Rotary Ultrasonic Grinding Research Articles

Investigation on three-dimensional surface roughness evaluation of engineering ceramic for rotary ultrasonic grinding machining

Surface roughness has considerable influence on its quality and function of products in precision and ultra-precision machining, and the same situation applies to engineering ceramic for rotary ultrasonic grinding machining (RUGM). This paper presents a new parameter, called fractal root mean square deviation, for evaluating engineering ceramic three-dimensional (3D) surface roughness of RUGM. Based on engineering ceramics surface of RUGM is typical isotropic, the mathematical model of fractal root mean square deviation was established, and it possesses double characteristics of absolute measurement and multi-scale. Then validation has been implemented, and fractal root mean square deviation is superior to evaluate engineering ceramic 3D surface roughness with better resolution and sensitivity. Furthermore, the relationship between main factor parameters and fractal root mean square deviation was proposed. The evaluation parameter and the results could be implemented in practice to get higher quality surface.

Design of five-axis ultrasonic assistant compound machine tool

A compound machine tool was designed, which combined rotary ultrasonic assisted grinding, electrical discharge machining (EDM) and multi-axis milling. Experimental results indicated that its positioning accuracy was less than 5.6 µm and its repetitive positioning accuracy was less than 1.8 µm; the vibration amplitude of ultrasonic grinding system was uniform and stable, and the EDM system worked well and stably. A smooth surface of K9 optical glass component was achieved by the grinding method.

Investigation on surface micro-crack evaluation of engineering ceramics by rotary ultrasonic grinding machining

Rotary ultrasonic grinding machining (RUGM) is regarded as the most powerful machining method for engineering ceramic. However, there are micro-cracks on the machined surface inevitably for lower fracture roughness of material. As part of surface integrity, effective parameter and unified criterion are not proposed for micro-crack evaluation. In the paper, surface micro-crack evaluation of engineering ceramics by RUGM was investigated. Micro-crack generation area ratio calculation model and information dimension calculation model were established. On the basis of those, a new evaluation parameter, called micro-crack fractal density, was proposed to reveal the characteristics of micro-crack. The parameter was proved to evaluate micro-crack evolution rule effectively with the advantages of statistics and multi-scale. Meanwhile, the factors affecting micro-crack fractal density evaluation were investigated. It is found that the micro-crack fractal density increases with cutting force rising, while it decreases as fracture toughness rises. The results provide the support for surface integrity evaluation of engineering ceramics.

Study on Grinding Force of High Volume Fraction SiCp/Al Composites with Rotary Ultrasonic Vibration Grinding

High volume fraction SiCp/Al composites were grinded in rotary ultrasonic vibration aided grinding in this experiment, exploring the effects of different grinding parameters (grinding depth, grinding wheel speed, feed rate) on grinding force and the material removal mechanism with ultrasonic grinding. The results showed that grinding force of ultrasonic grinding is lower than the ordinary grinding in the same grinding parameters. Studying on material removal mechanism of ultrasonic vibration grinding is bound to have important theoretical and practical significance for the improvement of grinding processes and the development of mechanical according to the advantages of grinding and ultrasonic machining. Keywords: High volume fraction SiCp/Al composites; ultrasonic grinding; grinding force

Grinding strategies for machining the off-axis aspherical reaction-bonded SiC mirror blank

Demand for large-scale off-axis aspherical mirrors is increasing in next-generation space-borne optical imaging systems. In this paper, a variable-axis single-point grinding strategy is developed for precisely, cost-effectively figuring silicon carbide (SiC) mirror blanks that have high-order high-gradient off-axis aspherical surfaces on a precision five-axis machining center. The grinding strategies also include tool path generation/optimization, feeding direction control and wheel wear reduction/compensation. Applying the developed grinding strategies, by only one grinding cycle, a near-circular 372-mm SiC mirror blank is successfully grounded to 7.8 m in peak to valley, which is comparable to the reported machining accuracy of the BoX ultraprecision grinding machine. Moreover, the wheel need not have to be dressed during the whole grinding cycle due to the rotary ultrasonic grinding method. Therefore, this paper offers an efficient and economic solution for grinding off-axis aspherical and free from surfaces to micron-level accuracy, thus significantly decreasing the subsequent lapping/polishing production cycle time. 2014 中文 Optics Letters.

