MK7120型精密数控磨床砂轮架及垂直进给机构和立柱设计【说明书+CAD】
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Investigation on the spindle thermal displacement and its compensationof precision cutter grindersYung-Cheng Wanga, Ming-che Kaoa, Chung-Ping ChangbaInstitute of Mechanical Engineering, National Yunlin University of Science and Technology, No. 123, Uni. Road, Section 3, 640 Douliu, Yunlin, TaiwanbDepartment of Mechanical Engineering, National Central University, Taiwana r t i c l ei n f oArticle history:Received 24 July 2010Received in revised form 7 March 2011Accepted 16 March 2011Available online 30 March 2011Keywords:Cutter grinderSpindle thermal displacementLaser displacement sensorCompensation mechanisma b s t r a c tThe axial performance of cutter grinders will have direct effects on the precision of groundcutters. Therefore, error elimination will be beneficial for the precision improvement ofcutter grinders. One of the main axial error sources is the spindle thermal displacement.General cutter grinders are not equipped with the cooling systems, because of their rel-ative lower rotating frequencies (8000 rpm), small working range and slower thermal gra-dient. On condition without cooling, there will be obvious thermal errors at the beginninghours of operations or the restarting of machines. That will cause materials waste andlower working efficiency.In this investigation, an efficient measurement system and the compensation mechanismhave been established for the minimization of thermal displacements. About 80% of thethermal displacement can be reduced and the thermal displacement error becomes lessthan 5lm. With this solution, the precision of cutter grinders can be improved.? 2011 Elsevier Ltd. All rights reserved.1. IntroductionPrecision cutter grinders (Fig. 1) can be widely appliedin either traditional mechanical industries or high-techindustries. The so-called maternal genetic effect availablein products would mean that the precision of products de-pends mainly on the machine tools, of which the errors canbe classified as: geometrical errors, temperature rise errorsand dynamic errors, etc. According to relevant studies,4070% of errors of machine tools result from the thermaldisplacement 1,2, where the main source of heat lies inthe friction between spindle and transmission belt, andthat between spindle and ball bearings.So far, some companies have developed the sensors laidinside the spindles by which to compensate the errors ofthermal displacement 3. Yet machines equipped withsuch spindles would increase working cost for small andmiddle sized cutter grinder manufacturers, while therewill be certain limits on the varieties and adoption of spin-dles, and on the promotion of performances of usedmachines.In this study, we have integrated an optical displace-ment sensor system, a temperature sensor system, and asignal acquisition and analysis system to construct anindependent module measurement system of spindle, bymeans of which it can be easy to find out the mathematicalcorrelation between temperature and thermal displace-ment for the spindle of cutter grinders. That can be usedto test the quality of spindles and also provides the basisfor compensation of thermal displacement during practicalmanufacturing process.2. Construction of measurement systemTemperature sensors and a displacement sensor wereinstalled in the measurement system (Figs. 2 and 3). Fromthe spindle test system, temperature and displacement sig-nals have been gained. After processes of signal converters0263-2241/$ - see front matter ? 