高速切削30CrNi3MoV淬硬钢切屑形成机理的试验研究

通过30CrNi3MoV淬硬钢的高速切削试验,观察和测量不同切削条件下切屑形态的演变过程、锯齿状切屑形成的临界切削条件、切削力.结果表明,切削速度和刀具前角是影响切屑形态和切削力的主要因素,随着切削速度的提高,在某一临界切削速度下,切屑形态由带状屑转变为锯齿状切屑,随着刀具前角由正前角逐渐变为负前角,临界切削速度明显减小,当锯齿状切屑形成时,切削力大幅度降低.使用金属切削过程中绝热剪切临界切削条件判据对锯齿状切屑形成临界切削速度预测的结果表明,锯齿状切屑形成的根本原因是主剪切区内发生周期性的绝热剪切断裂.     

车铣加工切削机理分析

车铣加工通过将车刀更换为铣刀,增加铣刀转动自由度,基于工件转动和铣刀转动的合成运动,完成对工件的加工.车铣加工具有断屑更容易、切削温度低、切削力小等优点,即使工件低速旋转,也能实现高速切削.对车铣加工的切削机理进行了分析,具体包括刀具磨损机理、切屑形成机理、工件表面质量、难加工材料切削等.     

车床的防护装置

自从在车床上采用具有高度生产能力的加工方法起,防护切屑和工作安全的问题就有著重大的实际意义。 在车削过程中,除了带状切屑外,常常产生飞溅的切屑。这种切屑是在加工脆性金属和合金以及加工钢料时形成的,后者视钢的质量、切削刀具的几何形状、断屑的专门方法、切削用量和其他原因而定。当普通带状切屑被卡盘卡住而撕碎并以大速度将其扔抛时,也可能形成飞溅的切屑。在高速切削时所形成飞屑的条件下工作,无论对工人或对周围的人都是有危险的。 为了在各种车削加工的机床上预防飞屑的伤害事故,现寸最合理的方法是采用防护屏。防护屏不仅可…     

超声振动钻削切屑形成机理及实验研究

针对难加工材料钻孔不易断屑、加工难度高等问题,采用超声振动技术进行加工.对振动钻削的切屑形成机理进行分析,建立了切削刃的运动轨迹方程,推导出了不同相位差下的切削刃运动轨迹和切屑厚度方程,研究了切削厚度变化情况和断屑特性,得到了振动钻削中的完全几何断屑的条件.最后,通过201不锈钢钻削实验,对得出的切屑进行对比分析,验证了断屑条件,进而实现了对难加工材料钻孔切屑的有效控制.     

复杂槽型数控车刀片断屑预报系统的研究

针对数控车削加工过程中切屑折断难以预测问题,依据切屑折断界限理论建立了极限进给量和极限切削深度的预报数学模型:以上述数学模型为核心,开发了复杂槽型数控车刀片的断屑预报系统.为了验证预报结果的准确性,选取了典型的复杂断屑槽型车刀片切削45钢的断屑试验结果与预报结果进行了对比,对比结果显示二者基本一致,从而证明断屑预报结果的准确性和断屑预报系统具有一定的实用性.     

45钢高速切削过程中切屑形成的数值模拟

为了研究45钢高速加工中切屑形成机理,建立了高速加工的正交切削有限元模型,研究了45钢高速切削有限元建模过程中的Johnson-Cooks材料模型,刀屑接触模型及切屑分离准则等关键技术.利用建立的有限元模型对45钢的高速切削过程中的切屑成形进行了数值模拟,并研究了不同切削速度对切屑锯齿化程度的影响规律,得到了不同切削速度下的切屑锯齿化程度.     

喷气排屑旋风铣切内螺纹

过去认为:对小直径大螺距的内螺纹加工不宜采用旋风铣切,其原因是排屑困难,切屑和刀头产生撞挤,易打坏刀刃,同时切屑堆积孔内,散热很慢,加剧了刀刃的磨损,直至不能使用。针对这一问题,我们研制了喷气排屑旋风铣,铣切内螺纹刀杆。     

简易控制切屑的防护装置

在车床上没有现代化的断屑装置,并且工件材料长,处于连续切削的情况下,图示的切屑保护装置是非常适用的。工作时,长切屑常缠绕在工件上危险地旋转。本保护装置强迫切屑向下,     

