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%.     

Modelling, simulation and experimental investigation of cutting forces during helical milling operations

The kinematics of helical milling on a three-axis machine tool is first analysed. An analytical model dealing with time domain cutting forces is proposed in this paper. The cutting force model is established in order to accurately predict the cutting forces and torque during helical milling operations as a function of helical feed, spindle velocity, axial and radial cutting depth and milling tool geometry. The forces both on the side cutting edges and on the end cutting edges along the helical feed path are described by considering the tangential and the axial motion of the tool. The dual periodicity which is caused by the spindle rotation, as well as the period of the helical feed of the cutting tool, has been included. Both simulation and experiments have been performed in order to compare the results obtained from modelling with experiments.     

In-process estimation of radial immersion angle using cutting force in face milling

In this paper, a on-line estimation method of the radial immersion angle using cutting force is presented. The ratio of cutting forces in feed and cross-feed directions acting on the single tooth at the immersion angle is a function of the immersion angle and the ratio of radial to tangential cutting force. It is found that the ratio of radial to tangential cutting force is not affected by cutting conditions and axial rake angle, which implies that the ratio determined by one preliminary experiment can be used regardless of the cutting conditions for a given tool and workpiece material. Using the measured cutting force during machining and predetermined ratio, the radial immersion ratio is estimated in process. Various experimental results show that the proposed method works within5% error range.     

螺旋铣孔工艺的切削稳定性及工艺参数规划

以螺旋铣孔工艺时域解析切削力建模、时域与频域切削过程动力学建模、切削颤振及切削稳定性建模为基础,研究了螺旋铣孔的切削参数工艺规划模型和方法。切削力模型同时考虑了刀具周向进给和轴向进给,沿刀具螺旋进给方向综合了侧刃和底刃的瞬时受力特性;动力学模型中同时包含了主轴自转和螺旋进给两种周期对系统动力学特性的影响,并分别建立了轴向切削稳定域和径向切削稳定域的预测模型,求解了相关工艺条件下的切削稳定域叶瓣图。在切削力和动力学模型基础之上,研究了包括轴向切削深度、径向切削深度、主轴转速、周向进给率、轴向进给率等切削工艺参数的多目标工艺参数规划方法。最后通过试验对所规划的工艺参数进行了验证,试验过程中未出现颤振现象,表面粗糙度、圆度、圆柱度可以达到镗孔工艺的加工精度。     

Development of cutting force prediction model for carbon fiber reinforced polymers based on rotary ultrasonic slot milling

Carbon fiber reinforced polymers (CFRP) have got widely increased applications in aviation, defense and other industries due to their properties of high specific strength/stiffness, high corrosion resistance and low-thermal expansion. The issues like excessive cutting forces and machining damages are encountered in machining due to heterogeneity, anisotropy and low heat dissipation of these materials. The cutting forces are required to be predicted/minimized through modeling. In this article, the novel axial and feed cutting force model has been developed and validated through rotary ultrasonic slot milling of CFRP composites. The variations less than 10% have been found between the measured and corresponding simulated values of the cutting forces. However, some higher variations have also been observed in the few cases mainly due to heterogeneity and anisotropy of such material. The cutting depth is a significant parameter for axial and feed forces, while the feed rate is significant for the axial force. Both the forces decreased with the increase of spindle speed, while they increased with the increase of feed rate and cutting depth. The developed models have been found to be robust and can be applied to optimize the cutting forces for such materials at the industry level.     

硬质合金刀具车削Cr12Mn5Ni4Mo3Al不锈钢的试验研究

使用硬质合金刀具YW2进行Cr12Mn5Ni4Mo3Al不锈钢的干车削试验。分析了切削速度对车削力及表面粗糙度的影响,并采用扫描电子显微镜(SEM)观察刀具的磨损形貌。研究结果表明:使用硬质合金刀具YW2干车削Cr12Mn5Ni4Mo3Al不锈钢时,在小进给量和小背吃刀量切削的条件下,车削三向力的大小顺序为:径向力轴向力切向力;受积屑瘤的影响,表面粗糙度呈现出随车削速度的变化先减小后增大的变化趋势;硬质合金刀具后刀面磨损较轻微,而沿刀尖周围出现了较严重的粘结现象,前刀面上出现了较严重的划痕现象,低速时,前刀面还出现了贝壳状的剥落现象。     

