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編號(hào)
無(wú)錫太湖學(xué)院
畢業(yè)設(shè)計(jì)（論文）
相關(guān)資料
題目：基于UG的車(chē)床夾具虛擬設(shè)計(jì)及運(yùn)動(dòng)仿真
信機(jī) 系 機(jī)械工程及自動(dòng)化專(zhuān)業(yè)
學(xué) 號(hào)： 0923801
學(xué)生姓名： 李珊珊
指導(dǎo)教師： 彭勇（職稱(chēng)：副教授 ）
（職稱(chēng)： ）
2013年5月25日
目 錄
一、畢業(yè)設(shè)計(jì)（論文）開(kāi)題報(bào)告
二、畢業(yè)設(shè)計(jì)（論文）外文資料翻譯及原文
三、學(xué)生“畢業(yè)論文（論文）計(jì)劃、進(jìn)度、檢查及落實(shí)表”
四、實(shí)習(xí)鑒定表
無(wú)錫太湖學(xué)院
畢業(yè)設(shè)計(jì)（論文）
開(kāi)題報(bào)告
題目：基于UG的車(chē)床夾具虛擬設(shè)計(jì)及運(yùn)動(dòng)仿真
信機(jī) 系 機(jī)械工程及自動(dòng)化 專(zhuān)業(yè)
學(xué) 號(hào)： 0923801
學(xué)生姓名： 李珊珊
指導(dǎo)教師： 彭勇 （職稱(chēng)：副教授 ）
（職稱(chēng)： ）
2012年11月25日
課題來(lái)源
工程生產(chǎn)實(shí)際
科學(xué)依據(jù)（包括課題的科學(xué)意義；國(guó)內(nèi)外研究概況、水平和發(fā)展趨勢(shì)；應(yīng)用前景等）
（1）課題科學(xué)意義
在現(xiàn)代生產(chǎn)制造中，機(jī)床夾具是一種不可或缺的工藝設(shè)備，它直接影響著零件的加工精度、生產(chǎn)率和產(chǎn)品的制造成本等，所以機(jī)床夾具設(shè)計(jì)是一項(xiàng)重要的技術(shù)工作，它是各機(jī)械制造企業(yè)新產(chǎn)品投產(chǎn)、老產(chǎn)品改進(jìn)和工藝更新中的一項(xiàng)重要生產(chǎn)技術(shù)準(zhǔn)備工作，也是每一個(gè)從事機(jī)械加工工藝的技術(shù)人員必須掌握的基礎(chǔ)知識(shí)，在機(jī)械制造以及生產(chǎn)技術(shù)中占有極其重要的地位。
（2）國(guó)內(nèi)外研究狀況、水平和發(fā)展趨勢(shì)
夾具最早出現(xiàn)在1787年，至今經(jīng)歷了三個(gè)發(fā)展階段。第一階段表現(xiàn)為夾具與人的結(jié)合。在工業(yè)發(fā)展初期，機(jī)械制造的精度較低，夾具僅僅作為加工工藝過(guò)程中的一種輔助工具；第二階段是隨著機(jī)床、汽車(chē)、飛機(jī)等制造業(yè)的發(fā)展，夾具的門(mén)類(lèi)才逐步發(fā)展齊全，逐漸發(fā)展成為系統(tǒng)的主要工藝裝備之一；第三階段，即近代由于世界科學(xué)技術(shù)的進(jìn)步及社會(huì)生產(chǎn)力的迅速提高，夾具與機(jī)床有了緊密結(jié)合。
現(xiàn)代生產(chǎn)要求企業(yè)所制造的產(chǎn)品品種經(jīng)常更新?lián)Q代，以適應(yīng)市場(chǎng)的需求與競(jìng)爭(zhēng)，特別是近年來(lái)，數(shù)控機(jī)床、加工中心、成組技術(shù)、柔性制造系統(tǒng)（FMS）等新加工技術(shù)的應(yīng)用，對(duì)機(jī)床夾具提出了如下新的要求：1）能迅速而方便地裝備新產(chǎn)品的投產(chǎn)，以縮短生產(chǎn)準(zhǔn)備周期，降低生產(chǎn)成本；2）能裝夾一組具有相似性特征的工件；3）能適用于精密加工的高精度機(jī)床夾具； 4）能適用于各種現(xiàn)代化制造技術(shù)的新型機(jī)床夾具； 5）采用以液壓站等為動(dòng)力源的高效夾緊裝置，以進(jìn)一步減輕勞動(dòng)強(qiáng)度和提高勞動(dòng)生產(chǎn)率； 6）提高機(jī)床夾具的標(biāo)準(zhǔn)化程度。
現(xiàn)代機(jī)床夾具的發(fā)展方向主要表現(xiàn)為標(biāo)準(zhǔn)化、精密化、高效化和柔性化等四個(gè)方面。
研究?jī)?nèi)容
① 根據(jù)提供的畢業(yè)設(shè)計(jì)資料理解設(shè)計(jì)要求，查閱相關(guān)中外資料。
② 確定車(chē)床組合夾具結(jié)構(gòu)及定位、夾緊方案。
③ 對(duì)車(chē)床組合夾具進(jìn)行三維建模，生成工程圖，完成爆炸圖及裝夾工件的動(dòng)作演示。
④ 完成車(chē)床組合夾具加工工序和工藝方案及繪制工序圖。
⑤ 閱讀和翻譯英文文獻(xiàn)。
⑥ 撰寫(xiě)畢業(yè)設(shè)計(jì)論文。
擬采取的研究方法、技術(shù)路線(xiàn)、實(shí)驗(yàn)方案及可行性分析
（1）研究方法
借閱相關(guān)書(shū)籍雜志，充分利用圖書(shū)館及網(wǎng)絡(luò)資源。
（2）技術(shù)路線(xiàn)
收集資料，設(shè)計(jì)尺寸，做定位、夾緊設(shè)計(jì)，三維建模，運(yùn)動(dòng)仿真。
（3）實(shí)驗(yàn)方案
