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  • 刀具历史发展
  • 本站编辑:穆格精密工具(杭州)有限公司发布日期:2019-06-07 06:47 浏览次数:
刀具的发展在人类进步的历史上占有重要的地位。中国早在公元前28~前20世纪,就已出现黄铜锥和紫铜的锥、钻、刀等铜质刀具。战国后期(公元前三世纪),由于掌握了渗碳技术,制成了铜质刀具。当时的钻头和锯,与现代的扁钻和锯已有些相似之处。
然而,刀具的快速发展是在18世纪后期,伴随蒸汽机等机器的发展而来的。1783年,法国的勒内首先制出铣刀。1792年,英国的莫兹利制出丝锥和板牙。有关麻花钻的发明最早的文献记载是在1822年,但直到1864年才作为商品生产。
那时的刀具是用整体高碳工具钢制造的,许用的切削速度约为5米/分。1868年,英国的穆舍特制成含钨的合金工具钢。1898年,美国的泰勒和.怀特发明高速钢。1923年,德国的施勒特尔发明硬质合金。
在采用合金工具钢时,刀具的切削速度提高到约8米/分,采用高速钢时,又提高两倍以上,到采用硬质合金时,又比用高速钢提高两倍以上,切削加工出的工件表面质量和尺寸精度也大大提高。
由于高速钢和硬质合金的价格比较昂贵,刀具出现焊接和机械夹固式结构。1949~1950年间,美国开始在车刀上采用可转位刀片,不久即应用在铣刀和其他刀具上。1938年,德国德古萨公司取得关于陶瓷刀具的专利。1972年,美国通用电气公司生产了聚晶人造金刚石和聚晶立方氮化硼刀片。这些非金属刀具材料可使刀具以更高的速度切削。
1969年,瑞典山特维克钢厂取得用化学气相沉积法,生产碳化钛涂层硬质合金刀片的专利。1972年,美国的邦沙和拉古兰发展了物理气相沉积法,在硬质合金或高速钢刀具表面涂覆碳化钛或氮化钛硬质层。表面涂层方法把基体材料的高强度和韧性,与表层的高硬度和耐磨性结合起来,从而使这种复合材料具有更好的切削性能。
刀具按工件加工表面的形式可分为五类。加工各种外表面的刀具,包括车刀、刨刀、铣刀、外表面拉刀和锉刀等;孔加工刀具,包括钻头、扩孔钻、镗刀、铰刀和内表面拉刀等;螺纹加工工具,包括丝锥、板牙、自动开合螺纹切头、螺纹车刀和螺纹铣刀等;齿轮加工刀具,包括滚刀、插齿刀、剃齿刀、锥齿轮加工刀具等;切断刀具,包括镶齿圆锯片、带锯、弓锯、切断车刀和锯片铣刀等等。此外,还有组合刀具。
按切削运动方式和相应的刀刃形状,刀具又可分为三类。通用刀具,如车刀、刨刀、铣刀(不包括成形的车刀、成形刨刀和成形铣刀)、镗刀、钻头、扩孔钻、铰刀和锯等;成形刀具,这类刀具的刀刃具有与被加工工件断面相同或接近相同的形状,如成形车刀、成形刨刀、成形铣刀、拉刀、圆锥铰刀和各种螺纹加工刀具等;展成刀具是用展成法加工齿轮的齿面或类似的工件,如滚刀、插齿刀、剃齿刀、锥齿轮刨刀和锥齿轮铣刀盘等。
各种刀具的结构都由装夹部分和工作部分组成。整体结构刀具的装夹部分和工作部分都做在刀体上;镶齿结构刀具的工作部分(刀齿或刀片)则镶装在刀体上。
刀具的装夹部分有带孔和带柄两类。带孔刀具依靠内孔套装在机床的主轴或心轴上,借助轴向键或端面键传递扭转力矩,如圆柱形铣刀、套式面铣刀等。