Analytical modelling of slot milling exit burr size

A computational model was recently proposed by authors to approximate the tangential cutting force and consequently predict the thickness of the exit up milling side burr. To calculate the cutting force, the specific cutting force coefficient with respect to material properties was used. The model was sensitive to material yield strength and few cutting and tool geometrical parameters. However, the effects of cutting speed, tool coating, and tool rake angle on burr size were neglected. Other phenomena that could affect the burr size such as friction and abrasion were not taken into account either. Therefore, in the current work, a mechanistic force model is incorporated to propose a burr size prediction algorithm. The tangential and radial forces are calculated based on using specific cutting force coefficients in each direction. Furthermore, using the new approach, the burr size is predicated and the effects of a broad range of cutting parameters on burr size and friction angle are evaluated. Experimental values of burr size correlated well with prediction. It was found that the cutting speed has negligible effects on force and burr size. Lower friction angle was recorded when using larger feed per tooth. Consequently, thinner exit up milling side burr was obtained under high friction angle.     

Modeling of cutting force coefficients in cylindrical turning process based on power measurement

The cutting force is an important physical quantity in metal cutting, and the cutting force coefficients are the basis for establishing the cutting force model. In this paper, the relation between the cutting power and the cutting force coefficients is established. A cutting power model was established with a linear relationship between the spindle power and material removal rate (MRR). The power-based model of the main cutting force coefficients is proposed by extracting the linear equation coefficients of the power-MRR function. The power-based model of feed force coefficients is established as a quadratic polynomial equation between the motor power of the feed axis and feed rate. And the cutting force coefficients and the edge force coefficients of feed force are expressed respectively by the two orders of coefficients of the equation. The thrust force coefficients are indirectly calculated from the relation between tangential cutting force and thrust force with friction angle of tool-chip. The power-based models were verified by a series of cutting tests regarding material properties, cutting parameters, and axial directions. The results show that the cutting force coefficients obtained by measuring the cutting power have good correspondence with that identified by dynamometer.     

Chatter and dynamic cutting force prediction in high-speed ball end milling

Machine tool chatter is a serious problem which deteriorates surface quality of machined parts and increases tool wear, noise, and even causes tool failure. In the present paper, machine tool chatter has been studied and a stability lobe diagram (SLD) has been developed for a two degrees of freedom system to identify stable and unstable zones using zeroth order approximation method. A dynamic cutting force model has been modeled in tangential and radial directions using regenerative uncut chip thickness. Uncut chip thickness has been modeled using trochoidal path traced by the cutting edge of the tool. Dynamic cutting force coefficients have been determined based on the average force method. Several experiments have been performed at different feed rates and axial depths of cut to determine the dynamic cutting force coefficients and have been used for predicting SLD. Several other experiments have been performed to validate the feasibility and effectiveness of the developed SLD. It is found that the proposed method is quite efficient in predicting the SLD. The cutting forces in stable and unstable cutting zone are in well agreement with the experimental cutting forces.     

Cutting torque and tangential cutting force coefficient identification from spindle motor current

This article presents an enhanced methodology for cutting torque prediction from the spindle motor current, readily available in modern machine tool controllers. This methodology includes the development of the spindle power model which takes into account all mechanical and electrical power losses in a spindle motor for high-speed milling. The predicted cutting torque is further used to identify tangential cutting force coefficients in order to predict accurately the cutting forces and chatter-free regions for milling process planning purposes. The developed model is compared with other studies available in the literature, and it demonstrates significant improvements in terms of the completeness and accuracy achieved. The developed model is also validated experimentally, and the obtained results show good compliance between the predicted and the measured cutting torque. The developed enhanced procedure is very appealing for industrial implementation for cutting torque/force monitoring and tangential cutting force coefficient identification.     

