數(shù)控車(chē)削中心工件誤差實(shí)時(shí)預(yù)報(bào)外文文獻(xiàn)翻譯/中英文翻譯/外文翻譯

畢業(yè)設(shè)計(jì) (論文 )外文資料翻譯   系   別：       機(jī)電信息系         專(zhuān)   業(yè)：  機(jī)械設(shè)計(jì)制造及其自動(dòng)化  班   級(jí)：             姓   名：                 學(xué)   號(hào)：          外文出處 :   Int J Adv Manuf Technol       附   件：  1. 原文 ；  2. 譯文             2013 年 01 月   Int J Adv Manuf Technol (2001) 17:649653 2001 Springer-Verlag London Limited Real-Time Prediction of Workpiece Errors for a CNC Turning Centre, Part 1. Measurement and Identification X. Li Department of Manufacturing Engineering, City University of Hong Kong, Hong Kong     This paper analyses the error sources of the workpiece in bar turning,  which  mainly  derive  from  the geometric  error  of machine  tools,  i.e. the  thermally  induced  error,  the error arising from machineworkpiecetool system deflection induced by the cutting forces. A simple and low-cost compact measuring system combining a fine touch sensor and Q-setter of machine tools (FTSFQ) is developed, and applied to measure the work- piece dimensions. An identification method for workpiece errors is also presented. The workpiece errors which are composed of the geometric error, thermal error, and cutting force error can be identified according to the measurement results of each step. The model of the geometric error of a two-axis CNC turning centre is established rapidly based on the measurement results by using an FTSFQ setter and coordinate measuring machine (CMM). Experimental results show that the geometric error can be compensated by modified NC commands in bar turning. Keywords: Dimension  measure；  Error  identification；  Geo- metric error； Turning 1.  Introduction      In recent years, ultraprecision machining has made remarkable progress. Some special lathes have been able to make ultra- precision machining, to less than a submicron and nanomicron tolerances a possibility. A common second approach is that the grinding is used to achieve a high level of dimensional accuracy after turning. However, the condition of the cutting tool (diamond) and workpiece (aluminium) have restricted the application  of  ultraprecision  lathes.  The  second  approach increases the number of machine tools and machining processes used 1, which results in an increase in the manufacturing cost.       At present, most CNC lathes are equipped with a positioning resolution of 1 urm. Various machinin g errors in finish turning, however, degrade the accuracy to a level of approximately10 urm, so that when turning carbon steel, a machining error predictably arises in excess of 2030 urm. For improving mach- ining accuracy, the method of careful design and manufacture has been extensively used in some CNC lathes. However, the manufacturing  cost based on the above method will rapidly increase when the accuracy requirements of the machine tool system are increased beyond a certain level. For further improv- ing machine accuracy cost-effectively, real-time error prediction and compensation based on sensing, modelling and control techniques have been widely studied 2, so ultraprecision and finish tuning can be performed on one CNC lathe.  The positioning resolution of the cutting tools and workpiece is reduced so that it cannot maintain high accuracy during machining because of the cutting-force-induced  deflection of the machineworkpiecetool system, and the thermally induced error, etc. In general, a positioning device using a piezo-eletric actuator is used to improve the working accuracy, but the method introduces some problems, such as, the feedback strat- egy, and the accuracy of sensors, which add to the manufactur- ing cost of the products. However, if the workpiece error can be measured by using a measurin g instrument, or predicted by using a modelling, the turning program produced by modified NC  commands  can  be  executed  satisfactorily  on  a  CNC machine tool. Thus, a CNC turning centre can compensate for the normal machining error, i.e. the machine tool can machine a product with a high level of accuracy using modified NC commands, in real time.       