Taguchi method based optimisation of drilling parameters in drilling of AISI 316 steel with PVD monolayer and multilayer coated HSS drills

This paper focuses on the optimisation of drilling parameters using the Taguchi technique to obtain minimum surface roughness (Ra) and thrust force (Ff). A number of drilling experiments were conducted using the L16 orthogonal array on a CNC vertical machining centre. The experiments were performed on AISI 316 stainless steel blocks using uncoated and coated M35 HSS twist drills under dry cutting conditions. Analysis of variance (ANOVA) was employed to determine the most significant control factors affecting the surface roughness and thrust force. The cutting tool, cutting speed and feed rate were selected as control factors. After the sixteen experimental trials, it was found that the cutting tool was the most significant factor on the surface roughness and that the feed rate was the most significant factor on the thrust force. The results of the confirmation experiments showed that the Taguchi method was notably successful in the optimisation of drilling parameters for better surface roughness and thrust force.     

航天铝合金ZL205A数控车削力模型的建立

采用理论分析和经验相结合的方法,确定了航天材料ZL205A数控车削力的数学模型,并通过试验分析确定了模型的参数。结果表明:该模型确定的切削力理论值和实际值吻合,说明用该模型来预测加工中的切削力可行,为进一步的加工变形研究奠定了基础。     

超高强钢数控车削温度和车削力模型的建立

通过对D406A钢切削性能的分析,在理论分析和实践经验的基础上,确立了D406A数控车削温度和车削力的数学模型;经过试验设计和分析计算,确定了模型中的参数。试验结果表明：用所建立的模型来预测加工中的车削温度和车削力是完全可行的。     

Behavior of austenitic stainless steels at high speed turning using specific force coefficients

Turning operation has been widely studied, and it is a well-known process. However, still today some limitations exist in the processing of some materials, mainly due to the poor or inexistent characterization. Such is the case of austenitic stainless steels, which in spite of being materials of high economic and technological value, their behavior to machining is still not well understood in some aspects. There are not reliable and updated technological data about austenitic stainless steels at industry. This fact is especially significant when considering technological development conducted by a continuous increment of cutting speeds. Nowadays, there is not a reliable mechanistic model for austenitic stainless steels turning adjusted for high cutting speeds. In this paper, a mechanistic model for cutting force prediction is presented. This model was developed for machining with nose radius tools considering the effect of the edge force due to the rounded cutting edge. In addition, a set of machining tests were carried out to obtain the specific force coefficients expressions for austenitic stainless steels using the mechanistic approach at high cutting speeds. The specific cutting coefficients were obtained applying the force model as an inverse model. This paper presents expressions for shearing and edge cutting coefficients which are valid for a wide range of cutting conditions. Results were validated by comparing the values estimated by the model with the ones obtained by experimentation.     

异形PDC齿切削破岩提速机理研究

在室内切削实验基础上基于有限元二次开发建立了异形齿切削及全钻头破碎非均质花岗岩的三维数值仿真模型,研究了12种形状聚晶金刚石复合片（PDC）齿切削非均质岩石过程中的切向力、法向力、岩屑、破岩比功,并研究了齿形对全尺寸钻头破岩效率的影响。研究结果表明：锥形齿的切向力最小,破岩比功最高,对应的锥形齿钻头的进尺也最小;三平面齿的法向力和切向力均为最大;破岩比功最低的齿为双曲面齿;进尺最大的全钻头齿形为更易吃入岩石的鞍形齿、双曲面齿以及斧形齿。     

非圆车削的解析测力方法

针对最小相位及非最小相位受控系统,分别提出了相应算法,根据系统输出位置信号及输入的控制力信号,辨识出动态切削力信息。不使用测力传感器,从而消除了附加测力传感器所产生的不利因素,为深入研究数控非圆车削加工特性及动态切削力误差补偿提供了一种新手段。     

Development of chatter detection in milling processes

The aim of this research is to develop an in-process detection of the chatter for the actual milling processes regardless of any cutting condition within the small data processing time by utilizing the dynamic cutting forces obtained during cutting. The proposed method introduces three parameters, which are calculated and obtained by taking the ratio of the average variances of the dynamic cutting forces of three force components, to identify the chatter. The algorithm was developed and implemented on five-axis computer numerical control machining center to detect the chatter in ball-end milling and end milling processes. The chatter and the nonchatter can be simply detected during the in-process cutting by mapping the obtained values of three parameters in the reference feature spaces regarding the determined threshold values. The experimental results showed that the proposed method can be effectively used to detect the chatter during cutting even though the cutting conditions are changed.     

