Electrochemical slurry jet micro-machining of tungsten carbide with a sodium chloride solution

Electrochemical slurry jet micro-machining (ESJM) is a new non-conventional process that couples abrasive slurry jet machining (ASJM) and electrochemical jet machining (ECJM) concurrently. A micro-jet of abrasive particles and electrolytic solution is made to impinge on the target while applying a DC potential between the jet nozzle and the workpiece. ESJM can be used to remove material that is difficult to machine through a combination of erosion, corrosion and synergistic effects. This study focuses on ESJM of tungsten carbide (WC) using a pH-neutral NaCl electrolyte rather than an alkaline solution which is more commonly used in the electrochemical processing of WC. For the studied process parameters, it was shown that the erosion due to ASJM alone was not able to erode the WC, and that the corrosion under ECJM was slow and produced unacceptably wide channels. The combined ESJM process however, was found to involve erosion of the developed oxide layer and subsequent exposure of un-corroded WC, leading to a much higher machining current density, corrosion rate, and machining localization than using ECJM alone. It was also found that the total abrasive kinetic energy, working voltage and solution concentration strongly affected the machining current density, material removal rate and aspect ratio (depth to width ratio). The results indicate that ESJM has a high potential to machine difficult-to-cut metals efficiently and economically.     

The effects of blast lag in abrasive jet machined micro-channel intersections

Abrasive jet micro-machining (AJM) uses compressed air carrying abrasive solid particles to micro-machine a variety of features into surfaces. If the feature sizes are less than the size of the abrasive jet footprint, then a patterned erosion-resistant mask is used to protect the substrate material, leaving exposed areas to define the features. Previous investigations have revealed a ‘blast lag’ phenomenon in which, for the same dose of abrasive particles, narrower mask openings lead to channels that are shallower than wider ones. Blast lag occurs when using AJM on brittle substrates because of the natural tendency to rapidly form a V-shaped cross-sectional profile which inhibits abrasive particle strikes on the narrow vertex at the feature centerline. In this paper, the blast lag phenomenon is studied when using AJM to machine a network of microfluidic channels. It is found that, in some cases, differences in blast lag occurring at channel intersections and within the channels themselves, can lead to channel networks of nonuniform depth. A previously developed surface evolution model is adapted to allow prediction of the onset of blast lag in the channels and intersections and thus explain these differences. Finally, methods to eliminate the differences are discussed.     

Erosive smoothing of abrasive slurry-jet micro-machined channels in glass,PMMA, and sintered ceramics: Experiments and roughness model

Abrasive slurry jet micro-machining (ASJM) was used to machine channels in glass, PMMA, zirconium tin titanate, and aluminum nitride. The channel roughness was measured as a function of the ASJM process parameters particle size, dose, impact velocity, and impact angle. The steady-state roughness of the channels was reached relatively quickly for typical ASJM abrasive flow rates. The roughness of channels having depth-to-width aspect ratios up to about 0.25 could be reduced by approximately 35% compared to the roughest channel by decreasing particle impact velocity and angle. However, machining at such conditions reduced the specific erosion rate by 64% on average. It was therefore quicker to post-blast reference channels (225 nm average root mean square (R_rms) roughness) using process parameters selected for peak removal. It was also found that the roughness of reference channels could be reduced by about 78% by post-blasting using 3 μm diameter silicon carbide particles at 15° jet incidence. The smoothest post-blasted channels had an R_rms roughness of about 23 nm in glass, PMMA, and zirconium tin titanate, and 170 nm in aluminum nitride. Computational fluid dynamics was used to predict the particle impact conditions that were used in a model to predict the steady-state roughness due to ductile erosion with an average error of 12%.     

基于流体自激的磨料水射流加工仿真与实验

针对先进陶瓷材料的高效、精密加工,提出了一种基于流体自激的新型磨料水射流加工方法——自激振荡磨料水射流加工(SEO-AWJM).采用ANSYS Fluent大涡模拟模型进行了流体仿真,仿真结果表明:当入口流速为135 m/s,腔长为4 mm时,下游喷嘴出口脉冲率最大达到28.47％.射流束的脉冲特性使得工件表面停滞层周...     