正交车铣瞬时切削面积的建模与分析

通过对正交车铣运动学的分析建立了偏心正交车铣过程中的圆周刃切削深度、圆周刃切削厚度、端面刃切削深度和端面刃切削厚度的最大值表达式。运用所建立的数学模型,通过对切屑形成模型的研究建立了正交车铣瞬时切削面积的数学模型。应用正交试验法研究了正交车铣切削参数(切削深度、铣刀齿数、铣刀转速、偏心量和轴向进给量)对瞬时切削面积的影响规律:铣刀齿数影响最大,依次为切削深度、轴向进给量、铣刀转速和偏心量和运用极差分析探讨了以上五个切削参数对最大瞬时切削面积的影响趋势,最大瞬时切削面积随铣刀转速、偏心量和刀具齿数的增加而减小,随切削深度、轴向进给量的增大而增大。     

冷却方式对H13A硬质合金切削性能试验分析

在MAZARK车铣加工中心和高速铣床上选用切削速度150m/min和200m/min进行顺铣干/湿切削加工,采用H13A硬质合金刀具对TC4钛合金进行高速车铣和高速铣削加工试验。分别对比分析两种加工方式下冷却方式不同时的刀具磨损形态,结果表明:干切削时,无论正交车铣或高速铣削,刀具都是以粘结磨损为主;正交车铣干切削时,刀具表面有较多的切屑粘结物,易形成积屑瘤;切削液条件下,刀面粘结物相对减少,切屑粘走刀具材料,形成较多的粘结凹坑;铣削干切削时,粘结到刀面的切屑较正交车铣少,但切屑粘走刀具材料更为严重,前刀面出现较深的月牙洼,采用切削液时前刀面出现层状剥落。试验表明,当金属切除率一定时,正交车铣干切削金属切出总量最大,刀具寿命最长,湿切削加工时刀具寿命较短,切削液对刀具磨损形态和刀具寿命影响较大,可能与热交变应力和Co元素流失有关。试验结果表明,H13A刀具正交车铣钛合金干切削时切削性能较好。     

硬质合金刀具高速车铣和铣削TC4钛合金磨损试验对比

采用H13A未涂层硬质合金刀具对TC4钛合金进行高速正交车铣和铣削试验,并从刀具磨损破损形态、磨损机理及其寿命等方面进行对比分析。研究表明:高速正交车铣和铣削钛合金时,前、后刀面主要以粘结磨损为主,车铣加工时在切削刃口易形成积屑瘤及连续切屑,但对刀具材料粘结较轻;高速铣削时,对刀具材料粘接较重,在前刀面刃口附近形成凹坑及崩刃;后刀面最大磨损的位置不相同。试验对比了相同切削条件时刀具使用寿命,结果表明采用正交车铣加工可以获得更长的刀具使用寿命。     

Studies on high-efficiency and high-precision orthogonal turn-milling-The effects of relative cutting speed and tool axis offset on tool flank temperature

The cutting-edge temperature on the flank face in dry turn-milling of medium carbon steel (ISO C45) is measured using a two-color pyrometer with an optical fiber. In turn-milling, undeformed chip geometry is complex due to its dependence on several factors including diameter of the cutting tool, number of tooth, diameter of the workpiece, tool-work revolution speed ratio, depth of cut, feed per tooth, tool axis offset, and the cutting distance. In this study, the undeformed chip is analyzed and visualized by the 3D-CAD system, and the effects of the cutting parameters in turn-milling, especially relative cutting speed and tool axis offset on tool flank temperature, are investigated. It is interesting that the relative cutting speed does not significantly affect the tool flank temperature, where it increases by approximately 20 °C at most when relative cutting speed increases from 124 m/min to 217 m/min. In addition, tool flank temperature varies by approximately 40 °C when the tool axis offset is changed from 0 mm to 9.2 mm due to the change in the undeformed chip geometry.     

切削铝基复合材料时的切屑变形及影响因素研究

切屑形态特征和变形系数是研究切削变形程度的重要手段和参数,是计算其他切削过程参数的基础.通过硬质合金和聚晶金刚石(PCD)刀具车削SiC增强铝基复合材料,并观察切屑SEM照片,检测切屑的变形尺寸,研究切屑形态和变形系数.结果表明,切屑形态为小螺卷状,呈节状锯齿形.切削速度与变形系数的关系曲线呈驼峰形,随着进给量和刀具前角的增大,切屑变形系数减小.     

