A Global Correction Process for Flat Optics With Patterned Polishing Pad

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Weisi Li ◽  
Ping Zhou ◽  
Zhichao Geng ◽  
Ying Yan ◽  
Dongming Guo
Keyword(s):  
Optical Glass ◽  
Removal Rate ◽  
Surface Profile ◽  
Prediction Method ◽  
Correction Method ◽  
Polishing Process ◽  
Polishing Pad ◽  
Edge Exclusion ◽  
Optics Fabrication ◽  
Surface Figure

To improve the efficiency of flat optics fabrication, a global correction method with the patterned polishing pad is developed in this paper. Through creating grooves on a polishing pad, the contact pressure distribution on the optics surface can be adjusted to change the material removal rate (MRR) distribution during polishing. Using the patterned pad, the selective removal ability of the polishing process is greatly enhanced. The predictability and stability of the MRR distribution are the preconditions to efficiently implement the proposed global correction method. Relying on the MRR distribution prediction method proposed and validated in this paper, the pad pattern can be designed based on the original surface figure of the workpieces. The designed groove pattern is created on the polishing pad using the custom-developed equipment. Then, the optical glass is polished on the designed pad with the optimized polishing time. A flat optical glass sample (Φ 100 mm) is polished with the global correction method to show its feasibility and advantage. The correction instance shows that the peak-to-valley (PV) value of the surface profile (with 3 mm edge exclusion) dropped from 1.17 µm to 0.2 µm in 14 min using a polyurethane pad with two ring grooves. Comparing with the conventional polishing process, which usually takes hours or days, the global correction method proposed in this paper can improve the efficiency of the optics manufacturing significantly.

Effects of the Profile of Workpiece Surface on Material Removal Rate Distribution in Polishing Process

2016 ◽  
Vol 851 ◽  
pp. 149-154
Author(s):  
Zhen Gang Wu ◽  
Dong Shan He ◽  
Ping Zhou ◽  
Dong Ming Guo
Keyword(s):  
Material Removal Rate ◽  
Material Removal ◽  
Removal Rate ◽  
Surface Profile ◽  
Prediction Method ◽  
Quantitative Prediction ◽  
Polishing Process ◽  
Workpiece Surface ◽  
Coefficient Distribution ◽  
Polishing Pad

Accurate prediction of the material removal rate (MRR) distribution is very important for the control of the polishing process. However, the widely used prediction method of MRR based on the Preston equation is still incapable of predicting the roll-off phenomenon in polishing process. One of the reasons is that many of the researchers’ neglected the effect of the surface profile of the workpiece on the MRR. In this paper, the evolutionary process of MRR distribution with the change of surface profile using two different polishing pad is studied, it is found that MRR varies gradually with the change of surface profile and tends to be uniform finally. Based on the analysis of contact pressure considering the actual surface profile of workpiece and modified Preston equation, the distribution of MRR is analyzed. It is found that the Preston coefficient distribution on workpiece surface is stable when the surface profile variation is small and shows obvious differences from the center to the edge of the workpiece. Through the comparison it is found that correlation between the regularities of Preston coefficient distribution and the type of polishing pad is significant. The research results in this paper will play an important guiding role in the quantitative prediction method research of polishing process.

Prediction of Surface Profile Evolution of Workpiece and Lapping plate in Lapping Process

2021 ◽  
pp. 1-34
Author(s):  
Zhichao Geng ◽  
Ping Zhou ◽  
Lei Meng ◽  
Ying Yan ◽  
Dongming Guo
Keyword(s):  
Optical Glass ◽  
Removal Rate ◽  
Surface Profile ◽  
Copper Plate ◽  
Modeling Method ◽  
Plate Interface ◽  
Inclination Angles ◽  
Material Removal Rate Model ◽  
The Right ◽  
Evolution Modeling

Abstract Lapping has a history of hundreds of years, yet it still relies on the experience of workers. To improve the automaticity and controllability of the lapping process, a modeling method of friction and wear is developed to predict the surface profile evolution of the workpiece and lapping plate in the lapping process. In the proposed method, by solving the balance equations of resultant force and moment, the inclination angles of the workpiece can be calculated, thus more accurate contact pressure distribution of the workpiece/lapping plate interface can be calculated. Combined with the material removal rate model, the continuous evolution process of the workpiece and lapping plate can be predicted in the lapping process. The modeling method was validated by a lapping test of a flat optical glass (Φ 100 mm) with a composite copper plate. The results show that the proposed method can predict the evolution of the surface profile of the workpiece and lapping plate with high accuracy. Consequently, the lapping plate can be dressed at the right time point. Benefit from this, in the validation test the PV value of the workpiece (with 5 mm edge exclusion) was reduced from 5.279 μm to 0.267 μm in 30 min. The proposed surface profile evolution modeling method not only improves the lapping efficiency but also provides an opportunity to understand the lapping process.

