切削力傳感器

1、切削力傳感器電阻應(yīng)變傳感器測(cè)量系統(tǒng)在數(shù)控車床切削力測(cè)量中的應(yīng)用為了便于測(cè)量和研究數(shù)控車床切削力，適應(yīng) 生產(chǎn)中設(shè)計(jì)和使用數(shù)控機(jī)床和刀具的需要，一般都把總切削力Fr分解成三個(gè)互相垂直方向的 力Fz、Fy、Fx三個(gè)分力來(lái)測(cè)量分析。該系統(tǒng) 切削力的檢測(cè)裝置，我們采用電阻應(yīng)變片傳感 器設(shè)計(jì)組成的八角環(huán)測(cè)力儀，作為測(cè)定X、 Y、Z三個(gè)方向切削力的傳感器。其中的八角 環(huán)是彈性元件，在環(huán)的內(nèi)外壁相應(yīng)的應(yīng)變節(jié)點(diǎn)上 分別粘貼四片電阻應(yīng)變片，以克服測(cè)試過(guò)程中 的交叉干擾，把四片電阻應(yīng)變片按全橋方式聯(lián)結(jié) 分別構(gòu)成三個(gè)測(cè)量電橋，以提高測(cè)試靈敏度。在數(shù)控車床車削時(shí)，切削力經(jīng)工件轉(zhuǎn)動(dòng)傳遞于 車刀上，再由車刀刀桿傳遞到八角環(huán)

2、，八角環(huán)的 變形使緊貼在其上的電阻應(yīng)變片也隨之變形，電阻值R就會(huì)隨之發(fā)生變化（R ? $R ）。當(dāng)應(yīng)變 片受拉伸時(shí)，電阻絲直徑變細(xì)，電阻值增大 （R+$R）,應(yīng)變片受壓縮變形時(shí)，電阻絲直徑變 粗，電阻值變?。≧-$R）,電橋會(huì)輸出與切削力 成正比例電信號(hào)。由于電阻應(yīng)變片的電阻變化 很小，為了適合單片機(jī)控制系統(tǒng)進(jìn)行相應(yīng)的數(shù) 據(jù)處理，必須將信號(hào)放大到 0 5V后才能輸入單片機(jī)。電阻應(yīng)變片組成的測(cè)量電橋電路如圖2所示。F ig ur e. 2 T he measuring electr ic br idge co mpo sed of the r esistance strain g aug es這

3、是由四個(gè)電阻應(yīng)變片作為電橋橋臂所組成的全橋測(cè)量電路，R1、R2、R3、R4分別為四個(gè)橋臂 的電阻。當(dāng) A、C端加以一定的電壓 U時(shí)，則B、R 1 R3-R 2R4$( R + 4U R2 ) ( R3=+) U電壓$U = 0,即電橋處于平衡狀態(tài)。在進(jìn)行切削力測(cè)量前，還須對(duì)電橋進(jìn)行調(diào)節(jié)，使其處于平衡缺點(diǎn)：不宜在外界環(huán)境變化比較大的地方使用， 對(duì)于大應(yīng)變有較大的非線性、輸出信號(hào)較弱。優(yōu)點(diǎn)：精度高，測(cè)量范圍廣壽命長(zhǎng)，結(jié)構(gòu)簡(jiǎn)單, 頻響特性好，能在惡劣條件下工作，易于實(shí)現(xiàn) 小型化、整體化和品種多樣化。輪輻式切削力傳感器輪輻式傳感是利用輪輻受載后的變形檢取應(yīng) 變，通過(guò)敏感元件（如電阻應(yīng)變片）來(lái)實(shí)現(xiàn)力一

4、電信號(hào)的轉(zhuǎn)換。這種傳載器根據(jù)輪輻的橫截面形 式分為變輻式和等輻式兩種，本文僅論述便于加 工的等輻式傳感器。如圖1示，該傳感器的形狀 恰似一車輪，輪毅和輪緣由對(duì)稱的四根輻條連接 組成以輪緣為固定支座的交叉梁。b)圖i輪圾式切削力但感器示意三向切削力可由輪毅傳至輪輻。這種傳感器是基 于剪輻式壓力傳感器的設(shè)想提出的川。為保證傳 感器的性能可靠，其中輪毅和輪緣的剛度應(yīng)適當(dāng) 取大c輪輻的截面為矩形，既保持梁的特性，又 不致使傳感器橫向尺寸過(guò)大。為分析方便，首先 討論傳感器在徑向切削力F :單獨(dú)作用下的情 況。根據(jù)對(duì)稱結(jié)構(gòu)，取傳感器在同一直線上由兩 輪輻及輪毅、輪緣組成的一跨，可簡(jiǎn)化成圖Za) 示超靜定梁