一种螺旋刃球头铣刀的高速加工铣削力模型

研究了高速加工中球头铣刀的铣削力特性。通过综合运用理论建模法和经验系数法,并引入高速切削时引起切屑动量改变所需的作用力,建立了高速切削条件下球头铣刀的铣削力模型。实验验证结果表明,理论计算值与实验测量值吻合良好。     

Evaluation of machinability according to the changes in machine tools and cooling lubrication environments and optimization of cutting conditions using Taguchi method

This study analyze the effect of machine tools, cooling lubrication environments and cutting conditions on surface roughness and cutting force, and propose the combination of cutting conditions which minimizes the effect of machine tool variables on the dispersion of cutting force and surface roughness by treating the changes in machine tool itself and the installation environments as a noise factors. To do so, the Taguchi method is used to establish an experiment plan, and flat end milling is carried out to measure cutting force and surface roughness. The research results show that in the case of cutting force, the effect of cutting conditions is dominant, and changes in machine tools and cooling lubrication environments barely have effect on cutting force. However, in the case of surface roughness, all of the cutting conditions, machine tool and cooling lubrication environment variables have impact. In order to select a combination of cutting conditions insensible to changes in machine tools, considerations for feed per revolution and axial depth of cut turn out most important in the aspect of cutting force, and considerations for feed per revolution is most important in the surface roughness.     

双转台五轴机床空间误差补偿技术研究

几何误差、热误差和切削力误差占到了机床总误差的75%,对这3项误差进行控制是提高机床加工精度的关键所在。以双转台五轴机床的空间误差作为研究对象,通过对加工位置、主要热源及电动机电流等相关因素进行分析,确定空间误差建模所需的位移变量、温度变量和切削力变量。以现有的多种误差建模方法为基础,通过对信息融合技术进行研究,提出一种机床空间误差的多模型融合预测方法,建立综合反映几何误差、热误差和切削力误差的最优空间误差模型。最后以DSP为核心,设计空间误差补偿器,实施空间误差补偿,验证补偿效果。结果显示,建立的模型预测精度较高,残差小于2μm,而实施空间误差补偿后,加工零件的轮廓误差也由15μm降到了5μm,补偿效果明显。     

Application of response surface methodology for determining cutting force model in turning of LM6/SiCP metal matrix composite

In the present investigation an attempt is made to evaluate the effect of certain cutting variables on cutting forces in straight turning of aluminum metal matrix composites under dry cutting condition. Cutting speed, depth of cut and weight percentage of SiC_P are selected as the influencing parameters. The application of response surface methodology and face centered composite design for modeling, optimization, and an analysis of the influences of dominant cutting parameters on tangential cutting force, axial cutting force and radial cutting force of aluminum metal matrix composites produced through stir casting route. Experiments are carried out using aluminum (LM6) alloy reinforced with silicon carbide particles. The mathematical models are developed and tested for adequacy using analysis of variance and other adequacy measures using the developed models. The predicted values and measured values are fairly close, which indicate that the developed models can be effectively used to predict the responses in the turning of aluminum metal matrix composites. The contour plots of the process parameters revel that the low cutting forces are associated with the lowest level of depth of cut and the highest level of cutting speed and the sensitivity analysis revealed that cutting speed is most significant factor influencing the response variables investigated.     

Nano-scale friction: A review

Frictional force is a resistant force that must be overcome to achieve relative motion between two components in contact. The economical and technological benefits of controlling friction and wear are tremendous. However, due to the complex nature of the phenomena, clear understanding of the mechanisms are yet to be achieved, particularly at the nano-scale where surface forces tend to dominate the tribological behavior of the system. In this paper the results of numerous theoretical, experimental, and numerical works on the fundamental mechanisms of friction at the nano-scale are reviewed. It is shown that friction coefficient values for nano-scale systems are quite varied depending on the conditions under which the system is investigated. As for the mechanism that causes friction at the nano-scale, interaction of the atoms plays a vital role. Furthermore, factors such as atomic radius, interatomic potential energy, and lattice parameters contribute to the degree of atomic interaction.     

