Grinding Characteristics Research Articles

The Experimental Analysis of Modifier on Fluid Magnetic Abrasivetool

Fluid magnetic abrasivetool is a kind of suspension, which is composed of soft magnetic particles, surfactants, base liquid and so on so forth, so it can have strong magnetorheological characteristics and grinding characteristics. The stability of magnetorheological fluid is one of the most important indicator to evaluate the quality of magnetorheological fluid. Sodium hexametaphosphate and PAA have perfect function to maintain dispersionstability and retrogradation, adding nano-silica can improve the retrogradation of magnetic abrasivetool, which can modify redispersibility of magnetic abrasivetool.

702 ELID研削用アシカーボン砥石の開発および性能評価(OS7-(1)オーガナイズドセッション《精密/微細加工と評価》)

702 ELID研削用アシカーボン砥石の開発および性能評価(OS7-(1)オーガナイズドセッション《精密/微細加工と評価》)

Surface formation characteristics in elliptical ultrasonic assisted grinding of monocrystal silicon

The characteristics of surface formation in elliptical ultrasonic assisted grinding (EUAG) of monocrystal silicon were investigated by grinding and single abrasive scratching experiments. In grinding experiments, an elliptical ultrasonic vibrator, on which a thin sheet shaped monocrystal silicon substrate was attached, was installed on a CNC surface grinder equipped with a diamond grinding wheel. By contrast, the vibrator attached with the substrate was set up on a multi-axis CNC controlled machining centre equipped with a single diamond tool to perform the scratching tests. The obtained results show that the grinding forces are reduced by 30%, the surface quality is improved significantly and the surface roughness is decreased by around 25% during EUAG compared with those in conventional grinding without ultrasonic vibration. There is a transition of material removal mode from the permanent contact to the unsuccessive contact between workpiece and abrasive by increasing the ratio of ultrasonic vibration amplitude to the depth of cut.

Investigation on cooling efficiency of grinding fluids in deep grinding

The cooling efficiency of grinding fluids in deep grinding, at different material removal rates and grinding speeds, has been investigated. Two ‘inverse’ methods have been proposed to determine the level of convective heat transfer coefficients of grinding fluids, by matching the theoretical and experimental grinding fluid burn-out thresholds or matching the theoretical and measured grinding temperatures. Instead of using a constant chip melting temperature to estimate the energy partition to the grinding chips, the chip temperature and chip energy were calculated using the newly developed approach considering the variation of chip size, deformation and heat transfer at the abrasive/work interface. The variation of grinding heat taken away by the process fluids and grinding chips under different process parameters has been calculated, which shows the importance of cooling effects by the grinding fluids and the transition of thermal characteristics of deep grinding from cooling dominant to ‘dry’ grinding regime, where a large percentage of grinding heat is taken away by the grinding chips.

3370 Reciprocating Plunge Profile Grinding of Nickel-Based Superalloy Nimonic 80A with Ultrafine-Crystalline cBN Wheel

The purpose of this research is to clarify the grinding characteristics of the ultrafine-crystalline cBN wheel in a reciprocating plunge profile grinding of nickel-based superalloy. Reciprocating plunge V-groove grinding experiments of Nimonic 80A superalloy were conducted using the ultrafine-crystalline and mono-crystalline cBN vitrified bonded wheels. Both radial and profile wear of the ultrafine-crystalline cBN (cBN-U) wheel are less than those of the conventional mono-crystalline cBN (cBN-B) wheel, hence the steady grinding ratio of the cBN-U wheel is around 10 times higher than that of the CBN-B wheel. Grinding force in grinding with the cBN-U wheel are 10〜20 % lower than that in grinding with the cBN-B wheel. The surface roughness of groove bottom ground by the cBN-U wheel is around 10 % lower than that in grinding with the cBN-B wheel. Thus, the ultrafine-crystalline cBN wheel is suitable for the applications with a high dimensional accuracy in the profile grinding for nickel-based superalloys, because it gives less profile wear, and hence better form retention than the conventional cBN-B wheel.

