Polishing Tool Research Articles

A Novel Polishing Method for Extending the Service Life of Magnetic Compound Fluid

Magnetic field-assisted magnetic compound fluid (MCF) ultra-precision machining technology is regarded as an effective method to obtain a smooth surface. However, due to the evaporation and splashing of water in the polishing fluid during processing, the service life of the MCF slurry is reduced. This paper presents a material removal model for MCF polishing, and a novel experimental apparatus is proposed to extend the service life by supplying MCF components into the MCF slurry. Firstly, in order to obtain the ideal polishing tool, the appearance morphologies and the formation process of the MCF slurry were observed by an industrial camera. On this basis, the optimum parameters were determined by multi-factor and multi-level orthogonal experiments. Finally, the investigation of the MCF service life was carried out under the optimal processing parameters. The main findings are summarized as follows. (1) Excellent MCF polishing tools are obtained when the eccentric distance r is 4 mm and the MCF slurry supply V is 1 mL. (2) When the eccentric distance increases from 2 mm to 4 mm, the forming time of the MCF tool decreases sharply, but when the eccentricity exceeds 4 mm, the decreasing trend becomes slow. The molding time grows steadily as the supply is increased. (3) When the machining gap Δ, the MCF carrier speed nc, the eccentricity r, and the revolution speed of magnetic nm are 1 mm, 500 rpm, 4 mm, and 600 rpm, respectively, the ideal machining effect can be obtained. (4) It could be proven that the polishing device is feasible to extend the service time of the MCF slurry by adding MCF components.

3D-printed functionally-graded lattice structure with tunable removal characteristics for precision polishing

Functionally-graded lattice structure (FGLS) has fascinating properties such as lightweight, tunable stiffness, minimized stress concentration, and excellent energy absorption. The advent of 3D printing has provided feasible and reliable manufacturing solutions for FGLS, which has been boosting wider applications of FGLS. In this paper, 3D-printed polishing tools with tunable removal characteristics are developed based on FGLS. The gradient in stiffness is achieved by varying the strut thickness of different cells. Four FGLS with different gradients are designed and printed. The normal contact pressure between the tools and a rigid plate is modelled by the finite element method and experimentally validated with a pressure mapping system. The polishing performance of the developed polishing tools is investigated on both ductile and brittle materials in a machining centre. Results demonstrate that the removal profiles of the polishing tools strictly follow the change of the lattice gradient regardless of the workpiece materials, which mainly affect the depth of the polished footprints. Besides, the surface roughness Sa after polishing reaches as low as 26 nm for the optical glass, indicating a drastic improvement of more than 90%. These findings enable the fabrication of polishing tools with desired tool influence functions on-demand for form error figuring in the computer-controlled optical surface finishing. Besides, the design strategy presented in this paper will open a new realm of producing functional tools in the field of ultraprecision manufacturing. • Functionally-graded lattice structure (FGLS) is designed for polishing. • Contact pressure of FGLS wheel is studied by FEA and validated by experiments. • The FGLS-based polishing tools can produce desired tool influence functions. • The surface finish of optical glass has been improved by > 90% after polishing. • The wear rate of polishing pads is material-dependent.

Study on Polishing of Polycrystalline AlN Using Sol–Gel Polishing Tool

Polycrystalline aluminum nitride has extensive application prospects in substrate materials, insulating layer materials, and packaging materials. Polycrystalline aluminum nitride is sintered from powder. The traditional mechanical polishing method is easy to cause aluminum nitride grains to fall off to form pits. In this paper, to improve the polishing effect, based on the hydration of polycrystalline aluminum nitride, a sol-gel (SG) polishing tool was proposed to polish polycrystalline aluminum nitride. The polishing process was divided into rough polishing and fine polishing. The diamond particle size of the SG tool used for rough polishing was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$40\mathbf {\mathrm {\mu }}\text{m}$ </tex-math></inline-formula> . The diamond particle size of the SG tool used for fine polishing was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\mathbf {\mathrm {\mu }}\text{m}$ </tex-math></inline-formula> . Moreover, the polycrystalline AlN was processed with or without deionized water. The results showed that in the rough polishing stage, the material removal rate (MRR) of the polishing method without deionized water was four times higher than that of the polishing method with deionized water. However, in the fine polishing stage, the MRR of the polishing method with deionized water was slightly higher than that of the polishing method without deionized water. The results showed that mechanical removal is the primary material removal method in the rough polishing stage. In the fine polishing stage, hydration can improve the polishing effect of polycrystalline aluminum nitride.