2011 Elsevier Ltd. All rights reserved.doi:10.1016/j.measurement.2011.03.018Corresponding author. Tel.: +886 5 5342601x4122; fax: +886 55312062.E-mail address: wangyc.tw (Y.-C. Wang).Measurement 44 (2011) 11831187Contents lists available at ScienceDirectMeasurementjournal homepage: /locate/measurementFig. 1. Five-axis cutter grinder.Fig. 2. Module measurement system of spindle.Fig. 3. Installation of sensors.1184Y.-C. Wang et al./Measurement 44 (2011) 11831187and signal acquisitions, they would be recorded and ana-lyzed in the measurement program, by which the correla-tion between temperature drift and thermal displacementcan be established (Fig. 4).2.1. Temperature measurement systemTemperature sensors were fixed on the experimentalmachine, in which the spindle was installed. To acquirethe internal temperature relatively proximate to that ofthe spindle and reduce the influences of external environ-ment, the temperature sensor was installed inside the wallof spindle holder to contact the surface of spindle nearly.The PT-100 temperature sensor 4 was selected to mea-sure the temperature on different positions of spindle.It is generally appropriate to restrict the current of PT-100 within the range of 0.5 mA2 mA. Its resolution canbe set at 0.1 ?C. After testing it can be shown that temper-ature drifts of all temperature sensors are similar (Fig. 5).To simplify the measurement process and obtain a betterFig. 4. Signal processing.Fig. 5. Temperature changes of different positions.Fig. 6. Different starting temperatures.Y.-C. Wang et al./Measurement 44 (2011) 118311871185resolution, only temperatures of the top position are mea-sured for analysis, because of its more temperaturechanges.2.2. Displacement measurement systemFor thermal displacement measurement of the rotatingspindle, high resolution in submicrometer range and non-contact measurement method are required. Thus the tradi-tional mechanical measurement devices are unsuitable forit.What used in this study was a laser displacement mea-surement device with the resolution of 0.2lm 5. The sta-bilitytestwascarriedoutundergeneralworkingcondition, while the drift of displacement signal was lessthan 2lm. That would meet the requirement of thermaldisplacement measurement.3. Experiments and resultsBoth the structure of machine tool and its surroundingconditions can become the factors affecting the processingprecision. Obviously, the system errors of machine toolcannot be maintained at a fixed level and can vary as timegoes by. Besides, the thermal deformation created due tothe operation of machine tool can lead to the thermal dis-placement, whose development can be very intricate 6.Though theoretical simulations as differential equationsand finite element method can provide a great deal ofinformation for the analysis of thermal displacement, themost effective way of analysis of such development wouldbe the direct measurement of thermal displacement bymeans of experiments. Therefore, this investigation wasbased on measurements of temperature and thermal dis-placement of spindles. With these data, their correlationcan be formulated and then the formulation is appliedfor compensation of thermal displacement, while onlythe temperature is measured during practical manufactur-ing process.It is impossible for ordinary processing factory to placethe machine tool in a state of constant starting tempera-ture. Besides, the starting temperatures of operation candiffer in each of the four seasons. To inspect the effect ofdifferent starting temperature, measurements were madeon different starting temperatures of spindle on the cuttergrinder. For instance, in Fig. 6, this test shows