试验指导书：五轴数控磨刀机原理及实践

1、实验指导书五轴数控磨刀机原理及实践要加工出合格的工件，必须根据工件的加工工艺要求，正确地设计和使用刀具，以保证 达到工件所要求地尺寸、形状精度和表面质量。金属切削刀具的种类很多，对于标准刀具， 需要根据刀具的工作原理和结构特点正确地选择和使用；对于非标准刀具则需要根据工件的 加工要求进行专门的设计和制造。经过精心准备，制造工程基础教学组与德国saacke公司培训中心尝试进行校企合作 开展学生实验课程的工作。本次实验的主要目的是结合生产实际，通过先进的制造设备及手 段，使学生能够掌握刀具的设计原理，合理选择刀具设计参数，正确设计刀具结构，熟悉刀 具从设计到制造的全过程。实验目的结合生产实际，给学

2、生介绍先进的生产理念，作为课堂内容的拓展和补充，加深对 所学知识的理解；锻炼实验设计能力和动手能力，熟悉刀具由设计到制造的全过程；掌握有关磨削加工的知识，了解刀具磨床的结构及工作原理，；掌握钻头设计、加工的全过程；指导人员德国Saacke公司中国工程师、德国工程师（英语交流）、实验指导教师实验内容由Saacke公司的指导人员负责讲解，并利用该公司所提供的五轴数控磨刀机及相应的 CAD/CAM软件，参加实验的每组同学完成所选刀具的设计和制造。本实验主要包括以下内容：讲解Saacke五轴新概念刀具磨床的结构及工作原理。讲解钻头、铣刀等刀具设计、加工原理讲解有关磨削加工的知识，包括砂轮、切削液等在刀

3、具设计加工仿真软件上完成相应刀具的CAM设计在Saacke五轴刀具磨床上完成所设计刀具的加工实验设备、仪器及工具机床：uw型五轴数控磨床软件：NUMROTO plus试件：45#钢棒料（细长棒料）计算机千分表、游标卡尺刀具角度测量仪准备工作熟悉钻头、铣刀的结构特点、设计原理和制造方法；熟悉本指导书附录中关于磨削的知识；牢记操作注意事项及操作安全。UW II型五轴数控磨床简介图1. 1】型五轴数控磨床UW型五轴数控磨床，功率15KW,可以用于刀具的制造和修磨，并可配置自动上下 料装置，以满足大批量生产的需要。机床采用Windows操作系统，人机对话式窗口，界面 友好，旁边有图形支持窗口，可对加工

4、刀具进行三维立体显示和加工模拟，并且留有用户开 发界面。在磨头上装有三维Renishaw测头，可以对刀具的长度、直径、螺旋角等参数进行 自动测量，并自动输送到计算机中，方便可靠。该机床主要技术参数如下：技术特点： 转塔式磨头，装有三根砂轮芯轴，可配9片砂轮磨轴马达功率15KW 数字控制 磨轴转速2,000-8,000 rpm一 工件头直接驱动，转速600 rpm (可选)自动上料系统(可选)每个托盘最多可装40把刀具工件参数： TOC o 1-5 h z 最大直径300mm全磨制最大直径250mm全磨制最大切削刃长350mm实验报告实验目的实验内容实验步骤实验结果利用刀具设计加工CAD/CAM

5、软件系统NUMROTO plus完成相应刀具的 CAM设计利用UW型五轴数控刀具磨床和棒料加工出所设计的刀具给出设计加工的钻头的测量角度实验分析与总结分析所设计钻头结构特点和刀具几何参数对加工的影响；分析五轴数控磨床的工作原理以及砂轮的特性由哪些因素决定；分析切削液的种类及切削液的使用情况对磨削加工的影响；对本次实验的感想与建议；建议建议大家在实验前做好准备工作，在实验中每组同学可进行分工，以提高实验效率。附录GrindingGeneral introductionGrinding means cutting with geometrically not defined edges. The

6、rotating grinding bodies are composed of bound abrasive grains and imbedded pores, functioning as chip chambers. 我Advantages of grindingHigh surface quality of the ground partsGood machinability of hard and difficult to machine materialsHigh time grinding volume. Partially, similar values as for pla

7、ning and turning are possible.Surface grinding machinesOn surface grinding machines plane surfaces are machined by the periphery or by the face of the grinding wheel (figure). There are different kinds of machines: one execution with horizontal and vertical grinding spindle, the other with long and

8、with rotary table.Long tables are meant for bigger resp. longer working pieces.Round or rotary tables are suited for smaller pieces. Smaller pieces do not need the change of direction at the end. Therefore a continuous feed motion is possible.On grinding machines the tool (grinding wheel) is effecti