Feed Cutting Force Estimation from the Current Measurement with Hybrid Learning

It is very important to use reliable and inexpensive sensors to obtain useful information about manufacturing processing, such as cutting force, for monitoring automated machining. In this paper, the feed cutting force is measured using an inexpensive current sensor installed on the a.c servo motor of a CNC turning centre. The factors that affect a feed drive system are analysed in detail, and a model of the feed drive system for estimating feed cuttinng force is presented. The feed cutting force is estimated using feed motor current measurement and neuro-fuzzy techniques. Experimental results demonstrate that this medthod can accurately estimate feed cutting force within an error of 5%.     

基于径向力的可转位浅孔钻加工孔径误差研究

为研究可转位浅孔钻在切削过程中的钻孔孔径误差,基于可转位浅孔钻的理论几何模型,并利用经典斜切理论得到浅孔钻的径向力、力矩关于刀片几何参数和切削参数的计算公式。选取常用切削参数组合,将计算得的径向合力及力矩作为边界条件,通过ANSYS有限元分析刀体挠度,得出相关钻孔孔径误差的理论值。利用统计学回归方法建立相应数学模型,并通过切削试验验证数学模型的精确性。基于建立的数学模型,通过调节切削参数,可预测并控制孔径误差值,实现浅孔钻在半精加工中对孔径余量的精确控制,有效拓展可转位浅孔钻的应用范围。     

Feedrate optimisation/scheduling on sculptured surface machining: a comprehensive review, applications and future directions

Free-form or sculptured surface milling is one of the continually used manufacturing processes for die/mould, aerospace (especially turbine blades), precision machine design, bio-medical devices and automotive industries. Developments of machining technologies for quality enhancement of machining results have become a very important fact in current real industry. Therefore, reducing milling time, tool wear, cutter deflection and improving surface texture quality and machining operations through adaptation and optimisation of tool feedrates based on changing surface geometry in sculptured surface machining is a great step in this direction. Various feedrate optimisation strategies have different feedrate rescheduling control parameters such as chip thickness, material removal rate (MRR), min(mrr,chip,force), max(expo.Acc/dec) and resultant forces. Some commercial CAM softwares come with MRR-based feedrate optimisation algorithms which have a very short calculation time. However, commercial feedrate scheduling systems have some limitations in generating the scheduled feedrates because they use the MRR or the cutting force model which is dependent on milling conditions. However, for the processes in which machining precision/accuracy is very important, it is inevitable that mechanistic force-based feedrate optimisation approaches, for which the calculation time is improved, will be integrated into commercial CAM software packages. Here, developing only the mechanistic cutting force-based algorithm is not enough. In this paper, improvement and optimisation of machining feedrate value, which is one of the cutting parameters which has a tremendous effect on the precise machining of free-form surfaces, was discussed by using the virtual machining framework. For this purpose, the boundary representation solid modelling technique-based free-form milling simulation and feedrate optimisation system integrated with commercial CAD/CAM software is developed for three-axis ball-end milling. This review study includes the information regarding the following topics: The algorithms developed for the feedrate value optimisation, MRR calculation approaches, cutting force computation methods, details of algorithms, the effects on the surface accuracy, the effects on the machining time, the capabilities of the present commercial CAM software packages, the encountered difficulties and overcoming those difficulties, recent developments and future research directions.     

Theoretical model for cutting force in rotary ultrasonic milling of dental zirconia ceramics

Rotary ultrasonic machining or ultrasonic vibration assisted grinding has superior performance in machining hard and brittle materials, such as dental zirconia ceramics. However, there are few reports about cutting force modeling of rotary ultrasonic milling (RUM) for dental ceramics, especially for cutting force model in feed direction. In this study, the theoretical model of cutting force both in axial direction and feed direction is proposed under the assumption that brittle fracture is the primary mechanism of material removal in RUM of dental ceramics. The effective cutting time and material removal volume have been analyzed to develop the cutting force model. Besides, the number of active abrasive particles has been calculated for the first time during the modeling. The effect of overlapping and intersection of fracture zone in peripheral direction on material removal volume has also been considered via the parameters K ₁ and K ₂. In addition, the relationships between the cutting force and input variables are revealed through the theoretical model. Finally, pilot experiments of RUM on dental zirconia ceramics are conducted to verify the theoretical model. The experimental results are consistent well with the model predictions. Therefore, the theoretical model can be applied to evaluate the cutting force in RUM of dental ceramics.     