GRIN pad polishing

AbstractA new concept for CNC polishing pads is given by the gradient index (GRIN) pad polishing tools. Instead of gluing polishing foils as a layer onto metallic tool holders that have the spherical surface to be polished, 3D‐printed GRIN pads are applied directly to the CNC tool axis.

Design and Analysis of a Compliant End-Effector for Robotic Polishing Using Flexible Beams

The contact force between the polishing tool and the workpiece is crucial in determining the surface quality in robotic polishing. Different from rigid end-effectors, this paper presents a novel compliant end-effector (CEE) for robotic polishing using flexible beams. The flexibility of the CEE helps to suppress the excessive displacement caused by the inertia of the polishing robot and avoids damaging the polishing tool and workpiece surface. In addition, the contact force can also be precisely estimated via the measurement of the CEE’s displacement using a capacitive position sensor. The design, modeling and experimental validation of the CEE are presented. Firstly, the analytical model of the CEE is established using the stiffness matrix method. Subsequently, the analytical model is verified by finite element analysis. Further, a prototype is manufactured, and its characteristics and performance are experimentally tested. The equivalent stiffness is measured to be 0.335 N/μm, and the first natural frequency along its working direction is 42.1 Hz. Finally, the contact force measurement using the CEE is compared with a force sensor. Under open-loop condition, the resolution of the contact force measurement is found to be 0.025 N, which makes the fine tuning of the contact force possible in robotic polishing.

A Model-Based Trajectory Planning Method for Robotic Polishing of Complex Surfaces

Off-line programming of the polishing tool trajectory for complex workpieces is challenging due to the nontrivial material removal model and the polishing accuracy requirement. Current tool trajectory planning methods are mainly developed for some simple surfaces but cannot handle the increasingly complicated industrial parts, such as the wheel hubs. This article first develops a numerical contact mechanics model for the point-sampled complex workpieces. The contact pressure distribution and the material removal depths on the workpiece point cloud can be predicted efficiently. A novel high-priority subregion searching algorithm is developed to track the most-worth-polishing workpiece points. By selecting the path pattern as direction-parallel, the path direction, tool dwell times, and the path spacings inside each extracted subregion are optimized to minimize the deviation from the desired material removal depths. The effectiveness of the proposed method is verified by performing disk polishing simulations on workpieces with different shapes. A robotic polishing experiment is also conducted on a wheel hub. Both simulation and experimental results show that reasonable tool trajectories can be generated on the workpiece, and the desired material removal depths can be achieved. Note to Practitioners—In robotic polishing industries, it is crucial to plan the tool trajectory (tool path and feed velocity) to achieve desired material removal depths on the workpiece surface, which means high surface quality. In this article, a model-based tool trajectory planning method for robotic polishing of complex surfaces that are represented by the point cloud form is presented. The advantage of using the point cloud is that workpiece surfaces with varying curvatures and complex features, e.g., grooves and holes, need not be expressed explicitly. The proposed method generates high-priority subregions according to the updated material removal distribution dynamically. In this work, the polishing path pattern is chosen as direction-parallel. Based on an efficient numerical contact mechanics and material removal model, the path locations and the tool dwell times inside each subregion are optimized to minimize the deviation between the actual and the desired material removal depths. When the desired material removal depths are attained in an extracted subregion, the algorithm finds the next high-priority subregion until the whole workpiece is well polished. The trajectory planning method can be integrated into an industrial robot with the force-control module. Future work is to integrate the roughness model into the tool trajectory planning method.