Effects of High Frequency Vibration on the Surface Quality in Rotary Ultrasonic Machining of Glass BK7

Both rotary ultrasonic machining (RUM) and conventional grinding (CG) experiments were performed on the glass BK7 specimen to investigate the effects of high frequency vibration on the surface quality. The surface morphologies produced in the two machining processes were assessed and the associated material removal mechanisms were explored. Also, the influence of the spindle speed on the surface roughness was discussed. It was found that the mechanisms of the material removal involved in the RUM process were material pulverization and brittle fracture, while ductile flow and brittle fracture prevailed on the material removal in CG process. The increased spindle speed would reduce the lateral cutting depth of each abrasive, and promote the shielding effects of the lateral cracks generated by the previous abrasive, leading to the reduction of the surface roughness in both RUM and CG processes.

Investigation on the cutting force of machining process for Si<SUB align="right">3N<SUB align="right">4 engineering ceramics

In order to understand the machining process of Si3N4 ceramics and to achieve the precision machining for components and parts of Si3N4, cutting force of face machining with conventional grinding and rotary ultrasonic grinding methods was investigated. In the paper, the machining processes of conventional grinding machining and rotary ultrasonic grinding machining (RUGM) were simulated by finite element method (FEM), based on the motion trails of diamond abrasive particles on the tool. The cutting force was predicted from the simulated models. Then the cutting force of face machining was obtained through the experiments of the two machining operations with the same process parameters. The experimental results show that the cutting force of RUGM is about 25% less than that of conventional grinding for face machining. It is consistent with the simulation results. Meanwhile, the differences of cutting force between conventional grinding and RUGM were analysed and were proved by the work of single grit in a unit.

EXPERIMENTAL STUDY ON THE CUTTING FORCE DIFFERENCE BETWEEN ROTARY ULTRASONIC MACHINING AND CONVENTIONAL DIAMOND GRINDING OF K9 GLASS

A comprehensive experimental study on the cutting force differences between rotary ultrasonic machining (RUM) and conventional diamond side grinding, drilling and face grinding is conducted on K9 glass. By analyzing the experimental results and the kinematics of diamond grits, it can be seen that the reasons for the cutting force differences between with and without ultrasonic vibration are not same for the three machining processes. The cutting force difference of conventional diamond side grinding and RUM can be explained by analyzing the trajectory of diamond grits, while the cutting force difference of conventional diamond drilling and RUM is mostly dependent upon the difficulty level of removing chips. As a transitive form, the cutting force difference between conventional diamond face grinding and RUM is affected by both the diamond grits' trajectory and the difficulty level for removing chips. In addition, it is also noticed that different cutting tools have different reduction percentages of cutting forces in RUM compared with conventional diamond grinding. The findings are helpful for researchers to have a further understanding in RUM.

旋转超声磨削加工中影响磨具寿命的结构参数优化

This paper focused on improving machining precision and reducing the machining errors caused by tool wearing in a Rotary Ultrasonic Grinding Machining(RUGM).The relation model between the ultrasonic vibration tool life and the grit sizes,grit concentration and the inner circle radius of a tool was established,and the parameters affecting ultrasonic vibration tool life were optimized.First,the second order model of ultrasonic vibration tool life was established for a bronze-bonded ultrasonic vibrating tool with Response Surface Methodology(RSM),and the model was fitted based on Box-Behnken experiments.Then the ultrasonic vibration tool life model was checked by effectiveness and significance tests.Finally,the cross-fertilization between the various influence factors and the tool life was analyzed through fitting the response surface and the contour between ultrasonic vibration tool life and factors,and the ultrasonic vibration tool parameters were optimized.The results indicate that the wear capacity of ultrasonic vibration tool is only 0.006 9 mm,after removing 9 600 mm3 for Si3N4 ceramics materials with density of 85%,when the grit size is D98.85,grit concentration is 77.36,and the inner circle radius of the tool is 5.34 mm.It satisfies the finish machining requirements for RUGM.