明確設(shè)計(jì)要求，認(rèn)真調(diào)查研究，收集設(shè)計(jì)資料，確定夾具的結(jié)構(gòu)方案，根據(jù)設(shè)計(jì)要求作出三維建模及工程圖，做運(yùn)動(dòng)仿真。
（4）可行性分析
大學(xué)里，我學(xué)習(xí)了機(jī)械制圖、機(jī)械制造工藝學(xué)、機(jī)床夾具設(shè)計(jì)等等，熟悉UG軟件。在設(shè)計(jì)中，結(jié)合自己所學(xué)的知識(shí)以及老師的指導(dǎo)，根據(jù)要求，合理選擇加工工藝，設(shè)計(jì)出合適的車(chē)床夾具，繪制出零件圖及裝配圖。
研究計(jì)劃及預(yù)期成果
研究計(jì)劃：
2012年11月12日-2012年12月2日：收集資料，撰寫(xiě)開(kāi)題報(bào)告、文獻(xiàn)綜述；
2012年12月3日-2013年1月20日：完成零件三維造型及圖紙轉(zhuǎn)化，確定工藝總體方案；
2013年1月21日-2013年3月1日：完成工藝規(guī)程設(shè)計(jì)；
2013年3月4日-2013年3月22日：完成夾具的全部零件圖；
2013年3月25日-2013年4月5日：完成夾具的總裝圖及運(yùn)動(dòng)仿真；
2013年4月8日-2013年4月19日：完成夾具設(shè)計(jì)的說(shuō)明書(shū)；
2013年4月22日-2013年4月26日：詳細(xì)審閱設(shè)計(jì)計(jì)算、說(shuō)明書(shū)及圖紙并修改；
2013年4月29日-2013年5月25日： 遞交畢業(yè)設(shè)計(jì)資料，準(zhǔn)備答辯材料，并進(jìn)行答辯。
預(yù)期成果：
設(shè)計(jì)中各個(gè)部件的選擇需要具體分析和理論計(jì)算，方案擬定正確；設(shè)計(jì)計(jì)算根據(jù)來(lái)源可靠，計(jì)算數(shù)據(jù)準(zhǔn)確無(wú)誤，定位夾緊元件選用正確規(guī)范；機(jī)械結(jié)構(gòu)圖紙繪制要求視圖完整、符合最新國(guó)家標(biāo)準(zhǔn)，圖面整潔、質(zhì)量高（圖紙繪制要求采用計(jì)算機(jī)繪圖）；用UG完成夾具的所以零件圖、組裝圖，以及夾具的三維圖形；基于UG進(jìn)一步進(jìn)行爆炸及運(yùn)動(dòng)仿真。
特色或創(chuàng)新之處
使用UG運(yùn)動(dòng)仿真，效果明顯，方便改變參量，能夠直觀判斷設(shè)計(jì)結(jié)果。
已具備的條件和尚需解決的問(wèn)題
① 可以利用圖書(shū)館及網(wǎng)絡(luò)資源，已學(xué)過(guò)UG的基礎(chǔ)知識(shí)；
② 使用UG的運(yùn)動(dòng)仿真有待加強(qiáng)。
指導(dǎo)教師意見(jiàn)
指導(dǎo)教師簽名：
年 月 日
教研室（學(xué)科組、研究所）意見(jiàn)
教研室主任簽名：
年 月 日
系意見(jiàn)
主管領(lǐng)導(dǎo)簽名：
年 月 日
英文原文
Development of the 3D-Designed Lathe Fixture of a Float Brake Caliper
PAN Jin-kun1, ZUO Wan-li2, LU Dong-sheng2
1School of Mechanical Engineering, Nanjing Institute of Technology, Nanjing 211167, P. R. China
2College of Mechanical& Power Engineering, Nanjing University of Technology, Nanjing 210009, P. R. China
Abstract：According to the technique requests of the brake caliper in the process of production, a special fixture of float brake caliper has been developed based on 3D design in this paper. The development process and verified data from 3D modeling and kinematics simulation for this special fixture show that this 3D-designed process can conveniently forecast the assembly interference of the fixture and accurately add the mass of lead brick before the prototype is made. In this way the flutter caused by the unbalanced lathe fixture can be eliminated and the precision of run-out tolerance in cylinder hole compared with machine tool spindle can be improved, thus the processing quality of the cylinder hole in a brake caliper can be greatly guaranteed.