微磨料浆体射流的浆体配制及钻孔性能研究

微磨料浆体射流技术是在微磨料水射流加工技术基础上发展起来的一种新技术。通过添加分散剂和悬浮剂来提高浆体的沉降稳定性;为了配制出优质钻孔浆体,研究了磨料质量浓度、磨料种类、分散剂体积分数和悬浮剂体积分数对钻孔加工的影响,并研究了分散剂体积分数和悬浮剂体积分数对浆体沉降稳定性的影响。研究结果表明：磨料质量浓度存在最佳取值;分散剂并非一定能改善颗粒的沉降稳定性,这与磨料种类、磨料质量浓度和分散剂体积分数等有关;悬浮剂能够改善浆体的悬浮性,其体积分数影响浆体的沉降稳定性和钻孔效果。     

磨料水喷嘴的优化设计

为提高磨料水射流加工设备中磨料水喷嘴加工性能,通过实验研究了磨料水喷嘴几何形状对喷嘴磨损的影响,并研究了磨料水喷嘴机械结构和加工性能,最终确定优化加工条件.     

超高压磨料射流切割喷嘴装置研制及其应用

通过对水射流中磨粒粒子运动形式的分析,认为结构设计参数主要是磨料射流内部靶距和磨料混合管长度,试验结果表明内部靶距为12mm,混合管长度为50mm切割效果较好,据此设计并研制磨粉射流切割喷嘴装置.并验证了设计的合理性.     

磨料射流切割机的试验研究

本文介绍了前混合式磨料射流切割机的结构,工作原理以及用该机对金属和非金属材料进行的切割试验,指出射流工作压力、喷射靶距、喷嘴横移速度、磨料重量比浓度等是影响工作能力的主要因素,喷嘴直径及其内腔结构、磨料粒子尺寸等也是影响割缝宽度及表面形态的因素.试验对此表明,它比纯高压水射流和后混合式磨料射流切割机性能优越,是一种新型的、有广阔应用前景的工业切割设备.     

Abrasive waterjet machining simulation by SPH method

Abrasive waterjet machining (AWJM) is a non-conventional process. The mechanism of material removing in AWJM for ductile materials and existing erosion models are reviewed in this paper. To overcome the difficulties of fluid–solid interaction and extra-large deformation problem using finite element method (FEM), the SPH-coupled FEM modeling for abrasive waterjet machining simulation is presented, in which the abrasive waterjet is modeled by SPH particles and the target material is modeled by FE. The two parts interact through contact algorithm. The creativity of this model is multi-materials SPH particles, which contain abrasive and water and mix together uniformly. To build the model, a randomized algorithm is proposed. The material model for the abrasive is first presented. Utilizing this model, abrasive waterjet penetrating the target materials with high velocity is simulated and the mechanism of erosion is depicted. The relationship between the depth of penetration and jet parameters, including water pressure and traverse speed, etc., are analyzed based on the simulation. The results agree with the experimental data well. It will be a benefit to understand the abrasive waterjet cutting mechanism and optimize the operating parameters.     

Effect of curing parameters and configuration on the efficacy of ultraviolet light curing self-adhesive masks used for abrasive jet micro-machining

Abrasive jet micro-machining (AJM) uses a high speed jet of particles to mechanically etch features such as micro-channels into a wide variety of target materials. Since the resulting air-particle jet is divergent, erosion resistant masks are required for patterning. Because of their ease of application, 50 and 100 μm thick commercially available ultraviolet (UV) light curing self-adhesive masks are potentially very useful in AJM. However, optimum curing parameters have until now been specified in terms of a curing time for a specific recommended curing unit, making extrapolation to other curing units impossible. Using masks to create straight 250–600 μm wide reference channels in borofloat glass, this paper quantified the optimum curing UV light energy density, and investigated the effect of differing UV exposure units (flat and cylindrical-backed), UV light energy densities, and mask configuration during curing, on the pattern transfer accuracy (before AJM), and the eroded micro-channel feature size. As expected, as long as the masks were cured at the same energy density, the pattern transfer accuracy did not depend on the curing unit. The most accurate pattern transfer to the mask film (widths within 5–7% of design) corresponded to energy densities between 516–774 and 387–516 mJ/cm² for the thick (100 μm) and thin (50 μm) masks, respectively. Under these conditions and for both exposure units, the average widths of the eroded channels after AJM were found to be within 3–9% of the intended design. Curing the masks outside this range resulted in eroded features that were approximately 15–20% and ∼5% larger than intended, for the thick and thin masks, respectively. The orientations of the channel patterns with respect to the curing cylinder axis did not affect the pattern transfer. However, when compared to the cylinder ends, curing at the midpoint along the cylinder length improved the pattern accuracy by approximately 3%, resulting in eroded features that were 10–20% closer to the design width. Finally, it was found that patterning multiple layers of masks improved the erosion resistance without compromising the feature width, enabling the AJM of higher aspect ratio features.     