带柄的刀具通常有矩形柄、圆柱柄和圆锥柄三种。车刀、刨刀等一般为矩形柄;圆锥柄靠锥度承受轴向推力,并借助摩擦力传递扭矩;圆柱柄一般适用于较小的麻花钻、立铣刀等刀具,切削时借助夹紧时所产生的摩擦力传递扭转力矩。很多带柄的刀具的柄部用低合金钢制成,而工作部分则用高速钢把两部分对焊而成。
刀具的工作部分就是产生和处理切屑的部分,包括刀刃、使切屑断碎或卷拢的结构、排屑或容储切屑的空间、切削液的通道等结构要素。有的刀具的工作部分就是切削部分,如车刀、刨刀、镗刀和铣刀等;有的刀具的工作部分则包含切削部分和校准部分,如钻头、扩孔钻、铰刀、内表面拉刀和丝锥等。切削部分的作用是用刀刃切除切屑,校准部分的作用是修光已切削的加工表面和引导刀具。
刀具工作部分的结构有整体式、焊接式和机械夹固式三种。整体结构是在刀体上做出切削刃;焊接结构是把刀片钎焊到钢的刀体上;机械夹固结构又有两种,一种是把刀片夹固在刀体上,另一种是把钎焊好的刀头夹固在刀体上。硬质合金刀具一般制成焊接结构或机械夹固结构;瓷刀具都采用机械夹固结构。
刀具切削部分的几何参数对切削效率的高低和加工质量的好坏有很大影响。增大前角,可减小前刀面挤压切削层时的塑性变形,减小切屑流经前面的摩擦阻力,从而减小切削力和切削热。但增大前角,同时会降低切削刃的强度,减小刀头的散热体积。
在选择刀具的角度时,需要考虑多种因素的影响,如工件材料、刀具材料、加工性质(粗、精加工)等,必须根据具体情况合理选择。通常讲的刀具角度,是指制造和测量用的标注角度在实际工作时,由于刀具的安装位置不同和切削运动方向的改变,实际工作的角度和标注的角度有所不同,但通常相差很小。
制造刀具的材料必须具有很高的高温硬度和耐磨性,必要的抗弯强度、冲击韧性和化学惰性,良好的工艺性(切削加工、锻造和热处理等),并不易变形。
通常当材料硬度高时,耐磨性也高;抗弯强度高时,冲击韧性也高。但材料硬度越高,其抗弯强度和冲击韧性就越低。高速钢因具有很高的抗弯强度和冲击韧性,以及良好的可加工性,现代仍是应用最广的刀具材料,其次是硬质合金。
聚晶立方氮化硼适用于切削高硬度淬硬钢和硬铸铁等;聚晶金刚石适用于切削不含铁的金属,及合金、塑料和玻璃钢等;碳素工具钢和合金工具钢现在只用作锉刀、板牙和丝锥等工具。
硬质合金可转位刀片现在都已用化学气相沉积法涂覆碳化钛、氮化钛、氧化铝硬层或复合硬层。正在发展的物理气相沉积法不仅可用于硬质合金刀具,也可用于高速钢刀具,如钻头、滚刀、丝锥和铣刀等。硬质涂层作为阻碍化学扩散和热传导的障壁,使刀具在切削时的磨损速度减慢,涂层刀片的寿命与不涂层的相比大约提高1~3倍以上。
由于在高温、高压、高速下,和在腐蚀性流体介质中工作的零件,其应用的难加工材料越来越多,切削加工的自动化水平和对加工精度的要求越来越高。为了适应这种情况,刀具的发展方向将是发展和应用新的刀具材料;进一步发展刀具的气相沉积涂层技术,在高韧性高强度的基体上沉积更高硬度的涂层,更好地解决刀具材料硬度与强度间的矛盾;进一步发展可转位刀具的结构;提高刀具的制造精度,减小产品质量的差别,并使刀具的使用实现最佳化。
刀具材料大致分如下几类:高速钢、硬质合金、金属陶瓷、陶瓷、聚晶立方氮化硼以及聚晶金刚石。
这里主要提下陶瓷,陶瓷用于切削刀具的时间比硬质合金早,但由于其脆性,发展很慢。但自上世纪70年代以后,还是得到了比较快的发展。陶瓷刀具材料主要有两大系,即氧化铝系和氮化硅系。陶瓷作为刀具,具有成本低、硬度高、耐高温性能好等优点,有很好的前景。