The workpiece error derives from the error in the relative movement between the cutting tool and the ideal workpiece. For a two-axis turning centre, this relative error varies as the condition of the cutting progresses, e.g. the thermal deflection of the machine tool is time variant, which results in different thermal errors. According to the various characters of the error sources of the workpiece, the workpiece errors can be classified as geometric error, thermally induced error, and cutting-force- induced error. The main affecting factors include the position errors of the components of the machine tool and the angular errors of the machine structure, i.e. the geometric error. The thermally induced errors of the machine tool (i.e. the thermal error), and the deflection of the machining system (including the machine tools, workpiece, and cutting tools) arising from cutting forces, are called the cutting-force error.      This paper analyses the workpiece error sources in turning. The errors of a machined workpiece are mainly composed of the geometric error of the machine tools, the thermally induced error, and the error arising from machineworkpiecetool sys- tem deflection induced by the cutting forces. A simple and low-cost measuring instrument for the workpiece dimensions, which combines a fine touch sensor and machine tool Q-setter (FTSFQ), is described, and applied to measure the workpiece error. A new method for identifying the geometric error, the thermal error, and the cutting-force error is also presented for a two-axis turning centre. Finally, the modelling of the geo- metric error of a CNC turning centre is presented, based on the measurement  results using the FTSFQ and CMM. The geometric  error  can  be  compensated  by the  modified  NC command method. 2.  Error Sources in Turning     The machine tool system is composed of the drive servo, the machine tool structure, the workpiece and the cutting process. The major error sources derive from the machine tool (thermal errors, geometric  errors, and forced vibrations),  the control (drive servo dynamics and programming errors) and the cutting process (machine tool and cutting tool deflection, workpiece deflection, tool wear, and chatter) 3.  Errors derived from the machine tool include thermal errors (machine thermal error and workpiece thermal errors), geo- metric errors, and forced vibrations, which dominate machining accuracy.  The thermal  errors and geometric  errors are the dominant factors with respect to machining accuracy in fine cutting. However, machine tool errors can be decoupled from the other error sources and compensated 4. The error derived from forced vibration can be reduced through balanced dynamic components and vibration isolation 3.   The errors derived from the controller/drive dynamics are related to the cutting force disturbances and the inertia of the drive and the machine table. These errors can be reduced by an  interpolator  with  a deceleration  function  5  or by  an advanced feed drive controller 6, these errors, reduced by using the above methods, are small when compared with other error sources.   