503 ナノカーボンELID添加研削液による,チタン加工の特性調査(切削・研削・研磨加工I)

503 ナノカーボンELID添加研削液による,チタン加工の特性調査(切削・研削・研磨加工I)

ELID grinding characteristics of Ti alloy using electrolyzed reduced water

ELID grinding characteristics of Ti alloy using electrolyzed reduced water

High-efficiency grinding of cold-work die steel with ultrafine-crystalline cBN abrasive grains

This paper presents the grinding characteristics of newly developed ultrafine-crystalline cBN (UcBN) abrasive grains in high-efficiency grinding of cold-work die steel. This new UcBN grain possesses an ultrafine crystal structure composed of sub-micron sized primary crystal grains. The fracture strength of the UcBN grain is about 3.7 times higher than that of conventional monocrystalline cBN grain. The grinding ratio in grinding with the UcBN grain is eight to 11 times higher than those in grinding with conventional typical monocrystalline and polycrystalline cBN grains.

Physical, gravimetric and functional characterization of various milling fractions of popped gorgon nut (Euryale ferox)

Studies were carried out on the milling characteristics to increase the usability of popped gorgon nut (makhana). It was conditioned to 6.2, 9.4 and 12.3% (db) moisture content and ground in a hammer mill at feed rates of 3, 6 and 9kg/h. The differential screen analysis showed that increase in moisture content decreased the percent weight retained in the pan and produced more medium sized particles (0.592-0.157mm). The Bond's work index, Kick's constant and average particle size increased but total surface area decreased with the increase of conditioning level. However, feed rate showed the antagonistic effect on these parameters. Various grinding characteristics were significantly affected either individually or in combination (interaction) by the conditioning level as well as the feed rate and could be well correlated in terms of Bond's work index, Kick's constant, total surface area, average particle size, effectiveness of milling and bulk density for popped makhana.

Surface finishing of flat pieces when submitted to lapping kinematics on abrasive disc dressed under several overlap factors

Abstract In machining of pieces that require surface finishing levels finer than grinding can offer, it is necessary to use specific finishing processes. However, these processes, which have lapping as the most classic representative, are usually difficult to setup and demand much time in setting the large number of variables. This paper discusses the investigation of an abrasive process for finishing of flat workpieces based on the combination of important grinding and lapping characteristics. Instead of loosing abrasive grains between the workpiece and the lapping plate, a resinoid grinding wheel of hot-pressed silicon carbide is fixed on the plate of a device resembling to a lapping machine. The grinding wheel is dressed with a single-point diamond for maintaining its form flat and mainly for interfering in the workpieces surface finishing by varying of the overlap factor (Ud). It was noticed that the studied process can simplify the setup and make it easier than in lapping, which is a painstaking process. The surface roughness values and flatness deviations showed to be comparable to those achieved in lapping, or even better. The best surface roughness and flatness deviation found were Ra = 0.8 nm and 0.4 μm with Ud = 3, respectively. The workpiece material was made of quenched and tempered SAE 4340 steel, reaching a hardness of 60 HRC. The process was also monitored by acoustic emission (AE), which indicates to be a promising and suitable technique to be used in this process. Compared to lapping, there is an additional advantage of a less contaminated workpiece surface with a shiny appearance.

Grinding characteristics, material removal and damage formation mechanisms in high removal rate grinding of silicon carbide

Development of advanced ceramics such as silicon carbide has gained significant importance because of their desirable properties. However, their engineering applications are still limited owing to the limitations in developing damage-free and economical machining techniques. It is often desired to increase the machining rate to improve productivity while maintaining the desired surface integrity. The success of this approach, however, requires a fundamental understanding of the material removal and damage formation mechanism in grinding. In this paper, high removal rate grinding of silicon carbide was investigated with respect to material removal and basic grinding parameters using a diamond grinding wheel. The results showed that the material removal was primarily due to the microfracture and grain dislodgement under the grinding conditioned selected. For grain dislodgement removal mode, the relationship for the removal rate in scratching based on a simple fracture mechanics analysis has been established. This research provides valuable insights into the surface and subsurface integrity and material removal mechanism during high removal rate grinding of silicon carbide.