Study on Chamber Structure Optimization and Nozzle Aperture of Fluid Jet Polishing Tool

The design of fluid jet polishing (FJP) tool is an important part of the FJP process.By studying effects of different tool chambers on flow-beam velocity and pressure,the paper determines the optimal type of polishing tool and provides the optimal design method.It studies those removal rates and shapes of removal function under different apertures by establishing FJP discrete phase model and flushing erosion model for simulation and experiment.The results show that in structure,the chamber shall be designed to be larger in diameter and shorter in length,and ensure the fluid movement direction is consistent with the nozzle discharge direction,so as to improve the quality of the flow beam.As the decrease of nozzle aperture, the removal rate increases and the proportion of low removal area in the center of M-shaped removal function decreases.Under experimental conditions,the Gaussian removal function can be obtained when the aperture is smaller than 0.25mm.This paper provides a reference for the real design of jet polishing tool structure.

Whole Elliptical Surface Polishing Using a Doughnut-Shaped MCF Polishing Tool with Variable Tilt Angle

Elliptical elements are essential optical surfaces for modifying optical systems. For polishing the whole elliptical surface using doughnut-shaped MCF polishing tool with variable tilt angle, an experimental investigation was conducted in this work. Firstly, a flat workpiece was polished to determine the polishing feasibility. It was found that the middle portion of the polishing tool had optimal ability to remove materials, and the surface roughness Sa at the material removal peak was changed from 134 nm to 17.5 nm within 50 min of polishing. A smoother surface could be obtained using MCF2 slurry and MCF3 slurry, but the use of MCF1 slurry resulted in a rough surface. Then, the effects of working gap h, revolution speed of MCF polishing tool and polishing time on the polishing results were tested to study the polishing characteristics. Sa 9.6 nm and glossiness 278 Gu were obtained, and form error improved from 2.3 μm to 1.3 μm. Finally, the MCF polishing tool was dried to observe the microstructure of the MCF polishing tool after polishing. Abrasive particles were distributed evenly after polishing. It was seen that the abrasive particles were grabbed by the ferric clusters, and the α-celluloses were interleaved between the clusters.

Rapid polishing process for the x ray reflector.

X ray mirrors are symmetrical workpieces along the length and width and are widely used in various optical systems. Unlike the center-symmetric circular mirror, it is more difficult to suppress the edge effect of the x ray mirror during the polishing process, which greatly limits the polishing accuracy and polishing efficiency. Based on this, the unique edge effect of x ray mirrors is investigated in depth in this paper. First, the causes and distribution laws of the edge effect of the x ray mirror were obtained by analyzing the inherent structure of the computer controlled optical surface (CCOS) and the motion trajectory of the polishing tool. Second, a mathematical model was established based on the material removal states of different regions on the x ray mirror. Finally, a combined polishing process based on the influence function of different shaped tools is proposed and experimentally verified. The results show that the edge effect on the x ray mirror is significantly weakened and its surface errors peak to valley (PV) and RMS are increased by 21.5 times and 47.9 times, respectively. This indicates that the combined polishing process has a good suppression effect on the edge effect of the x ray mirror.

Factor structure and psychometric properties of Polish version of Parental Bonding Instrument (PBI) among adults and adolescents.

Parental Bonding Instrument (PBI) by Parker et al., is a widely known and used tool in studies on the assessment of parenting behavior in adult, adolescent and child populations. This tool has had many translations and adaptations globally. In Poland, the factor structure and psychometric properties of PBI have not been studied so far. The aim of the presented research was to perform such an analysis both in the group of adults and adolescents. The data from four research projects, in which the 25-item version of the PBI translated into Polish was used, were analyzed. Data from 698 participants in total, including 473 adults and 225 adolescents were collected. Exploratory factor analyzes was performed for both mother and father version. A study of the reliability of individual factors, stability over time (test-retest) and an analysis of criterion validity were carried out. Both in the group of adults and adolescents, obtained a three-factor structure, acceptable reliability and stability over time. Moreover PBI correlated with another Polish tool in line with the adopted hypotheses, showing satisfactory criteria validity.

