Investigation on the burr formation mechanism in micro cutting

It is desirable to minimize burr formation for improving part quality. This paper presents an investigation on the burr formation mechanism in micro cutting by taking into consideration the stress distribution around the cutting edge arc. The influences of the uncut chip thickness and the cutting edge radius on burr formation were investigated. Poisson burr is attributed to the side flow of the stagnation material at the bottom of the cutting edge arc. The stress distribution at the cutting edge arc has great influence on Poisson burr formation. The burr height decreases to the minimum value and then increases with reducing the uncut chip thickness due to the change of the maximum stress distribution. An optimum machining strategy also is suggested in micro milling of snake-shaped groove microstructure.     

Influence of cutting edge radius on surface integrity and burr formation in milling titanium

The influence of the cutting edge micro geometry on cutting process and on tool performance is subject to several research projects. Recently, published papers mainly focus on the cutting edge rounding and its influence on tool life and cutting forces. For applications even more important, however, is the influence of the cutting edge radius on the integrity of the machined part. Especially for titanium, which is used in environments requiring high mechanical integrity, the information about the dependency of surface integrity on cutting edge geometry is important. This paper therefore studies the influence of the cutting edge radius on surface integrity in terms of residual stress, micro hardness, surface roughness and optical characterisation of the surface and near surface area in up and down milling of the titanium alloy Ti–6Al–4V. Moreover, the influence of the cutting edge radius on burr formation is analysed. The experiments show that residual stresses increase with the cutting edge radius especially in up milling, whereas the influence in down milling is less pronounced. The influence of the cutting edge radius on surface roughness is non-uniform. The formation of burr increases with increasing cutting edge radius, and is thus in agreement with the residual stress tests.     

Effect of polar organic substance on burr formation in orthogonal cutting

The initiation of burr formation is characterized by the initial negative shear angle and the initial tool distance which are obtained from the minimum energy principle and energy conservation at the chip/burr transition point. Specially in this report the rollover burr is dealt as a specific case of the chip formation process in the final stage of cut, which the tool moves toward the end of workpiece. The purpose of this paper is to experimentally invesigate the burr formation mechanism near the end of cut by using a copper with various cutting conditions and tool geometries, and the influence of the surface active medium, that was used to reduce the burr size and improve the machinability, upon the mechanism of burr formation in the orthogonal cutting using the milling machine.     

Finite element simulation for burr formation near the exit of orthogonal cutting

A coupled thermo-mechanical model of plane-strain orthogonal metal cutting including burr formation is presented using the commercial finite element code. A simulation procedure based on Normalized Cockroft–Latham damage criterion is proposed for the purpose of better understanding the burr formation mechanism and obtaining a quantitative analysis of burrs near the exit of orthogonal cutting. The cutting process is simulated from the transient initial chip formation state to the steady state of cutting, and then to tool exit transient chip flow by incrementally advancing the cutting tool. The predicted burr profile is compared with experimental data and found to be in reasonable agreement. The effect of the tool conditions and cutting conditions on the burr formation process was also investigated.     

微细铣削毛刺形成研究

微细铣削是在广泛材料范围内制造精密三维微小零件的一种柔性的、经济的加工方法,微细铣削的主要问题之一是有毛刺产生,对微细铣削过程中毛刺的形成及其影响因素进行实验研究与分析,得到微细铣削过程中各因素对毛刺形成影响的一般规律,在此基础上,通过合理地选择切削参数以及刀具路径规划,达到减小毛刺的目的。     

Defining the effects of cutting parameters on burr formation and minimization in ultra-precision grooving of amorphous alloy

Amorphous nickel phosphorus (Ni-P) alloy is a suitable mold material for fabricating micropatterns on optical elements for enhancing their performances. Ultra-precision cutting is preferred to be used to machine the mold material for high precision in a large workpiece. However, burrs and chippings always form and are detrimental especially when fabricating micropatterns. The formation mechanisms of burrs and chippings have not yet been revealed precisely in the cutting processes of amorphous alloys, because their cutting behavior is more complex and less discussed in existing researches than that of crystalline metals. In the present study, the burr formation process of amorphous Ni-P is defined and a three-dimensional cutting model using energy method is proposed to predict and minimize burrs and chippings. Microgrooving experiments were conducted with different undeformed chip geometries using three types of cutting tools to observe burr formation processes. Large burrs and chippings were formed when cutting with a tapered square tool and a tilted triangle tool. These large burrs and chippings were found to be induced by large slippages that are unique to amorphous alloys. It was revealed that burrs and chippings appear when the angle between the chip flow direction and the groove edge is less than a critical value. Energy method was used to predict the chip flow directions and the calculated results agree with the experimental ones, which proved that the energy method is valid for designing an appropriate undeformed chip geometry to reduce burrs and chippings in ultra-precision grooving.     