Jet properties and mixing chamber flow in a high-pressure abrasive slurry jet: part I—measurement of jet and chamber conditions

Techniques to enhance the performance of a high-pressure abrasive slurry jet micro-machining process (HASJM) were investigated by altering the conditions within the jet. The slurry flow rate was controlled using six inlet tubes (cross-sectional areas of 0.2, 0.46, 1.27, 1.77, 3.08, and 4.51 mm²), and was found to have a large effect on the conditions within the mixing chamber. The tubes permitted the use of high-concentration slurry solutions, which resulted in increased machining rates and the ability to machine glass targets without cracking by using a minimum particle concentration of 17 wt%. Slurry tubes producing large slurry flow rates caused the mixing chamber to flood, resulting in a much lower jet velocity. The size of the smallest slurry tube size that caused the mixing chamber to flood was dependent on the pump operating pressure, and varying from 1.27 mm² at 134 MPa, to 1.5 mm² at 233 MPa. Mixing chamber flooding significantly reduced the erosion rate of the jet and increased the machining time, as discussed in the second part of this two-part paper. Mixing chamber pressures were found to be low enough to cause boiling, which increased the jet diameter and the width of features that could be machined without a mask.     

Abrasive Waterjet Machining Simulation by Coupling Smoothed Particle Hydrodynamics / Finite Element Method

In dealing with abrasive waterjet machining(AWJM) simulation,most literatures apply finite element method(FEM) to build pure waterjet models or single abrasive particle erosion models.To overcome the mesh distortion caused by large deformation using FEM and to consider the effects of both water and abrasive,the smoothed particle hydrodynamics(SPH) coupled FEM modeling for AWJM simulation is presented,in which the abrasive waterjet is modeled by SPH particles and the target material is modeled by FEM.The two parts interact through contact algorithm.Utilizing this model,abrasive waterjet with high velocity penetrating the target materials is simulated and the mechanism of erosion is depicted.The relationships between the depth of penetration and jet parameters,including water pressure and traverse speed,etc,are analyzed based on the simulation.The simulation results agree well with the existed experimental data.The mixing multi-materials SPH particles,which contain abrasive and water,are adopted by means of the randomized algorithm and material model for the abrasive is presented.The study will not only provide a new powerful tool for the simulation of abrasive waterjet machining,but also be beneficial to understand its cutting mechanism and optimize the operating parameters.     

Direct 3D mask modeling for nonplanar workpieces in microabrasive jet machining

Recently, a new microengraving technology, microabrasive jet machining, has been studied as a machining technology for highly brittle materials. The technology implements the machining by using an abrasive jet and it uses mask structures to achieve microscale geometrical accuracy. The mask structure selectively blocks the abrasive jet at the portions of the surface that are not to be machined. Modeling and fabrication of the mask structure are thus key processes in microabrasive jet machining. Microstereolithography is believed to be a better means of mask fabrication for general planar and nonplanar workpieces. However, it is not easy to model a precise 3D mask structure from a given pattern image. Because of inconsistencies between the computer-aided design (CAD) model and the actual workpiece, mask structures modeled from workpiece CAD models often fall off. We therefore propose an automated modeling algorithm for the corresponding 3D nonplanar mask structure by using measured geometry directly. The algorithm takes the workpiece geometry as section images acquired from computer tomography and generates the CAD mask model directly from the section and mask images. Application software was developed to verify the algorithm and was tested by verification and actual cases.     

