Cutting forces, chip formation, and tool wear in high-speed face milling of AISI H13 steel with CBN tools

High-speed face milling experiments of AISI H13 steel (46–47 HRC) with cubic boron nitride (CBN) tools were conducted in order to identify the characteristics of cutting forces, chip formation, and tool wear in a wide range of cutting speed (200–1,200 m/min). The velocity effects are focused on in the present study. It was found that, at the cutting speed of 800 m/min, which can be considered as a critical value, relatively low mechanical load, relatively low degree of chip segmentation, and relatively long tool life can be obtained at the same time. Both the cutting forces and the degree of chip segmentation firstly decrease and then increase with the cutting speed, while the tool life exhibits the opposite trend. By means of analyzing the wear mechanisms of tools tested under different cutting speeds, it was found that, as the cutting speed increases, the influences of fracture and chipping resulting from mechanical load on tool wear were reduced, while the influences of adhesion, oxidation, and thermal crack accelerated by high cutting temperature became greater. There exist obvious correlations among cutting forces, chip formation, and tool wear.     

Effect of cutting speed on cutting forces and wear mechanisms in high-speed face milling of Inconel 718 with Sialon ceramic tools

In this paper, a series of milling tests were carried out in order to identify the effects of cutting speed on cutting forces and tool wear when high-speed face milling Inconel 718 with Sialon ceramic tools. Both down-milling and up-milling operations were conducted. The cutting forces, tool wear morphologies, and the tool failure mechanisms in a wide range of cutting speeds (600–3,000 m/min) were discussed. Results showed that the resultant cutting forces firstly decrease and then increase with the increase of cutting speed. Under relatively lower cutting speeds (600 and 1,000 m/min), the dominant wear patterns is notching. Further increasing the speed to more than 1,400 m/min, the notching decreases a lot and flank wear becomes the dominant wear pattern. In general, at the same cutting speed, flaking on the rake face and notching on the flank face are more serious in down-milling operation than that in up-milling operation with the same metal removal volume. However, the surface roughness values for down-milling are lower than that for up-milling.     

Analysis of PCBN tool failure mechanisms in face milling of hardened steel using damage equivalent stress

The International Journal of Advanced Manufacturing Technology - An attempt was made in the present study to apply damage mechanics to investigate the polycrystalline cubic boron nitride (PCBN)...     

Tool wear and tool life characteristics of unconventional sintered carbides in the intermittent cutting of hardened steel

Carbides coated with TiC, TiN, TiC/TiN or TiC/Al₂O₃ coatings on a tough hard material base and TiC-containing hard material of modified composition and structure were used to investigate tool-wear and tool-life characteristics in face milling of martensitic steel of hardness 300–600 HV. Tool-life behaviour with increasing hardness and cutting speed was determined. Characteristic wear mechanisms are discussed on the basis of light and scanning electron microscopy observations.     

高硬度淬硬钢高速铣削过程的切削温度研究

通过设计在不同加工工艺参数条件下高速铣削高硬度(48HRC～ 68HRC)淬硬钢试验,研究了切削温度信号的特征,分析了切削温度与淬硬钢材料硬度、切削工艺参数的关系.结果 表明:随着淬硬钢材料硬度的增大,切削温度呈现递增趋势,4种淬硬钢的切削温度随材料硬度变化顺序为:PM60＞SKD11＞S136＞P20,其中,PM60...     

铣刀磨损量监测和剩余寿命预测方法研究

研究在线诊断端面铣刀磨损量和预测铣刀剩余寿命的方法。首先通过实验采集Y向铣削力作为监测信号,分析铣削力与刀具磨损量VB和刀具磨损时间之间的关系。然后,通过铣削力信号分析提取出有效监测特征向量,此特征向量作为BP神经网络的输入,用于刀具磨损量的监测和剩余寿命的预计。最后,通过实验证明,该神经网络模型误差很小,利用该方法能够正确地进行在线监测和预测。     

Surface roughness analysis of hardened steel after high-speed milling

The work refers to analysis of various factors affecting surface roughness after end milling of hardened steel in high-speed milling (HSM) conditions. Investigations of milling parameters (cutting speed v(c) , axial depth of cut a(p) ) and the process dynamics that influence machined surface roughness were presented, and a surface roughness model, including cutter displacements, was elaborated. The work also involved analysis of surface profile charts from the point of view of vibrations and cutting force components. The research showed that theoretic surface roughness resulting from the kinematic-geometric projection of cutting edge in the workpiece is significantly different from the reality. The dominant factor in the research was not feed per tooth f(z) (according to the theoretical model) but dynamical phenomena and feed per revolution f.     