结构


编辑
整体式
刀体和刀齿制成一体。
整体焊齿式
刀齿用硬质合金或其他耐磨刀具材料制成,并钎焊在刀体上。
镶齿式
刀齿用机械夹固的方法紧固在刀体上。这种可换的刀齿可以是整体刀具材料的刀头,也可以是焊接刀具材料的刀头。刀头装在刀体上刃磨的铣刀称为体内刃磨式;刀头在夹具上单独刃磨的称为体外刃磨式。
可转位式
(见可转位刀具):这种结构已广泛用于面铣刀、立铣刀和三面刃铣刀等。

常见问题


编辑
尺寸不够精准: 解决方法:
1.过度切削 减低切削时的深度及宽度
2.机器或固定具缺乏准度 修理机器及固定具
3.机器或固定具缺乏刚性 改变机器\固定具或是切削设定
4.刃数太少 使用多刃端铣刀
铣刀发展很快,业内人称是旋转类刀具,如图所示只是整体硬质合金铣刀,其实,现在更多的铣刀应用在孔加工和型腔加工,这种铣刀大多是安装刀片的!

铣削

了解铣刀,就要先了解铣削知识
在优化铣削效果时,铣刀的刀片是另一个重要因素,在任何一次铣削时如果同时参加切削的刀片数多于一个是优点,但同时参加切削的刀片数太多就是缺点,在切削时每一个切削刃不可能同时切削,所要求的功率和参加切削的切削刃多少有关,就切屑形成过程,切削刃负载以及加工结果来说,铣刀相对于工件的位置起到了重要作用。在面铣时,用一把比切削宽度大约大30%的铣刀并且将铣刀位置在接近于工件的中心,那么切屑厚度变化不大。在切入切出的切屑厚度比在中心切削时的切削厚度稍稍薄一些。
为了确保使用足够高的平均切屑厚度/每齿进给量,必须正确地确定适合于该工序的铣刀刀齿数。铣刀的齿距是有效切削刃之间的距离。可根据这个值将铣刀分为3个类型——密齿铣刀、疏齿铣刀、特密齿铣刀。
和铣削的切屑厚度有关的还有面铣刀的主偏角,主偏角是刀片主切削刃和工件表面之间的夹角,主要有45度、90度角和圆形刀片,切削力的方向变化随着主偏角的不同将发生很大的变化:主偏角为90度的铣刀主要产生径向力,作用在进给方向,这意味着被加工表面将不承受过多的压力,对于铣削结构较弱的工件是比较可靠。
主偏角为45度的铣刀其径向切削力和轴向大致是相等的,所以产生的压力比较均衡,对机床功率的要求也比较低,特别适合于铣削产生崩碎切屑的短屑材料工件。

种类用途

大体上分为:
1.平头铣刀,进行粗铣,去除大量毛坯,小面积水平平面或者轮廓精铣;
2.球头铣刀,进行曲面半精铣和精铣;小刀可以精铣陡峭面/直壁的小倒角。
3.平头铣刀带倒角,可做粗铣去除大量毛坯,还可精铣细平整面(相对于陡峭面)小倒角。
4.成型铣刀,包括倒角刀,T形铣刀或叫鼓型刀,齿型刀,内R刀。
5.倒角刀,倒角刀外形与倒角形状相同,分为铣圆倒角和斜倒角的铣刀。
6.T型刀,可铣T型槽;
7.齿型刀,铣出各种齿型,比如齿轮
8.粗皮刀,针对铝铜合金切削设计之粗铣刀,可快速加工.

铣削方式

相对于工件的进给方向和铣刀的旋转方向有两种方式:
第一种是顺铣,铣刀的旋转方向和切削的进给方向是相同的,在开始切削时铣刀就咬住工件并切下最后的切屑。
第二种是逆铣,铣刀的旋转方向和切削的进给方向是相反的,铣刀在开始切削之前必须在工件上滑移一段,以切削厚度为零开始,到切削结束时切削厚度达到最大。
在三面刃铣刀、某些立铣或面铣时,切削力有不同方向。面铣时,铣刀正好在工件的外侧,切削力的方向更应特别注意。顺铣时,切削力将工件压向工作台,逆铣时切削力使工件离开工作台。
由于顺铣的切削效果最好,通常首选顺铣,只有当机床存在螺纹间隙问题或者有顺铣解决不了的问题时,才考虑逆铣。
在理想状况下,铣刀直径应比工件宽度大,铣刀轴心线应该始终和工件中心线稍微离开一些距离。当刀具正对切削中心放置时,极易产生毛刺。切削刃进入切削和退出切削时径向切削力的方向将不断变化,机床主轴就可能振动并损坏,刀片可能碎裂而加工表面将十分粗糙,铣刀稍微偏离中心,切削力方向将不再波动——铣刀将会获得一种预载荷。我们可以把中心铣削比做在马路中心开车。
铣刀刀片每一次进入切削时,切削刃都要承受冲击载荷,载荷大小取决于切屑的横截面、工件材料和切削类型。切入切出时,切削刃和工件之间是否能正确咬合是一个重要方向。
当铣刀轴心线完全位于工件宽度外侧时,在切入时的冲击力是由刀片最外侧的刀尖承受的,这将意味着最初的冲击载荷由刀具最敏感的部位承受。铣刀最后也是以刀尖离开工件,也就是说刀片从开始切削到离开,切削力一直作用在最外侧的刀尖上,直到冲击力卸荷为止。当铣刀的中心线正好位于工件边缘线上时,当切屑厚度达到最大时刀片脱离切削,在切入切出时冲击载荷达到最大。当铣刀轴心线位于工件宽度之内时,切入时的最初冲击载荷沿切削刃由距离最敏感刀尖较远的部位承受,而且在退刀时刀片比较平稳的退出切削。
对于每一个刀片来说,当要退出切削时切削刃离开工件的方式是重要的。接近退刀时剩余的材料可能使刀片间隙多少有所减少。当切屑脱离工件时沿刀片前刀面将产生一个瞬时拉伸力并且在工件上常常产生毛刺。这个拉伸力在危险情况下危及切屑刃安全。