Inverse methods to gradient etch three-dimensional features with prescribed topographies using abrasive jet micro-machining: Part II—Verification with micro-machining experiments

Cross sectional shape and centerline waviness along the length of a micro-channel can affect different characteristics of microfluidic flow, including heat transfer, pressure distribution and dissipation, and separation of flow. Current existing technologies that allow such micro-machining have many limitations. The accompanying paper presented inverse techniques that can be used to predict the required non-uniform velocity to gradient etch, using abrasive jet micro-machining (AJM), micro-channels and pockets with a wide variety of prescribed textures and cross-sectional shapes. Methods to predict the final three-dimensional (3D) profiles of such features were also presented. In this paper, the velocity functions predicted using the inverse methods were used to machine micro-channels with prescribed centerline depths that varied linearly, parabolically and sinusoidally, pockets with prescribed textures in two directions, and micro-channels with prescribed W-shaped cross sections. Two different erosive efficacy sources were used, one resulting from an adjustable shadow mask and one using a maskless technique. The inverse and 3D shape prediction techniques were verified by comparing the measured feature topographies with those that were initially prescribed. The effect of process parameters such as source shape and the machined feature size on the accuracy of machined features and predictions of the models were also discussed. Overall, the inverse techniques were found to be very effective for predicting the process parameters required to machine a wide variety of desired micro-channel and pocket topographies.     

Studies on Recharging of Abrasives in Abrasive Water Jet Machining

The objective of this work is to find the effect of the recharging of local garnet abrasives (origin: southern India) while cutting aluminium using abrasive water jet machining. The influence of the specially formulated optimised abrasive test sample, pressure, traverse rate, and abrasive flowrate, on the American Foundrymen’s Society fineness number, depth of cut, top and bottom kerf width, kerf taper, and surface roughness are studied. The performance of the test sample has been compared with that of commercial grade abrasive with mesh size 80. Additionally, recharging studies are carried out after screening out particles of less than 90 μm. These tests help to determine the optimum recharging required.     

磨料水射流的切割机制

研究了100MPa～400MPa高水压下磨料水射流（AWJ）的切割机制。根据射流与材料之间的相互作用过程,建立和验证了AWJ切割过程模型。揭示了典型材料的切割特征（切割深度、切口宽度和冲蚀量）与切割变量（水压、靶距和切割速度等）的相关规律,以及磨料、材质两大因素的影响。获得了结果对AWJ切割技术的开发和应用具有指导意义和实用价值。     

Application of Taguchi design for quality characterization of abrasive water jet machining of TRIP sheet steels

In the present paper, the influence of sheet thickness, nozzle diameter, standoff distance, and traverse speed during abrasive water jet machining (AWJM) of transformation-induced plasticity (TRIP) sheet steels on surface quality characteristics (kerf geometry and surface roughness) was investigated. The experiments were designed using Taguchi methodology and carried out by AWJ Machining TRIP 700 CR-FH and TRIP 800 HR-FH steel sheets. As response variables, mean kerf width and average surface roughness were selected. The experimental results were analyzed using analysis of means and analysis of variance methods in order to correlate the AWJM process parameters the response variables. In addition, regression models were obtained using the experimental results and validated with six independent experiments. The reported results indicate that the proposed methodology can satisfactorily analyze the surface roughness and the mean kerf in AWJM; moreover, it can be considered as valuable tools for process planning in workshop.     

应用模糊理论预测磨料水射流切深模型的建立

以理论为基础,应用磨料水射流切割加工时的工艺参数:水射流压力、射流横移速度和磨料流量等实验数据,建立一个模糊控制模型。这个模糊控制模型可以预测在任何给定一组加工参数时,可获得的切割深度。给出磨料水射流切割铝合金实例。     

磨料浆体流针阀体研磨技术研究

提出了一种基于磨料浆体射流技术的针阀体喷孔研磨技术。该技术利用针阀体喷孔的节流作用使射流发生,靠浆料的研磨作用来去除针阀体内流道毛刺,对喷孔孔口进行倒角,以提高其流量系数。加工时,通过流量控制系统实时监测、控制针阀体的实时流量与终止流量,来控制其流量离散度。实际加工实验表明,该技术可以提高针阀体流量系数到0.85左右,同批针阀体流量离散度控制在±1%以下,达到国外同类技术的先进水平。     

基于磨料水射流的螺杆转子加工新方法研究

螺杆转子传统加工过程中存在刀具磨损和过高切削热量等难题。为此,将具有无刀具磨损、切削热量低、绿色环保特点的磨料水射流加工方法引入螺杆转子加工研究之中,提出了磨料水射流多轴联动加工螺杆转子的新方法,以提高转子加工精度和效率。采用任意拉格朗日与欧拉方法构建了转子加工模拟模型,将模拟分析结果与实验数据进行比较,验证了模拟模型的正确性。最后,通过磨料对水射流多轴联动加工模拟结果的分析,证明了螺杆转子加工新方法的合理性。