铣削工艺参数对锡铋合金表面粗糙度特征影响及试验分析

目的对锡铋合金表面粗糙度特征进行研究分析,提高表面加工质量。方法采用正交试验设计方法,以最小表面粗糙度作为优化指标,以主轴转速、铣削深度、进给速度、铣削宽度作为影响因素,进行精密铣削试验研究。结果利用方差分析确定了进给速度是锡铋合金铣削表面粗糙度最重要的影响因素,并基于田口方法优化分析得到了锡铋合金铣削加工工艺最优组合。结论采用田口法对锡铋合金铣削工艺参数优化,有效地减少了加工表面粗糙度,提高了工件表面质量。     

Machining assessment of nano-crystalline hydroxyapatite bio-ceramic

Hydroxyapatite (HAP) is a widely used bio-ceramic in the fields of orthopedics and dentistry. This study investigates the machinability of nano-crystalline HAP (nHAP) bio-ceramic in end milling operations, using uncoated carbide tool under dry cutting conditions. Efforts are focused on the effects of various machining conditions on surface integrity. A first order surface roughness model for the end milling of nHAP was developed using response surface methodology (RSM), relating surface roughness to the cutting parameters: cutting speed, feed, and depth of cut. Model analysis showed that all three cutting parameters have significant effect on surface roughness. However, the current model has limited statistical predictive power and a higher order model is desired. Furthermore, tool wear and chip morphology was studied. Machined surface analysis showed that the surface integrity was good, and material removal was caused by brittle fracture without plastic flow.     

Evaluation of vegetable based cutting fluids with extreme pressure and cutting parameters in turning of AISI 304L by Taguchi method

Many problems such as health and environment issues are identified with the use of cutting fluids (CFs). There has been a high demand for developing new environmentally friendly CFs such as vegetable based cutting fluids (VBCFs) to reduce these harmful effects. In this study, performances of six CFs, four different VBCFs from sunflower and canola oils with different ratios of extreme pressure (EP) additives, and two commercial types of CFs (semi-synthetic and mineral) are evaluated for reducing of surface roughness, and cutting and feed forces during turning of AISI 304L austenitic stainless steel with carbide insert tool. Taguchi’s mixed level parameter design (L₁₈) is used for the experimental design. Cutting fluid, spindle speed, feed rate and depth of cut are considered as machining parameters. Regression analyses are applied to predict surface roughness, and cutting and feed forces. ANOVA is used to determine effects of the machining parameters and CFs on surface roughness, cutting and feed forces. In turning of AISI 304L, effects of feed rate and depth of cut are found to be more effective than CFs and spindle speed on reducing forces and improving the surface finish. Performances of VBCFs and commercial CFs are also compared and results generally show that sunflower and canola based CFs perform better than the others.     

Analysis of machined surface quality in a single-pass of ball-end milling on Inconel 718

The ball-end milling process is widely used for generating three-dimensional sculptured surfaces with definite curvature. In such cases, variation of surface properties along the machined surface curvatures is not well understood. Therefore, this paper reports the effect of machining parameters on the quality of surface obtained in a single-pass of a ball-end milling cutter with varying chip cross-sectional area. This situation is analogous to generation of free form cavities, pockets, and round fillets on mould surfaces. The machined surfaces show formation of distinct bands as a function of instantaneous machining parameters along the periphery of cutting tool edge, chip compression and instantaneous shear angle. A distinct variation is also observed in the measured values of surface roughness and micro-hardness in these regions. The maximum surface roughness is observed near the tool tip region on the machined surface. The minimum surface roughness is obtained in the stable cutting zone and it increases towards the periphery of the cutter. Similar segmentation was observed on the deformed chips, which could be correlated with the width of bands on the machined surfaces. The sub-surface quality analysis in terms of micro-hardness helped define machining affected zone (MAZ). The parametric effects on the machining induced shear and residual stresses have also been evaluated.     

Process capability study of laser assisted micro milling of a hard-to-machine material

Laser assisted micro milling (LAMM) is capable of generating three-dimensional micro scale features in hard-to-machine materials. This paper compares the process capability of LAMM with conventional micro milling of a hardened tool steel. In particular, the potential advantages of LAMM over micro milling with respect to cutting forces, tool wear, material removal rate, burr formation and surface roughness are investigated when micro milling hardened A2 tool steel (62 HRC). The results show that LAMM has significant advantages over micro milling, especially in terms of cutting forces, material removal rate and tool wear. The average reduction in the resultant cutting force is found to be up to 69% with laser assist. In addition, tool wear is found to be substantially less with laser assist even when the material removal rates are increased by a factor of six over the tool manufacturer recommended cutting conditions.     