Key words: 3D design; brake calipers; lathe fixture
1 Introduction
In the production of the float disc brake caliper of an automobile, due to the complexity of its structure, a special fixture is needed for installing and clamping the brake caliper. According to the technique requests of the brake caliper in the processing, a special fixture of float brake caliper is developed based on 3D design in this paper and its 3D model is assembled virtually. Through the mechanism simulation function of 3D design software, the balance of a lathe fixture is analyzed [1]. The results show that the design process can expediently forecast some factors which affect the quality of technical equipment such as assembly interference [2] and the machining stability of the lathe fixture before the proto type is made. This design process can not only avoid the design errors in the traditional design, but also improve the design quality of products.
2 3D design of the special lathe fixture
The manufacture object of the special fixture is the brake caliper of a float disc brake, shown as Figure 1; its machining surface is the cylinder hole of the brake. The figure shows: when the cylinder hole is being processed, its axis and the machine spindle rotation axis must be in coincidence. Due to irregular shape structure of the brake caliper, the flutter which is caused by the unbalance mass posed by the fixture and the work piece would affect the machining accuracy and roundness of the cylinder hole size in the actual processing, and some precision requirement of geometric tolerance such as parallelism between the two cylinder holes. To avoid the problems in the design process of the lathe fixture of the brake caliper, a special fixture is developed based on 3D design in this paper.
According to the shape structural characteristics of the brake caliper and the clamping requirements of the lathe fixture, the cylinder hole should be completed after a clamping of the lathe fixture in the whole processing. The flange needs the mounting hole of machine tool spindle and location hole of the fixture on both sides of the center as a middle ware connecting the machine tool spindle and the fixture. It is ensured that the axis of the processing cylinder hole of the caliper body which is located and clamped on the fixture and the machine spindle axis of rotation need coincidence [3] , as shown in Figure 2.
The modeling process of other parts of the special fixture is not depicted in detail in this paper，please refer to Reference[4] . Then these parts are assembled into two components, up and down, as shown in Figure 3 and Figure 4. The whole fixture is divided into two components when it is being assembled. This can avoid the parts being missed or installed wrongly in the assembly process. In the component down, as the benchmark of flange, the counter balance is fixed with bolts. The counter balance would be regulated in balance when the fixture is produced.
In the component up, as the benchmark of the fixture, the locating plate is fixed with seven bolts. Then as the benchmark of the locating plate, the upper half part of two threaded studs are rotated into the locating plate, and the pressure plate is clamped on the threaded studs by bolts. In the fixture, the pressure plate is in direct contact with the work piece, so it is under great stress. Therefore, the material of 45Mn2 is selected, which needs treatment of quenching and tempering. Matching block need not to be fixed into the fixture during the initial assembly and the mass of matching block is determined by the result of motion simulation.
Figure 1 Brake calipers Figure 2 Flange
Figure 3 Component down Figure 4 Component up
After the assemblies of component up and component down are completed, they are combined in a new component unit, with the bolts and nuts, as shown in Figure 5 shows. Due to adopting hierarchical assembly [5] , it is rational in the practical production process and the parts management is easy, which can effectively shorten the design cycle.
Figure 5 Component unit1
3 Balance analysis of the kinematics of the special lathe fixture
The mass of each part needs to be determined before the process of kinematics simulation of the special lathe fixture. As is shown in Figure 6, the material and density of each part is defined by menu command [mechanism] / [quality attributes], as Table 1 shows, the volume and mass of part are calculated out by 3D design software. We select carbon steel as the material of other standard parts such as the bolts and nuts, its density is 7.85g / cm3. In the process of defining the mass on Pro /E, unit conversion also needs attention.