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The development of knives occupies an important position in the history of human progress. As early as the 28th century BC to the 20th century BC, copper cones and copper cones, drills, knives and other copper knives have appeared. In the late Warring States period(3rd century BC), copper knives were made due to the mastery of carburizing technology. The drills and saws at that time were somewhat similar to modern flat drills and saws.
However, the rapid development of knives was accompanied by the development of steam engines and other machines in the late 18th century. In 1783, Lene of France first produced a milling cutter. In 1792, Mosley in the United Kingdom produced silk cones and teeth. The earliest documented invention of the burdock was in 1822, but it was not until 1864 that it was produced as a commodity.
At that time, the knives were made of overall high-carbon tool steel, and the cutting speed was about 5 meters/minute. In 1868, Mushete of the United Kingdom made tungsten alloy tool steel. In 1898, Taylor and White of the United States invented high-speed steel. In 1923, Shileteer of Germany invented cemented Carbide.
When alloy tool steel is used, the cutting speed of the tool is increased to about 8 m/h, when high-speed steel is used, it is more than twice as high, and when cemented carbide is used, it is more than twice as high as high-speed steel. The surface quality and dimension accuracy of the workpiece produced by cutting are also greatly improved.
Due to the relatively high price of high-speed steel and cemented Carbide, tools have been welded and mechanically clamped. From 1949 to 1950, the United States began to use convertible blades on car knives and soon applied them to milling knives and other knives. In 1938, Deguodegusa obtained a patent for ceramic knives. In 1972, General Electric of the United States produced polycrystalline artificial diamonds and polycrystalline cubic boron nitride blades. These non-metallic tool materials allow the tool to be cut at higher speeds.
In 1969, Shanteweike, Sweden, obtained a patent for the production of titanium carbide coated carbide carbide blades using chemical vapor deposition. In 1972, Bangsha and Lagulan of the United States developed a physical vapor deposition method that coated the surface of cemented carbide or high-speed steel tools with titanium carbide or titanium nitride rigid layers. The surface coating method combines the high strength and toughness of the matrix material with the high hardness and wear resistance of the surface layer, so that the composite has better cutting performance.
Tools can be divided into five categories according to the form of the workpiece surface. Tools for processing various outer surfaces, including tool, planer, milling cutter, outer surface drawing knife and file cutter; Holes processing tools, including drill bit, hole drill, boring tool, reamer and inner surface drawing knife; Thread processing tools, including screw cones, plate teeth, automatic opening and closing thread cutting heads, thread tool and thread milling cutter; Gear machining tools, including hob, cutter, razor, Bevel gear machining tools; Cut cutting tools, including toothed circular saw blades, strip saws, bow saws, cutting knives, saw blades, milling cutters, etc.. In addition, there are combination knives.
According to the cutting movement and the corresponding blade shape, the tool can be divided into three categories. Universal tools, such as tool, planer, milling cutter(excluding forming cutter, shaping cutter and shaping cutter), boring cutter, drill bit, hole drill, reamer and saw; Forming tools, the blades of such tools have the same or close to the same shape as the section of the machined workpiece, such as forming tool, shaping cutter, forming milling cutter, drawing knife, conical reamer and various thread machining tools; The spreading tool is a tooth surface or similar workpiece of a gear that is processed by an expansion method, such as a hob, a cutter, a razor, a Bevel gear planer, and a Bevel gear milling cutter.
The structure of various tools consists of clamping parts and working parts. The clamping part and the working part of the integral structure tool are made on the knife body; The working part of the toothed structure tool(knife tooth or blade) is mounted on the knife body.
The clamping part of the tool has two kinds of holes and handles. Holed tools rely on the inner hole set on the spindle or axis of the machine tool to transmit torsional torque through axial or end surface bonds, such as cylindrical milling cutter, sleeve milling cutter and so on.
