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.     

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.     

Influence of size effect on burr formation in micro cutting

Burr is an important character of the surface quality for machined parts, and it is even more severe in micro cutting. Due to the uncut chip thickness and the cutting edge radius at the same range in micro cutting process, the tool extrudes the workpiece with negative rake angle. The workpiece flows along the direction of minimum resistance, and Poisson burr is formed. Based on the deformation analysis and experiment observations of micro cutting process, the factor for Poisson burr formation is analyzed. It is demonstrated that the ratio of the uncut chip thickness to the cutting edge radius plays an important role on the height of Poisson burr. Increasing the uncut chip thickness or decreasing the cutting edge radius makes the height of exit burr reduce. A new model of micro exit burr is established in this paper. Due to the size effect of specific cutting energy, the exit burr height increases. The minimum exit burr height will be obtained when the ratio of uncut the chip thickness to the cutting edge radius reaches 1. It is found that the curled radius of the exit burr plays an important role on the burr height.     

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.     

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.     

Elementary chip formation in metal cutting

Elementary-chip formation in the machining of hard materials is considered. Formulas are presented for the geometric parameters of the elementary chip as a function of the machining conditions.     

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.     

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.     

金属切削加工表面缺陷的形成机理及统计预测方法综述

切削加工表面存在的裂纹、凹坑等缺陷会降低零件的疲劳强度和耐腐蚀性,引起零件过早的损坏,研究缺陷的生成机理,提出有效的加工表面缺陷的预测方法,对提高产品的质量以及保证产品生产效率具有重要意义。阐述了加工表面缺陷的生成机理,分析了加工参数对表面缺陷的影响;总结了现有的缺陷统计分析与预测的研究成果,综述了表面缺陷对工件耐腐蚀性的影响。     

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.     

超硬刀具加工复合材料的切削性能和切削机理

复合材料属于难加工材料 ,用超硬刀具切削复合材料最为有效。作者用杭州华汇金刚石技术研究所研制的CVD金刚石厚膜刀具对两类复合材料 ,进行了切削试验 ,取得了良好效果。本文列出了部分试验数据 ,并初步探讨了切削机理。     

金属切削中如何选择切削液

概述了切削液的种类和性能,介绍了目前切削液的使用情况,重点探讨了在不同的材料、不同的切削方法、各种常见刀具及良好的经济效益下选择切削液的基本原则.     

切削液腐蚀金属工件表面的机理探讨

在原子水平上分析了切削液与金属表面反应的速率,认为静电感应电位是腐蚀产生的关键因素,并在实验室观察了铁合金表面的腐蚀现象,发现当钻头与工件表面存在静电电位差(约20V)时容易在工件表面形成微米级腐蚀斑点。采用能量色散X射线光谱仪(Energy Dispersive X-Ray Spectroscopy,EDX)对腐蚀斑点化学成分的分析表明,氧、硫和氯元素是导致腐蚀发生的主要原因。     

钢筋矫直切断机剪切机构研究分析

对钢筋矫直切断机的剪切机构进行了研究分析，确定了避免连切的条件约束，使得剪切机构参数得以优化。     

材料切削性能的模糊综合评判

介绍了一套材料加工参数智能推理系统的研究。重点讨论了模糊理论在该系统中的运用，采用模糊综合评判、模糊聚类原理，根据用户输入材料的物理机械性能，快速确定材料的切削加工性能。将材料按切削加工性能等级分类可简化材料切削参数推理，有利于新材料切削参数的确定。     

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     

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...     

Characteristics and mechanism of top burr formation in slotting microchannels using arrayed thin slotting cutters

This paper investigates the characteristics and mechanism of top burr formation, and the influence of cutting conditions on top burr formation in slotting microchannels on stainless steel (SS304L) using arrayed thin slotting cutters. Saw-like top burr that is a combination of Poisson part and tear part was observed in the experiments. A 3D finite element model was developed for analysis of the top burr formation processes. The mechanism of top burr formation was proposed based on a series of stress contours and the progressive deformation of microchannel edge obtained from simulation. The process of top burr formation can be divided into four stages: Poisson part initiation, Poisson part development, tear part formation and tear part toppling. The top burr height was found to be largely determined by feed and cutting speed, while the top burr width was found to be strongly influenced by cutting depth, feed and cutting speed.