the resultedthermal displacement curves are fast no differences whenthe starting temperature was 19 ?C and 27 ?C separately.Thus for a spindle, the thermal displacement is only depen-dent on temperature changes, the starting temperature ofoperation should have no influence on it.Because the rotary speed of spindle is different at thepractical applications, it is necessary to investigate, if therotary speed of spindle will affect the thermal displace-ment amount due to a fast or slow speed. According tothedisplacementdifferencebetween3000 rpmand6000 rpm as measured (Fig. 7), a fast or slow rotary speedFig. 7. Thermal displacements in different rotary speeds.Fig. 8. Results of compensation.1186Y.-C. Wang et al./Measurement 44 (2011) 11831187would only result in a difference of the temperaturechanges, but have no effects on the thermal displacementamount. And there would be a very high repeatability.Thus, this feature can even more benefit the compensationofthermaldisplacement.ThecorrectionequationisL3000= 3.44T + 5.68 at 3000 rpm, and L6000= 3.95T + 4.95at 6000 rpm. (where L is the displacement, and T is thetemperature change)Above experiments show that temperature and thermaldisplacement changes of one spindle can be used to estab-lish a correlation, when both changes are increasing. Toverify this correlation also suitable for falling temperature,experiments for rising and falling temperature have beenperformed. The results show that the curve of thermal dis-placement in rising temperature can match with that infalling temperature. Hence, the physical properties of thespindle would not change due to either rising or fallingtemperature.According to the thermal displacement curve fromexperiments, results of compensation for thermal displace-ment of spindle are shown in Fig. 8. By the correlation ac-quired in previous experiments, the spindle is operated at aspeed of 6000 rpm and the thermal displacement will be34lm after 2 h. By the compensation of each 2 ?C temper-ature interval, the thermal displacement can be reduced toapproximately 4lm. That corresponds to a relativereduction of about 80%. By the compensation process theprecision of cutter grinder will be enhanced distinctly.4. ConclusionBy the application of temperature and displacementsensors, the correlation equation between thermal dis-placement and temperature has been formulated. Andwith this equation, thermal displacement of spindle canbe compensated during the manufacturing process.The experimental results have shown that effectivecompensation could make it possible to use the theoreticalestimate for compensation. By compensation processes foreach of above experiments, the thermal displacement canbe reduced to 4lm in short time. The reduction ratio isabout 80%.It was obviously proved that the processing error couldbe decreased to the range of micrometer so that theenhancement of the precision and working efficiency couldbe indeed achieved.AcknowledgmentThe authors would like to thank the support ofTopWork company that offers relevant equipments andprecious experience for experiments.References1 M. Rahman et al., Error compensation in machine tools a review partII:thermalerrors,InternationalJournalofMachineTools&Manufacture 40 (2000) 12571284.2 H.J. Pahk et al., Thermal error measurement and compensationtechniques for the 5 degree of freedom spindle drifts in CNCmachine tools, In: Proceedings of the I MECH E Part C, Journal ofMechanical Engineering Science, vol. 215, no. 4, 2001, pp. 469485(24 April 2001).3 Tekehiko Kodera, Kazuhiro Yohoyama, Kazuo Miyaguchi, YutakaNagai, Takamasa Suzuki, Masami Masuda, Takanori Yazawa, Real-timeestimationofball-screwthermalelongationbaseupontemperature distribution of ball-screw, JSME International Journal,Series C 47 (4) (2004).4 /datasheet-pdf/view/157816/RHOPOINT/PT100.html.5 MICRO-EPSILON:SpindleGrowthSystemforMachineTooling,.6 S.R. Postlethwaite, D.G. Ford, D. Morton, Dynamic calibration of CNCmachine tools, International Journal of Machine Tools & Manufacture37 (3) (1997) 287294.Y.