Owing to the demand for high productivity, high feedrates and large depths of cut are required, which result in large cutting forces. Therefore, the cutting-force induced deflections of the machine  tool (spindle),  tool holder, workpiece,  and cutting tool make significant contributions to machining accu- racy during the cutting process. In addition, tool wear and machine tool chatter are also important error sources in the cutting process. However, these effects are neglected here so as to focus on the main error sources.    In short, the error of a machined workpiece, i.e. the total machining error (iTot), is composed mainly of the geometric errors of the machine tool(s) (iG), the thermally induced error (iT), and the error (iF) arising from the deflection of the machineworkpiecetool system induced by the cutting forces. Hence,    iTot iG + iT + iF (1)     In the next section, we present a novel compact measuring instrument and a new analytical approach for measuring and identifying workpiece errors in turning. 3.  A Compact Measurement System       Contact sensors, such as touch trigger probes, have been used to measure workpiece dimensions in machining. In machining practice, the measuring instrument is attached to one of the machines  axes to measure a surface on the workpiece.  A TP7M or MP3 associated with the PH10M range of motorised probe heads or a PH6M fixed head have been used widely in the automated CNC inspection environment owing to their high level of reliability and accuracy and integral autojoint. Though the probeheads are of adequate accuracy (unidirectional repeatability at stylus tip (high sensitivity): 0.25 urm； pre-travel variation 360 (high sensitivity): 0.25 urm ), and versatile in application, they have clear drawbacks, including complexity of construction, high price ($4988), and the need for careful maintenance.     To  overcome  these  drawbacks  of  touch  trigger  probes, Ostafiev  et al.  7  presented  a novel  technique  of contact probing for designing a fine touch sensor. The cutting tool itself is used as a contact probe. The sensor is capable of yielding measurement accuracy comparable to that of the best touch trigger probe in use. Moreover, the principle of operation and construction of the sensor is extremely simple, the cost of the sensor is low, and the maintenance is very easy. In this paper, this sensor will be used to measure the diameter of a workpiece associated with the Q-setter.     A touch sensor is mounted on a CNC turning centre. When we manually  bring the tool nose into contact  with it, an interrupt signal is generated for the NC unit to stop an axis. Moreover, it can write in an offset and a workpiece coordinate shift automatically. This function facilitates set-up when replac- ing a tool, and this convenient function is called the “Quick Tool Setter” or “Q-setter”. Based on the above principle, we can operate a switch, which is  controlled by fine touch sensor, between the Q-setter and NC unit. When the tool tip touches the workpiece surface, the fine touch sensor can send a control signal to the switch, to turn it to the “off” state. See Fig. 1, the fine touch sensor replaces the Q-setter function, to stop an axis and write in an offset and a workpiece coordinate shift automatically. Therefore, the fine touch sensor associated with Fig. 1. Flow diagram of a fine touch sensor fixed on a CNC controller  a Q-setter (FTSFQ) can be used to inspect the diameter of the workpiece, the method is shown in Fig. 2.     