Study on physical and technological effects of precise turning with self-propelled rotary tool

This study is focused on some physical and technological aspects of a precise turning with Self-Propelled Rotary Tool (SPRT). As part of experiment, the cutting forces, on-line insert run-out and machined surface topography were investigated. Turning tests were carried in the range of variable feeds, depths of cut and cutting speeds for a hardened 41Cr4 steel with the use of a coated carbide round indexable inserts. The effect of cutting conditions on the tool rotation and the dynamics of cutting force signal were evaluated. In particular, changes of cutting forces vs. cutting lengths for different cutting parameters were analyzed in terms of the cutting insert rotation, and Power Spectral Density (PSD) analysis. Moreover, the original method based on cutting force oscillations was employed to estimate the on-line insert run-out. Ultimately, the analysis of a machined surface topography was conducted, considering the interactions between the process inputs and outputs. It was shown that application of high cutting speeds and feeds during SPRT turning can lead to the improvements in surface finish, as well as the stabilization of cutting force values.     

Specific cutting force, tool wear and chip morphology characteristics during dry drilling of austempered ductile iron (ADI)

Dry machining is being recognized as ecological machining due to its less environmental impact and manufacturing cost. However, the choice of dry machining is mainly influenced by the workpiece material properties, machining operation and cutting conditions. The recent emergence of austempered ductile iron (ADI) can be considered a significant economic advantage to the increasing industrial demand for cost- and weight-efficient materials. However, due to its microstructure-induced inherent properties, ADI is considered hard-to-machine material. Thus, the dry drilling of ADI is investigated in this paper. The ADI material used in the present study is produced using an innovative process route for near net shape casting production. Drilling experiments are conducted on a DMU80P Deckel Maho five-axis machining centre using PVD-coated carbide tools under dry cutting environment. The dry drilling of ADI under different cutting conditions is evaluated in terms of specific cutting force and tool wear analysis. The influence of cutting conditions on chip morphology and surface roughness is also investigated. The experimental results revealed that the combination of the low feed rate and higher cutting speed leads to the higher mechanical and thermal loads on the tool's cutting edge, resulting in higher specific cutting force values. This behaviour is further supported by the chip morphology analysis, which revealed the formation of segmented chips at higher cutting speed with segment spacing increase with an increase in feed rate. Depending upon the cutting parameters, different modes of tool failures including crater wear, flank wear, chipping, breakage and built-up edge were observed. Surface roughness analysis revealed the influence of tool wear and chip morphology on the machined surface finish.     

基于DEFORM-3D的金属锯切过程力能仿真研究

运用金属切削力学理论与方法对圆锯机锯切过程的力能参数进行理论计算,得到锯切过程的平均锯切力和平均锯切功率。基于DEFORM-3D软件建立金属锯切有限元模型,仿真得到平均锯切力值,与理论计算得到的平均锯切力误差为3.5%;实验得到圆锯机主电动机锯切过程中的平均锯切功率值,与理论计算得到的平均锯切功率误差为3.8%。力能参数理论计算、DEFORM-3D有限元仿真、实验测试数据对比,表明用DEFORM-3D有限元研究金属锯切机理是一种可行的方法,为锯切机理的研究提供了参考。     

基于不同比例的双刃切削的研究

基于PRO/E平台建模,将模型的.STL文件导入DEFORM-3D有限元软件进行仿真,在保证切削面积相等的前提下,选择主副刃参与切削的不同的长度比例,分析在不同的切削长度比例下,切削力大小的变化趋势,并通过三维切削理论公式定性进行分析。结果表明:在切削面积相等的前提下,当主副刃参与切削的长度比例为1:1时,切削力最小,仿真曲线的变化趋势与理论公式的定性分析曲线大致吻合,并证实了仿真分析的可行正确性。