5、，載荷及剪力圖。如不計(jì)中間輪毅高 度影響，得到Zb )的原形梁，并作出相應(yīng)的彎 矩由超靜定協(xié)調(diào)條件得到：S2搏感器簡(jiǎn)化力學(xué)矍通過(guò)改變?cè)谳嗇椛腺N片的位置，可分別以彈性 輻體的彎曲、剪切或拉壓應(yīng)變作為傳感器的輸入 信號(hào)。而這幾類輪輻傳感器的工作原理是不同 的。一般的輪輻傳感器主要用于單向重載荷的壓 力檢測(cè)，為撼高其剛度多利用純剪狀態(tài)下輪輻 截面應(yīng)力分布規(guī)律,在與傳感器軸線45”方向 布片（圖2a）,即所謂的剪輻式荷重傳感器川， 這種形式傳感器的特點(diǎn)是傳感器的靈敏度只與 筋板抗剪截面積吞X孔有關(guān)，因此可縮短輪輻 體長(zhǎng)度，進(jìn)而減小傳感器的體積，同時(shí)也大大 提高了傳感器的剛度。顯然，這種設(shè)計(jì)方案對(duì)單 向

6、的重載檢測(cè)是適用的。但切削力傳感器的情況則復(fù)雜得多，由干切剝力的方向未知，通常要 同時(shí)測(cè)出其在三個(gè)既定方向的切削分力Fx、Fz、Fy。而徑向切削力FY 一般小于500kgf , 如仍采用上述剪輻式原理設(shè)計(jì)，勢(shì)必使輪輻截 而積過(guò)小，以至不能滿足其它二向分力和貼片 的要求。因此采用圖1 (b )的布片形式，即用 輪輻的拉壓變形分別測(cè)定Fz、Fy二向切削分力, Fy采用輻板的端面布片，還過(guò)輪輻的彎曲變形 來(lái)測(cè)定?？紤]到主切削分力 Fz、Fy,而通常彎 曲形與相同結(jié)構(gòu)的拉壓形傳感器比較，前者的 靈敏度較高，所以采用圖工(b)的設(shè)計(jì)方案可使 傳感器在Fz、Fy分力作用下的輸出差距縮小， 便于二次儀表的選

7、配。同時(shí)，這種方案也使傳感 器具有較好的抗干擾載荷能力，可通過(guò)橋路自 動(dòng)補(bǔ)償各向切削分力間的相互干擾及偏心載荷 的影響。用薄壁圓筒式切削力傳感器測(cè)定傳感器中部為空心薄壁圓筒，外表面粘貼有 兩組電阻應(yīng)變片。傳感器的兩端有法蘭盤，以此 用螺釘聯(lián)接安裝在試材夾具與制材跑車擱凳之 間。電阻應(yīng)變片R和R縱向粘貼在圓筒表面Z 方向的位置上，相互錯(cuò)開(kāi)180,接成半橋。應(yīng)變 片R3、R4、R、R 6與軸線交叉傾斜45角， 周向均勻分布，接成全橋。鋸切時(shí)，帶鋸條對(duì)木 材切削力的切向分量Fx和法向分量Fy分別在 薄壁圓筒上形成彎矩 M和扭矩Mx測(cè)Fx的電橋 輸出反映彎矩M的大小，與F x成正比。測(cè)Fy 的電橋輸出

8、反映扭矩 Mk的值，與Fy成正比。為 便于數(shù)據(jù)處理，切削試驗(yàn)時(shí)，保持力臂a不變。 在鋸切過(guò)程中，切削分力Fx和Fy的作用點(diǎn)是 不斷變化的，但彎矩M和扭矩Mk不受力點(diǎn)變化 的影響，所以電橋的輸出也不受力點(diǎn)變化的影 響。這是在木材切削力傳感器的設(shè)計(jì)和安裝中必 須滿足的一個(gè)條件。與之相反，薄壁圓筒上Z向 彎矩因受Fx作用位置前后變化的影響，所以不 能用來(lái)測(cè)Fy力。由于R、R、R、R貼片位置 的對(duì)稱性，切向分力Fx在測(cè)Fy的電橋中理論上 無(wú)輸出。因?yàn)閼?yīng)變片R和R的中心位于通過(guò)圓 筒中心線平行于z軸的平面內(nèi)，所以Fy產(chǎn)生的 z向彎矩在測(cè)Fx的電橋中理論上也無(wú)輸出。各 電橋輸出信號(hào)的單一性是多分量切削力傳