Stabilization of Removal Rate in Small Tool Polishing of Glass Lenses

2019 ◽  
Vol 13 (2) ◽  
pp. 221-229 ◽  
Author(s):  
Urara Satake ◽  
Toshiyuki Enomoto ◽  
Teppei Miyagawa ◽  
Takuya Ohsumi ◽  
Hidenori Nakagawa ◽  
...  
Keyword(s):  
Wear Resistance ◽  
Material Removal Rate ◽  
Time Variation ◽  
Material Removal ◽  
Removal Rate ◽  
Polishing Process ◽  
Polishing Pad ◽  
The Stability ◽  
Polishing Pads ◽  
Glass Lenses

The demand for improving the image quality of cameras has increased significantly, especially in industrial fields such as broadcasting, on-vehicle, security, factory automation, and medicine. The surface of glass lenses as a key component of cameras is formed and finished by polishing using small tools. The existing polishing technologies, however, exhibit serious problems including an unstable material removal rate over time. In our previous work, the mechanism of time variation in material removal rate was clarified. Based on the findings, a vibration-assisted polishing method using polishing pads containing titanium dioxide particles was developed for improving the stability of the material removal rate with the accumulated polishing time. Our experiments revealed that the proposed polishing method suppressed the time variation significantly in the material removal rate. The developed polishing pads, however, possessed a short life because of their poor wear resistance; as such, they could not be applied to the mass-production process of lenses. In this study, we applied the vibration-assisted polishing method to the polishing process using commercial polishing pads that exhibit sufficient wear resistance for practical use. To investigate the effect of vibration on the stability of the material removal rate, polishing experiments and the observation of slurry flow on the surface of the polishing pads during the vibration-assisted polishing process were conducted. Based on the findings, a new polishing method utilizing a large-amplitude high-frequency vibration applied to the polishing pressure was developed. In addition, a new polishing method utilizing the overhang of a polishing pad, where the polishing pad was moved to hang over the edge of the workpiece for incorporating periodic dressing processes of the polishing pad surface during the polishing process, was also developed. Our polishing experiments revealed that both the proposed polishing methods improved the stability of the material removal rate significantly over the course of the polishing process.

Study on Compound Machining of Polyurethane Polishing Pad and Cluster Abrasive Brush Based on MR Effect

2011 ◽  
Vol 487 ◽  
pp. 238-242 ◽  
Author(s):  
Min Li ◽  
Qiu Sheng Yan ◽  
Jia Bin Lu ◽  
Jing Fu Chai
Keyword(s):  
Material Removal Rate ◽  
Material Removal ◽  
Removal Rate ◽  
Machining Process ◽  
Machining Parameters ◽  
Polishing Process ◽  
Workpiece Material ◽  
Crystal Silicon ◽  
Polishing Pad ◽  
Mr Effect

Method of compound machining is used to process single crystal silicon and SrTiO3 ceramic substrates, and the factors on effects of compound machining are studied such as magnetic field intensity, processing time, rotating speed of lapping plate and lapping pressure. The results show that the roughness of work pieces processed by compound machining are smaller than that by lapping based on cluster MR effect and polyurethane pad polishing process, while the material removal rate is higher than polyurethane pad polishing process, therefore, compound machining shows its synergistic effect between lapping based on cluster MR effect and polyurethane pad polishing process. The type and properties of workpiece material, and machining parameters both have a significant impact on the roughness and material removal rate of compound machining process of polyurethane polishing pad and cluster abrasive brush based on MR effect.

scholarly journals Dynamic Pad Surface Metrology Monitoring by Swing-Arm Chromatic Confocal System

2020 ◽  
Vol 11 (1) ◽  
pp. 179
Author(s):  
Chao-Chang A. Chen ◽  
Jen-Chieh Li ◽  
Wei-Cheng Liao ◽  
Yong-Jie Ciou ◽  
Chun-Chen Chen
Keyword(s):  
Surface Topography ◽  
Removal Rate ◽  
Chemical Mechanical Planarization ◽  
Surface Profile ◽  
Performance Level ◽  
Wafer Surface ◽  
Surface Metrology ◽  
Effective Lifetime ◽  
Polishing Pad ◽  
Swing Arm