Figure 6 Dissection figure of the fixture
Table 1 Material and density of the main parts of fixture
Number
Part name
Material
Density (g/cm3)
1
counter balance
A3
7.85
2
flange
HT200
7.2
3
fixture
HT200
7.2
4
matching block
lead
11.37
5
locating
45
7.85
6
pressure plate
45Mn2
7.85
Establishing component unite, and then, component unit1 would be assembled on the main shaft as the benchmark of machine spindle axis by the way of “connection-pin connection”, as is shown in Figure7. After entering a mechanic model, the gravity is set in a default value. In the column of “direction”, we set X: -1, other: 0. Added in a motor, its rotation rate is 360 r/min. Then a “run” is established with its settings, “dynamic type” and “opening gravity” in the column of “external load”. Till then, the kinematics simulation process can run. In order to reduce flutter of the cylinder hole, the balance of a special fixture is taken as the key analysis in this paper [6,7] .The objective of balance analysis is to make the holistic centroid of the fixture and the work piece in the machine spindle axis of rotation. Thus, we should determine the holistic centroid of the fixture and the work piece first. Then the distance between holistic and spindle axis can be obtained. The distance between the holistic and spindle axis should incline to zero as far as possible by adjustment of the mass of the matching block.
The detailed locations of centroids in three directions of X, Y, Z can be obtained through the measuring function of Pro /E. Because of setting the machine spindle axis of rotation as the Z axis, the distance of the centroid relative to the centre rotation can be determined only in need of the maximum of the centroid at the direction of X or Y. The measurement results of fixture simulated motion without a matching block is shown in Figure 8. When the fixture turned about 90°, the maximum deviation distance of the centroid is – 22.08 mm in the direction of X. Only by doing that can we know that the centroid is not on the axis; as a result it does not meet the balance requirement.
Figure 7 Component unite Figure 8 Position curve of centroid without matching block
In order to meet the balance requirement a matching block need to be added to adjust the centroid, as shown in Figure 4. After adding the matching block, return to analyze and then re-measure. The result is that the centroid is still not on the axis, but the distance of the centroid relative to the axis is shortened. In the case of increasing the thickness of the matching block, the modification and measurement is executed again and again in the simulation process. Through a number of tests, an ideal distance of the centroid relative to the axis is obtained. The value is 1.5 10-7mm, as Figure 9 shows, so it can be considered that the centroid is on the axis, and the result satisfies the balance requirements.
According to the simulation result with a matching block, a lead brick whose thickness is 30 mm, volume is 3.72 105mm3, mass is 4.23 kg is casted in the specified groove of fixture to meet the balance requirements.
The comparison of measured data of run-out tolerance between the new design and the old design is shown in Table 2.
Figure 9 Position curve of centroid with matching block
Table 2 Measured data of run-out tolerance
Measurement time
New design
Old design
1
0.016mm
0.048mm
2
0.017mm
0.050mm
3
0..015mm
0.046mm
4
0.018mm
0.047mm
5
0.020mm
0.046mm
4 Conclusions
According to the technological requirements of the cylinder of brake caliper in the processing, Pro /E is adopted in the development of 3D design, and the kinematics simulation research is done on the fixture combined with its mechanical simulation functions. The development process and verified data from 3D modeling and kinematics simulation for this special fixture show that 3D-designed process can conveniently forecast the assembly interference of the fixture and accurately add the mass of lead brick before the prototype is made. In this way we can eliminate the flutter caused by the unbalanced lathe fixture and improve the precision of run-out tolerance in the cylinder hole compared with the machine tool spindle, thus ensuring the processing quality of the cylinder hole in the brake caliper.
References
[1] Zhu L Y, Li B, Pro /ENGINEER motion simulation and finite element analysis. Beijing: Posts& Telecom Press, 2004( In Chinese)
[2] Ding JH, Wu G Q, Application of Pro /E software in product development. Machine Building& Automation, (7) : 17 ~ 18, 22, 2006 ( In Chinese)
[3] Anon, Adhesives and automobiles. Assembly Headquarters, ( 1) : 52~ 59, 2008
[4] Wan Z J, Luo X G, Automobile Oil-Pipe-Check-Tool Design Based on Pro /E Model. Automobile Technology & Material, ( 7) : 17 ~18, 22, 2006( In Chinese)
[5] Qin G H, Zhang W H. Advanced design methods for machine tool fixture. Beijing: Aviation Industry Press, 2006( In Chinese)
Brief Biographies
PAN Jin-kun is a lecturer in the School of Mechanical Engineering, Nanjing Institute of Technology. His research interest is in mechanical design and theory.
ZUO Wan-li is a postgraduate student in College of Mechanical and Power Engineering of Nanjing University of Technology. His research interest is in mechanical design and theory.
LU Dong-sheng is a postgraduate student in College of Mechanical and Power Engineering of Nanjing University of Technology. His research interest is in mechanical design and theory.
