001) single crystal wafer

Firstly, this paper presents an orthogonal test of six factors and five levels, called the chemical mechanical polishing (CMP) process parameters experiment, for determining the best process parameters and ranking the influencing factors from primary to secondary. The three most important factors are the polishing pressure, the polishing liquid concentration and the relative velocity ratio of polishing disk to polishing carrier. Then, based on this analysis, the three factors and three levels of the quadratic orthogonal regression test are put forward. A mathematical model impacting the surface roughness has also been set up. Finally, this work has achieved a polished wafer, whose material removal rate (MRR) is in the range of 70–90 nm/hand the surface roughness (Ra) is between 0.3 nm and 0.5 nm.

Investigations on the automatic precision polishing of curved surfaces using a five-axis machining centre

Polishing is usually indispensable process when better surface roughness is required for the parts such as injection mold. However, polishing process is often performed by manual operations. In this paper, an automatic polishing method for the metal parts with curved surfaces is proposed based on a machining centre. In order to realize the control of contact force, the relationship between the displacement of polishing disk and the force impacted on the polished part is first established. Then, within the contact zone between the polishing disk and the polished part, a pressure distribution model is derived for planar and curved surface polishing according to the specific process parameters. On this basis, the model of removal depth distribution along the vertical direction of feed is built for each polishing pass, and thus a suitable stepover size is further obtained so as to reduce the fluctuations of remove depth to most extent. Finally, an effective planning algorithm of cutter location data in polishing is proposed for a given CNC machine tools, and validation experiments are performed on planar and curved parts. The results show that the proposed automatic polishing scheme is able of achieving a mirror effect surface and keep a good global uniformity, at the same time it improves the polishing efficiency and realizes the integration with milling process.

Kinematics of 2 Reciprocating Endodontic Motors: The Difference between Actual and Set Values

IntroductionThe aim of this study was to evaluate the kinematics of 2 reciprocating motors and compare it with manufacturers' declared values. MethodsVDW Silver (VDW, Munich, Germany) and ATR Tecnika (Tecnika, Pistoia, Italy) were used in the study in 5 working modes: continuous rotation at 400 rpm on VDW Silver and ATR Tecnika and reciprocating motion on ATR Tecnika at 400 rpm and on VDW Silver in Reciproc and WaveOne mode. The polishing disk with an optical target was inserted in the contra-angle and recorded with a 1000–frames per second video camera. The direction and the amount of rotation were analyzed by computer, and the following kinematics parameters were calculated: engaging and disengaging angles, cycle rotational speeds, engaging and disengaging rotational speeds, net cycle angle, total cycle angle, and number of cycles to complete full rotation. One-way analysis of variance followed by planned pair-wise comparisons was used to compare kinematics parameters. The alpha error was set to 0.05. ResultsAnalysis of variance revealed a difference between actual and set values of all 3 reciprocating modes in all kinematics parameters (P < .001). No significant difference between the actual engaging angle of Reciproc and that of the WaveOne mode was found. For reciprocating motion on the ATR Tecnika at 400 rpm, the actual engaging and disengaging angles were 8- and 9-fold greater, respectively, compared with set angles (P < .001). ConclusionsThe kinematics of reciprocating instrumentation is more complex than it seems as described only with angles and rotational speed. Actual kinematics values differ from manufacturers' declared values.

光束整形系统异形元件的研制

In order to realize the aspheric cylindrical mirror of high precision processing,and solve the difficult problems in this field,the aspheric cylindrical mirror processing and testing methods are deeply researched. Classical and modern processing methods are adopted and odd-form component for beam shaping system are fabricated in this paper,which is composed of aspheric cylindrical mirror and cylindrical mirror. A unique production of polishing disk is proposed aiming at the problem that the surface shape is controlled hardly. Results show that the surface error is 0. 848 7μm by the profilometer detecting,which can meet the operational requirement of the optical elements.

Study on Surface Feature of Large Die and Polishing Quality during Floating Polishing

During the transferring process of the large die surfaces, there are extensive needs of die surface polishing. Since almost large die surfaces are free-form surfaces, currently, these are almost manually implemented. In order to overcome this barrier, in this paper, firstly, large die surfaces were geometrically characterized, and their polishing processes for the die surfaces features were then analyzed; secondly, the polishing pattern and structure of the floating polishing head were studied, finally, the affecting factors of polishing quality about the floating polishing were studied experimentally versus roughness of polished surfaces with the developed floating polishing experimental prototype in this paper. The affecting factors of polishing quality include the rotation speed of polishing discs, normal acting force on polishing disc, loci of polishing disc movement, feeding rate of polishing disc, grit of abrasive particles, and inclined angle of the acting force on disc, are synchronized and analyzed. These research results are used as operating guides for applications of the floating die polisher.