When the cutting tool tip touches the workpiece surface, a “beep” sound is heard and the switching “OFF” signal appears and the axis stops automatically, as far the Q-setter. A new “tool offset” XT-W is obtained by the NC unit (display of CNC). Before touching the workpiece surface, the cutting tool tip touches the Q-setter, and the “tool offset” XT-Q  is obtained. Thus, the on-machine workpiece diameter Don -m ach ine  is given by the following Eq.: Don-machine 2 H + XT-Q XT-W  (2) where XT-Q   is the tool offset when the cutting tool contacts the Q-setter XT-W   is the  “tool  offset”  when  the cutting  tool contacts the workpiece surface H is the distance from the centre of the Q-setter to the centre of the spindle in the x-axis direction and is  provided by the machine tool manufacturer, for the Seiki-Seicos L II Turning centre, it is 85.356 mm.     Ostafiev and Venuvinod 8 tested the measurement accuracy of the fine touch sensor, performing on-machine inspection of turned parts, and found that the method was capable of achiev- ing a measurement accuracy of the order of 0.01 urm under shop floor conditions. However, the measurement accuracy of the fine touch sensor together with the Q-setter obtained an accuracy of about urm  because the results of the measurement system are displayed by  the CNC system, and the readings accuracy of the CNC system is up to 1 urm. 4.  Identification of Workpiece Errors       From the above analysis of error sources of the workpiece, the total error iTot  of machined parts is mainly composed of the following errors in a turning operation: . iG  the geometric errors of machine tools. . iT  the thermally induced error. Fig. 2. Inspection for the diameter of a workpiece by using the fine touch sensor with the Q-setter of a machine tool. . iF  the cutting force induced error. To analyse  the error sources  of a machined  workpiece, Liu & Venuvinod 9 used Fig. 3 to illustrate the relationship amongst dimensions associated with different error components in turning.     In Fig. 3, Ddes  is the desired dimension of the workpiece； Do m w  is the dimension obtained by on-machine measurement using FTSFQ immediately after the machining operation； Do m c is the dimension obtained by on-machine measurement using FTSFQ after the machine has cooled down； and Dpp  is the dimension obtained by post-process process measurement using a CMM  after  the  workpiece  has  been  removed  from  the machine.    When the workpiece has been machined, and removed from the machine tool system, it is then sent for inspection of the dimensions using a CMM. This procedure is called post-process inspection, by  which we obtain it Dpp  value. As the positioning error of the CMM is very much smaller than the desired measurement accuracy, the total error is iTot (Dpp Ddes)/2  (3) The  dimension  Domw   is  obtained  through  on-machine measurement using FTSFQ immediately after machining, i.e. the  machine  is  still  in  the  same  thermal  state  as at the time of machining. The measurement is made with the same positioning  error  as  that  which  existed  during  machining. Hence, the positioning error in this state would be equal to (iG  + iT), i.e. (Dpp Domw)/2 iG + iT (4) When the machine has completely cooled down, i.e. without thermal error, the dimension  Domc   can be obtained by on- machine measurement using FTSFQ. The measurement has a positioning error equal to the geometric error of the machine at the location of measurement. Hence, the positioning error in this state would be equal to (iG), i.e. (Dpp Domc)/2 iG  (5) Combining Eqs (4) and (5), the thermally induced error iT is (Domc Domw)/2 iT (6) Hence, taking Eqs (1), (3), and (4) into account, the cutting- force-induced error owning to the deflection of the machine workpiecetool system iF  is (Domw Ddes)/2 iF (7) Fig. 3. The relationships among dimensions.     