Vibration-assisted Grinding Research Articles

Force and thermal effects in vibration-assisted grinding

Because it reduces forces and temperatures, vibration-assisted grinding has the potential to improve the feasibility of dry grinding. This paper presents an experimental study of force and temperature effects in dry and wet grinding at vibration frequencies below ultrasonic. Based on a moving line heat source model, heat flux quantities were estimated from subsurface temperature measurements. Reductions in force of up to 30 % were observed for dry grinding with 2,360 Hz vibration assistance. For the same condition, heat flux into the workpiece reduced by 42 %. The paper presents evidence that vibration assistance has a beneficial effect on the convective heat transfer rate.

Research on the system matching model in ultrasonic vibration-assisted grinding

In this paper, the ultrasonic vibration-assisted grinding is studied, and a new method is provided to solve the problem of matching the machine tool system and the ultrasonic system. By establishing the matching model, this problem is theoretically solved optimally. Moreover, the abrasive grain motion equations, the removal rate model, and grinding force prediction model are presented. Then the grinding force and the processing quality in system matching are researched by numerical simulation. When ultrasonic system parameters exceed the critical value, the surface scallop height of workpiece becomes lower with single-grain track and intergranular track overlapping. The grinding force decreases as the spindle speed, vibration amplitude, and vibration frequency increase. And the grinding force increases as the grinding depth and feed rate increase. Thus, the surface morphology of the workpiece and the change trends of the grinding force can be predicted through the system matching model. As a result, the best ultrasonic equipment can be decided accordingly to cooperate with the machine tool for grinding.

Experimental Research on Ultrasonic Torsional Vibration-Assisted Grinding of Hard and Brittle Materials

An experimental study of quartz glass grinding with ultrasonic torsional vibration assistance is presented. The grinding forces and surface roughness are measured. The results show that the grinding force and surface roughness with ultrasonic torsional vibration assistance are much less than those in conventional grinding. The grinding force increases with the feed rate of workpiece and the depth of grinding, and decreases with the speed of wheel spindle. This research indicates that the ultrasonic torsional vibration-assisted grinding can enhance grinding performance and be an effective method for the machining of hard and brittle materials.

Chemo-mechanical manufacturing of fused silica by combining ultrasonic vibration with fixed-abrasive pellets

Vibration-assisted grinding, in which harder abrasives than materials to be machined are employed, has been a viable and effective approach to increasing material removal rate (MRR) and/or reducing surface roughness of ground surfaces. We transfer this ideology to fused silica polishing by incorporating ultrasonic vibration into recently developed fixed-abrasive pellets in an attempt to enhance MRR and/or to improve manufactured surface quality. A prototype ultrasonic vibrator, the heart of the polishing head, was designed and the related experimental work was performed on an in-house built setup in conjunction with the constructed head. The vibrator is devised for the generation of 2-D tool path despite using only one actuator in lieu of two actuators in conventional 2-D ultrasonic machining systems. We then combined the ultrasonic vibration with fixed abrasive polishing pellets to machine fused silica glass. Machining experiments reveal that MRR is considerably increased up to >50% upon the introduction of ultrasonic vibration (UV) whilst surface roughness is not degraded appreciably. It was also noted that a overwhelmingly greater deal of polishing debris was dispelled during ultrasonic vibration assisted polishing than conventional bound-abrasive polishing, which may account for the greater MRR in UV assisted polishing.

Experimental Study on Minimum Quantity Lubrication in Mechanical Micromachining

Mechanical micromachining is a promising technique for making complex microstructures. It is challenging to apply mechanical micromachining in the industry due to the low strength of micro tools. Therefore, it is not easy to accurately control the product dimension error and to raise the production rate. In this paper, the applications of minimum quantity lubrication (MQL) in micro-milling and micro-grinding are presented. MQL is considered as a green manufacturing technology in metal cutting due to its low impact on the environment and human health. This study compares the tool wear and surface roughness in MQL micromachining to completely dry condition based on experimental investigations. The supply of MQL in vibration-assisted grinding is also studied. It is found that the use of MQL results in longer tool life and better surface roughness in mechanical micromachining.

Experimental Study on Vibration-Assisted Grinding

This paper presents experimental studies of vibration-assisted grinding with small-amplitude vibration (in the order of 1 μm) in terms of ground surface finish and tool life. The objectives are to obtain finer surface finishes on molds and longer tool life. The investigation shows that vibration-assisted grinding can improve surface finishes when compared with conventional grinding. Two different vibration frequencies are conducted in the experiments. Results show that surface finish and tool life are influenced by different process parameters. In vibration-assisted grinding, the best surface finish is obtained by using higher frequency of 11.4 kHz and lower feed rates. In this study, vibration-assisted grinding can extend tool life more than twice as that in conventional grinding. It is also shown that tool life in vibration-assisted grinding can be significantly improved by using minimum quantity lubrication (MQL).