中文譯文
基于三維設(shè)計(jì)的浮動(dòng)式制動(dòng)卡鉗的車(chē)床夾具的研制[1]
潘金坤1，左萬(wàn)里2，路東升2
1南京工程學(xué)院機(jī)械工程學(xué)院，南京 211167，中華人民共和國(guó)
2南京工業(yè)大學(xué)機(jī)械與動(dòng)力工程學(xué)院，南京210009，中華人民共和國(guó)
摘要：根據(jù)制動(dòng)卡鉗在生產(chǎn)過(guò)程中的技術(shù)要求，本文研究的是一個(gè)基于三維設(shè)計(jì)的浮動(dòng)式制動(dòng)卡鉗的專(zhuān)用夾具。根據(jù)專(zhuān)用夾具的三維建模和運(yùn)動(dòng)仿真的開(kāi)發(fā)過(guò)程和驗(yàn)證數(shù)據(jù)顯示，三維設(shè)計(jì)過(guò)程可以在原型建模之前方便的預(yù)測(cè)夾具的組裝干涉和準(zhǔn)確添加在鉛磚的質(zhì)量。通過(guò)這種方式，可以消除由擺動(dòng)引起的車(chē)床夾具的不平衡和改善在缸孔與機(jī)床主軸的跳動(dòng)公差精度，因此制動(dòng)卡鉗的缸孔加工質(zhì)量可以很大程度的被保證。
關(guān)鍵字：三維設(shè)計(jì)；制動(dòng)卡鉗；車(chē)床夾具
1 緒言
汽車(chē)的浮動(dòng)盤(pán)式制動(dòng)器卡鉗的生產(chǎn),由于其結(jié)構(gòu)的復(fù)雜性,需要專(zhuān)用夾具來(lái)安裝和夾緊制動(dòng)卡鉗。制動(dòng)器是汽車(chē)涉及行駛安全性的關(guān)鍵部件，隨著汽車(chē)工業(yè)的發(fā)展，車(chē)速越來(lái)越高，載荷越來(lái)越大，而對(duì)制動(dòng)器的尺寸要求越來(lái)越小。這意味著制動(dòng)器部件單位面積所承受的載荷及吸收的能量會(huì)大大增加，因而對(duì)制動(dòng)器性能的要求也越來(lái)越高。對(duì)行駛的汽車(chē)進(jìn)行制動(dòng)時(shí)，將摩擦部件(摩擦片)壓到車(chē)輛的轉(zhuǎn)動(dòng)部件（制動(dòng)盤(pán)）上，摩擦使轉(zhuǎn)動(dòng)部件減速或停止運(yùn)動(dòng)，因此發(fā)熱是動(dòng)摩擦的必然結(jié)果。根據(jù)制動(dòng)卡鉗在加工中的技術(shù)要求，本文研究一個(gè)基于三維設(shè)計(jì)的浮動(dòng)制動(dòng)卡鉗的專(zhuān)用夾具和它的模型的虛擬裝配。通過(guò)三維設(shè)計(jì)軟件的機(jī)構(gòu)仿真功能，分析車(chē)床夾具的平衡性[1]。結(jié)果顯示這個(gè)設(shè)計(jì)過(guò)程可以方便的預(yù)測(cè)一些影響技術(shù)設(shè)備質(zhì)量的因素，例如在樣機(jī)里的裝配干涉和車(chē)床夾具的加工穩(wěn)定性[2]。這個(gè)設(shè)計(jì)過(guò)程不僅可以避免在傳統(tǒng)設(shè)計(jì)里的設(shè)計(jì)誤差，還可以提高產(chǎn)品的設(shè)計(jì)質(zhì)量。
2 專(zhuān)用車(chē)床夾具的三維設(shè)計(jì)
專(zhuān)用夾具的制造對(duì)象是浮動(dòng)盤(pán)式制動(dòng)器的制動(dòng)卡鉗，如圖1所示；其加工表面是制動(dòng)器的缸孔。這個(gè)圖顯示:當(dāng)缸孔被加工時(shí),它的軸必須符合機(jī)器主軸的旋轉(zhuǎn)軸。由于制動(dòng)卡鉗的不規(guī)則形狀結(jié)構(gòu)，夾具的不平衡質(zhì)量引起的擺動(dòng)和工件會(huì)影響缸孔實(shí)際加工中的加工精度和圓度，和一些形狀公差的精度要求例如兩缸孔之間的平行度。為了避免制動(dòng)卡鉗的車(chē)床夾具在設(shè)計(jì)過(guò)程中的這些問(wèn)題，在本文研究了專(zhuān)用夾具的三維設(shè)計(jì)。