So far, the machining error is composed of the geometric error, the thermal error, and the cutting-force-induced error and can be identified using the above procedure. The thermal error and the force-induced  error  modellings  is addressed  in Li 10. Here, the geometric error of machine tool is measured and modelled. 5.  Modelling of Geometric Error       The geometric error of a workpiece is mainly affected by the offset of the spindle, and the linear error and the angular errors of the cross-slide for a two-axis CNC turning centre. Here, only the geometric error of workpiece in the x-axis direction is taken into account for a bar workpiece. This is expressed by the following formula. iG i(s) (x) hT-Q   ix(x) (8) where i(s)  is the spindle offset along the x-axis direction (x)  is the angular error (yaw) of the cross-slide in the x, y-plane ix(x)  is the linear displacement error of the cross- slide along the x-axis direction     The spindle offset is a constant value independent of the the machining position. The angular error term and the linear error term are functions of the cross-slide position x.     In this paper, the FTSFQ is mounted on a Hitachi Seiiki, HITEC-TURN 20SII two-axis turning centre. The FTSFQ cali- bration instrument was developed to measure rapidly the dimen- sion of the workpiece in the x-axis direction on the two-axis CNC turning centre when the machine has completely cooled down, i.e. without the effect of thermal error. The geometric error can be computed  by using Eq. (5) according  to the measured results. First, the diameter of a precision ground test bar is measured at 10 positions, 20 mm apart, by a CMM, their values Dppi  (i 1, 2, . . ., 10) are recorded. Then, the test bar is mounted on the spindle, and its diameter is also measured at 10 positions, 20 mm apart, by  the FTSFQ. The measurement arrangement is shown in Fig. 4, the readings are Do m cl  (i 1, 2, . . ., 10). Thus, the geometric error at each point along the x-axis for the bar workpiece are computed as follows: iGi (Dppi   DGi)/2  (9)  From starting point B to point A, the results are shown in Fig. 5 for diameters of 30, 45, 60, and 75 mm. The workpiece Fig. 4. Diagram of the geometric error measurement of the workpiece using FTSFQ. Fig. 5. Geometric errors of the workpiece along the z-axis. geometric  errors in the z-axis direction  are the same. The workpiece geometric errors, however, increase along the x-axis direction, as shown in Fig. 6. These average geometric errors are 7.1036, 9.0636, 10.7764, 12.5955 (urm) for dia- meters 30, 45, 60, and 75 mm, respectively. Hence, the geo- metric  errors  of the  two-axis  CNC  turning  centre  can be calculated by the following Eq.: iG(x) 0.121x 3.519  (10)  where x is the diameter of the workpiece (mm), iG(x) (urm) is the geometric error of the workpiece. 6.  Compensation of Geometric Error        To compensate for the geometric error in the direction of the depth of cut, the tool path can be shifted in accordance with the error. The NC commands in turning are modified, at a minimum resolution 1 urm, in the direction of the depth of cut. The calculated geometric error exceeded 1 urm according to the equation (10), as illustrated in Fig 7.      Figure 8 shows that the workpiece errors include the geo- metric error, the thermal error and the cutting force error. The tool path determined by the calculated geometric error, and the workpiece error are compensated for by the modified NC command method. In this example, we used a cutting speed of 4 m s 1, a feedrate of 0.2 mm rev 1, a depth of cut of Fig. 6. The average geometric error for the different diameters Fig. 7. Compensation of geometric error. Fig. 8. Compensation of geometric error by a modified NC command. 