-C. Wang et al./Measurement 44 (2011) 118311871187对精密铣刀研磨机主轴热位移及其补偿的调查摘要：刀具研磨机的轴向性能对刀具的精度有直接影响。因此，消除误差有利于提高研磨机的精度。轴向误差主要来源之一是主轴热位移。因为通用铣刀研磨机相对旋转频率较低( 8000 rpm)，工作范围小和慢热梯度的原因，他们一般不配备冷却系统。在没有冷却的前提条件下，在机床开始运行的前几个小时或者重新启动机床时，会出现明显的热误差，这会造成材料的浪费和工作效率的降低。 在本次调查中,为使热位移最小化，建立了一个高效的测量系统和补偿机制。大约可以减少80%的热位移，使热位移误差少于5m。采用此方案可以使刀具磨床的精度得到改善。关键字：铣刀研磨机、主轴热位移、激光位移传感器、补偿机制1、 引言精密铣刀研磨机(如图1所示)可以广泛应用在传统的机械工业和高科技行业。所谓的母性遗传效应的产品就意味着产品的精度主要取决于机床,其误差可以分为:几何误差、温升误差和动态误差等。根据相关研究,机床40%-70%的误差源于热位移1,2,其热量主要来源于轴与传动皮带间的摩擦以及轴和轴承之间的摩擦。到目前为止,一些公司已经开发了位于主轴里面的传感器，用于补偿热位移误差3。然而对于中小型制造商而言，配备这样主轴的机床会使工作成本增加，虽然这会对主轴的多样性和采用方案以及使用机床的推广性能有所限制。在这项研究中,我们集成了光学位移传感器系统、温度传感器系统、信号采集与分析系统来构造一个具有独立的模块测量系统的主轴,通过它可以很容易找到刀具磨床主轴温度和热位移之间的相关性。这样可以用来测试主轴的性能质量,也提供了在实际加工过程中热位移补偿的基础。2、 测量系统的构成如图2和图3所示，温度传感器和位移传感器安装在测量系统内。从主轴测试系统可获得温度和位移信号。在信号转换和采集完成后, 测量程序会对这些信号进行记录和分析,同时建立起温度漂移和热位移之间的关系（如图4所示）。图1 五轴刀具磨床图2 主轴的模块测量系统图3 传感器的安装图4 信号处理2.1 温度测量系统温度传感器固定在装有主轴的实验机上。为了获得主轴相对近似的内部温度并减少外部环境对其的影响,把温度传感器安装在主轴托架的内壁上以便与主轴近表面接触。采用铂热电阻温度传感器4来测量主轴不同的位置的温度。一般适当地将当前的铂热电阻限制在0.5 mA-2mA的范围内。它的分辨率可以设定在0.1。如图5所示，测量后所有温度传感器的温度漂移都是相似的。因为温度变化多，所以只有测量分析了温度最高的位置，才能简化测量过程并获得较高的分辨率。图5 不同位置的温度变化2.2 位移测量系统对于旋转主轴的热位移测量，亚微米范围的高分辨率的非接触测量方法是必需的。因此，传统的机械测量装置并不适合它。这项研究曾采用分辨率为0.2m的激光位移测量装置5。当在一般工作条件下进行稳定性测试时，位移信号的漂移小于2m，满足热位移测量的要求。3、 实验和结果机床的结构和周边条件都可以成为影响加工精度的因素。显然，机床的系统误差不能维持在一个固定的水平,它可以随着时间的流逝而发生变化。除此之外，由于机床的操作，创建的热变形会导致热位移，这个过程是非常复杂的6。尽管作为微分方程的理论模拟和有限元方法可以提供大量分析热位移的信息，但是分析这种发展过程的最有效的方法是通过实验直接测量热位移。因此，该研究基于主轴的温度和热位移测量，在实际加工的过程中测量温度时，他们的相关性可以通过这些数据制定，然后再将其应用于热位移补偿。对普通加工厂而言，将机床的起始温度控制在常温内是不可能的。此外，机床操作的起始温度一年四季不同。为了检测不同的起始温度的影响，测量了刀具磨床主轴上不同的起始温度。举例而言，如图6所示，这个测试表明当起始温度分别为19和27时，热位移曲线速度是没有差异的。因此，主轴的热位移仅依赖于温度变化，操作的起始温度对其并没有影响。由于在实际应用中主轴的转速不同，所以有必要研究主轴转速的快慢是否会影响热位移量。如图7所示，根据测量的3000 rpm和 6000 rpm的位移差别，快或慢的转速只会导致温度变化的差异，并有一个非常高的可重复性，但对热位移量没有影响。因此，这一特性对热位移补偿大有益处。在3000 rpm时，修正方程为L3000 = 3.44 T+ 5.68，在6000 rpm时，修正方程为L6000 = 3.95T + 3.95。(其中L是位移，T是温度变化)以上实验表明，当所有变化都在增加时，主轴的温度和热位移的变化可以用于建立一个相关性。为了验证这种相关性同样适合温度的下降，进行了温度上升和下降的实验。结果表明，温度升高的热位移的曲线与温度下降热位移的曲线相适应。因此，主轴的物理性质不会因为温度的上升或下降发生改变。根据实验得出的热位移曲线，主轴的热位移补偿的结果如图8所示。根据之前的实验可知，当主轴以每分钟6000转的速度旋转操作时，热位移在2 小时后达到34m。每2的间隔补偿可以使热位移减少约4m，相对减少约80%。通过补偿，刀具磨床的精度明显提高。图6 不同起始温度图7 不同旋转速度下的热位移图8 补偿的结果4、 结论通过应用温度和位移传感器，热位移和温度之间的相关方程已经制定。有了这个方程，主轴在生产过程中的热位移就可以得到补偿。实验结果表明，有效补偿可以使理论预估补偿成为可能。通过上述每个实验的补偿过程，热位移在短时间内可减少为4m，减速比约为80%。这显然证明了加工误差可以减小到测微计的范围内，真正地提高精度和工作效率。感谢感谢Top Work提供相关设备和宝贵的实验经验的支持。参考文献1 M. Rahman et al. 机床误差补偿-回顾部分2：热误差.国际机床制造期刊40 (2000) 12571284.2 H.J. Pahk et al.数控机床五自由度旋转主轴的热误差测量及补偿技术.机械工程科学杂志第四期215卷.2001：469485(2001年4月24日).3 Tekehiko Kodera, Kazuhiro Yohoyama, Kazuo Miyaguchi, YutakaNagai, Takamasa Suzuki, Masami Masuda, Takanori Yazawa.基于滚珠丝杠温度分布的滚珠丝杠热伸长的实时估计.国际JSME杂志C系列 47 (4) (2004).4 /datasheet-pdf/view/157816/RHOPOINT/PT100.html.5 MICRO-EPSILON: 机床主轴增长系统.6 S.R. Postlethwaite, D.G. Ford, D. Morton.数控机床的动态准. 国际机床制造期刊37 (3) (1997) 287294.湘潭三峰数控机床有限公司参观实习报告学院 机电工程学院 学号 1103010124班级 机械设计制造及其自动化一班 姓名 赫荣玉 指导老师 邓朝晖 1前言参观实习是我们进行毕业设计的前提，是一门必修课。参观实习使我们深入到一线生产实践之中，对机床的生产制造过程有一个直观感性的认识，从而对机床的总体布局、各部件的加工制造及其作用有了初步了解，为顺利完成毕业设计打下良好的基础。上周四，在学长的带领下，我们参观了湘潭三峰数控机床有限公司磨床生产车间，通过参观及学长的讲解，我们对磨床的生产流程有了一定的了解，对所学理论知识有了一定的感性认识。虽然参观的时间很短，但是受益匪浅。2公司简介 湘潭三峰数控机床有限公司成立于2006年12
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