根據(jù)制動(dòng)卡鉗的形狀結(jié)構(gòu)特點(diǎn)和車(chē)床夾具的夾緊要求，在整個(gè)加工過(guò)程中，缸孔應(yīng)該在車(chē)床夾具夾緊后來(lái)完成。法蘭需要機(jī)器主軸的安裝孔和夾具兩邊的中心定位孔作為中介來(lái)連接機(jī)器主軸和夾具。確?？ㄣQ機(jī)體加工缸孔的軸的定位和在夾具的夾緊和機(jī)器旋轉(zhuǎn)主軸的相互配合[3]，如圖2所示。
在本文中，專(zhuān)用夾具的其他部分的建模過(guò)程不進(jìn)行詳細(xì)描述，請(qǐng)參考文獻(xiàn)[4]。然后這些零件組裝成兩個(gè)部分，上部分和下部分，如圖3和圖4所示。在裝配時(shí)，整個(gè)夾具分兩個(gè)部分。這樣在裝配過(guò)程中避免零件被少裝或安裝錯(cuò)誤。在下部分，作為法蘭的基準(zhǔn)由螺栓來(lái)實(shí)現(xiàn)平衡的固定。在夾具生產(chǎn)過(guò)程中，柜臺(tái)平衡會(huì)被平衡調(diào)節(jié)。在正常工作狀態(tài)下，根據(jù)浮鉗盤(pán)式制動(dòng)器工作原理，在靜力的某一平衡狀態(tài)下，制動(dòng)鉗受力如下:（1）制動(dòng)盤(pán)反作用力通過(guò)內(nèi)側(cè)摩擦, 活塞和制動(dòng)液介質(zhì)作用在制動(dòng)鉗體的油缸側(cè)壁。（2）制動(dòng)盤(pán)反作用力通過(guò)外側(cè)摩擦塊對(duì)鉗體產(chǎn)生一個(gè)推力。（3）與支架相接螺栓孔處有來(lái)自支架對(duì)鉗體的作用力。
在上部分，作為夾具的基準(zhǔn)，用七個(gè)螺栓來(lái)固定定位板。然后，作為基準(zhǔn)的定位板，上半部分由兩個(gè)螺紋釘定在定位板上，和壓緊板通過(guò)螺栓被夾緊。在夾具里，壓緊板是直接接觸工件的，所以它收到巨大的壓力。因此，材料選擇45Mn2，需要淬火和回火的熱處理。在初始裝配中，配合塊不需要固定在夾具上，配合塊的質(zhì)量在運(yùn)動(dòng)仿真的結(jié)果中可以得到。
在上部分和下部分裝配完成后，他們由螺栓和螺母組成了一個(gè)新的單元1，如圖5所示。由于采用層次化裝配[5]，在實(shí)際生產(chǎn)過(guò)程中它是合理的，部分管理是簡(jiǎn)單的，可以有效的縮短設(shè)計(jì)周期。
3 專(zhuān)用車(chē)床夾具的運(yùn)動(dòng)學(xué)平衡性分析
每個(gè)零件的質(zhì)量需要在專(zhuān)用夾具的運(yùn)動(dòng)仿真過(guò)程特性之前確定。如圖6所示，每個(gè)零件的材料和密度是由菜單欄里的[機(jī)構(gòu)]/[質(zhì)量屬性]來(lái)確定的，如表1所示，零件的體積和質(zhì)量是由三維設(shè)計(jì)軟件計(jì)算的。我們選擇碳素鋼作為其他標(biāo)準(zhǔn)零件的材料，如螺栓和螺母，其密度是7.85g / cm3。在Pro/E里的定義質(zhì)量的過(guò)程，也要注意單位轉(zhuǎn)換。
建立組件單元，然后，組件單元1將通過(guò)“連接銷(xiāo)連接”安裝在主軸上作為機(jī)器主軸的基準(zhǔn)，如圖7所示。在進(jìn)入力學(xué)模型后，重力是一個(gè)設(shè)定的默認(rèn)值。在矢量列表中，我們?cè)O(shè)置X:-1，其他：0。添加一個(gè)電動(dòng)機(jī)，它的轉(zhuǎn)速是360 r/min。然后建立在外部負(fù)載列表里的動(dòng)態(tài)式和打開(kāi)重力的設(shè)置為運(yùn)行。直到那時(shí)，運(yùn)動(dòng)學(xué)仿真過(guò)程才可以運(yùn)行。為了減少缸孔的擺動(dòng)，專(zhuān)用夾具的平衡是本文的關(guān)鍵分析[6,7]。平衡性分析的目的是夾具和工件在機(jī)床的旋轉(zhuǎn)主軸的整體重心。因此，我們首先要確定夾具和工件的整體質(zhì)心。然后整體和主軸之間的距離就可以得到。整體和主軸之間的距離應(yīng)該趨向于零，盡可能調(diào)整配合塊的質(zhì)量。