Cutting performance of coated carbide tools in high-speed face milling of AISI H13 hardened steel

In the present study, high-speed face milling of AISI H13 hardened steel was conducted to investigate the cutting performance of coated carbide tools. The characteristics of chip morphology, tool life, tool wear mechanisms, and surface roughness were analyzed and compared for different cutting conditions. It was found that as the cutting speed increased, the chip morphology evolved in different ways under different milling conditions (up, down, and symmetric milling). Individual saw-tooth segments and sphere-like chip formed at the cutting speed of 2,500 m/min. Owing to the relatively low mechanical load, longest tool life can be obtained in up milling when the cutting speed was no more than 1,000 m/min. As the cutting speed increased over 1,500 m/min, highest tool life existed in symmetric milling. When the cutting speed was 500 m/min, owing to the higher mechanical load, the flaked region on the tool rake face in symmetric milling was much larger than that in up and down milling. There was no obvious wear on the tool rake face at the cutting speed of 2,500 m/min due to the short tool-chip contact length. In symmetric milling, the delamination of tool material, which did not occur in up and down milling, was caused by the relatively large cutting force. Abrasion had great effect on the tool flank wear in symmetric milling. With the increment of cutting speed, surface roughness decreased first and then increased rapidly. Lowest surface roughness can be obtained at the cutting speed of about 1,500 m/min.     

Effects of cutting conditions on microhardness and microstructure in high-speed milling of H13 tool steel

In the present study, high-speed side milling experiments of H13 tool steel with coated carbide inserts were conducted under different cutting parameters. The microhardness and microstructure changes of the machined surface and subsurface were investigated. A finite element model, taking into account the actual milling process, was established based on the commercial FE package ABAQUS/Explicit. Instantaneous temperature distributions beneath the machined surface were analyzed under different cutting speeds and feed per tooth based on the model. It was found that the microhardness on the machined surface is much higher than that in the subsurface, which indicates that the surface materials experienced severe strain hardening induced by plastic deformation during the milling process. Furthermore, the hardness of machined surface decreases with the increase of cutting speed and feed per tooth due to thermal softening effects. In addition, optical and scanning electron microscope (SEM) was used to characterize the microstructures of cross sections. Elongated grains due to material plastic deformation can be observed in the subsurface, and white and dark layers are not obvious under present milling conditions. The thickness of plastic deformation layer beneath the machined surface increases from 3 to 10 μm with the increase of cutting speed and feed per tooth. The corresponding results were found to be consistent and in good agreement with the depth of heat-affected zone in finite element analysis (FEA).     

Cutting force in face milling with tool wear

The proposed mathematical model includes not only the cutting forces due to processes in the shear zone but also the component of the force due to processes at the tool’s real surface. The model takes account of the different configuration of the replaceable multifaceted plates and the forces at radial and linear sections of the mill tooth.     

A predicted modelling of tool life of high-speed milling for SKD61 tool steel

This paper presents an abductive network for predicting tool life in high- speed milling (HSM) operations. The abductive network is composed of a number of functional nodes. These functional nodes are well organised to form an optimal network architecture by using a predicted squared error criterion. Once the cutting speed, feed per tooth, and axial depth of cut are given, tool life can be predicted based on the developed network. Experimental results have shown that the abductive network can be used to predict HSM end mill life under varying cutting conditions and the prediction error of HSM tool life is less than 10%.     

An investigation of heat partition and tool wear in hard turning of H13 tool steel with CBN cutting tools

This paper presents results of an investigation into the tool life and the tool wear behaviour of low content CBN cutting tools used in hard turning of hardened H13 tool steel. The approach followed here required both experimental work and finite element thermal modelling. The experiments involved measuring the cutting forces, cutting temperatures, tool wear, and the contact area. Using the measured cutting forces and the contact area in the orthogonal cutting model, we calculated the heat flux on the tool and applied it in the FE thermal analysis. The temperatures history from the analysis was matched with the experimental data to estimate the fraction of heat entering the tool for both conventional and high speeds. The heat partition into the tool was estimated to be around 21–22% for conventional speeds, whereas for high-speed turning, it was around 14%. The tool wear, however, was found to be dominated by chipping for both cutting speeds and could be reduced considerably by reducing the amount of heat entering the tool.     

