開題報告學 生 姓 名學 院專 業(yè) 及 班 級學 號指 導 教 師年 03 月 15 日畢業(yè)設計(論文)開題報告題 目 數(shù)控激光切割機床總體和垂直進給系統(tǒng)設計作者姓名 所學專業(yè) 機械設計制造及其自動化1、研究的意義,同類研究工作國內(nèi)外現(xiàn)狀、存在問題(列出主要參考文獻)Ⅰ、研究的意義:激光切割機是光、機、電一體化高度集成設備,科技含量高,與傳統(tǒng)機加工相比,激光切割機的加工精度更高、柔性化好,有利于提高材料的利用率,降低產(chǎn)品成本,減輕工人負擔,對制造業(yè)來說,可以說是一場技術革命。激光切割加工是用不可見的光束代替了傳統(tǒng)的機械刀,具有精度高,切割快速,不局限于切割圖案限制,自動排版節(jié)省材料,切口平滑,加工成本低等特點,將逐漸改進或取代于傳統(tǒng)的金屬切割工藝設備。激光刀頭的機械部分與工件無接觸,在工作中不會對工件表面造成劃傷;激光切割速度快,切口光滑平整,一般無需后續(xù)加工;切割熱影響區(qū)小,板材變形小,切縫窄(0.1mm~0.3mm);切口沒有機械應力,無剪切毛刺;加工精度高,重復性好,不損傷材料表面;數(shù)控編程,可加工任意的平面圖,可以對幅面很大的整板切割,無需開模具,經(jīng)濟省時。參考文獻:[1] 張學仁.數(shù)控電火花線切割加工技術. 哈爾濱:哈爾濱工業(yè)出版社,2000Ⅱ、國內(nèi)外現(xiàn)狀:激光被譽為二十世紀最重大的科學發(fā)現(xiàn)之一,它剛一問世就引起了材料科學家的高度重視。1971 年 11 月,美國通用汽車公司率先使用一臺 250W CO2 激光器進行利用激光輻射提高材料耐磨性能的試驗研究,并于 1974 年成功地完成了汽車轉向器殼內(nèi)表面(可鍛鑄鐵材質)激光淬火工藝研究,淬硬部位的耐磨性能比未處理之前提高了 10 倍。這是激光表面改性技術的首次工業(yè)應用。多年以來,世界各國投入了大量資金和人力進行激光器、激光加工設備和激光加工對材料學的研究,促使激光加工得到了飛速發(fā)展,并獲得了巨大的經(jīng)濟效益和社會效益。如今在中國,激光技術已在工業(yè)、農(nóng)業(yè)、醫(yī)學、軍工以及人們的現(xiàn)代生活中得到廣泛的應用,并且正逐步實現(xiàn)激光技術產(chǎn)業(yè)化,國家也將其列為“九五”攻關重點項目之一?!笆濉钡闹饕ぷ魇谴龠M激光加工產(chǎn)業(yè)的發(fā)展,保持激光器年產(chǎn)值 20%的平均增長率,實現(xiàn)年產(chǎn)值 200 億元以上;在工業(yè)生產(chǎn)應用中普及和推廣加工技術,重點完成電子、汽車、鋼鐵、石油、造船、航空等傳統(tǒng)工業(yè)應用激光技術進行改造的示范工程;為信息、材料、生物、能源、空間、海洋等六大高科技領域提供嶄新的激光設備和儀器。Ⅲ、存在問題:近年來,我國從日、德、美、西班牙等國家先后引進數(shù)控機床先進技術和合作、合資生產(chǎn),解決了機床的可靠性、穩(wěn)定性問題,數(shù)控機床開始正式生產(chǎn)和使用,并逐步向前發(fā)展。激光切割的適用對象主要是難切割材料,如高強度、高韌性材料以及精密細小和形狀復雜的零件,因而數(shù)控激光切割在我國制造業(yè)中正發(fā)揮出巨大的優(yōu)越性。任何東西都有兩面性,有了優(yōu)點也會有缺點。不是所有的材質都可以使用激光切割加工的,不同的激光機切割不同的材質,不得不承認不夠線切割好,因為線切割可以對任何的材質進行切割。主要問題還有研發(fā)投入少,市場無序競爭,創(chuàng)新意識不足,企業(yè)之間合作太少。2、研究目標、內(nèi)容和擬解決的關鍵問題(根據(jù)任務要求進一步具體化)Ⅰ、研究目標:數(shù)控激光切割機床總體和垂直進給系統(tǒng)設計Ⅱ、研究內(nèi)容:(1)分析數(shù)控激光切割機床的整體傳動方案;(2)垂直進給系統(tǒng)結構的總體方案設計;(3)零部件的校核與設計相關的計算 ;(4)裝配圖的設計、零件工作圖的設計;(5)本設計的優(yōu)缺點分析 ;(6)編寫設計說明書.Ⅲ、擬解決的關鍵問題:(1)激光切割頭;(2)橫向縱向進給系統(tǒng);(3)垂直進給系統(tǒng);其中,橫向縱向及垂直進給系統(tǒng)全部由伺服電機來驅動。2、特色與創(chuàng)新之處本品在導軌上使用直線滾動導軌,相對于普通機床所用導軌,直線滾動導軌定位精度高,降低機床造價并節(jié)約電力,還可以長期維持機床的高精度。在激光刀頭方面,普通數(shù)控激光切割機 Z 軸拖動重量在 5kg 以上時,應采用重力平衡設施,而高性能數(shù)控激光切割機的 Z 軸拖動重量在 2kg 以上就必須施加重力平衡設施,本品采用氣缸拖動方式該方式重量輕、體積小、易安裝,還可根據(jù)要求調(diào)整氣缸的平衡力。3、 擬采取的研究方法、步驟、技術路線設計本產(chǎn)品應該先實地考察現(xiàn)有的數(shù)控激光切割機床,并觀察其工作特點,比較不激光切割機床以及其他切割機比如線切割,水切割之間的差異,得出現(xiàn)有的激光切割機床的優(yōu)點和劣勢。然后取長補短,提出整體方案。再把方案給指導老師批閱,聽取老師的建議,改正不合理的地方,一步步完善方案,最后進過細致的設計,分析,計算以得到最終的方案。技術路線:一,總體方案分析二,機械部分 XY 工作臺和 Z 軸機構設計 三,滾珠絲杠傳動系統(tǒng)設計 四,導軌選擇 五,步進電機及傳動系統(tǒng)設計 六,剛度分析 七,消除齒側間隙和預緊 八,數(shù)控系統(tǒng)的設計 4、擬使用的主要設計、分析軟件及儀器設備Auto-CAD 計算機輔助繪圖軟件6、參考文獻[1] 張學仁.數(shù)控電火花線切割加工技術. 哈爾濱:哈爾濱工業(yè)出版社 2000[2] 李廣弟.單片機基礎.北京:北京航空航天大學出版社出版,2002[3] 鄭玉華.典型機械(電)產(chǎn)品構造. 