In-process estimation of radial immersion ratio in face milling using cutting force

In order to prevent tool breakage in milling, maximum total cutting force is regulated at a specific constant level, or threshold, through feed rate control. Since the threshold is a function of the immersion ratio, an estimation of the immersion ratio is necessary to flexibly determine the threshold. In this paper, a method of in-process estimation of the radial immersion ratio in face milling is presented. When an insert finishes sweeping, a sudden drop in cutting forces occurs. These force drops are equal to the cutting forces that act upon a single insert at the swept cutting angle and they can be acquired from cutting force signals in the feed and cross-feed directions. Average cutting forces per tooth period can also be calculated from the cutting force signals in two directions. The ratio of cutting forces acting upon a single insert at the swept angle of cut and the ratio of average cutting forces per tooth period are functions of the swept angle of cut and the ratio of radial to tangential cutting force. Using these parameters, the radial immersion ratio is estimated. Various experiments are performed to verify the proposed method. The results show that the radial immersion ratio can be estimated by this method regardless of other cutting conditions.Nomenclature F_T, F_R tangential and radial forces - F_X, F_Y cutting forces in feed direction and cross feed direction - dF_X, dF_Y cutting force differences before and after the immersion angle in X and Y direction - K_s specific cutting pressure - a depth of cut - r ratio between tangential force and radial force - s_t feed per tooth - instantaneous angle of cut - _s swept angle of cut - _T tooth spacing angle - w radial width of cut - R cutter radius - z number of inserts     

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.     

Effects of Cutting Parameters on Tool Insert Wear in End Milling of Titanium Alloy Ti6A14V

Titanium alloy is a kind of typical hard-to-cut material due to its low thermal conductivity and high strength at elevated temperatures, this contributes to the fast tool wear in the milling of titanium alloys. The influence of cutting conditions on tool wear has been focused on the turning process, and their influence on tool wear in milling process as well as the influence of tool wear on cutting force coefficients has not been investigated comprehensively. To fully understand the tool wear behavior in milling process with inserts, the influence of cutting parameters on tool wear in the milling of titanium alloys Ti6Al4 V by using indexable cutters is investigated. The tool wear rate and trends under different feed per tooth, cutting speed, axial depth of cut and radial depth of cut are analyzed. The results show that the feed rate per tooth and the radial depth of cut have a large influence on tool wear in milling Ti6Al4 V with coated insert. To reduce tool wear, cutting parameters for coated inserts under experimental cutting conditions are set as: feed rate per tooth less than 0.07 mm, radial depth of cut less than 1.0 mm, and cutting speed sets between 60 and 150 m/min. Investigation on the relationship between tool wear and cutting force coefficients shows that tangential edge constant increases with tool wear and cutter edge chipping can lead to a great variety of tangential cutting force coefficient. The proposed research provides the basic data for evaluating the machinability of milling Ti6Al4 V alloy with coated inserts, and the recommend cutting parameters can be immediately applied in practical production.     

Effects of cutting parameters on tool insert wear in end milling of titanium alloy Ti6Al4V

Titanium alloy is a kind of typical hard-to-cut material due to its low thermal conductivity and high strength at elevated temperatures, this contributes to the fast tool wear in the milling of titanium alloys. The influence of cutting conditions on tool wear has been focused on the turning process, and their influence on tool wear in milling process as well as the influence of tool wear on cutting force coefficients has not been investigated comprehensively. To fully understand the tool wear behavior in milling process with inserts, the influence of cutting parameters on tool wear in the milling of titanium alloys Ti6Al4V by using indexable cutters is investigated. The tool wear rate and trends under different feed per tooth, cutting speed, axial depth of cut and radial depth of cut are analyzed. The results show that the feed rate per tooth and the radial depth of cut have a large influence on tool wear in milling Ti6Al4V with coated insert. To reduce tool wear, cutting parameters for coated inserts under experimental cutting conditions are set as: feed rate per tooth less than 0.07 mm, radial depth of cut less than 1.0 mm, and cutting speed sets between 60 and 150 m/min. Investigation on the relationship between tool wear and cutting force coefficients shows that tangential edge constant increases with tool wear and cutter edge chipping can lead to a great variety of tangential cutting force coefficient. The proposed research provides the basic data for evaluating the machinability of milling Ti6Al4V alloy with coated inserts, and the recommend cutting parameters can be immediately applied in practical production.     