Research on constant force polishing method of curved mold based on position adaptive impedance control

The quality and life of the injected product are affected by surface quality of curved mold, and reasonable polishing method is the key to obtain the high-quality surface of curved mold. Small polishing tool is controlled by constant displacement polishing in the conventional method of robot polishing. The polishing force is adjusted to affect the surface quality of mold during mold polishing. The shortcomings of traditional control method of robot are investigated by simulation, and the constant force control approach is proposed to maintain stable force, which is achieved by a position-based impedance control algorithm. The polishing experiments of curved mold are conducted by using two control methods with constant displacement control polishing (CDCP) and constant force control polishing (CFCP), respectively. The experimental results show that the CFCP method can maintain polishing force stability and the reduction of surface roughness in the three groups of experiments using CDCP method is much lower than that of CFCP method, respectively. The feasibility of constant force control polishing method (CFCP) is verified.

Response surface methodology based parametric study for AISI H13 die steel using customized designed 3D printed Ti64 multi-nozzle polishing tool

The work presents a study on FJP polishing of AISI H13 die steel using 3D printed multi nozzle (dual orifice) polishing tool and Silicon Carbide (SiC) abrasive slurry. It presents a simultaneous effect of feed rate and spindle rotation on the percentage change in surface roughness (%[Formula: see text]). Central Composite Design (CCD) method was used to design the experimentation plan and Analysis of Variance (ANOVA) was performed to evaluate the optimum values of the process parameters. The regression model developed for the FJP process was validated by polishing the AISI H13 workpiece with 39[Formula: see text] average initial surface roughness with the optimized process parameters; feed rate of [Formula: see text] and spindle rotation of [Formula: see text]. The optimized FJP parameters were able to generate the surface roughness of [Formula: see text]. The results obtained from the confirmatory experiments were found to be very close to the predicted results which validated the developed regression model. To further enhance the polishing efficiency, the optimum process parameters were used to polish AISI H13 die steel workpiece, the surface roughness was reduced from 390 to 110 nm in 15 min with 12 number of passes which shows the reduction in peaks and valleys with surface improvement of 71.79%.

Design and Analysis of an Inverted XY-3RPS Hybrid Mechanism for Polishing of Complex Surface

Aims: An inverted XY-3-RPS hybrid mechanism was designed to apply ultraviolet-induced nano-particle colloid jet machining to polish the complex surface. Background: The hybrid mechanism has been widely used in the ultra-precision polishing field for installing different polishing tools on the moving platform to meet different machining requirements because of its wide working space, good dynamic performance and large bearing capacity. Objective: The main objective of this study is to establish an inverted XY-3-RPS hybrid mechanism for UV-induced nanoparticle colloid jet machining, to realize the ultra-precision polishing of complex surfaces by UV-induced nanoparticle colloid jet machining. Methods: The three-dimensional model of the inverted XY-3-RPS hybrid mechanism was established, and the kinematics and dynamics were analyzed. The Jacobian velocity matrix of the inverted XY-3- RPS hybrid mechanism is derived by vector construction and differential methods, and the dexterity index under different proportional parameters is optimized and simulated. The output Jacobian matrix and stiffness matrix are obtained using the virtual work principle, and their static analysis is carried out. Based on Lagrange dynamics theory, the dynamic mathematical model of the inverted XY-3-RPS hybrid mechanism is established, and its kinematics is verified by software joint simulation. Through dynamic simulation, the variation curves of motion, force and kinetic energy of the mechanism are obtained, which provides a theoretical basis for applying the hybrid mechanism in complex curved surface polishing. Results: The analysis shows that it has the best dexterity index when the ratio of moving and the fixed platform is 2:1. The kinematic simulation results show that the hybrid mechanism moves reliably under the given trajectory. The dynamic simulation results show that the force analysis of each kinematic pair and the kinetic energy change curve of each part changes smoothly, and the dynamic performance is stable under different trajectories. Conclusion: The parameter design and structural design of the inverted XY-3-RPS hybrid mechanism meet the requirements of ultra-precision polishing of complex surfaces.