This study aims to develop a dynamic pad monitoring system (DPMS) for measuring the surface topography of polishing pad. Chemical mechanical planarization/polishing (CMP) is a vital process in semiconductor manufacturing. The process is applied to assure the substrate wafer or thin film on wafer that has reached the required planarization after deposition for lithographic processing of the desired structures of devices. Surface properties of polishing pad have a huge influence on the material removal rate (MRR) and quality of wafer surface by CMP process. A DPMS has been developed to analyze the performance level of polishing pad for CMP. A chromatic confocal sensor is attached on a designed fixture arm to acquire pad topography data. By swing-arm motion with continuous data acquisition, the surface topography information of pad can be gathered dynamically. Measuring data are analyzed with a designed FFT filter to remove mechanical vibration and disturbance. Then the pad surface profile and groove depth can be calculated, which the pad’s index PU (pad uniformity) and PELI (pad effective lifetime index) are developed to evaluate the pad’s performance level. Finally, 50 rounds of CMP experiments have been executed to investigate the correlations of MRR and surface roughness of as-CMP wafer with pad performance. Results of this study can be used to monitor the pad dressing process and CMP parameter evaluation for production of IC devices.

Research on the Surface Change of the Large Optic Plane Wafer In the Fast Polishing Process

2010 ◽  
Vol 97-101 ◽  
pp. 1811-1814
Author(s):  
Jing Lin ◽  
Wei Yang ◽  
Yin Biao Guo
Keyword(s):  
Pressure Distribution ◽  
Material Removal Rate ◽  
Material Removal ◽  
Removal Rate ◽  
Skin Model ◽  
Polishing Process ◽  
Surface Change ◽  
Rotational Movement ◽  
Polishing Pad

This paper researches on the surface change of the wafer in the fast polishing process. Firstly, the revised skin model is used to analyze the pressure distribution when the wafer stays beyond the polishing pad. Secondly, using the skin model and the Preston Equation MRR=k×p×v, the material removal rate is simulated and the surface change is predicted when the large optic plane wafer both has the rotational movement and the linear translation movement. Thirdly, the experiment is done to verify the simulation and prediction. The experiment result is similar to the simulation result. The paper shows a designed movement to predict the surface change.

Achieving High Flatness of Workpiece Edge Shape by Considering Polishing Pressure

2010 ◽  
Vol 447-448 ◽  
pp. 71-75
Author(s):  
Takahiro Miyake ◽  
Toshiyuki Enomoto
Keyword(s):  
Semiconductor Devices ◽  
Silicon Wafers ◽  
Polishing Process ◽  
Model Based ◽  
Polishing Pad ◽  
Experimental Analyses ◽  
Polishing Pads ◽  
Polishing Pressure

In recent years, the achievement of further high flatness of workpiece edge shape is strongly required in mirror finishing. Especially, the edge roll off of silicon wafers as the substrates of semiconductor devices is demanded to decrease in the polishing process for raising the yield of IC chips. Many theoretical and experimental analyses for the edge roll off generation have been already done to meet the demand. The analyses, however, cannot fully account for the obtained edge shape in actual polishing. Concretely, the influence of the polishing pressure as one of the key polishing conditions on the edge roll off has not been clarified. In this study, the influence of the polishing pressure on the edge shape was investigated by the polishing experiments and the edge roll off generation analyses using the model based on the viscoelasticity of the polishing pad, which was proposed in the previous study. And it was revealed that an appropriate polishing pressure is needed to be set for achieving high flatness of workpiece edge shape with the consideration of the properties of applied polishing pads.

Parametric Study of Micro Machining Three Dimensional Microstructure with the Tiny-Grinding Wheel Based on the EMR Effect

2010 ◽  
Vol 447-448 ◽  
pp. 193-197
Author(s):  
Wei Qiang Gao ◽  
Qiu Sheng Yan ◽  
Yi Liu ◽  
Jia Bin Lu ◽  
Ling Ye Kong
Keyword(s):  
Magnetic Field ◽  
Material Removal Rate ◽  
Feed Rate ◽  
Material Removal ◽  
Rotation Speed ◽  
Optical Glass ◽  
Removal Rate ◽  
Grinding Wheel ◽  
Machining Time ◽  
Fluctuation Phenomenon