Handled knives usually have rectangular handles, cylindrical handles, and conical handles. Car knives, planer knives, etc. are generally rectangular handles; The conical handle bears axial thrust by the taper and transmits torque by means of friction. Cylinder handles are generally suitable for smaller cutting tools such as burdock drills and vertical milling cutters. The torsion torque is transmitted by the friction force generated when clamping. The handles of many handled knives are made of low-alloy steel, while the work part is welded with high-speed steel.
The working part of the tool is the part that produces and processes the chip, including the blade, the structure that breaks or rolls the chip, the space where the chip or chip can be stored, and the channel of the cutting liquid. The working part of some knives is the cutting part, such as the cutter, planer, boring cutter and milling cutter; The working parts of some knives include cutting parts and calibration parts such as drill bits, hole drill, reamer, inner surface drawing knives, and silk cones. The cutting part is used to remove the chip with the blade, and the calibration part is used to repair the cut surface and guide the cutter.
The structure of tool working part includes integral, welding and mechanical clamping. The overall structure is to make a cutting edge on the blade; The welding structure is to braze the blade to the steel blade; There are two kinds of mechanical clamping structures. One is to clamp the blade on the blade body, and the other is to clamp the brazed knife head on the blade body. Carbide tools are generally made of welded structures or mechanical clamping structures; Ceramic tools are mechanical clamping structure.
The geometric parameters of tool cutting have a great influence on cutting efficiency and machining quality. Increasing the front angle can reduce the plastic deformation of the cutting layer when the cutting surface is squeezed, and reduce the friction resistance of the cutting debris flowing through the front, thereby reducing the cutting force and cutting heat. However, increasing the front corner will reduce the strength of the cutting edge and reduce the heat dissipation volume of the knife head.
In selecting the tool's angle, it is necessary to consider the influence of a variety of factors, such as workpiece materials, tool materials, processing properties(rough, refined), etc., and must be reasonably selected according to the specific circumstances. In general, the tool angle refers to the marking angle used for manufacturing and measurement. When the actual work is done, the actual work angle and the angle of marking are different due to the different installation positions of the tool and the change in the direction of cutting movement, but the difference is usually small. small.
Tools must be made of materials of high temperature hardness and wear resistance, necessary bending strength, impact toughness and chemical inertia, good workmanship(cutting, forging, heat treatment, etc.), and not easily deformed.
Usually when the hardness of the material is high, the wear resistance is also high; When the bending strength is high, the impact toughness is also high. However, the higher the hardness of the material, the lower its bending strength and impact toughness. High speed steel has high bending strength and impact toughness, and good processability. Modern is still the most widely used tool material, followed by cemented Carbide.
Polycrystalline cubic boron nitride is suitable for cutting high hardness quenched steel and hard cast iron. Polycrystalline diamonds are suitable for cutting non-ferrous metals, alloys, plastics, and fiberglass. Carbon tool steel and alloy tool steel are now used only as tools such as file, plate teeth and silk cones.
The cemented carbide convertible blades have now been coated with titanium carbide, titanium nitride, alumina hard layer or composite hard layer by chemical vapor deposition. The physical vapor deposition method under development can be used not only for cemented carbide tools, but also for high-speed steel tools such as drill bits, rollers, silk cones and milling cutters. Hard coatings act as barriers to chemical diffusion and heat conduction, slowing the tool's wear speed during cutting, and the life of coated blades is about 1 to 3 times higher than that of uncoated blades.
Due to the high temperature, high pressure, high speed, and parts that work in corrosive fluid media, more and more difficult to process materials are used, and the level of automation and the requirements for machining accuracy are getting higher and higher. In order to adapt to this situation, the development direction of tools will be to develop and apply new tool materials; Further development of the tool's vapor deposition coating technology, the deposit of higher hardness coating on the high toughness and high strength substrate, to better solve the contradiction between hardness and strength of tool materials; Further develop the structure of the transpose tool; Improve the manufacturing precision of the tool, reduce the difference in product quality, and optimize the use of the tool.
Tool material is large