金属切削毛刺专家系统的研究进展

毛刺是金属切削加工中产生的常见现象之一,它的尺寸和形状直接影响到工件的尺寸精度和形位精度,甚至影响到工件的使用性能及其寿命.随着机械制造业朝着高精度,高效率和自动化方向发展,对切削加工精度的要求越来越高.由于专家系统具有数据结构化,数据和应用程序的高度独立性、数据共享,并将数据冗余减少到最小限度等优点,在金属切削毛刺形成研究与控制上逐步得到了越来越广泛的应用,对加工精度起到了很好的效果.在分析现有毛刺研究成果的基础上,与专家系统进行了对比与分析,体现出了专家系统在毛刺研究领域应用具有的优点,并阐述了现有的金属切削毛刺专家系统的研究现状,指出了尚存在的一些问题,从而为今后毛刺专家系统的发展提供借鉴.     

Investigation on the influence of material microstructure on cutting force and bur formation in the micro cutting of copper

The International Journal of Advanced Manufacturing Technology - In recent years, the demands for micro components are increasing in various industries. Mechanical micromachining is one of the best...     

Effect of workpiece structure on burr formation in micro-drilling

The effect of workpiece structure and drill diameter on burr formation in drilling was investigated. The characteristic results are that burr formation is reduced when the grain size of the workpiece increases, and this effect of grain size becomes especially important when the drill diameter is very small and its tool edge is dull or worn. These facts are explained as follows: since the number of crystal grains covered by drilling a part is small when the workpiece structure grain size is large and drill diameter is small, the effect of crystal anisotropy on working stresses becomes smaller and the effect of the crystal boundaries on drilling work per revolution becomes smaller for micro-drill feed. Therefore, chips are easily separated from the workpiece during plastic deformation, and only small burrs will be produced in micro-drilling     

积屑瘤状态对微细切削表面轮廓特征的影响

研究了微细切削条件下,刀具前刀面上的积屑瘤状态对切削表面轮廓特征的影响,为合理选择和控制微细切削刀具的切削条件,以及评价微细切削的表面形貌特征提供实验依据.利用表面粗糙度仪分别提取了无积屑瘤、积屑瘤生长、稳定和脱落等4种积屑瘤状态下的切削表面轮廓,选取幅值密度函数(ADF)、自相关函数(ACF)和功率谱密度函数(PSD...     

The effects of grain size and feed rate on notch wear and burr formation in wrought Alloy 718

The effect of two different workpiece material grain sizes, 16 and 127 μm, on the depth-of-cut notch wear, chip morphology, and burr formation was studied in a turning operation. A material from the same batch of wrought superalloy Alloy 718 was heat-treated to achieve the two microstructures. The machining was performed at two feed rates, 0.1 and 0.2 mm/revolution. Uncoated cemented carbide tools were used. Both grain size and feed rate were found to influence the chip morphology and the sideflow which were also associated with both the notch wear and the burr formation. The effect of the grain size on the notch wear was larger than that of the feed rate under the tested conditions, with larger grains being more detrimental than smaller ones.     

Prediction of burr formation during face milling using a hybrid GMDH network model with optimized cutting conditions

In this paper, a combined hybrid group method for data handling and optimization approach is introduced to predict burr types formed during face milling. The hybrid group method for data handling (hybrid GMDH) network was constructed for realizing predictive models for the machining of aluminum alloy, and differential evolution was selected for the optimization of burr formation problem resulting in finding optimal parameter for minimizing burr formation. Burr type was included as a parameter resulting in a classification scheme in which the burr type becomes the group label and it is therefore possible in the future to classify a machining process into any of these burr types. The resulting hybrid GMDH output was in agreement with experimental results, thereby validating the proposed scheme for modeling and prediction of burr formation in milling operations.     