Study of grinding and polishing tools in automated processing of curved stone

The grinding and polishing of curved stone involve many steps, limiting the process's efficiency. This study proposes a one-step grinding and polishing process to simplify the process and achieve efficient machining. It is achieved by developing the grinding and polishing tools and realizing the entire process on the robotic processing platform, and the tool design is based on the surface roughness of the machined workpiece. The grinding tool is made by selecting the appropriate glue to achieve the connection from carving to polishing. Similarly, the polishing tool is made by selecting the appropriate gel compound system to achieve a high glossiness curved stone surface. The results show that the grinding tool made of epoxy resin YT-CC301 can reduce the curved stone's roughness from 16.281 µm to below 400 nm, and the connection from carving to polishing can be realized by one step. The polishing tool made of sodium alginate and carboxylated chitosan gel compound system or sodium alginate and sodium carboxymethyl cellulose gel compound system can polish the surface of the ground curved stone to the roughness of less than 15 nm, and the surface glossiness can reach more than 120. Therefore, a single step of grinding and polishing of curved stone is achieved.

A robotic polishing parameter optimization method considering time-varying wear

In the automatic polishing process, the wear of polishing tools and the change of polishing parameters will affect the Preston coefficient, which makes it difficult to establish an accurate material removal model to achieve stable and excellent polishing quality. In this paper, a robotic polishing parameter optimization method considering time-varying wear is proposed to address these issues. First, combining the rich information in the theoretical modeling method with the data-driven regression method, a material removal regression model incorporating prior knowledge is proposed, which greatly reduces the large amount of experimental data required by the original regression model. The proposed model is able to track the wear variation of the sandpaper as well as the effect of polishing parameters. Then, based on the proposed prediction model, the genetic algorithm is used to optimize the polishing parameters in order to achieve better machining quality and less energy consumption. Finally, the experimental verification is carried out on the hybrid robot polishing test bench. The results show that the proposed material removal regression model incorporating prior knowledge has higher prediction accuracy and less required experimental data than existing models. The proposed robot polishing parameter optimization method can effectively compensate for tool wear and ensure the consistency of material removal during polishing while reducing energy consumption.

Surface Quality Control Strategy of Aspherical Mold Based on Screw Feed Polishing of Small Polishing Tool.

For small aspherical molds, it is difficult for the existing polishing method to take into account the correction of the surface error and the control of the uniformity of the surface roughness (SR) distribution, because the polishing tool is always larger than the small mold. Therefore, we used viscoelastic polyester fiber cloth to wrap the small steel ball as a polishing tool to adapt to the surface shape change of the aspherical mold, and designed a semi-flexible small polishing disc tool with microstructure, which can better adapt to the curvature change of aspherical surface and obtain better SR Ra. At the same time, a combined polishing method of constant speed and variable speed for screw feed was proposed to improve the uniformity of SR distribution in the paper. Then, a series of theoretical analysis and experimental verification were carried out in this paper to predict the tool influence function (TIF) of the two polishing tools and the effectiveness of the combined polishing method. In the experiment, a TIF bandwidth of about 0.46 mm was obtained with a small spherical polishing tool, which favors the surface shape correction of the small aspherical mold. The experiment of uniform removal with a small polishing disc tool was carried out to quickly reduce the Ra. Finally, the surface quality of the aspherical mold was effectively improved, combined with the constant speed and variable speed polishing modes of screw feed of the small spherical polishing tool and the smoothing effect of the small polishing disc tool. The peak valley (PV) of two small aspherical molds with an optical effective diameter less than 13 mm converged from 0.3572 μm and 0.2075 μm to 0.1282 μm and 0.071 μm, respectively. At the same time, the SR dispersion coefficient was reduced from 27.9% and 41.6% to 14.2% and 12.7%, respectively. The study provides a good solution for the surface quality control of small aspherical molds.

Fabrication and application of CNT fiber-ultra-fine diamond composites via electrophoretic deposition and instantaneous Joule-heating method

One-dimensional carbon nanotube (CNT) fibers combined with three-dimensional ultra-fine diamond have a synergistic effect that can be used in a variety of applications. The current challenge is how to combine the two materials quickly and efficiently. To actualize the combination of the two materials, a two-step method is adopted in this study. The electrophoretic deposition method, which allows ultra-fine diamond particles to adhere uniformly and controllably to the surface of carbon nanotube fibers. The instantaneous Joule-heating method can realize the instantaneous high-temperature recombination of diamond and CNT fibers. CNT fibers' flexibility and thermal conductivity are combined with ultra-fine diamond's high hardness in this composite. A polishing tool was made by knitting ultra-fine diamond/CNT fiber threads on non-woven fabric and used to dry polish potassium dihydrogen phosphate (KDP) crystals. CNT fibers were examined for wear, surface morphology, and KDP surface roughness before and after processing. The results reveal that the composite material-prepared tool has greater wear resistance and machining efficiency.

