Zeng Wen Liu

Study on the Effect of Standoff Distance on Processing Performance of Alumina Ceramics in Two Modes of Abrasive Waterjet Turning Patterns

Abrasive waterjet (AWJ) turning is an emerging technology, which plays an important role in machining cylindrical parts with the distinct advantages of negligible thermal effects and extremely low cutting force. This paper presents an experimental study of abrasive waterjet turning (AWJT) of Al2O3 ceramics. The machining process and performance in terms of the depth of penetration (DOP), surface roughness (Ra) and actual impact angle (β) are discussed to understand the effect of standoff distance (SOD) on the processing performance at two different turning modes. Based on the results of these investigations, there is a significant change of DOP and Ra at different SOD in radial mode turning and the optimal SOD of gaining maximum DOP and the minimum Ra is about 5.5mm.However, the DOP is nearly independent on the SOD in offset mode turning. Smaller Ra and DOP can be obtained in offset mode. Furthermore, the results indicate that the roundness error of cylinder parts is probably improved with the proper SOD interval in radial mode turning and it is suitable for machining cylinder part with considerably different radial size. The offset mode turning as the next operation after radial mode turning is recommended to process workpiece with excellent roundness. In this way, by understanding the effect of SOD on processing alumina ceramics, the paper establishes a good basis for developing strategies for optimizing processing parameters in order to generate the desired part geometry and achieve better surface quality.

An Experimental Research on Abrasive Water Jet Polishing of the Hard Brittle Ceramics

Abrasive water jet (AWJ) technology, due to its potential advantages, is a promising machining method for precision machining brittle materials. In this research, the AlN ceramics was polished using an AWJ machining system. A considerable processing quality has been achieved and a reduction up to 62% of the surface roughness has been obtained. Effects of different process parameters on the surface roughness of the polished workpiece were analyzed. Under the current conditions of the experiments, using a lower impact angle, smaller abrasives and a lower nozzle traverse speed may be appropriate for polishing AlN ceramics.

Study on Machining System of Precision Micro Abrasive Water Jet and Polish Experiment

This paper conducts a study on a precision micro abrasive waterjet (PMAWJ) machining system. A new kind of precision micro abrasive water jet system is designed and tapped. The flux and the flow velocity of the PMAWJ system are tested by experiments. Using the micromachining system, a group of polishing experiments is conducted for two kinds of hard-brittle materials such as silicate glass and silicon nitride. The results show the feasibility and the advantage of the PMAWJ machining system for polishing hard-brittle materials.

Erosion Mechanism of Ultrasonic Vibration Abrasive Waterjet in Micro Machining

In this paper, a study on erosion mechanism of Ultrasonic Vibration Abrasive Waterjet is presented. Theoretical analysis of the total effective erosion kinetic energy of UVAWJ is performed. By using a UVAWJ machining system with an Ultrasonic Vibration Power Workbench, the comparative experiment is conducted. The erosion surfaces of the single crystal silicon substrate were measured by Optical Profiler and observed with Scanning Electron Microscope. The material removal mechanisms are discussed. It is concluded that the erosion by UVAWJ, with the aid of high-frequency ultrasonic vibration, can obtains a high material removal, less cracks and good finish surface.

A Technological Study on Granite Grinding

It is desirable that the precision of the shape and the dimension of stone products in top grade decoration is getting higher. Grinding is one of the main technology in machining stone which ensures the precision of the shape and the dimension of stone products, and influences the machining efficiency. This investigation aims to experimentally find out the reasons causing grinding wheel wear and the factors influencing smoothness. It is found that the wear of grinding wheel is mainly caused by the hardness and removal quantity of stone. The harder the stone, the shorter the life of grinding wheel. The greater the removal quantity of stone, the bigger the wear of grinding wheel. The surface smoothness of stone is mainly related to the size of abrasives and the spindle speed. The smaller the abrasives and the higher the speed, the higher the smoothness.