Characteristics of chip generation by vertical elliptic ultrasonic vibration-assisted grinding of brittle materials

China National Natural Science Foundation [50905150]; Fundamental Research Funds for the Central Universities [2010121040]

Ultrasonic vibration-assisted grinding of micro-structured surfaces on silicon carbide ceramic materials

Precision grinding of silicon carbide ceramic micro-structured moulds is becoming more common in the area of the moulding of glass materials. However, in micro-structured grinding of super-hard and brittle materials, problems frequently occur in terms of chipping and rounding of micro-structural edge features. In order to overcome these technological constraints, a promising method using ultrasonic vibration of workpiece materials is proposed. The design of a novel ultrasonic vibration apparatus and the experimental investigation of ultrasonic vibration assisted grinding of SiC micro-structures are presented. The experimental results show that the application of ultrasonic vibration can enhance the ground surface quality and improve the edge features of micro-structures.

An experimental study of ultrasonic vibration-assisted grinding of polysilicon using two-dimensional vertical workpiece vibration

An experimental study of polysilicon grinding with ultrasonic vibration assistance was presented. The two-dimensional (2D) vertical vibration was applied on the workpiece directly and vibrated perpendicular to both the workpiece and grinding wheel. The grinding forces were measured using a three-component dynamometer, and the surface conditions were examined using a surface profilometer and a laser microscope. The experimental results showed that the grinding force and surface roughness with ultrasonication were much less than those in conventional grinding. In the case of ultrasonication, the wheel speed and worktable feed rate would have a more positive effect on the grinding force decrement/increment, especially for the tangential force while the wheel depth of cut had a negative effect. The surface condition of the ground polysilicon surface was improved with the assistance of ultrasonication. This research indicated that the 2D ultrasonic vibration-assisted grinding technique can be an effective method for the high-efficiency machining of hard brittle polysilicon material.

Thrust Force Directional Vibration-Assisted Ductile-Mode Grinding of Single-Crystal Si

Under optimum grinding conditions, a constant grinding force is exerted on a workpiece during ductile-mode grinding of BK7 glass. Based on the results, the cutting force, specific grinding energy, and depth of cut for a single grain were calculated. It was found that a single grain was easily removed from the material. However, grinding is impossible because surface burning occurs on the workpiece. In order to avoid burning, a single-crystal silicon wafer (1,0,0) surface was ground with thrust force directional vibration-assisted grinding. The normal grinding force with vibration was comparatively low, but was quite stable. The removal rate was approximately three times greater than that without vibration. The results indicate that the successive abrasive grains of the grinding wheel remove the material intermittently.

Recent developments in grinding of advanced materials

This article discusses the recent developments in grinding of advanced materials. Eighty-four journal papers published recently are briefly introduced. The topics are advances in grinding of brittle materials, grinding of silicon, dressing/truing of grinding wheels, grinding fluids, grinding of mirrors and vibration-assisted grinding, measuring/monitoring of grinding, optimization of grinding, modelling and simulation of grinding, and size effect. Ductile mode grinding of brittle materials has been and will continue to be an intensive research area because of its increasing industrial applications and academic demands for fundamental understanding of the ductile mode grinding mechanism. Highly precision manufacturing of silicon substrates faces more and more new challenges. Grinding of silicon continues to be a popular research topic. Using lasers to true and dress grinding wheels has attracted great research interest, because it has significant advantages over mechanical processes. Environmentally friendly grinding fluids are increasingly highly demanded. Vibration-assisted grinding is promising. Monitoring, modelling and optimization of grinding processes help to understand grinding mechanisms and achieve better grinding performance. The size effect is more prominent in grinding than turning and can be used for obtaining a controlled work-hardening surface layer with higher wear resistance and hardness.

Using vibration-assisted grinding to reduce subsurface damage

This paper discusses a technique for reducing subsurface damage and/or increasing material removal rate (MRR) in ceramics grinding. An indentation damage model shows that intermittent unloading can produce a lateral crack before the median crack fully develops. It shows that upon reloading, the lateral crack shields against further median crack penetration. Furthermore, intermittent unloading produces shielding even for oblique indentation events and intermediate locations of lateral cracks. Single-grit scratch tests provide experimental validation of the beneficial effects of intermittent unloading. A magnetostrictive actuator modulated the workpiece to create the intermittent unloading. Simulation studies predict that force per grit can be doubled under modulated conditions without an increase in normal damage in the finished workpiece. Our experimental observations show a 62% increase in MRR with minimal associated increase in depth of penetration of the median crack. Alternatively, the experimental results also show that modulations could be used to reduce the depth of median crack penetration by 24% at the same MRR. In addition, we observed that damage depth increases with an increase in the ratio of cutting speed to modulation frequency. Finally, both depth of cut modulation and cutting direction modulation were effective in reducing subsurface damage.