質(zhì)心的具體三個(gè)方向因子的X,Y,Z可以通過(guò)Pro/E的測(cè)量功能得到。因?yàn)樵O(shè)置機(jī)床的旋轉(zhuǎn)主軸為Z軸，質(zhì)心相對(duì)于旋轉(zhuǎn)中心的距離只需要質(zhì)心在X或Y方向的最大值來(lái)確定。沒(méi)有配合塊的夾具虛擬運(yùn)動(dòng)的測(cè)量結(jié)果如圖8所示。當(dāng)夾具轉(zhuǎn)動(dòng)90°，質(zhì)心的最大偏差距離在X方向是-22.08mm。只有這樣做，我們可以知道質(zhì)心不在軸上；作為它不能滿(mǎn)足平衡要求的條件。
表1 夾具主要零件材料與密度
編號(hào)
零件名稱(chēng)
材料
密度(g/cm3)
1
平衡塊
A3
7.85
2
法蘭盤(pán)
HT200
7.2
3
夾具體
HT200
7.2
4
配重塊
鉛
11.37
5
定位板
45
7.85
6
壓板
45Mn2
7.85
為了滿(mǎn)足平衡條件的配合塊需要添加調(diào)整質(zhì)心，如圖4所示。在添加配合塊后，回歸分析，然后重新測(cè)量。結(jié)果是質(zhì)心依然不在軸上，但質(zhì)心相對(duì)于軸的距離縮短了。對(duì)于配合塊的厚度增加，修改，測(cè)量是一次又一次的執(zhí)行仿真過(guò)程。通過(guò)大量的測(cè)試，得到質(zhì)心相對(duì)于軸的理想距離。這個(gè)值是1.5 10-7mm，如圖9所示，因此它可以被認(rèn)為是質(zhì)心在軸上和滿(mǎn)足平衡需求的結(jié)果。
根據(jù)配合塊的運(yùn)動(dòng)仿真結(jié)果，一個(gè)鉛磚的厚度是30mm,體積是3.72105mm3,質(zhì)量是4.23kg是滿(mǎn)足平衡性要求的專(zhuān)用槽夾具。在新的設(shè)計(jì)與舊的設(shè)計(jì)之間的跳動(dòng)公差的測(cè)量數(shù)據(jù)的比較如表2所示。
表2 跳動(dòng)公差測(cè)量數(shù)據(jù)
測(cè)量次數(shù)
新設(shè)計(jì)
舊設(shè)計(jì)
1
0.016mm
0.048mm
2
0.017mm
0.050mm
3
0..015mm
0.046mm
4
0.018mm
0.047mm
5
0.020mm
0.046mm
制動(dòng)器在車(chē)輛安全性方面起著相當(dāng)重要的作用，直接影響到這些車(chē)輛的正常行駛，因而制動(dòng)器總成及其零部件的安全可靠性倍受關(guān)注。運(yùn)用CAD/CAE 技術(shù)對(duì)某浮鉗式盤(pán)式制動(dòng)器的關(guān)鍵零件進(jìn)行了有限元分析，分析結(jié)果表明制動(dòng)鉗體等關(guān)鍵零件滿(mǎn)足設(shè)計(jì)強(qiáng)度要求。當(dāng)制動(dòng)時(shí)，活塞在液壓力的作用下推動(dòng)內(nèi)摩擦塊沿著導(dǎo)向銷(xiāo)軸向移動(dòng)，以一定的壓力壓向制動(dòng)盤(pán)，同時(shí)制動(dòng)鉗鉗體也在液壓反向力作用下將外制動(dòng)盤(pán)以一定壓力壓向制動(dòng)盤(pán)，這時(shí)摩擦襯片便于制動(dòng)盤(pán)間產(chǎn)生摩擦力，從而達(dá)到制動(dòng)的目的。在制動(dòng)過(guò)程中，當(dāng)受力的平衡狀態(tài)下，制動(dòng)鉗鉗體受力為：（1）制動(dòng)盤(pán)反作用力通過(guò)內(nèi)側(cè)摩擦塊，活塞和制動(dòng)液作用在鉗體的油缸側(cè)壁。（2）制動(dòng)盤(pán)反作用力通過(guò)外側(cè)摩擦塊對(duì)鉗體產(chǎn)生一個(gè)推力。（3）與支架相接螺栓孔處又來(lái)自支架對(duì)鉗體的作用力。制動(dòng)器支架的受力情況為：①制動(dòng)盤(pán)與摩擦襯塊間的摩擦力
通過(guò)制動(dòng)底板傳到支架的一側(cè)，來(lái)自與支架滑槽相觸的是制動(dòng)底板對(duì)滑槽的壓力，而壓力的大小取決與摩擦片圓周摩擦力的大?。虎谥Ъ芄潭ㄌ巵?lái)自轉(zhuǎn)向節(jié)的反作用力；③與鉗體相接處來(lái)自鉗體的反作用力。通過(guò)對(duì)該浮鉗盤(pán)式制動(dòng)器的關(guān)鍵零件進(jìn)行受力分析，這些作用力將作為載荷邊界條件添加到有限元分析模型中。