A new modelling method of material removal profile for electrorheological polishing with a mini annular integrated electrode

This paper addresses the problem of material removal in electrorheological (ER) polishing with a mini annular integrated electrode both theoretically and experimentally. The model of the material removal profile in ER polishing is proposed based on the evaluation of the amount of material removed from the surface along the direction orthogonal to the tool path. Firstly, the electric field distribution around the tool head is deduced theoretically. On this basis, the contact pressure model in the ER polishing area is established. Considering the feed rate and tool spindle speed of ER polishing, the distribution of the relative sliding velocity in the polishing area is modeled. On the basis above, the innovative approach to calculate the material removal profile is developed for the ER tool polishing along a straight path. The model is validated by a series of designed polishing experiments, which demonstrates that the material removal model established in this paper has high prediction accuracy of material removal profile in ER polishing.

Intimate contact development for automated fiber placement of thermoplastic composites

The consolidation step in the automated fiber Placement (AFP) of thermoplastic composites is crucial for development of interlaminar bonding strength. Two mechanisms contribute to the interlaminar bond strength development in the interface between the incoming tow and the substrate: (a) the development of intimate contact between the two surfaces and (b) the formation of a fusion bond across those contacting surfaces known as healing. So far, a number of different theoretical intimate contact models have been proposed in the literature to study intimate contact development for different manufacturing processes. However, very limited experimental methods are available to measure degree of intimate contact. To fill this gap, a new experimental approach based on topology of the tape surface is introduced to quantify the degree of intimate contact for the AFP process. The new approach is based on the Bearing Area Curve (BAC) of the surface profile of the tape. To implement the new procedure, an unidirectional strips of carbon fiber/PEEK were laid down on the polished steel tool with different placement rates, compaction forces, hot gas torch (HGT) temperatures, and tool temperatures. The degree of intimate contact is calculated based on the proposed experimental approach and compared with prediction models from the literature. Furthermore, the effect of AFP process parameters on the degree of intimate contact is studied using BAC method and the effective intimate contact model. The results showed that the development of intimate contact is significantly governed by the torch and tool temperature.

The Effect of Various Polishing Systems on the Surface Roughness of Two Resin Composites—An In Vitro Study

The long-term success of a composite restoration largely depends on its smoothness, which can be achieved by the appropriate polishing tools and material selection. The purpose of this study was to evaluate the surface roughness of two composite materials after the application of selected polishing systems. Filtek Ultimate (FU) and Filtek Z250 (FZ) were tested. Forty specimens of each material were prepared. After polymerization under a Mylar strip, the surface roughness of five samples from each group was measured. Subsequently, all specimens were ground by 600 grit sandpaper. The surface roughness of five samples per group was tested again. The samples from each group were randomly assigned to eight subgroups, and polished by Sof-Lex, Sof-Lex Diamond Polishing System, Super Snap, One Gloss, Astrobrush, Stainbuster, Enamel Shiny, and Jiffy Polishing System. The collected data were analyzed using the Shapiro–Wilk and Kruskal–Wallis tests. The lowest Ra coefficient after polishing is found in the Super Snap groups (FU—0.077 μm, FZ—0.085 μm). The lowest Rlr coefficient is measured in the Enamel Shiny group for FU (1.000), and for Sof-Lex, Sof-Lex Diamond Polishing System, and Jiffy Polishing Kit for FZ (1.001), and only slightly higher for Super Snap (FU—1.001, FZ—1.002). The roughest-measured surface is in the One Gloss group for FU (Ra—0.657 µm, Rlr—1.009), and Astrobrush group for FZ (Ra—0.525 μm, Rlr—0.011). Additionally, it was not confirmed that the nanoparticle material (FU) demonstrates better results than the microhybrid one (FZ). Different polishing systems produce varying surface roughness. The most effective polishing system is Super Snap. The structure of composites does not significantly affect their surface roughness after polishing.