Electro-magneto-rheological (EMR) fluids, which exhibit Newtonian behavior in the absence of a magnetic field, are abruptly transformed within milliseconds into a Bingham plastic under an applied magnetic field, called the EMR effect. Based on this effect, the particle-dispersed EMR fluid is used as a special instantaneous bond to cohere abrasive particles and magnetic particles together so as to form a dynamical, flexible tiny-grinding wheel to machine micro-groove on the surface of optical glass. Experiments were conducted to reveal the effects of process parameters, such as the feed rate of the horizontal worktable, feeding of the Z axis, machining time and machining gap, on material removal rate of glass. The results indicate that the feed rate of the worktable at horizontal direction has less effect on material removal rate, which shows a fluctuation phenomenon within a certain range. The feed rate of the Z axis directly influences the machining gap and leads to a remarkable change on material removal rate. Larger material removal rate can be obtained when the feeding frequency of Z direction is one time per processing. With the increase of rotation speed of the tool, material removal rate increases firstly and decreases afterwards, and it gets the maximum value with the rotation speed of 4800 rev/min. The machining time is directly proportional to material removal amount, but inversely proportional to material removal rate. Furthermore, material removal rate decreases with the increase of the machining gap between the tool and the workpiece. On the basis of above, the machining mode with the tiny-grinding wheel based on the EMR effect is presented.

Mechanochemical Polishing of Single Crystal Diamond with Mixture of Oxidizing Agents

2006 ◽  
Vol 315-316 ◽  
pp. 852-855 ◽  
Author(s):  
Cheng Yong Wang ◽  
C. Chen ◽  
Yue Xian Song
Keyword(s):  
Surface Roughness ◽  
Single Crystal ◽  
Smooth Surface ◽  
Removal Rate ◽  
Polishing Process ◽  
Iron Plate ◽  
Oxidizing Agents ◽  
Single Crystal Diamond ◽  
Lower Temperature ◽  
And Control

In order to achieve the smooth surface of diamond, several kinds of mixture oxidizing agents have been used to polish the single crystal diamond by a designed polishing apparatus. The existing of graphite and amorphous carbon has been found in the surface of diamond after polishing. The mechanochemical actions of oxidizing agents and the polishing iron plate have been proved. The mixture of oxidizing agents can decrease the polishing temperature so that the super-smooth surface of single crystal diamond can be achieved at lower temperature. The method provided is benefit not only to simplify polishing device and control the polishing process, but also to improve the removal rate and surface roughness.

Numerical Simulation and Experimental Validation of Pure Water Jet Machining of Ti-6Al-4V

2020 ◽  
Author(s):  
Greg Pasken ◽  
J. Ma ◽  
Muhammad P. Jahan ◽  
Shuting Lei
Keyword(s):  
Predictive Modeling ◽  
Metal Cutting ◽  
Removal Rate ◽  
Pure Water ◽  
Surface Profile ◽  
Predictive Modelling ◽  
Water Jet ◽  
The Other ◽  
Orifice Diameter ◽  
Cutting Processes

Abstract The most common problem when machining titanium using traditional metal cutting processes is that tools rapidly wear out and need to be replaced. This study examines the ability of a pure water jet to machine Ti-6Al-4V via simulations using ABAQUS’s Smoothed Particle Hydrodynamics (SPH). These simulations are then validated experimentally at two pressures, 138 MPa and 317 MPa. Using a Maxiem water jet built by Omax, experiments are conducted by creating a series of 5 lines that are 5 inches (127 mm) long placed 0.5 inches (12.7 mm) apart on a 1 mm thick Ti-6Al-4V workpiece. Predictive modeling is also conducted using the two additional pressures 400 MPa and 621 MPa as well as three orifice diameters 0.254 mm, 0.3556 mm, and 0.4572 mm. The simulations are validated at both pressures and had a percent error less than 2.6% which were within the standard deviation of the experimental results. The predictive modeling indicates that the pressures above 317 MPa create a near identical percent increase from the orifice diameter but the kerf has a more noticeable decrease in width of cut as the pressure increases. The 138 MPa has the smoothest surface profile compared to the other pressures. The volume of removed material decreases as the pressure increases but the material removal rate (MRR) increases as the pressure increases. This is due to the velocity of the water increasing as the pressure increases causing a lower run time. The 621 MPa is the best pressure to machine Ti-6Al-4V as it has a better MRR than the other pressures used in the predictive modelling.

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