9、ng the cutting movement. Depending on the machine type or design, the plunge and the feed motion are effected either by the working piece or by the tool.Surface cylindrical grinding machinesOn these machines the working piece is mostly clamped between the centers. It gets a rotary motion. The cuttin

10、g movement is effected by the grinding wheel. The grinding wheel can be fed from behind to the working piece.Long working pieces require a longitudinal feed (figure), which is mostly effected by the working piece. Here a slide (working piece slide) is required, which can be adjusted to different str

11、oke lengths. The working piece table is fixed on the slide.Machines with a horizontal spindle are mostly usedfor periphery grinding. In figure * you can see differentexamples of use. Vertical spindles are often used for face grinding.On both machine types the slides are mostly hydraulically operated

12、. Hydraulic drives are vibration free, the feed is infinitely variable. High quality slide guides and good lubricant conditions on the guide surfaces are very important in order to avoid the stick-slip-effect. Also very important are good spindle bearing assemblies.References/characteristics of a gr

13、inding wheelOn figure 1 (pagel) you can see the body of a grinding wheel. The figure shows the abrasive grains, the bonding material and the pores. When selecting the suitable grinding wheel, five decisions have to be made.1. Abrasive material (chemical composition of the abrasive grain). The most i

14、mportant abrasive materials are:corundum A, silicon carbide C, boron nitride B and diamond D. Corundums are mainly composed of aluminium oxide (Al2O3). You have to differ between several degrees of purity. Normal corundum: 94.97H% AI2O3, special fused alumina: more than 99% AI203. Corundums are for

15、example suited for the grinding of long cutting materials. Silicon carbide is harder. It is suited for the grinding of short cutting materials as for examplegray iron, chill casting, carbide.2. Granulation (grain size)In the standard designation the grain size is specified with a number, for ex. 80.

16、It specifies the number of meshes (per inch)of a filter by which the grains wereEgrobmtCtcl.,sdvfcin310121416 2G24.二 m303660- ； : A VW100120 160 1802/0 2402S0 320 400 bOO 600 aoo1000 1200 .sorted out.Hardness (Resistance of the grains against breaking out of the bonding).As every cutting tool does -

17、 grains are dulling after a certain time. When the wheel hardness is selected correctly, the dulled grain breaks out due to the higher loading and allows therefore, that new, sharp grains can work. The material of the working piece has a big influence on the hardness selection. Here you have to cons

18、ider:Hard materials require soft wheels, soft materials require hard wheels.When hard materials are machined the grains are dulled earlier and have to disconnect earlier from the bonding. The hardness (one letter for ex. nMH) refers to the stationary wheel.ABCDau&erst weichEFG一Sehr weichH1JotKweichL

19、MNOmittrlPQRShartTUVwsehr hartXYZ一auBerst hartSAACKE Workshop GRINDING contact zone).During internal grinding the grain is charged less and rests therefore longer in the bonding. So the wheel seems harder. In the following you find other possibilities, how to increase the active hardness (preconditi

20、on: the other machining data stay the same).setting a new grinding wheel (due to the bigger diameter)increasing the cutting speed (chip section gets smaller).reducing the cutting depth.Selection : Jot comment for selection:The cutter has a hardness of 61 HRC. Here you should use a grinding wheel sof

21、ter than Jot.For the selection however, measure and form precision have to be taken into consideration.Soft grinding wheels wear out faster. And so it is more difficult to keep the given form and measure tolerances.Structure (space portion of grains, bonding material and pores)123456789 10 11 12 13

22、14IThe pores are necessary as chip sections. Their size and quantity have also influence on the hardness (see above). A wheel being too tight is too hard and has too low efficiency.With a wheel being too open, it might be difficult do get a certain surface quality.As characteristic for the structure

23、 a number is used.Selection: structure 5Bonding (material, which binds the grains)The bonding is also responsible for the hardness and especially for the elasticity of the grindingwheel. The bonding has to endure a mechanical and also a very high thermal loading. In the following there are mentioned

24、 2 important groups:kind of bonding CharacteristicsCeramic Bondings VArtificial res inBondingsBgood hardness graduation possibilities resistance against water and oilindifference to high heating, butsensitivity to impactsmuch more elastic than ceramic bondings (especially important for thin grinding

25、 wheels)By the elastic attitude the grains areprotected against overload.Selection: V (Ceramic Bonding)The standard designation of the chosen grinding wheel is:Grinding wheel DIN69120*250*25*76A60Jot5VCheck and dressing of the grinding wheels, rules for prevention of accidents During grinding the da

26、nger of accidents is very high. When the grinding wheel breaks, the parts flying around may cause a deadly accident, if they are not caught by a protecting device. The following rules for prevention of accidents are also including the field of free form grinding, (grinding of knifes, scissors, etc.)