Empirical models and optimal cutting parameters for cutting forces and surface roughness in hard milling of AISI H13 steel

In the present research, an attempt has been made to experimentally investigate the effects of cutting parameters on cutting forces and surface roughness in hard milling of AISI H13 steel with coated carbide tools. Based on Taguchi’s method, four-factor (cutting speed, feed, radial depth of cut, and axial depth of cut) four-level orthogonal experiments were employed. Three cutting force components and roughness of machined surface were measured, and then range analysis and analysis of variance (ANOVA) are performed. It is found that the axial depth of cut and the feed are the two dominant factors affecting the cutting forces. The optimal cutting parameters for minimal cutting forces and surface roughness in the range of this experiment under these experimental conditions are searched. Two empirical models for cutting forces and surface roughness are established, and ANOVA indicates that a linear model best fits the variation of cutting forces while a quadratic model best describes the variation of surface roughness. Surface roughness under some cutting parameters is less than 0.25 μm, which shows that finish hard milling is an alternative to grinding process in die and mold industry.     

Effects of cutting edge geometry, workpiece hardness, feed rate and cutting speed on surface roughness and forces in finish turning of hardened AISI H13 steel

In this study, the effects of cutting edge geometry, workpiece hardness, feed rate and cutting speed on surface roughness and resultant forces in the finish hard turning of AISI H13 steel were experimentally investigated. Cubic boron nitrite inserts with two distinct edge preparations and through-hardened AISI H13 steel bars were used. Four-factor (hardness, edge geometry, feed rate and cutting speed) two-level fractional experiments were conducted and statistical analysis of variance was performed. During hard turning experiments, three components of tool forces and roughness of the machined surface were measured. This study shows that the effects of workpiece hardness, cutting edge geometry, feed rate and cutting speed on surface roughness are statistically significant. The effects of two-factor interactions of the edge geometry and the workpiece hardness, the edge geometry and the feed rate, and the cutting speed and feed rate also appeared to be important. Especially honed edge geometry and lower workpiece surface hardness resulted in better surface roughness. Cutting-edge geometry, workpiece hardness and cutting speed are found to be affecting force components. The lower workpiece surface hardness and honed edge geometry resulted in lower tangential and radial forces.     

微细铣削切削力正交实验研究

在自行研制的三轴联动微细铣床上,选取典型微三维零件特征进行铣槽和侧铣两种工况正交铣削实验,对微细切削力进行测量和分析。深入研究了主轴转速、轴向切深、每齿进给量等工艺参数对微细切削力的影响规律,以优化加工参数,提高微铣削的加工效率和加工精度。     

Real-Time Prediction of Workpiece Errors for a CNC Turning Centre, Part 4. Cutting-Force-Induced Errors

A neural network method is presented for predicting cutting-force-induced errors in real-time during turning operations based on the estimated cutting forces. Workpiece errors can be considerably affected by the deflections of the machine–workpiece–tool system. A model of the elastic deflections of the machine–workpiece–tool system due to the cutting force in turning developed. A novel radial basis function (RBF) neural network is used to map the relationship between the cutting-force components (radial, axial and tangential) and the consequent dimensional deviation of the finished parts caused by the combined deflections of the machine–workpiece–tool system. Cutting tests were performed on a two-axis CNC turning centre and the experimental results showed that the prediction accuracy of the maximum diameter error of the workpiece was within 15%. The trained RBF neural network was able to predict the cutting force induced error in real-time during turning.     

切削参数对剃齿切削力及齿形中凹误差的影响

将剃齿径向力试验指数公式引入金属切削力理论公式中,建立了剃齿切削力模型,基于单一变量原则定量分析了切削参数对剃齿切削力的影响规律,阐述了基于切削参数的齿形中凹误差形成机理。通过有限元法及试验验证了模型的有效性。结果表明：剃齿切削力与径向进给量和轴向进给量成正相关,与主轴转速成负相关,其中径向进给量对剃齿切削力的影响最大;节圆附近的剃齿切削力达到峰值,表明该位置形成过切,随着误差的复映易形成剃齿齿形中凹误差。