Performance-Based Predictive Models and Optimization Methods for Turning Operations and Applications: Part 3—Optimum Cutting Conditions and Selection of Cutting Tools

This paper presents a summary of recent developments in developing performance-based machining optimization methodologies for turning operations. Four major machining performance measures (cutting force, tool wear/tool life, chip form/chip breakability, and surface roughness) are considered in the present work, which involves the development and integration of hybrid models for single and multi-pass turning operations with and without the effects of progressive tool wear. Nonlinear programming techniques were used for single-pass operations, while a genetic algorithms approach was adopted for multi-pass operations. This methodology offers the selection of optimum cutting conditions and cutting tools for turning with complex grooved tools.     

CaO机械化学法去除土壤中DDTs的工艺参数优化

为了探究应用机械化学技术处理高浓度DDTs污染土壤的最优工艺,以CaO为球磨药剂,采用行星式球磨机对高浓度DDTs污染土壤进行球磨无害化处理研究,分析不同尺寸磨球配比、球磨机转速、球料比(磨球与物料的质量比)和物料比(CaO与土壤的质量比)对DDTs的去除效果,并通过响应面法优化工艺参数.结果表明:单独使用大球(直径20 mm)球磨4 h后,土壤中DDTs残余量为4 mg/kg;而单独使用其他更小尺寸(10和8 mm)的磨球或不同尺寸磨球组合处理下的DDTs残余量均超过80 mg/kg,与单独使用大球处理的效果有显著差异.单因素试验结果显示,去除土壤DDTs的最佳参数为转速500 r/min、球料比35∶1、物料比5∶10,在该工艺条件下球磨3 h后土壤中DDTs残余量为44 mg/kg,去除率可达99.6%.依据三因素三水平的Box-Behnken试验建立的响应面模型可较好地反映土壤中DDTs残余量与转速、球料比和物料比之间的关系,各因素对土壤中DDTs残余量的影响大小表现为球料比＞转速＞物料比;通过优化计算得到使DDTs残余量达到最低时的工艺参数为转速500 r/min、球料比24∶1、物料比5∶10,在该工艺条件下球磨3 h后土壤中DDTs残余量为369 mg/kg,可见响应面法优化并未能够筛选出最优的球料比.因此,CaO机械化学法无害化处理高浓度DDTs污染土壤的最优工艺参数为各单因素试验确定的工艺条件组合,即球磨转速500 r/min、球料比35∶1、物料比5∶10.      

The effect of spindle speed,feed-rate and machining time to the surface roughness and burr formation of Aluminum Alloy 1100 in micro-milling operation

This paper describes the characteristics and the cutting parameters performance of spindle speeds (n, rpm) and feed-rates (f, mm/s) during three interval ranges of machining times (t, minutes) with respect to the surface roughness and burr formation, by using a miniaturized micro-milling machine. Flat end-mill tools that have two-flutes, made of solid carbide with Mega-T coated, with 0.2 mm in diameter were used to cut Aluminum Alloy AA1100. The causal relationship among spindle speeds, feed-rates, and machining times toward the surface roughness was analyzed using a statistical method ANOVA. It is found that the feed-rate (f) and machining time (t) contribute significantly to the surface roughness. Lower feed-rate would produce better surface roughness. However, when machining time is transformed into total cut length, it is known that a higher feed-rate, that consequently giving more productive machining since produce more cut length, would not degrade surface quality and tool life significantly. Burr occurrence on machined work pieces was analyzed using SEM. The average sizes of top burr for each cutting parameter selection were analyzed to find the relation between the cutting parameters and burr formation. In this research, bottom burr was found. It is formed in a longer machining time compare the formation of top burr, entrance burr and exit burr. Burr formation is significantly affected by the tool condition, which is degrading during the machining process. This knowledge of appropriate cutting parameter selection and actual tool condition would be an important consideration when planning a micro-milling process to produce a product with minimum burr.     