1 mm (cutting length 100 mm), a diameter of 40 mm, mild steel workpieces, and DNMG 1506 04 QM  tools. The work- piece error was measured using our FTSFQ at 10 positions 10 mm apart. The workpiece errors were reduced by means of the compensation of the geometric error. The remaining work- piece error contains the thermal error and cutting force error, these will be discussed in part 2 10 and part 4 11. Experi- mental results suggest that the geometric error in finish turning can be compensated  for by the use of this simple method described above. 7.  Conclusions     Owing to increasing demand for higher precision coupled with lower costs in the machining  industry, there is a growing need for automated techniques leading to enhanced machining accuracy. In this paper, the workpiece error sources are ana- lysed for a two-axis CNC turning centre, which derive mainly from the geometric error of the machine tool, the thermally induced error, and the error arising from MFWT system deflec- tion induced by the cutting forces. A simple and low-cost measuring system combining a fine touch sensor and Q-setter for machine tools (FT SFQ) is developed to measure the work- piece error on-machine. The workpiece errors can be divided into the geometric error, the thermal error, and the cutting force error from the on-machine and post-process  measured results. The geometric error function of a two-axis CNC turning centre can be established rapidly from the measurements by using the FT SFQ and a CMM. Experimental results show the geometric error can be compensated for by the modifying the NC commands in finish turning. References 1. T. Asao, Y.  Mizugaki and M. Sakamoto, “Precision turning by means of a simplified predictive  function of machining  error”, Annals CIRP, 41(1), pp. 447451, 1992. 2. Jingxia  Yuan  and  Jun Ni,  “The  real-time  error  compensation technique for CNC machining systems”, Mechatronics,  8(4), pp.359380, 1998. 3. Sung-Gwang  Chen, A. Galip Ulsoy and Yoram Koren, “Error source diagnostic using a turning process simulator”, Transactions ASME Journal of Manufacturing  Science and Engineering, 120, pp. 409416, 1998. 4. V.  S. B. Kiridena and P. M. Ferreira, “Modeling and estimation of quasistatic machine-tool error”, Transactions NAMRI/SME, pp.211221, 1991. 5. Y. Koren, Computer Control of Manufacturing Systems, McGraw- Hill, 1983. 6. Y.  Koren and C. C. Lo, “Advanced controllers for feed drives”,Annals CIRP, 41(2), pp. 689698, 1992. 7. V. Ostafiev, I. Masol and G. Timchik, “Multiparameters intelligent monitoring system for turning”, Proceedings of SME International Conference, Las Vegas, Nevada, pp. 296300, 1991. 8. V.  A. Ostafiev and Patri K. Venuvinod, “A new electromagnetic contact  sensing  technique  for enhancing  machining  accuracy”. IMECE-97, ASME, 1997. 9. Z. Q. Liu and Patri K. Venuvinod, “Error compensation in CNC turning  solely  from  dimensional  measurements  of  previously machined parts”, Annals CIRP, 48(1), pp. 429432, 1999. 10. X. Li, “Real-time  Prediction  of workpiece  errors  for a CNCturning  centre.  Part 2. Modelling  and estimation  of thermally induced errors”, International Journal of Advanced ManufacturingTechnology, 2000. 11. X. Li, “Real-time  prediction  of workpiece  errors  for a CNC turning centre. Part 4. Cutting-force-induced errors”, InternationalJournal of Advanced Manufacturing Technology, 2000.  期刊或雜志名： Int J Adv Manuf Technol 出版社： Springer-Verlag London Limited 出版時(shí)間： 2001 數(shù)控車(chē)削中心 工件誤差實(shí)時(shí)預(yù)報(bào)  第 1 部分：測(cè)量和鑒定  李小俚  制造工程系，香港城市大學(xué)，香 港  本文分析了工件在加工旋轉(zhuǎn)時(shí)的誤差來(lái)源，其中主要來(lái)自機(jī)加工工具的幾何誤差，即熱誤差， 該誤 差 產(chǎn)生 于 機(jī)加工工件的切削力引起的刀具系統(tǒng)的偏轉(zhuǎn) 。