9、感器 又一個(gè)必須滿足的條件。因?yàn)?Z向力在兩個(gè)測(cè) 力電橋中都產(chǎn)生輸出，所以鋸切時(shí)不允許有Z 向力存在。一般地，薄壁圓筒式傳感器測(cè)切削力兩個(gè)正交分量時(shí)，第三方向的切削力分量必須 為零，否則將干擾兩向分力的測(cè)定結(jié)果。電橋系統(tǒng)框圖如圖2a所示。木材切削力的兩個(gè) 分量Fx二和Fy ,通過(guò)薄壁圓筒切削力傳感器變 為兩組電橋的輸出，經(jīng)動(dòng)態(tài)電阻應(yīng)變儀放大后， 輸人光線示波器，記錄在示波紙上。切削力分量 的記錄曲線如圖2b所示。根據(jù)記錄曲線的相對(duì) 高度hx和hy,算得切削力分量Fx和Fy的數(shù) 值。圖1薄壁畫制式切削力隹出賽Design, development and testing of a four-co

10、mponentmilling dynamometer for the measurement of cutting forceand torque參考文獻(xiàn)：Mechanical Systems And Signal Processing作者：Frank Unsacar ) Haci Saglam ) HakanLsik優(yōu)點(diǎn)：具有很高的線性度和較低的誤差， 它已制 定和提供必要的數(shù)據(jù)采集系統(tǒng)由硬件和軟件。測(cè) 功機(jī)可以衡量三個(gè)垂直切割力和扭矩期間同時(shí) 銃削和模擬測(cè)量值可以存儲(chǔ)在計(jì)算機(jī)數(shù)據(jù)采集 系統(tǒng)。這是旨在衡量iWj達(dá)5000的最大力量和靈 敏度的系統(tǒng)土 5 NoA three-force com

11、ponent analogue dynamometer capable of measuring cutting forces during milling was designed, developed and tested. A computer connection for data acquisition was also made and calibrated. The analogue data can be evaluated numerically on a computer and when required can be converted back to analogue

12、. The schematic representation of the cutting force measurement system is capable of measuring feed force ( F，)，thrust force(F) and main cutting force ( F) which occursduring milling operations as seen in Fig. 1 . This dynamometer consists of four elastic octagonal rings on which strain gauges were

13、mounted and necessary connections were made to form measuring the Wheatstone bridgesOn-line and real-time information of the cutting force data are automatically read and stored by a system during metal cutting. Since the output from Wheatstone bridge circuits is very low due to the high stiffness r

14、equirement of the dynamometer, the analogue signals coming from dynamometer amplified by strain gauge input modules (Advantech ADAM 3016) are then converted to digital signals and captured by PCI-1712 data acquisition card installed in MS-Windows-based PC. The stored data can be retrieved and used f

15、or analysis when required. The data acquisition software is capable ofaveraging and graphical simulation of force signals in process. The lists of the experimentalequipments used are shown in Table 1Experimental equipments and theirtechnical propertiesMachine Universal milling: Taksan, FU-315toolV/2

16、 附 250Dynamom Strain gauge-basedeterfour-component cutting forcedynamometerStrainHBM: LY 41-10/350; effectivegaugegauge length 10 mm; Gauge factor2.09 N%; gauge resistance350 國(guó).3% Q; transverse sensitivityof - 0.3%Strain ring Octagonal in shape; made of AISI 4140 steel; b=30 mm; r=32 mm; t=8 mmStrai

17、nAdvantech: ADAM 3016amplifierDataAdvantech: A/D converter; PCIacquisition 1712, 16 single channels (8 carddifferential), 1 10 MHzDataWritten in C; capable of recording,recordingsimulating and data processing.softwareVibrationCommtest Instrument vb3000:analyserrange 1 20.000 Hz, ISO 2372andpackageIS

18、O10816 standard.Accelerometer: frequency range 0.5 15 kHz, dynamic range 箔0 gCoupler/po Kistler: 5118B2; bandwidth 0.03, wer supply 0.006 Hz; gain 1。10。100 不 output voltage 40 V; operated by internal battery （4 內(nèi).5 V） or DC external voltage 6 28 VUniversal LLOYD instrument T50 Ktestingmachine The th