Multi-output fuzzy inference system for modeling cutting temperature and tool life in face milling

This paper proposes a method for cutting parameters identification using the multi-inputs-multi-outputs fuzzy inference system (MIMO-FIS). The fuzzy inference system (FIS) was used to identify the initial values for cutting parameters (cutting speed, feed rate and depth of cut) and flank wear using cutting temperature and tool life as outputs. The objective was to determine the influence of cutting parameters on cutting temperature and tool life. The model for determining the cutting temperature and tool life of steel AISI 1060 was trained (design rules) and tested by using the experimental data. The average deviation of the testing data for tool life was 11.6 %, while that of the cutting temperature was 3.28 %. The parameters used in these testing data were different from the data collected for the design rules. The test results showed that the proposed MIMO-FIS model can be used successfully for machinability data selection. The effect of parameters and their interactions in machining is analyzed in detail and presented in this study.     

CBN刀具车削淬硬钢表面粗糙度的试验与预测

利用正交设计方法,对立方氮化硼(CBN)刀具硬态干式车削淬硬钢Cr12Mo V时,切削用量三要素(切削速度、进给量和切削深度)对加工表面粗糙度的影响进行了分析,运用响应曲面法(RSM)建立了加工表面粗糙度的预测模型。研究结果表明:CBN刀具车削淬硬钢Cr12Mo V时对加工表面粗糙度影响最大的加工参数是切削速度,其次是进给量,切削深度对加工表面粗糙度的影响较小;预测模型能够高精度地对表面粗糙度进行预测,平均误差不超过9.7%。     

The cutting tool stresses in finish turning of hardened steel with mixed ceramic tool

Precision hard machining is an interesting topic in manufacturing die and mold, automobile parts, and scientific research. While the hard machining has benefit advantages such as short cutting cycle time, process flexibility, and low surface roughness, there are several disadvantages such as high tooling cost, need of rigid machine tool, high cutting stresses, and residual stresses. Especially, tool stresses should be understood and dealt with to achieve successful performance of finish hard turning with ceramic cutting tool. So, the influence of cutting parameters on cutting stresses during dry finish turning of hardened (52 HRC) AISI H13 hot work steel with ceramic tool is investigated in this paper. For this aim, a series finish turning tests were performed, and the cutting forces were measured in tests. After literature procedure about finite element model (FEM), FEM is established to predict cutting stresses in finish turning of hardened AISI H13 steel with Ceramic 650 grade insert. As shown, effect of the cutting parameters on cutting tool stresses in finish turning of AISI H13 steel is obtained. The suggested results are helpful for optimizing the cutting parameters and decreasing the tool failure in finish turning applications of hardened steel.     

切削速度对精密干式车削淬硬工具钢切削力的影响

通过使用PCBN刀具精密干式车削淬硬Cr12MoV工具钢(62±1 HRC)的试验,分析了切削速度对三向切削力的影响,得出了最优切削速度。试验表明:随切削速度提高,三向切削力先急剧增大,后急剧减小,再又缓慢增大。若从最小车削合力与提高加工效率两个角度来优化切削速度,则226 n/min是最优切削速度。试验结果也对精密干式切削淬硬工具钢具有实际指导意义与参考价值。     

高速铣削GH3039高温合金的切削用量研究

GH3039是一种镍基高温合金,对其切削加工时会产生很大的切削力,以至于对刀具磨损、加工精度和生产效率等均产生很大的影响。针对上述问题,提出使用硬质合金刀具来加工这种材料,利用线性回归方法,建立GH3039高温合金的铣削力模型,并通过极差分析得到合理的切削用量,为GH3039高温合金的实际铣削加工提供参考依据。     

Study on tool wear mechanisms in milling laser sintered material

This paper investigates tool wear mechanisms of a ball end mill in cutting laser sintered material. Cutting edge temperature is measured by using a three-color pyrometer with an optical fiber. Bulk carbon steel JIS S55C is selected as the standard steel. Experimental results show that tool life in cutting sintered material is shorter than that in cutting JIS S55C. Observations by SEM show that adhesion of the work material and micro chipping are the main wear mechanisms in cutting sintered material. The corresponding cutting edge temperature shows a continuous increase as wear evolves with cutting time.