一個(gè)簡(jiǎn)單和低成本的緊湊型測(cè)量系統(tǒng)相結(jié)合的靈敏的觸摸傳感器的工具（ FTS-Q）產(chǎn)生了，并應(yīng)用于測(cè)量工件表面 .并且還介紹了一種識(shí)別工件誤差的方法。工件的誤差是由幾何誤差，熱誤差組成的，而切屑力誤差根據(jù)每一步的測(cè)量結(jié)果是可以確定的。幾何誤差由 建立在快速的基礎(chǔ)上的兩軸 CNC 車(chē)削中心模型測(cè)量，測(cè)量結(jié)果由坐標(biāo)測(cè)量機(jī)（ CMM）用 FTS-Q 的方法顯示出來(lái)。 實(shí)驗(yàn)結(jié)果表明，在工具旋轉(zhuǎn)時(shí)，通過(guò) 修改數(shù)控指令，這種幾何誤差可以得到補(bǔ)償。  關(guān)鍵詞： 尺寸測(cè)量 ；錯(cuò)誤辨識(shí) ；幾何誤差 ；旋轉(zhuǎn)  1. 導(dǎo)言  近年來(lái)，超精密加工已取得了顯著進(jìn)展， 一些特殊的車(chē)床已能作出超一般的機(jī)械加工，實(shí)現(xiàn)了不到 1微米，甚至有實(shí)現(xiàn)超微米的可能性。而實(shí)現(xiàn)這種可能公用的一種方法是在開(kāi)機(jī)后用高水平的三維來(lái)實(shí)現(xiàn)磨削的準(zhǔn)確性。然而，有些切削工具（如鉆石）和一些工件（如鋁）應(yīng)限制應(yīng)用超精密車(chē)床。第二種實(shí)現(xiàn)的方法是增加機(jī)床數(shù)目的加工工藝 1 ，但是這將導(dǎo)致制造成本的增加。    目前，我國(guó)大部分 CNC 車(chē)床配備定位達(dá)到了 1微米。然而，在完成車(chē)削時(shí)，各種加工誤差的準(zhǔn)確性應(yīng)以某種程度的降低約 10 微米，所以，當(dāng)談到碳鋼時(shí)，加工誤差可以預(yù)見(jiàn)超出 20-30 微米。為提高加工的準(zhǔn)確性，這種精心設(shè)計(jì)的方法和制造已被廣泛應(yīng)用于一些 CNC 車(chē)床。然而按以上方法制造精度要求系統(tǒng)超出一般水平的機(jī)床時(shí)，生產(chǎn)的成本將會(huì)迅速的增加。為了進(jìn)一步改善提高機(jī)床精度的效益成本，實(shí)時(shí)的誤差預(yù)報(bào)以及基于傳感的補(bǔ)償建模與控制技術(shù)已得到了廣泛的研究 2 ，因此，超精密的加工校正，可以安排在一般的 CNC 車(chē)床。  定位解決了刀具和工件的切削，但它不能保證高度的準(zhǔn)確性，因?yàn)樵诩庸ぶ?，切削力?huì)影響機(jī)床 -工件 -刀具系統(tǒng)，并且熱也會(huì)導(dǎo)致誤差等。一般來(lái)說(shuō)，定位裝置采用壓電激勵(lì)器，用于改善工作的準(zhǔn)確性，但是，采用這種方法也帶來(lái)了一些問(wèn)題，例如反饋系統(tǒng)和精度傳感器，這些都會(huì)增加制造產(chǎn)品的成本。但是如果工件的誤差可以用測(cè)量?jī)x器測(cè)量，或者利用模型可以提前預(yù)知，再執(zhí)行已經(jīng)做好的修飾數(shù)控命令，那么將會(huì)充分利用好數(shù)控機(jī)床。因此，在一定時(shí)間內(nèi)，這種數(shù)控車(chē)削中心可以補(bǔ)償一般的加工誤差，即這 種機(jī)床采用可改性數(shù)控命令能制造出具有高水平精確度的產(chǎn)品。  工件的誤差來(lái)自刀具和工件的實(shí)際相對(duì)運(yùn)動(dòng)與理想相對(duì)運(yùn)動(dòng)的誤差。如果是雙軸車(chē)削中心，由于車(chē)削條件不同，導(dǎo)致相對(duì)誤差各不相同，如機(jī)床刀具的時(shí)變產(chǎn)生熱偏轉(zhuǎn)，導(dǎo)致不同的熱誤差。根據(jù)工件各種不同誤差來(lái)源，工件誤差可分為幾何誤差，熱誤差，以及切削疲憊誤差。主要影響因素包括：組成機(jī)床部分的位置錯(cuò)誤和機(jī)械結(jié)構(gòu)的角錯(cuò)誤，即幾何誤差。這種由于切削力產(chǎn)生的機(jī)床熱誤差（即熱誤差），和影響的加工系統(tǒng)（包括機(jī)床，工件和刀具），被稱(chēng)為切力誤差。  本文分析了工件在加工旋轉(zhuǎn)時(shí)誤差的來(lái)源 ：數(shù)控機(jī)床的幾何誤差，熱誤差，切削力產(chǎn)生的機(jī)械工件和刀具系統(tǒng)的偏離誤差。一個(gè)簡(jiǎn)單而低成本的測(cè)量?jī)x器，它具有良好的觸摸傳感器和機(jī)床的 FTSF-Q 裝置，能描述工件的尺寸，并用于測(cè)量工件的誤差。已經(jīng)有一種新的方法來(lái)確定幾何誤差，熱誤差，并且能夠回饋切力誤差到兩軸車(chē)削中心。最后，數(shù)控車(chē)削中心的造型幾何誤差由 FTSF-Q 和 CMM來(lái)測(cè)定。這種幾何誤差可以由改進(jìn)的數(shù)控指揮得到補(bǔ)償。  2.車(chē)削加工 中的誤差 來(lái)源  機(jī)床系統(tǒng)是由驅(qū)動(dòng)伺服，機(jī)床結(jié)構(gòu)，工件和切削過(guò)程組成。 主要誤差源來(lái)自機(jī)床（熱誤差，幾何誤差，和強(qiáng)迫振動(dòng)）  ，控制（伺 服驅(qū)動(dòng)器動(dòng)力學(xué)及編程錯(cuò)誤）  ，以及切割進(jìn)程（機(jī)床及刀具偏轉(zhuǎn)，工件偏轉(zhuǎn)，刀具磨損和顫振） 3 。其中對(duì)加工的準(zhǔn)確性占主導(dǎo)地位的誤差來(lái)自機(jī)床，包括熱誤差（機(jī)床熱誤差和工件的熱誤差），幾何誤差和強(qiáng)迫振動(dòng)。在加工精細(xì)工件時(shí)熱誤差和幾何誤差是主要的影響因素。然而，機(jī)床誤差不同與其他誤差來(lái)源，它可以得到補(bǔ)償 4 。均衡動(dòng)態(tài)部件以及隔離振動(dòng)可以減少由誤差衍生來(lái)的強(qiáng)迫振 動(dòng) 3 。   控制器和驅(qū)動(dòng)器的誤差來(lái)自切削力的干擾和機(jī)座的慣性，這些誤差可能減少一個(gè)接一個(gè)減速器的功能 5 ，或者一個(gè)先進(jìn)的伺服驅(qū)動(dòng)控制器 6 ，這些誤差，相對(duì)于其他誤差來(lái)源，利用上述方法可以在他們較小時(shí)得到減少。  由于需求大，生產(chǎn)率高，  等級(jí)要求自由和大深度的削減要求，而導(dǎo)致 產(chǎn)生較大切削力。因此，割力誘導(dǎo)撓度來(lái)自機(jī)床（主軸）  ，刀柄，工件，并且刀具在加工精度切削過(guò)程起了重要作用。此外，在切削過(guò)程，刀具磨損和機(jī)床顫振，亦是重要的誤差來(lái)源。不過(guò)，這些影響可以忽略，所以在這里把焦點(diǎn)放在主要誤差來(lái)源。  總之，加工一個(gè)工件的誤差，即總加工誤差 (Tot )，主要由機(jī)床幾何誤差 (G ), 熱誤差 ( T ),以及由切削力所產(chǎn)生的 機(jī)床 -工件 -刀具系統(tǒng)的撓度誘導(dǎo)誤差 ( F )組成，故：  Tot G + T + F    (1)  在下一節(jié)中，我們提出一個(gè)新的緊湊型測(cè)量?jī)x器和新的分析方法來(lái)衡量和確定工件的旋轉(zhuǎn)誤差。  3 .緊湊型測(cè)量系統(tǒng)  接觸傳感器，例如觸摸觸發(fā)探針，已用于測(cè)量工件尺寸加工。在加工實(shí)踐中，測(cè)量?jī)x器是附在機(jī)器其中的軸，以衡量一個(gè)工件的表面。一種 tp7m 或是 MP3 與ph10m 各種機(jī)動(dòng)探頭元件或 ph6m 固定頭由于其高的可靠性和準(zhǔn)確性以及完整的加工點(diǎn)，廣泛應(yīng)用于自動(dòng)化數(shù)控視察環(huán)境。