Development of a unique topology for a hard-turning micro-scale machine tool

A micro-scale machine tool (mMT) topology is developed for turning hardened steel bearing components. The topology utilizes the principle of leverage to increase accuracy and stiffness and incorporates decoupling to reduce unwanted motion of the tool. Performance specifications required that the static stiffness is at least 10 N/μm and dynamic stiffness is at least 30 N/μm in all directions. The kinematics for the topology are developed to enable control over the position and orientation of the tool tip. The effect of the topology on rake angle is determined and the topology is adjusted so as to minimize the rake angle variation during the cut. Cutting tests are performed to determine cutting parameters for achieving a low surface roughness and to estimate the accuracy of the machine. Tests show that the hard-turning mMT can achieve surface roughness below 25 nm Ra, diametrical accuracy of 1 μm and peak-to-valley roundness deviation (RONt) below 0.35 μm.     

荧光灯管芯柱玻璃中金属铅的机械化学硫化

以硫化钠为硫化剂,机械化学硫化荧光灯管芯柱玻璃中金属铅,实现金属铅向硫化铅快速转化.通过单因素实验,考察了不同机械化学硫化条件,即球磨时间、球磨转速和球料比对硫化率的影响,并通过XRD、SEM和粒度对硫化产物进行表征.结果表明,硫化率随球磨时间和球磨转速的增大而增大,随球料比的增大先增大后减小,当球磨转速为750r/min、球磨时间为120min、球料比为50：1g/g时,荧光灯管芯柱玻璃中金属铅的硫化率可达96.18%.XRD结果表明,荧光灯管芯柱玻璃中金属铅的机械化学硫化产物为PbS、SEM和粒度结果表明,荧光灯管芯柱玻璃的粒径随球磨转速和球磨时间的增加而减小.     

Evaluation of near-dry machining effects on gear milling process efficiency

One of the main environmental pollution sources related to machine building industry is the huge amount of cutting fluids which are supplied during the machining processes. In order to avoid the problems induced by cutting fluids' usage, considerable progress has been recently made in the field of near-dry machining (NDM). Converting conventional processes to minimal quantity lubrication (MQL) methods imposes new tasks' classification within the tribiological system in order to guarantee the process safety and product quality. This paper gives an overview on some requirements to be considered for a successful MQL application into industrial practice. Its last part is focused on the evaluation of NDM effects on the gear milling process efficiency, with respect to hob wear, surface quality, cooling effect, and environment protection.     

Investigation of chipping and wear of silicon wafer dicing

Wafer dicing chipping and blade wear processes in transient and steady stages were investigated. Dicing blades with two different diamond grit sizes were used to cut wafers. In the cutting experiments, the dicing blades with two different diamond grit sizes were used to cut wafers and for a given type of wafer, the cooling water temperature, cutting feed speed, and rotational speed were fixed. The chipping size, blade surface wear area and surface roughness of the wafer were measured at cutting distances of 50, 150, 300, 975, 1350, and 1900 m, respectively. Cutting debris of cutting distances of 300 m and 1900 m was collected and analyzed. The correlation between blade surface properties and chipping size was investigated. Based on this experimental system, attention is to pay to examine the correlation between blade surface properties and chipping size for transient stage and steady stage. In transient stage, the roughness of dicing blade increases rapidly. This will rapidly increase the chipping size. In steady stage, the chipping size decreases slowly with the decreasing roughness of blade surface. This concludes that blade surface condition is an important factor that affects the chipping size. Moreover, in transient stage, diamond grits that are salient or less bonded to the blade detach leave caves on the blade surface which increases surface roughness of the blade and the chipping size. In steady stage, the heights of grits become even and the chipping size decreases accordingly.     

地表参数对面源大气预测结果的影响性分析研究

为了研究地表参数取值对AERMOD中面源模拟预测浓度值的影响,文章通过改变粗糙度、反照率和波文比的取值来进行不同地表参数与预测结果的相关性分析,同时采用正交试验法来研究不同地表参数对预测结果的敏感性.相关性分析表明,不同地表参数和预测结果有着很高的相关性.敏感性分析表明,反照率数值变化对小时最大落地浓度的敏感性最大,粗糙度数值变化对日均和年均最大落地浓度的敏感性最大.通过研究可以看出在面源大气预测过程中合理选择地表参数值是准确预测的前提.     