Research on Computer Controlled Optical Surfacing (CCOS) Working Function at Wear State

The distribution of working pressure in CCOS has been studied when the polishing disc frayed. Combined with the planetary motion, the working functions at wear and ideal states were calculated separately, the result shows that the function peak is higher at wear state and it is a convex curve instead of a concave curve at ideal state. The impact of different wear loss on the working function has been also studied in this paper, one preliminary conclusion has been obtained that with the increasing of the wear loss, the working function peak will get higher and sharper, and the effective range of processing will decrease meanwhile. It can be predicted that although the removal rate may not change obviously at the initial stage of wear, the processing quality may decrease and the processing stability will be worse since the variation of the removal distribution.

Study on a New Glass Polishing Plate

This paper reports a polishing disk which can substitute for rare earth. Using alumina - cerium oxide core-shell composite abrasive as abrasive, unsaturated resin as bonding agent, abrasive tool can be prepared by adding a water soluble pore-forming agent, suitable heat absorbing agent and active stuffing and the suitable addition amounts which are 25.6%, 46.8%, 18.5%, 3.8% and 1.2%, respectively .This abrasive tool can conduct the temperature in the grinding zone rapidly. It also has high grinding efficiency smooth polishing surface and without cracks or scratches, which meet furthermore, it has the merits of low cost and extensive use prospect. The polishing effect of rare earth polishing disk, but the low cost make it suitable for wide promotion.

Experimental Research on Smooth Surface Polishing Based on the Cluster Magnetorheological Effect

A new planarization polishing method, based on the cluster magnetorheological (MR) effect and using MR fluid to form the flexible polishing pad, is presented in this paper to polish optical glass. To explore the machining characteristic of the viscid and flexible polishing pad based on the cluster MR-effect, some process experiments were conducted to reveal the influence of the machining gap, the speed of the polishing disc and the polishing time on the machining effect. The results indicate that the viscid and flexible polishing pad based on the cluster MR-effect under a strong magnetic field can reduce surface roughness effectively. When the strength of the magnetic field is 2000Gs, and the content of the carbonyl iron is 12%, the surface roughness can be reduced rapidly from the original Ra0.27μm to Ra1.4nm based on the cluster MR-effect.

Abrasive Particles Trajectory Analysis and Simulation of Cluster Magnetorheological Effect Plane Polishing

Abstract Kinematics model of abrasive particles for certain eccentric and linear interpolation swing uncertain eccentric, uncertain eccentricity of X direction and Y direction in plane polishing based on cluster magnetorheological(MR) effect are built and simulated by computer, and also obtain the influence law of key factors such as the speed ratio r of polishing disk and workpiece, the eccentricity e to polishing disk, the distance of abrasive particles P to the center of polishing disk, the ratio F of swing range A and swing speed V to polish quality. At last, polishing experiment for single crystal 6H-SiC is carried out on the experiment equipment of the cluster MR effect by selecting optimized parameters through the simulation results, which verified the correctness of the simulation results.

Influence of various polishing methods on pulp temperature

After orthodontic debonding, adhesive removal can lead to rises in pulp temperature, causing histological changes or pulp necrosis. The objective of this study was to measure increases in pulp temperature during adhesive removal using different instruments and various cooling procedures. A thermoelement was introduced into the pulp chamber of 10human incisors. The teeth were immersed in a 36°C water bath up to the cementoenamel junction. Two carbide burs, one polishing disk and two rubber points were used for polishing. All measurements were taken over a 10s period by a single investigator, under slight pressure and with constant motion. Three cooling procedures were examined: no cooling, air cooling and water cooling. Pulp temperatures were measured before polishing and after 10s of polishing. Without cooling, the two rubber points revealed clinically relevant temperature increases of 6.1°C and 12.4°C. Cooling with air and with water reduced pulp temperature in conjunction with all polishing methods. Air cooling was most efficient, except in combination with the polishing disk. Under these study conditions, carbide burs and polishing disks can be used safely and without risk to the pulp, even without cooling. On the other hand, rubber points cause a marked increase in pulp temperature when used without cooling.