在UG4.0 軟件建立該型號(hào)浮鉗盤(pán)式制動(dòng)器三維模型后，通過(guò)軟件集成技術(shù)將模型導(dǎo)入到UG 集成的有限元前處理模塊“simulation design”中自動(dòng)劃分網(wǎng)格[4]。網(wǎng)格劃分前，需要簡(jiǎn)化模型，可以減少分析求解所需要的時(shí)間。為了能準(zhǔn)確地反應(yīng)各零件的應(yīng)力、應(yīng)變及位移的規(guī)律，采用10 節(jié)點(diǎn)四面體單元作為劃分網(wǎng)格類(lèi)型。完成網(wǎng)格劃分后，可在屬性編輯器評(píng)價(jià)和修改網(wǎng)格屬性以改進(jìn)網(wǎng)格，這樣能在邊緣和高應(yīng)力處細(xì)化和改善網(wǎng)格。
通過(guò)定義好網(wǎng)格和作用邊界條件準(zhǔn)備好有限元模型。就可以執(zhí)行解算。需注意的是，為確保成功解算和精確結(jié)果，有限元模型的檢查是必需的，解算前先創(chuàng)建分析方案，將仿真文件導(dǎo)入Nastran 求解器解算，順利求解后在仿真導(dǎo)航器中可顯示計(jì)算結(jié)果，在后處理模塊中，顯示或編輯相關(guān)零件的位移，應(yīng)力或應(yīng)變等指標(biāo)。通過(guò)后處理模塊，我們能通過(guò)云圖直觀形象地得到位移，應(yīng)力應(yīng)變的變化和顯示，并可以以動(dòng)畫(huà)等方式顯示零件中最危險(xiǎn)的部位。我們能直接觀察和讀取活塞，制動(dòng)鉗支架和制動(dòng)鉗鉗體的應(yīng)力，并了解到各零部件是否滿(mǎn)足強(qiáng)度要求。
4 結(jié)論
根據(jù)制動(dòng)卡鉗的缸孔的技術(shù)要求在加工、Pro/E中結(jié)合夾具中的機(jī)械仿真功能采用三維設(shè)計(jì)的研究和運(yùn)動(dòng)學(xué)仿真的研究。根據(jù)專(zhuān)用夾具的三維建模和運(yùn)動(dòng)仿真的開(kāi)發(fā)過(guò)程和驗(yàn)證數(shù)據(jù)顯示，三維設(shè)計(jì)過(guò)程可以在原型建模之前方便的預(yù)測(cè)夾具的組裝干涉和準(zhǔn)確添加在鉛磚的質(zhì)量。這樣我們可以消除由車(chē)床夾具的不平衡引起的擺動(dòng)和提高缸孔與機(jī)床主軸的跳動(dòng)公差精度，從而保證制動(dòng)卡鉗的缸孔的加工質(zhì)量。
參考文獻(xiàn)
[1] 祝凌云，李斌．Pro/ENGINEER 運(yùn)功仿真和有限元分析.北京：人民郵電出版社，2004．
[2] 丁錦宏，吳國(guó)慶．Pro/E軟件在新產(chǎn)品設(shè)計(jì)中的應(yīng)用.機(jī)械制造與自動(dòng)化，2008(8):138-139,152．
[3] Anon, Adhesives and automobiles. Assembly Hesdquarters,2008(1):52-59．
[4] 秦國(guó)華，張衛(wèi)紅．機(jī)床夾具的現(xiàn)代設(shè)計(jì)方法.北京：航空工業(yè)出版社：（2006）．
[5] 萬(wàn)志堅(jiān)，羅顯光．基于Pro/E建模的汽車(chē)油管檢具設(shè)計(jì).汽車(chē)工藝與材料,2006(7):17-18,22．
簡(jiǎn)介
潘金坤是南京工程學(xué)院機(jī)械工程學(xué)院的一個(gè)講師，他的研究興趣在機(jī)械設(shè)計(jì)及理論。
左萬(wàn)里是南京工業(yè)大學(xué)機(jī)械與動(dòng)力工程學(xué)院的研究生，他的研究興趣是機(jī)械設(shè)計(jì)及理論。
路東升是南京工業(yè)大學(xué)機(jī)械與動(dòng)力工程學(xué)院的研究生，他的研究興趣是機(jī)械設(shè)計(jì)及理論。