雖然該探頭有足夠的精確度（針式特有的單項(xiàng)重復(fù)性（高靈敏度）： 0.25 微米 ；提前可設(shè)定的旋轉(zhuǎn) 360 （高靈敏度）：0.25 微米），并且可進(jìn)行多種功能，他們也有明顯的缺點(diǎn)，例如制造的復(fù)雜性，高價(jià)格（ 4988 美元），以及復(fù)雜的維修。   為了克服這些缺點(diǎn)， Ostafiev 等人 7 介紹了一種技術(shù)并以此設(shè)計(jì)了一個(gè)良好的觸摸傳感器：觸摸觸發(fā)探頭，該傳感器刀具本身就作為探針。該傳感器的測(cè)量精度是當(dāng)年觸摸觸發(fā)探頭最好的。此外練習(xí)使用這種傳感器是非常簡(jiǎn)單的，制造成本很低，而且維修保養(yǎng)是非常容易的。在本文中這個(gè)傳感器將作為 Q 裝置來(lái)測(cè)量工件直徑等一些相關(guān)的問(wèn)題。   觸摸感應(yīng)器應(yīng)安裝在一個(gè)數(shù)控車(chē)削中心上。作為數(shù)控單元，當(dāng)我們手動(dòng)把刀尖觸碰到主軸時(shí)，它會(huì)產(chǎn)生中斷信號(hào)。此外，它可以記錄一個(gè)工件自動(dòng)轉(zhuǎn)向的坐標(biāo)。這種功能方便隨時(shí)更換刀具。因此，擁有這種功能稱(chēng)為“快速換刀裝置”或“ Q 裝置”?；谏鲜鲈瓌t，我們可以設(shè)計(jì)一個(gè)由良好的觸摸傳感器構(gòu)成的開(kāi)關(guān)，控制 Q 裝置和 NC 單元。當(dāng)?shù)都庥|及工件表面，精細(xì)式觸摸傳感器能發(fā)出一個(gè)控制信號(hào)轉(zhuǎn)換，使之向 "關(guān)閉 "狀態(tài)。見(jiàn)圖 1。優(yōu)良式觸摸傳感器取代 了問(wèn)答式的 Q裝置功能，以防止軸在記錄的工件坐標(biāo)間偏移。       圖 1 觸摸傳感器固定在一個(gè) CNC 控制器的流程圖  因此，優(yōu)良的觸摸傳感器如圖 1，流程圖的數(shù)據(jù)由觸摸傳感器即固定的 Q裝置 (FTSFQ) 測(cè)得，可以用來(lái)檢查工件直徑，該方法是圖 2. 當(dāng)?shù)毒呒舛擞|及工件表面時(shí)，將發(fā)出“ 嗶嗶 ”的聲音，這是開(kāi)關(guān)的  “關(guān)”的信號(hào)，主軸將根據(jù) Q 裝置自動(dòng)停止。一個(gè)新的“刀具補(bǔ)償”WTX將由 NC單元提供 （展示數(shù)控）。在觸及工件表面前， 刀具尖端觸及 Q 裝置以及“刀具補(bǔ)償”QTX就已經(jīng)獲得 。因此，對(duì)于工件直徑machine-onD有下列關(guān)系：       machine-onD =2 H +QTX WTX    (2) 其中：  QTX ： 刀具切削時(shí) Q 裝置提供的刀具補(bǔ)償 ；  WTX： 刀具觸及工件表面時(shí)的刀具補(bǔ)償 ；   H 是 Q 裝置在 X 軸方向上離主軸的距離。這由機(jī)床制造商提供，如Seiki-Seicos L II 旋轉(zhuǎn)中心，它是 85.356 毫米。  Ostafiev 和 Venuvinod8 兩款觸摸傳感器在測(cè)試測(cè)量精度時(shí)，在演示機(jī)上能夠測(cè)量精度在 0.01 微米以下的精度條件。 然而，優(yōu)良的觸摸傳感器在測(cè)量精度時(shí)獲得的精度為微米，因?yàn)闇y(cè)量結(jié)果在系統(tǒng)中顯示出來(lái)時(shí)，數(shù)控系統(tǒng)和讀數(shù)精度系統(tǒng)最大是 1微米。  4. 確 定 工 件 的 錯(cuò) 誤  上述分析中工件的誤差源的總誤差Tot主要由以下在加工零件車(chē)削操作中的誤 差machine-onD組成：   G ： 的機(jī)床的幾何誤差。 T ：熱引起的錯(cuò)誤。 F ：切削力引起誤差。   圖 2 使用 Q-setter 的機(jī)床 利用 優(yōu)良的觸摸傳感器 對(duì) 工件的直徑 進(jìn)行 檢查    要分析一個(gè)加工工件的誤差源， 劉 Venuvinod 9 。 圖 3 用 來(lái)說(shuō)明在車(chē)削 時(shí)不同的誤差分量之間的尺寸關(guān)系。    另外 ， 在圖 3 中，desD是所希望的工件尺寸 ； omwD是在測(cè)量使用 FTSFQ 加工操作后立即獲得的維度 ； omcD是在 機(jī)床 FTSFQ 加工操作 后冷卻下來(lái)測(cè)量獲得的尺寸 ， 使用三坐標(biāo)測(cè)量機(jī)測(cè)量已經(jīng)從機(jī)器上取下的工件通過(guò)處理后獲得的尺寸。    當(dāng)工件被加工 時(shí) ，機(jī)床系統(tǒng)中使用 CMM 的尺寸進(jìn)行檢查。此過(guò)程被稱(chēng)為后工序檢驗(yàn) ， 由于 CMM 的定位誤差比所需的測(cè)量精度 更 小，總誤差是 ：  Tot = (ppD-desD)/2   (3) 通過(guò) 以 上獲得的尺寸omwD， 使用 FTSFQ 測(cè)量后立即加工，即機(jī)器在加工時(shí)仍然在相同的熱狀態(tài)。測(cè)量 時(shí) ，在加工過(guò)程中具有相同的定位誤差。因此，在該狀態(tài)下的定位誤差將等于 ( G+T )， i.e. (ppDomwD)/2 =G+ T   (4) 當(dāng)機(jī)器完全冷卻下來(lái)，即無(wú)熱誤差 時(shí) ，omcD尺寸可以通過(guò) FTSFQ 測(cè)量。測(cè)量等于測(cè)量的位置處機(jī)器具有 的 幾何誤差的定位誤差。因此，在該狀態(tài)下的定位誤差將是（G），即等于                      (ppD omcD)/2=G    (5)                         結(jié)合式（ 4）和（ 5），熱誘導(dǎo)的錯(cuò)誤，它是                    ( omcD omwD )/2 = T    (6)                           故 ， 以式（ 1），（ 3）和（ 4）考慮到，如果是機(jī)器的工件的刀具系統(tǒng)偏轉(zhuǎn)切割力引起的 誤差， F 是 ：                        ( omwD - desD )/2= F    (7)   圖 3 維之間的關(guān)系    到目前為止，由加工誤差的幾何誤差，熱誤差和切割力引起的誤差，可以使用上述步驟來(lái)識(shí)別。這里，機(jī)床的幾何誤差的測(cè)量和模擬解決熱誤差和力引起的錯(cuò)誤構(gòu)模 10 。  5.模 型 的 幾 何 誤 差   兩軸 CNC 車(chē)削中心滑動(dòng) 、 主軸偏移的工件的幾何誤差主要 由 線性誤差和角度誤差交叉的 影響 。這里，僅在 x軸方向上的工件的幾何誤差是由以下結(jié)構(gòu)式表示：  G = )(s (x)QTh)(xx   (8) 其中：    )(s： 十字滑塊在 x， y 平面沿 x 軸方向 (x)的偏移量是主軸的轉(zhuǎn)角誤差 ；   )(xx： 十字滑塊沿 x 軸方向的線性位移誤差 ；    獨(dú)立的加工位置主軸偏移量是一個(gè)恒定值 ， 轉(zhuǎn)角誤差項(xiàng)和線性誤差項(xiàng) 是 十字滑塊的位置 x的函數(shù)。    在本文中 ， 國(guó)際展貿(mào)中心將 FTSFQ 安裝在日立 Seiiki 開(kāi)發(fā)的 FTSFQ 校準(zhǔn)儀器 上，用來(lái)進(jìn)行 20SII 兩軸車(chē)削加工中心快速測(cè)量工 件中的 x 軸方向上的兩軸CNC 車(chē)削中心，當(dāng)該裝置已經(jīng)完全冷卻下來(lái)的維數(shù)，即沒(méi)有熱誤差的效果。可以通過(guò)使用公式計(jì)算的幾何誤差。（ 5）根據(jù)所測(cè)量的結(jié)果。首先，一個(gè)精確地測(cè)試棒的直徑在 10 個(gè)位置測(cè)量，除了 20 毫米，由 CMM 測(cè)量 它們的值 DPPI（ =1，2， .， 1