19、ickness t, radius r, and width of the circular strain ring b are the three basic icontrollable parameters that affect the rigidityand sensitivity. Since there is no effect of ringwidth b and modulus of elasticity (E) on the strain per unit deflection, d。can be taken as 30-1 mm to set up the rings se

20、curely 6.The deformation of circular ring under the effect of thrust force Ft and main cutting force F。 separately is shown in Fig. 2(b) and (c), respectively. As long as strain on A and B where the strain gauges are going to be fixed (Fig. 2(a) are within the elastic limits of the ring material, th

21、e strain and deflection due to the main cutting force should be considered for the purpose of the ring design for maximisation of sensitivity ( e/F) and stiffness ( F S).a)The strain gauges should be placed where the stress concentration has maximum value. The experiments have shown that good result

22、s are obtained for octagonal rings when the inclined gauges are at points 45 from the vertical instead of 39.6 required by the circular ring theory. The strain per unit deflection can be expressed as 6where 占 is the deflection in a radial directionand is the strain due to thrust forceFt. It isclear

23、that for maximum sensitivity andrigidity / 占 should be as large as possible. Thisrequires that r should be as small as possibleand t as large as possible. But small r bringsI some difficulties in mounting the internalI strain gauges accurately. Therefore, for a given size of r and b, t should be lar

24、ge enoughIto be consistent with the desired sensitivity. Ito et al. 7 performed a finite element analysisIfor the elastic behaviour of octagonal rings.IThey expressed that the octagonal ring isI substantially stiffer than the circular ring when t/r less then or equals to 0.05, theIdifference in disp

25、lacement of circular ring and octagonal ring is 10% if t/r greater then orIequals 0.25. In order to be consistent with this expression, the ring thickness and ring radius Iwere taken as 8 and 32 mm, respectively. Thus, the rate of t/r (8/32=0.25) providescorresponding sensitivity to stiffness ratio

26、d( Nr) for the octagonal ring.The cross-sensitivity can be expressed asstrain measured on axes that is normal to themain axes. It is desired that dynamometers_imust not be completely insensitive to thecross-strain. It is possible to measure thecutting forces independently and accurately aslong as th

27、e cross-sensitivity is small. The strain I errors will be less if this effect is within anacceptable range. These errors can arisebecause the strain gauges are not fittedsymmetrically to the ring axes and if the strain rings are not mounted in the direction ofmeasured force axes. The average errors

28、for cross-sensitivity in three axes were calculated in range of 0.6 T.7% as shown in Table 2(b).The results of tests performed on the dynamometerThe results of linearity testAxLoadOutput- CalibrationErrores(N)(mV)value-(mV)(%) TOC o 1-5 h z Ff2400128.3130.01.3Fc2400126.8125.01.4F5000134.2135.81.2The

29、 results of crosssensitivity testA Loa Output Averag xe d (mV/ Mm)e errors (N)(%) TOC o 1-5 h z XYZXYZFf24012-01.3-10. 08.86 3Fc 240 - 1 12 -2.2 -11.0.2 6.78Ft 500 1. 1.134.0.062211. 9,2The results of eccentricity testALoae=0e=50(%)xedmmmmOutputs(N)(mV)(mV)error TOC o 1-5 h z Ff10054.654.70.180Fc100

30、53.853.90.180Ft10025.8625.530.13% Output errorAccuracy=1000/1014.9=0.985The results of performance testA ( F( F(N)xe m Ns V)X 14. 245 55Y13.21014.9 NError=14.9/1005050=0.0150Z32.9Error=0.15%87 50In this study, strain gauge-based dynamometer has been designed and developed. It has beendevised and con

31、nected with necessary dataacquisition system consisting of hardware andsoftware. Dynamometer can measure three_iperpendicular cutting force components and torque simultaneously during milling and themeasured numerical values can be stored incomputer by data acquisition system. Thisdynamometer was de

32、signed to measure up to 5000 N maximum force and the sensitivity ofsystem is i5 N.The orientation of octagonal rings and straingauge locations were determined to obtain maximum output of ring minimum cross-sensitivity underdeformation.Tomeasure the dynamiccutting force,anaccelerometer was attached t

33、o the dynamometer in measurement direction and the dynamic cutting force calculation was also given. For data transfer between the dynamometer and PC, a proper experimental set-up was performed and suitable software was written. In order to determine accuracy, the dynamometer was calibrated statical

34、ly and dynamically and subjected to the linearity test, cross-sensitivity test, eccentricity test and performance test.The static calibration curves for Ff, F。and F* forces have shown that it has very high linearity (in errors 1.3%, 1.4% and 1.2%) and low cross-sensitivity errors (in range of 0.6 T.