高精度微孔镗削加工工艺的优化研究

为解决使用微细切削技术加工微小型孔时存在的钻削孔表面质量差、孔轴线偏斜等问题,将镗削加工方法应用到微小型孔的加工中。通过选取合适的镗削工艺参数,定性地建立了镗刀尺寸、进给速度、转速与表面质量、尺寸精度之间的关系,优化了镗削加工的工艺参数,极大地改善了微小型孔的表面质量与加工精度。在具有较高强度的3J33马氏体时效钢上对钻削出的Ф2.7 mm小孔进行了镗削加工试验,测量并分析了镗削孔表面粗糙度与尺寸数据。实验结果表明,微细孔镗削加工比钻削加工更能够保证零件的尺寸精度、形状精度,并得到更好的表面质量。     

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.     

Development of artificial neural network models to study the effect of process parameters on burr size in drilling

Burr size at the exit of the holes in drilling is a quality index and hence it becomes essential to predict the size of the burr formed in order to cater to the demand of product quality and functionability. In this paper, artificial neural network (ANN)-based models have been developed to study the effect of process parameters such as cutting speed, feed, drill diameter, point angle, and lip clearance angle on burr height and burr thickness during drilling of AISI 316L stainless steel. A multilayer feed-forward ANN; trained using error back-propagation training algorithm (EBPTA) has been employed for this purpose. The input-output patterns required for training are obtained from drilling experimentation planned through Box-Behnken design. The simulation results demonstrate the effectiveness of ANN models to analyze the effects of drilling process parameters on burr size.     

Characterization and modeling of burr formation in micro-end milling

Mechanical micromachining is increasingly finding applications in fabrication of components in various fields, such as, biomedical devices, optics, electronics, medicine, communications and avionics. In order to ensure adequate functionality, there are stringent requirements for form and finish in case of biomedical devices like cochlear implants and metallic optics. This necessitates that the post machined surface must be burr free. To address these issues in micromachining, this paper presents results of an experimental study to investigate the influence of main process parameters i.e. speed, feed rate, depth of cut, tool diameter and number of flutes on the formation of the various types of burrs i.e. exit burrs and top burrs produced during micro-end milling operation. The experiments performed using Taguchi method shows that three types of burr formation mechanisms prevail during micro-end milling operations; these are: lateral deformation of material, bending and tearing of the chip. Also, three types of burrs were observed include: Poisson burr, rollover burr in down milling and tear burr in up milling. Further, it is observed that the depth of cut and the tool diameter are the main parameters, which influence the burr height and thickness significantly. However, the speed and the feed rate have small to negligible effect on the burr thickness and height. Besides the experimental analysis, the paper presents an analytical model to predict the burr height for exit burr. The model is built on the geometry of burr formation and the principle of continuity of work at the transition from chip formation to burr formation. Note that prediction of burr height in micro-end milling is extremely challenging due to the complex geometry of material removal and microstructural effects encountered during cutting at that length scales. The model fares well and the prediction errors range between 0.65 and 25%.     

Experimental investigations of sideward burr formation in rotary machining

Burrs can be formed on the feed mark ridges and the edges of the machined parts in machining operations. These burrs are undesirable in terms of the surface quality, the precise dimensioning of the machined parts and the safety of operators. This paper demonstrates the effectiveness of using a rotary tool on minimizing the sideward burr formation in machining. In particular, the experimental relationships between the size of sideward burr and the cutting parameters (including tooling mechanism) are established first in rotary machining. Methods to control the size of sideward burr are then explained. The possible application of a rotary tool for deburring operations while engaged in machining is also explored.     

Study on burr formation in micro-machining using micro-tools fabricated by micro-EDM

The purpose of this study is to study burr formation in micro-machining using micro-tools. The micro-tools employed are fabricated by micro-EDM using the wire electro-discharge grinding (WEDG) method in the micro-EDM/milling machine we had already developed. Micro tungsten-carbide tool with a minimum of 31-μm in diameter had been fabricated. The simple-shaped micro-tool fabricated is able to perform the micro-machining operation which is a combination of micro-milling and grinding processes. Micro-slot and micro thin-walled structure had been produced on Al 6061-T6 materials successfully. Burr formation in micro-machining is investigated experimentally and classified into four types: primary burr, needle-like burr, feathery burr and minor burr. Formation mechanisms of these burrs and the relationship between their existence and the machining condition are discussed.     

冲裁毛刺形成过程的有限元分析

采用弹塑性有限元法,运用有限元分析软件,对板料的冲裁过程进行了数值模拟,分析冲裁过程中毛刺的形成机理.设置了一系列的模具间隙、模具圆角参数,来分析模具间隙的增大和模具的磨损变化对毛刺形状的影响.模拟的结果与试验数据相对照,来预测冲裁断面的质量,优化工艺参数.