Swept area modeling and cutter wear study in turn-milling

In turn-milling machining, we found the cutter wear concentrated on a small section around the corner of the cutter and affect the cutter life. In this paper, the idea of swept area is proposed firstly based on the analyses for cutter wear, and it can indicate the cutter wear. Balance of swept area will lead to balanced wear along cutting edge, and expressions of swept areas of infinitesimal elements on the cutting edge are given. Secondly, the cutting depth and cutting angle, which are the key parameters in calculating the swept area, are analyzed based on different contact situations between the cutter and workpiece, and the detailed calculating method is given. Then, the optimization model to balance swept areas along the cutting edge is established, and the cutting parameters including cutter offset and machining length are optimized. Finally, the orthogonal turn-milling machining experiments with different cutting parameters are conducted; the result shows that turn-milling with optimized parameters can actually balance the cutter wear and increase the cutter life.     

基于最大正交车铣切削效率的切削用量选择

针对正交车铣的最大切削效率问题,确定切削速度、轴向进给量、工件转速为正交车铣的切削用量优化设计变量,建立相应的切削用量优化设计目标函数。并根据实际切削过程中工艺参数和加工要求,建立约束条件方程,采用Matlab数学软件的序列二次规划法(SQP)获得正交车铣切削用量的最佳选择。     

金属切削加工中刀—屑紧密型接触长度的研究

以李—谢弗滑移线场模型为基础 ,从理论上推导了刀—屑紧密型接触长度lf1的计算公式 ,认为刀—屑紧密型接触长度是切削第一、第二变形区综合作用的结果 ;通过切削试验 ,讨论了切削参数对刀—屑紧密型接触长度的影响 ;将计算结果与试验结果相比较 ,分析了该理论公式的合理性及适用范围     

Research on rotary surface topography by orthogonal turn-milling

As a new technology in manufacturing, turn-milling broadens the application ranges of mechanical processing, wherein both cutting tool and workpiece are given a rotary motion simultaneously. The objective of the present work is to study workpiece surface topography during orthogonal turn-milling process. This study begins with two mathematical models, which describe theoretical surface roughness and topography of rotationally symmetrical workpiece. The models are built with the establishment of locus function according to orthogonal turn-milling principle. Then based on these models, the influence law of surface topography affected by various cutting parameters is found by some simulation methods. The law also matches with orthogonal turn-milling surface roughness and topography experiments. By analyzing the experimental results, some parameter selection criteria during orthogonal turn-milling processing are also proposed qualitatively and quantitatively. The comparison between the simulation and experimental results shows that a better surface quality and tiny oil storage structure can be obtained if the cutting parameters are chosen in reason. This conclusion provides a theoretical foundation and reference for the orthogonal turn-milling mechanism research.     

Microcutting using a micro turn-milling machine

A turn-milling machine, which is a device having two spindles that rotate a tool and workpiece, can be used to fabricate various shapes by cutting. However, little progress has been made in microcutting using a turn-milling machine. Therefore, a micro turn-milling machine designed especially for microtools was developed and used to fabricate micropins with various cross sections. Cemented tungsten carbide microtools, which are useful both as a milling cutter and as a turning tool, were processed by electrical discharge machining and employed for microcutting. As a result, various micropins were successfully fabricated, including not only cylindrical pins but also those with cross sections having square, triangle, and cross shapes. These noncylindrical micropins have the smallest reported cross-section dimensions for pins fabricated by cutting to the best of our knowledge. Furthermore, cutting characteristics such as the machined shape and surface quality were investigated, which showed that better micropin shapes were obtained by up-cut turn-milling than by down-cut turn-milling or by turning. In contrast, turning was superior to turn-milling in terms of the surface quality.     

正偏心正交车铣精加工切削层几何形状研究

针对未考虑正偏心正交车铣切削层几何形状而导致难以全面反映正交车铣切削层几何形状变化规律的问题,基于正交车铣运动规律,在不考虑动力学影响的情况下,对切削层的形成过程进行了静态分析。建立的正偏心正交车铣切削层几何形状的解析模型涉及铣刀侧刃和底刃的切入/切出角度、切削厚度和切削深度。通过试验验证了该解析模型的正确性,并分析了切削参数对铣刀切削层的影响。研究结果为正偏心正交车铣切削层几何形状的变化提供了定量的分析依据,为切削力和颤振的研究提供了理论指导。     

车铣复合加工的刀具磨损强度分析

在车铣复合加工中心上,进行了车铣加工高强度钢工件材料的刀具磨损强度实验,分析了车铣切削用量对刀具磨损强度的影响.研究表明,在影响车铣刀具磨损的切削用量中,切削速度对车铣刀具的磨损强度影响最大.并以车铣刀具的磨损实验为基础,以切削速度为变量,建立了车铣高强度钢的刀具磨损强度分析模型.