35、7%). In face-milling operations, appropriate results were obtained in cutting force measurements. As a result, recorded cutting force data were presented for evaluation. Also the natural frequency of dynamometer in X-, Y- and Z-directions satisfies the necessary rigidity and dynamic range.The result

36、s obtained from the machining tests performed at different cutting parameters showed that the dynamometer could be used reliably to measure cutting forces not only in milling but also in other machining processes as turning, grinding and shaping.The signal recording and processing unit can be used,

37、for example, to monitor or control processes. This type of measuring chain has proved successful for measuring force and torque.An overview of data acquisition system for cutting force measuring and optimization in milling參考文獻(xiàn)： Journal of Materials Processing Technology作者：F.Cus, J.Balic優(yōu)點(diǎn)：特別適合運(yùn)用在刀具磨

38、損檢測(cè)的領(lǐng)域，并 且能夠在運(yùn)作過(guò)程中監(jiān)測(cè)刀具的磨損情況。One of the most significant developments inthe manufacturing environment is the increasing use of tool and process monitoring systems. Many different sensor types, coupled with signal processing technologies are now available, and many sophisticated signal and information

39、 processing techniques have been invented and presented in research papers. However, only a few have found their way to industrial application. The aim of this paper is to present the cutting force measurement system for the ball-end milling. The system is based on LabVIEW software, the data acquisi

40、tion system and the measuring devices (sensors) for the cutting force measuring. The system collects the variables of the cutting process by means of sensors and makes transformation of those data into numerical values. Generally used measuring devices for cutting force measuring are piezoelectric d

41、ynamometer. Delivered signals are distorted due to their self-dynamic behaviour. Their dynamic characteristics are identified under normal machining operation. The proposed method is based on the interrupted cutting of aspecially designed workpiece that provides a strong broadband excitation. The th

42、ree components of the exciting force and the accelerationof the gravity centre of thedynamometer cover plate are measured simultaneously. The measured values are delivered to the computer program through the data acquisition system.The data obtained from the acquisition system, are a basis for the o

43、ptimization of the machining process cutting parameters.Application of AE and cutting force signals in tool condition monitoring in micro-milling參考文獻(xiàn)：CIRP Journal of Manufacturing Science and Technology作者：P.J.Arrazola優(yōu)點(diǎn)：靈敏度很高。Cutting forces and acoustic emission signals provide very useful informati

44、on for tool condition monitoring in micro-milling. An acoustic emission signal is free from mechanical disturbances like resonance vibrations, which is very important in micromachining applications, where spindle speeds have to be very high due to the small tool diameter. Despite the small material

45、removal rate in micromachining, the obtainedAE signal was strong, easy to register, and showed a very short reaction time to the tool workpiece contact, which makes it a very good means of detecting this contact and monitoring the integrity of the cutting process.The cutting force signals acquired i

46、n this study were severely disturbed by resonance vibrations in the dynamometer. In spite of this, the measurements still appeared to be very useful in tool wear monitoring.Signal feature integration in tool condition monitoring minimizes the diagnosis uncertainty, reducing the randomness in one SF

47、and providing a more reliable tool condition estimation. The number of SFs should be as big as possible, preferably originating from different sensors. Very good results can be achieved using cutting forces and acoustic emission. TCM based on AE only, as an AE sensor is much less expensive and easie

48、r to install, is worse than that based on four signals, yet still provides acceptable results.Tool condition monitoring strategies should be tested on tool lives that are different from the tool life used to train the system. A good practice is to repeat the test for every available tool life to avo

49、id selecting the best results,while ignoring the worst, less satisfactory results.Estimating cutting force from rotating and stationary feed motor currents on a milling machine參考文獻(xiàn)：International Journal of Machine Tools and Manufacture作者：Young-Hun Jeong ) Dong-Woo Cho 優(yōu)點(diǎn)：可使用的頻域范圍大。Automation and inc

50、reased productivity have improved manufacturing systems since numerical control was introduced to the industry. However, accurately determining cutting conditions remains difficult, and experienced operators still produce better results than unmanned machines. This has hindered continued growth of m

51、anufacturing systems. To resolve these problems, some important machining process and control tasks have been studied, such as in-process monitoring and adaptive control. These tasks require reliable and industrially adaptable sensors that can provide informative signals about the state of the machining process.The cutting fo