Effect of Wheel Additive On Chemo-Mechanical Grinding (CMG) of Single Crystal Si Wafer

Chemo-mechanical grinding (CMG) process is a promising process for large-sized Si substrate fabrication at low cost. However, effect of additive in CMG wheel is not completely understood yet. In this paper, three different CMG wheels were developed, in which one excluded additive and the other two contained two kinds of additive i.e. silicon dioxide and sodium carbonate. Grinding experiments were conducted to explore the influence of exclusion of additive and inclusion of different kinds of additive on CMG performance. The grinding characteristics of the three wheels were also analyzed and discussed to reveal the roles of wheel compositions in CMG process. This work provides some fundamental insights for the selection of different types of additive for optimization of CMG wheel.

Elliptical Ultrasonic Assisted Grinding (EUAG) of Monocrystal Sapphire – Surface Formation Characteristics

This study investigates surface formation characteristics in elliptical ultrasonic assisted grinding (EUAG) of monocrystal sapphire. During EUAG process, the workpiece is imposed to ultrasonically vibrate in two directions, i.e., vertical and parallel to work-surface, by using an elliptical ultrasonic vibrator. In our previous work, the vibrator has been produced by bonding a piezoelectric ceramic device (PZT) on a metal elastic body. When two alternating current voltages with a phase difference are applied to the PZT at the same frequency that is close to the resonant frequency of the longitudinal and bending mode of the vibrator, two dimensional ultrasonic vibrations are generated simultaneously, resulting in an elliptical motion on the end face of the vibrator. In this paper, to clarify the work-surface formation characteristics in EUAG of sapphire material, grinding experiments are carried out involving sapphire substrate. In experiments, work-surface roughness is measured, and the ground work-surface morphology is examined by scanning electron microscope (SEM). The experimental results are summarized as: (1) Compared with conventional grinding (CG), the elliptical vibration leads to a decrease of surface roughness up to 25% in EUAG; (2) The surface roughness has a monotonously increasing trend with the increasing wheel depth of cut in both EUAG and CG, but has little variation with the worktable feed rate. As the wheel speed increases, the surface roughness decreases until it reaches a minimum, and then increases in a monotonous trend in both EUAG and CG; (3) The surface quality in EUAG has a significant improvement, and it is prone to achieve the ductile regime grinding of sapphire compared with CG. These indicate that the elliptical ultrasonic assisted grinding is an efficient technique for high performance machining of monocrystal sapphire.

Nozzle-Type ELID Grinding Characteristics of Cemented Carbides

This paper reports a systematic investigation of a nozzle-type ELID grinding characteristics of cemented carbides. Two groups of experimental scheme were carried on by using fine grain cast iron diamond wheel and nozzle-type ELID grinding apparatus. The grinding forces were measured by a dynamometer and the ground surfaces were characterized using scanning electron microscopy (SEM) and atomic force microscope (AFM). The influences of electrolytic and grinding parameters on grinding force were discussed. The material removal mode and micro-morphology characteristics were also analyzed.

Processing Characteristics of Structured Lapping Films under Grinding Load Control

Pyramidal structured lapping film, which has minute pyramidal structures formed by abrasive grains and adhesives on polyester films, is newly developed finishing tool[1,2]. It is said that the tool has eminent grinding characteristics, mainly, good finished surface quality because chips generated during grinding process can escape into spaces between pyramidal structures, and high grinding efficiency because new abrasive grains come out from inside of the pyramidal structures during grinding process. However, finishing characteristics of this grinding tool have not yet been fully explained. In this research, the grinding experiments were conducted, focusing on the efficiency of grinding. The grinding forces were measured to examine the state of the surface of the tool. In addition, to improve the grinding efficiency using this tool, a method for changing the grinding load continuously while processing was used. This method was intended to enhance the effective chip generation and new abrasive grain emergence. As a result, stock removal of the workpiece was increased more than when the grinding load was kept constant. Moreover, using scanning electron microscope, this new grinding tool surface was observed, and its effectiveness was examined.