Effects of different surface treatments on the color stability of various dental porcelains

Background/purpose There is a lack of information in the few studies reporting on the stainability of dental porcelain materials. However no studies have been found that investigated effects of polishing methods and staining agents on the color stability of dental porcelains. The purpose of this study was to evaluate the effects of different polishing techniques on the color stability of various dental porcelains. Materials and methods Fifty-five specimens were prepared for each of feldspathic (Vita VMK 95, Ceramco III), low-fusing porcelain (Matchmaker), and machinable feldspathic porcelain blocks (Vitablocs Mark II). The prepared specimens were divided into 11 groups ( n = 5) representing different polishing techniques including a control (no surface treatment), glaze, and nine other groups which were finished and polished with a polishing disc (Sof-Lex), two porcelain polishing kits (NTI, Dialite II), a diamond polishing paste (Sparkle), a zirconium silicate-based cleaning and polishing prophy paste (Zircate), an aluminum oxide polishing paste (Prisma Gloss), and combinations of these. Specimens were stored for 48 hours at 37°C in a coffee solution. The color of all specimens was measured with a colorimeter before and after exposure, and color changes (ΔE) were calculated. Data were analyzed with a two-way analysis of variance, and mean values were compared by the Tukey’s honest significant difference test (α = 0.05). Results When comparing the four different porcelain materials, Ceramco III demonstrated the highest ΔE value. No significant difference was observed among the porcelain material groups of Mark II, Matchmaker MC, and VMK 95 (P = 0.074). When comparing the polishing techniques, the lowest ΔE values were observed in Group Gl for all porcelain materials tested. No significant difference was observed among Groups Sl, Di, and Pk, (P = 0.883), and these Groups demonstrated significantly higher ΔE values than Group Gl (P < 0.05). Conclusions Within the limitations of this study, the results suggest that feldspathic and low-fusing porcelain specimens were found to be more color-stable for glazed specimens versus polished specimens regardless of whether they were stained with the coffee solution. Glazed and polished specimens with different polishing materials demonstrated that the ΔE values were at an acceptable level for all of the porcelain materials tested (1 < ΔE < 3.7).

Comparison of Two-Step Versus Four-Step Composite Finishing/Polishing Disc Systems: Evaluation of a New Two-Step Composite Polishing Disc System

The purpose of this study was to evaluate surface finish and gloss of a two-step composite finishing/polishing (F/P) disc system compared with two multistep systems on five composites. Seventy-five disc-shaped composite specimens (D=10.0 mm, 2 mm thick, n=15 per composite) were made of microfill (Durafill-D), nanofill (Filtek Supreme-FS), nanohybrid (Premise-PR), and microhybrids (Filtek Z250-FZ, Esthet-EX). One side of each specimen was initially finished with a carbide bur. Five specimens of each resin composite were randomly assigned to receive full F/P by each of the disc systems: two-step (Enhance Flex NST-EF) and four-step (Sof-Lex-SL, Super-Snap-SS). Surface gloss was measured with a glossmeter and surface roughness was measured with a profilometer. Results were analyzed by two-way analysis of variance (ANOVA)/Tukey's (α<0.05). No difference in gloss was noted among the three F/P systems when used with D and EX; no difference between SL and EF when used with any composite, except for FS; and no difference between SL and SS when used with any composite. SL and EF showed similar surface roughness when used on all composites, except for EX. EF and SS showed similar surface roughness on PR. SL and SS showed similar surface roughness values on every composite, except for FZ. EF was capable of providing similar gloss and surface roughness to SL on four composites evaluated but was not able to produce as glossy or as smooth a surface as SS for three of the five composites.

Study on Contact Friction between Polishing Disk and Workpiece during Face Polishing with ANSYS

Since almost large die surfaces are free-form surfaces, currently, these are almost manually implemented. In order to overcome this barrier, floating polishing is a feasible polishing technology. The contact friction between polishing disk and workpiece is a key problem of floating polishing technology. This paper tries to study the contact friction between polishing disk and workpiece with ANSYS analysis software. At first, the paper focuses on the contact friction between polishing disk and plane workpiece by ANSYS analysis software, then focuses on the contact friction between polishing disk and cylinder and sphere workpiece with the software. The analysis results show the hypothesis of full friction condition is feasible. The research results will be used for developing the floating polishing.

Influence of Magnetic Field Strength on Polishing Effect of the Tiny-Grinding Wheel Cluster Based on the Magnetorheological Effect

A new tiny-grinding wheel cluster polishing method based on the Magnetorheological (MR) effect is presented to polish optical glass in this paper and some process experiments were conducted to reveal the influence of magnetic field strength, the content of carbonyl iron in the MR fluid and the speed of polishing disc on the material removal rate and the surface roughness of the glass workpiece. The results indicate that when the external magnetic field is applied, the material removal rate of the workpiece improves rapidly but the surface roughness increases slightly. When the Magnetic field strength is 100 Gs and the content of carbonyl iron is 3.5%, the material removal rate improves by a factor of 16.8% compared with that of the conventional polishing methods with dissociative abrasive particles, while the surface roughness of the workpiece increases unobviously.