27、Before dressing the grinding wheel you have first to effect an acoustic test. The wheel has to be kept in the bore and is slightly hit for ex. with a piece of hard wood. The sound must be high.The flanges must have the correct size (S1/3 D when using protective caps, S=2/3 D without protective caps,

28、 S=1 12 D for conical wheels. The flanges must have the same size. You must put intermediate layers out of elastic material between the abrasive wheels and the clamping flanges (for ex. rubber or felt). Thus irregularities on the grinding wheel surface shall be compensated.The grinding wheel must be

29、 easy to slip on the spindle.When you have simple grinding machines, the work rests have to be put close to the grinding wheel and have to be readjusted regularly.Please pay attention to the maximum rotation frequency. On the grinding wheel you can see the maximum allowable peripheral speed, for ex.

30、 on a blue stripe (blue: vc45m/s).Before the first start please take care that no tools or other things may be acquired by the grinding wheel.After each new setting you have to effect a test running of at least five minutes with the rated maximum rotating frequency.During grinding you have to wear p

31、rotective goggles.BalancingDuring grinding you work with high peripheral speeds and therefore also with high rotating frequencies. When using unbalanced grinding wheels, you have to expect unbalance and the corresponding centrifugal force. Unbalanced grinding wheels cause vibrations, which may impai

32、r the surface quality and reduce the life endurance of the grinding wheel and the machine.SAACKE Workshop GrindincThe grinding wheels have to be balanced together with their flanges. In many cases static balancing with compensation masses is sufficient. The grinding wheel satisfies in each position

33、the mass point. If there are high demands resp. very large wheels, you have to balance dynamically.Cylindrical grinding surface cylindrical grindingThe stud 025mm of the bevel pinion has a length of 20,3mm. If you have a grinding wheel width of 25mm it is possible to finish the diameter with one plu

34、nge-cut.This working method is called cross grinding.Due to the short production cycle it is very economical.After grinding the diameter, the endface has to be machined.This process is effected with the front face of the grinding wheel. By beveling it is possible to machine both surfaces in the same

35、 time with one plunge-cut.When you have big series cross - resp. profile grinding is effected.With this method a certain contour is completed by one plunge-cut.For longer parts you need either a longitudinal feed (swing grinding) or several plunge-cuts are placed side by side. The first possibility

36、you find more often, for ex. because by this method you can reach a continuous chip removal, the production time is reduced.For the swing grinding the grinding wheel has to have a littleoverrun (1/3 to 1/4 of the wheel width). If not, at the ends it will not be polished enough.For the bearing diamet

37、er 40 mm of the drive gear wheel the following shift is necessary:L =L+1/3 *BL : shift lengthI: pin length at theL = 54 mm + 1/3 *25 mm work piece (54mm)L 63 mmB : grinding wheel-width (25mm)During grinding the grinding wheel may be approached very sensitively; the scale division value amounts mostl

38、y to 1 pm. For automatic approach a margin (by a mechanical device) is possible.However, after deactivation of the feed the wheel continues grinding outsparking.That way the respect of the measure tolerances is very difficult. A measure control terminates the grinding process as soon as the required

39、 measure is reached.Centerless surface cylindrical grinding. The specialty of this method is that the work piece is not fixed in a clamping device, but lies free on a hard rest.A regulating wheel supports the work piece, in the same time the wheel transfers its peripheral speed on the work piece and

40、 enables so the grinding process.Plane or surface grindingFor the grinding of plane surfaces there exist parallels to milling. However the considerations of the milling cannot simply be transferred, because the tool has another structure and because you work with other speeds.During the face grindin

41、g there is a big contact area between the grinding wheel and the work piece surface. There are the following dangers:Intense heat generation (due to the big contact area). For hardened pieces the start temperature can be exceeded locally. That means: soft areas are generated.On a closed front face t

42、he chips and also the broken out grains have difficulties to come out. The wheel can be closed from the chips.1 Gecar Schle ctietbe2sg川沦lur Plynschlrf3 TCxem* xjm Scgrfxvcdon g” Wcrk?.t?jutn4 Tnpfsorwiifin zykndrBxh und& ochk;Possible counter measures are the following:Discontinuities in the grindin

43、g wheels (forex, segmental wheels).In some cases it is possible to incline the spindle. Hereby however there are form deviations at the work piece.The machining of the discontinued surfaces is favorable.Hereby the grains again and again hit free spaces, where the chips are kicked off and where is no friction. Also the single edges can “re-touch”.During periphery grinding the contact area between grinding wheel and work piece is relatively small. Therefore the metho