Experimental investigation on the surface integrity in machining for Si<SUB align="right">3N<SUB align="right">4 engineering ceramics

Conventional grinding and rotary ultrasonic grinding machining (RUGM) are applied in precision machining for Si3N4 engineering ceramics mostly. The surface integrity is of great difference with different processing operation. In the paper, the differences of surface integrity by the two machining methods were investigated. The comprehensive evaluation for surface integrity parameters of surface microstructure flaws and mechanical properties was investigated. The surface roughness, surface edge-chipping and surface residual stresses were observed and detected. The experiments results were analysed and discussed based on the material removal process, the motion trail of diamond grits, cutting force and tool wear for the different machining methods. The results show that the surface roughness and the residual stress for RUGM are worse than that for conventional grinding, since the effect of indentation fracture is more notable. However, the scope of edge-chipping is smaller for RUGM than that for conventional grinding due to lower cutting force.

Rotary Ultrasonic-Assisted Grinding of Ceramic Material

The engineering ceramic material is hard to machining with the hard and brittle characteristics, so we are using a precision machining method of the rotary ultrasonic assisted grinding. In this paper, a research on the rotary ultrasonic assisted grinding mechanism of zirconia ceramic material is described. We use an experimental method of the orthogonal combination to complete an experiment of the rotary ultrasonic grinding of zirconia ceramic material. According to the experiment, we explore how the various grinding parameters affect the surface roughness, and determine a set of the optimal grinding parameters.

Investigation on the bonding strength patterns of ultrasonic vibration tools and influence on working performance during rotary ultrasonic grinding

During rotary ultrasonic grinding process, working performance of ultrasonic vibration tools varies according to the bonding patterns between diamond grit and bond. In order to understand the influence of ultrasonic vibration tools on working performance, bonding patterns and bonding strength of ceramic-bonded, iron-bonded, and bronze-bonded tools were investigated. Influence of bonding strength on cutting force, tool wear, surface quality, and edge breakout were studied, coupled with the characteristics of ultrasonic vibration tools. The results show that cutting force in Z axis and tool wear reduce with the increase of bonding strength while the surface quality and edge breakout become worse.

旋转超声磨削加工中刀具结合剂类型与加工性能的关系

旋转超声磨削加工中刀具结合剂类型与加工性能的关系

Research on material removal rate in rotary ultrasonic grinding machining

To improve the material removal rate (MRR) of engineering ceramics in rotary ultrasonic grinding machining (RUGM), machining mathematical model of material removal rate was established based on analysis of fracture removal mechanism of the engineering ceramics. Parameters which affect the material removal rate of the rotary ultrasonic machining were studied, and by experiments the model was proved and the processing parameters of cutting area, feed rate and cutting speed were optimised to achieve higher material removal rate.

Air-Lubricated Pneumatic Workbench

The air-lubricated pneumatic workbench introduced in this paper is used in rotary ultrasonic machining which are widely used to machine hard and brittle materials. It is necessary to use special ultrasonic machine tool for rotary ultrasonic machining in the traditional ultrasonic machining, limiting the application of ultrasonic machining. A new type of rotary ultrasonic grinding cutter is developed, which can be mounted on the general purpose machine tool used to machine the hard brittle materials. The air-lubricated pneumatic workbench on which the workpiece is fixed can be used to precisely control the force between the workpiece and rotary ultrasonic grinding cutter when machining. Based on the experimental results of the pneumatic workbench which has been manufactured we find that the force between the workpiece and rotary ultrasonic grinding cutter can’t be easily controlled for the rolling bearings used in such workbench and the rolling friction force between the rolling bearing and guide way. This paper describes a novel pneumatic workbench where we replace the rolling bearing with air bearing which introduces essentially zero friction between the air bearing and guide way. The stiffness of the air-lubricated pneumatic workbench has been calculated in this paper.

Study on Ultrasonic Grinding Method and Mechanism of the Engineering Ceramic Material

It is one of the feasible methods to resolve the complex cavity processing by carrying on rotary ultrasonic grinding machining with the simple tools. On the basis of the theory processing engineering Ceramics, this paper designed the rotary ultrasonic grinding tools and analyzed the material removal mechanism by using rotary ultrasonic grinding NC engineering ceramics processing technology; and carried on a preliminary study to the rotary ultrasonic grinding processing mechanism.