A Study on Erosion Performance of Monocrystalline Silicon in Ultrasonic Vibration-Assisted Abrasive Water Jet Machining

Ultrasonic vibration-assisted machining (UVAM) is an effective and promising technology for processing hard and brittle materials, it has been explored in many experimental and theoretical investigations. In this paper, a study on the erosion performance of monocrystalline silicon with UVAM is presented and discussed. In the erosion experiments, monocrystalline silicon wafers were eroded by the abrasive water jet machine assisted with an ultrasonic vibration system. A contrast experiment was carried out firstly to study the influence of the ultrasonic vibration, and then an orthogonal experiment investigation was carried out to understand the effect of process variables (the abrasive particle diameter, jet impact angle, standoff distance, abrasive mass flow rate and ultrasonic vibration power) on the depth of erosion and material removal rate (MRR). The experimental results revealed that ultrasonic vibration-assisted abrasive water jet erosion (UVA-AWJE) can obviously improve the depth of the erosion and MRR compared with those in traditional AWJE and the variation trends of the effect of the abrasive particle diameter, jet impact angle, standoff distance and abrasive mass flow rate on the erosion performance in UVA-AWJE are very similar to those effect in the traditional AWJ machining.

An Experimental Study on Radial-Mode Abrasive Waterjet Turning of Alumina Ceramics

A study on the radial-mode abrasive waterjet turning (AWJT) process is presented and discussed. An experimental investigation is carried out to explore the influence of process parameters on the depth of turning and material removal rate (MRR) when turning 96% alumina ceramics. The experiment is designed by the multifactor orthogonal experiment methods. The effect of feed speed, water pressure, abrasive mass flow rate, nozzle tilted angle and surface speed are investigated by the range analysis and variance analysis. The results show that the feed speed is the most significant variables affecting the depth of turning. Based on the test conditions, it is found that the most efficient conditions to maximize depth of turning are at a jet angle of 105 degree, a water pressure of 310MPa, an abrasive mass flow rate of 11.5 g/s, a surface speed of 5.5m/s and a feed speed of 0.05mm/s. At last, the effect mechanism of process variables on the depth of turning is analyzed qualitatively.

Study on Jet Formation and Modeling for High Pressure Abrasive Water-Jet

High pressure abrasive water jet (HPAWJ) machining has many advantages in hard brittle material processing. In this paper, the hole formation on stone by HPAWJ is analyzed based on brittle and plastic fracture theories. The formation and construction of jet are studied. The distribution of jet velocity, abrasives and energy in the jet-beam section of HPAWJ is analyzed. It is shown that the cross-section of the hole is characterized by a ‘Reverse-bell’ shape on stones by a HPAWJ. The jet velocity of HPAWJ gets lower from jet center to jet margin and it’s distribution is consistent with normal distribution function along with jet center. The concentration of abrasives becomes smaller from jet margin to jet center and it’s distribution is consistent with normal distribution function along with jet margin. The distribution of jet velocity, abrasives and energy in the section of HPAWJ is modeled.

Study on Cutting Force of Diamond Cutter in Special-Shaped Stone Processing

The cutting force is the key factors influencing the processing precision and efficiency in special-shaped stone production. In this research, the cutting force is measured and analyzed in the process of special shaped cutter cutting stone. It is found that the relationship of cutting force with peripheral speed of cutter is nearly inverse proportional. The cutting force becomes smaller and smaller as the peripheral speed of cutter increases. The relationship of cutting force with feed rate is nearly proportional. The cutting force becomes larger and larger as the feed rate increases. The relationship between Fx, Fy and Fz is Fz > Fx > Fy. Enhancing the peripheral speed of cutter is a better way to increase the material removal rate.

Analysis and Modeling of Micro Abrasive Air Jet Cutting Aspect Ratio

Micro abrasive air jet machining technology is being increasingly used in the fields of micro cutting. Since the aspect ratio is a major interest characteristics of kerf in micro cutting, an experimental investigation is carried out to study the effect of cutting process parameters on the aspect ratio in this study. It is found that the aspect ratio increases with an increase in air pressure, abrasive flow rate and jet incidence angle, while decreases with an increase in nozzle traverse speed. Furthermore a predictive model for aspect ratio is developed using the dimensional analysis technique. It is shown that the model predictions are in good agreement with the experimental results. The research results may be meaningful to efficiently control the aspect ratio.