An Approach to Theoretical Modeling and Simulation of Face Milling Forces

A new approach to theoretical modeling and simulation of face milling forces is presented. The present approach is based on a predictive machining theory in which machining characteristic factors in continuous cutting with a single-point cutting tool can be predicted from the workpiece material properties, tool geometry, and cutting conditions. The action of a milling cutter is considered as the simultaneous work of a number of single-point cutting tools, and the milling forces are predicted from input data of workpiece material properties, cutter parameters and tooth geometry, cutting condition, cutter and workpiece vibration structure parameters, and types of milling. A predictive force model for face milling is developed using this approach. In the model, the workpiece material properties are considered as functions of strain, strain rate, and temperature. The ratio of cutter tooth engagement over milling is taken into account for the determination of temperature in the cutting region. Cutter runout is included in the modeling for the chip load. The relative displacement between the cutter and workpiece due to the cutter and workpiece vibration is also included in the modeling to consider the effect on the undeformed chip thickness. A milling force simulation system has been developed using the model, and face milling experimental tests have been conducted to verify the simulation system. It is shown that the simulation results agree well with experimental results.     

Experimental Evaluation of Cutter Orientation When Ball Nose End Milling Inconel 718™

High-speed machining (HSM), specifically end milling and ball end cutting, is attracting interest in the aerospace industry for the machining of complex 3D aerofoil surfaces in titanium alloys and nickel-based superalloys. Following a brief introduction on HSM and related aerospace work, the paper reviews published data on the effect of cutter/workpiece orientation, also known as engagement or tilt angle, on tool performance. Such angles are defined as ±β_fN and ±β_f.Experimental work is detailed on the effect of cutter orientation on tool life, cutting forces, chip formation, specific force, and workpiece surface roughness when high-speed ball end milling Inconel 718™. Dry cutting was performed using 8 mm diameter PVD-coated solid carbide cutters with the workpiece mounted at an angle of 45° from the cutter axis.A horizontal downward (-β_fN) cutting orientation provided the best tool life with cut lengths ∼50% longer than for all other directions (+β_fN, +β_f, and –β_f). Evaluation of cutting forces and associated spectrum analysis of results indicated that cutters employed in a horizontal downward direction produced the least vibration. This contributed to improved workpiece surface roughness, with typical mean values of ∼0.4 μm Ra as opposed to ∼1.25 μm Ra when machining in the vertical downward (–β_f) direction.     

Analytical model of metalworking fluid penetration into the flank contact zone in orthogonal cutting

Metalworking fluids (MWFs) are used widely in machining process to dissipate heat, lubricate moving surfaces, and clear chips. They have also been linked to a number of environmental and worker health problems. To reduce these impacts, minimum quantity lubrication (MQL) sprays of MWF delivered in air or CO₂ have been proposed. MQL sprays can achieve performance comparable with conventional water-based or straight oil MWFs while only delivering a small fraction of the fluid. This performance advantage could be explained by the enhanced penetration into the cutting zone that results from delivering MWF in high pressure and precise sprays. To explore this hypothesis, an analytical model of MWF penetration into the flank face of the cutting zone is developed and validated using experimental data. The model is based on a derivation of the Navier–Stokes equation and the Reynolds equation for lubrication and applied to an orthogonal cutting geometry under steady-state conditions. A solution to the model is obtained using a numerical strategy of discretizing the analytical scheme with two-dimensional centered finite difference method. Penetration into the cutting zone is estimated for MQL sprays delivered in air, CO₂ and N₂ as well as two conventional MWFs, straight oil and semi-synthetic emulsion. The model suggests that conventional MWFs, do not penetrate the cutting zone fully and fail to provide direct cooling to the flank zone where wear is most likely to occur. MQL sprays do penetrate the cutting zone completely. Using convective heat transfer coefficients from a previous study, a finite element heat balance is carried out on the tool to understand how each fluid impacts temperature near the flank tip of the tool. The results of the modeling effort are consistent with experimental measurements of tool temperature during turning of titanium (6AL4V) using a K313 carbide tool. The prediction of temperature near the flank indicates that MQL sprays do suppress temperatures near the flank effectively. These results help explain the low levels of tool wear observed for some MQL sprays, particularly those based on high pressure CO₂. This modeling framework provides valuable insight into how lubricant delivery characteristics such as speed, viscosity, and cutting zone geometry can impact lubricant penetration.     