Iron ore grindability improvement by microwave pre-treatment

The influence of microwave pre-treatment on grindability of iron ore (Orissa, India) was investigated by grindability tests. SEM analysis characterized the micro-fractures in microwave treated sample. This may be due to the thermal stress cracking resulted from microwave energy pre-treatment. XRD analysis showed the crystalline content of the sample. It was found that the microwave treated iron ore has peak more than that of untreated ore, i.e. the crystallinity increased with the microwave exposure time. The calculation of HGGI indicated increase in the ease of grinding or decrease in grindability index of the microwave treated ore. Grindability test showed that the microwave treated iron ore grinds much more rapidly initially than the untreated ore. The results showed that the breakage function of both microwave untreated and treated iron ore is dependent of the particle size. The grindability increased significantly as a result of microwave pre-treatment with the specific rate of breakage ( S i ) increasing by an average of 50%. It was concluded that microwave assisted grinding produced good results particularly for grinding characteristics.

Combined quality loss (CQL) concept in WPCA-based Taguchi philosophy for optimization of multiple surface quality characteristics of UNS C34000 brass in cylindrical grinding

The present study highlights a multi-objective optimization problem by applying Weighted Principal Component Analysis (WPCA) coupled with Taguchi method through a case study in cylindrical grinding of UNS C34000 Medium Leaded Brass. The study aimed at evaluating the best process environment which could simultaneously satisfy multiple requirements of surface quality. In view of the fact that traditional Taguchi method fails to solve a multi-objective optimization problem, to overcome this limitation, WPCA has been coupled with Taguchi method. Furthermore, to follow the basic assumption of Taguchi method, i.e., quality attributes should be uncorrelated or independent; which is not always satisfied in practical situation; the study applied WPCA to eliminate response correlation and to evaluate independent or uncorrelated quality indices called principal components which were aggregated by WPCA to compute overall quality index denoted as Multi-Response Performance Index. A combined quality loss was then estimated which was optimized (minimized) finally. The study combined WPCA and Taguchi method for predicting optimal setting. Optimal result was verified through confirmatory test. This indicates application feasibility of the aforesaid methodology proposed for multi-response optimization and off-line control of correlated multiple surface quality characteristics in cylindrical grinding.

The effect of ore blends on the mineral processing of platinum ores

This paper investigates whether blends of platinum ores display linear grinding and flotation characteristics or whether non-linear effects occur, i.e. synergistic/antagonistic effects. Ores from four different shafts are used in the study, i.e. Salene, Waterval UG2, Paardekraal and Townlands. Laboratory grinding and flotation tests are conducted on blends of the four ores using a statistical simplex lattice mixture design. Grinding results show no evidence that blends of ores display non-linear grinding characteristics. Flotation results show significant antagonistic effects in binary blends of the Salene ore with the other ore types. On the other hand, ternary/quaternary blends of ores result in synergistic effects. The study concludes that blends of platinum ores display non-linear (non-additive) characteristics when there are large differences in metallurgical properties between the ore types. The study demonstrates that appropriately designed mixtures experiments are an effective way to study the performance of ore blends in the laboratory.

Surface Roughness Characteristics of Fine ELID Cross Grinding for Silicon Wafers

Silicon is widely used as the most important substrate material in integrated circuit and micro electronic devices field. Electrolytic in-process dressing (ELID) grinding technique is an effective grinding process especially for machining hard and brittle material. In this paper, using super fine abrasive wheel, sets of ELID cross grinding experiment were conducted for investigating the influences of various grinding conditions including grain sizes, rotation speeds of grinding wheel, rotation speeds of workpiece and ELID conditions on surface roughness during grinding silicon wafers. Surface roughness characteristics of fine ELID cross grinding for silicon wafers were discussed. In an optimized condition, surface roughness of 2.2 nm in Ra can be achieved by using #20000 wheel.

Grinding characteristics in high speed grinding of engineering ceramics with brazed diamond wheels

An investigation was undertaken to explore the grinding characteristics and removal mechanisms in high speed grinding of three engineering ceramics—alumina, silicon nitride, and zirconia—by using brazed diamond wheels of two different grit sizes. The grinding forces and surface roughness were measured and the morphological features of ground workpiece surfaces were examined. The results indicate that material removal mechanisms are different for the three ceramics at high grinding speeds. For alumina, the removal is dominated by brittle fracture. For silicon nitride and zirconia, the ductile removal prevails in the grinding. For each of the three ceramics, grinding power per unit width is found to be nearly proportional to the rate of plowed surface area generated per unit time per unit width, indicating that the grinding energy expended is mainly associated with sliding and plowing.