机械清洗膜组件对膜通量影响的初步研究

试验设计了强化机械清洗膜组件M1和机械清洗膜组件M2,通过正交试验考察了污泥浓度、曝气量、运行膜通量和抽吸时间:间歇时间对2组膜组件的膜过滤特性的影响.结果表明,M1膜组件可以弱化不利条件如高污泥浓度(MLSS)、高运行膜通量和低曝气强度的影响;曝气量和运行膜通量是影响膜比通量的主要因素;并得到一组较佳的操作条件组合:污泥浓度6g/L、曝气量0.5m³/h、抽吸时间和间歇时间的比为12:1.在此条件下长期运行试验表明,M1和M2膜通量均可以维持在40L/(h·m²).通过测定2组膜组件的阻力分布,表明机械清洗可以大大减弱膜面泥饼层污染.     

Experimental investigation,intelligent modeling and multi-characteristics optimization of dry WEDM process of Al–SiC metal matrix composite

Dry wire electrical discharge machining (WEDM) is an environmentally friendly modification of the oil WEDM process in which liquid dielectric is replaced by a gaseous medium. In the present work, parametric analysis has been fulfilled while dry WEDM of Al–SiC metal matrix composite. Experiments were designed and conducted based on L₂₇ Taguchi's orthogonal array to study the effect of pulse on time, pulse off time, gap voltage, discharge current, wire tension and wire feed on cutting velocity (CV) and surface roughness (SR). Firstly, a series of exploratory experiments has been conducted to identify appropriate gas and wire material based on the values of cutting velocity. After selection of best gas and best wire, they were used for later stage of experiments. Analysis of variances (ANOVA) has been performed to identify significant factors. In order to correlate relationship between process inputs and responses, an adaptive neuro-fuzzy inference system (ANFIS) has been employed to predict the process characteristics based on experimental observation. At the end, an artificial bee colony (ABC) algorithm has been associated with ANFIS models to maximize CV and minimize SR, simultaneously. Then the optimal solutions that obtained through ANFIS-ABC technique have been compared with numbers of confirmatory experiments. Results indicated that oxygen gas and brass wire guarantee superior cutting velocity. Also, according to ANOVA, pulse on time and discharge current were found to have significant effect on CV and SR. In modeling of CV and SR by ANFIS, it was resulted that the proposed method has superiority in prediction of them in the ranges of factors beyond the training condition. Also, association of ANFIS with ABC can find the optimal combination of process parameters accurately according to the confirmatory experiments.     

Characteristics of abrasive waterjet cut-edges and the affect on formability and fatigue performance of high strength steels

The characteristic surface properties and internal workpiece transformations formed during the Abrasive Waterjet (AWJ) cutting process influences the formability and fatigue performance of steel cut-edges. This relatively established cutting technology is used in industry to generate specialist low production components, which may undergo continual loading cycles under operational service conditions. The fatigue performance of AWJ cut-edges can be critical since individual notch defects produced by the cutting process can act as initiation sites from where fatigue cracks can propagate. Due to the increased sensitivity of high strength structural steels to cut-edge fatigue, AWJ cut-edge defects have an ever more significant influence on fatigue performance. The relationship between the traverse cutting speed and the influence on the resulting properties of the cut-edge has been the critical area of investigation. The affects of traverse cutting speed on the surface roughness properties and cut-edge hardening through a process of plastic deformation of grains in the near edge region were observed to be influenced by the traverse cutting speed. It is these characteristic factors that were determined to influence the cut-edge ductility and fatigue performance of steel components. It is a combination of the AWJ properties that produces cut-edges, which are positive for the Hole Expansion Capacity (HEC) but negative for stress life and cyclic stress strain life fatigue performance of AWJ cut high strength steels.     

化学沉淀法处理高浓度氨氮废水工艺条件研究

以Na2HPO4和MgSO4为沉淀剂,对氯化铵、硫酸铵、氨水以及碳酸氨等四种高浓度氨氮废水进行化学沉淀法脱氮处理。正交试验的结果表明,废水初始pH值是影响氨氮去除率最主要的因素,Mg2+和PO43+的投加量与废水中氨氮的比值也对氨氮去除率有重要影响。单因素试验进一步优化表明,对于此四种氨氮废水,当初始氨氮浓度为1500mg/L时,去除氨氮的最佳工艺条件为:pH10.1～10.5,Mg:N和P:N的比例分别为1.2～1.4和1.0～1.2,此时各废水中氨氮的去除率可达到93%～99%,磷的利用率达到97%以上。