北京:北京科學出版社,2006[4] 陳嬋娟.數(shù)控機床設計. 北京:化學工業(yè)出版社,2006[5] 李秉操.單片機原理及其在工業(yè)控制中的應用. 陜西:陜西電子編輯部 1991注:1、開題報告是本科生畢業(yè)設計(論文)的一個重要組成部分。學生應根據(jù)畢業(yè)設計(論文)任務書的要求和文獻調(diào)研結果,在開始撰寫論文之前寫出開題報告。2、參考文獻按下列格式(A 為期刊,B 為專著)A:[序號]、作者(外文姓前名后,名縮寫,不加縮寫點,3 人以上作者只寫前 3 人,后用“等”代替。)、題名、期刊名(外文可縮寫,不加縮寫點)年份、卷號(期號):起止頁碼。B:[序號]、作者、書名、版次、(初版不寫)、出版地、出版單位、出版時間、頁碼。3、表中各項可加附頁。i摘 要激光切割的適用對象主要是難切割材料,如高強度、高韌性材料以及精密細小和形狀復雜的零件,因而數(shù)控激光切割在我國制造業(yè)中正發(fā)揮出巨大的優(yōu)性。本文設計了一臺單片機控制的數(shù)控激光切割機床,主要完成了:機床整體結構設計,Z 軸、XY 軸的結構設計計算、滾珠絲杠、直線滾動導軌的選擇及其強度分析;以步進電機為進給驅動的驅動系統(tǒng)及其傳動機構的分析設計計算。關鍵詞:CNC;激光切割機床;結構;設計iiABSTRACTLaser cutting machine tool was usually used for the hard-cutting material, such as high-strength material, high precision ductile materials, and smart and complicated components. So, CNC laser cutting has been playing an important role in China's manufacturing industry.This paper describes the design of a SCM-controlled CNC laser cutting machine tools. More attention was paid on the overall machine design, Z axis, XY axis in the design, ball-screw and the choice of linear motion guide and intensity analysis; the drive system into which stepper motor was put and the analysis of the drive system design.KeyWords:CNC;laser cutting machine tools;architectured ;esigniii目 錄第 1 章 緒論………………………………………………………………………11.1 課題背景…………………………………………………………………11.2 本課題主要研究內(nèi)容……………………………………………………11.3 國內(nèi)外研究現(xiàn)狀…………………………………………………………2第 2 章 總體方案的擬定………………………………………………………32.1 設計任務……………………………………………………………………32.2 總體方案的選擇和擬定……………………………………………………3第 3 章 激光切割系統(tǒng)的設計………………………………………………53.1 激光器……………………………………………………………………53.1.1 激光器的組成………………………………………………………53.1.2 激光切的分類………………………………………………………53.2 激光切割設備……………………………………………………………63.2.1 激光切割設備的組成………………………………………………63.2.2 激光切割用的激光器……………………………………………83.2.3 激光切割用割炬…………………………………………………93.3 激光切割頭設計…………………………………………………………10第 4 章 傳動系統(tǒng)設計………………………………………………………124.1 XY 工作臺設計…………………………………………………………124.1.1 主要設計參數(shù)及依據(jù)…………………………………………124.1.2XY 進給系統(tǒng)手里分析……………………………………………124.1.3 初步確定工作臺尺寸及估算質量………………………………124.2 Z 軸隨動系統(tǒng)設計………………………………………………………134.3 滾珠絲趕副設計計算………………………………………………… 144.3.1 滾珠絲桿的特點…………………………………………………144.3.2 主要參數(shù)…………………………………………………………144.3.3 導程計算…………………………………………………………154.3.4 確定當量轉速與當量載荷………………………………………164.3.5 初選滾珠絲桿副…………………………………………………17iv4.3.6 確定允許的最小螺紋底徑………………………………………174.3.7 確定滾珠絲桿副的規(guī)格代號……………………………………184.3.8 確定絲桿副的預緊力…………………………………………184.3.9 行程補償值與拉伸力…………………………………………184.3.10 確定滾珠絲桿副支承用的軸承代號,規(guī)格…………………194.3.11 滾珠絲桿副工作圖設計………………………………………204.3.12 傳動系統(tǒng)剛度…………………………………………………204.3.13 剛度驗算和精度選擇…………………………………………214.3.14 驗算臨界壓縮載荷……………………………………………224.3.15 驗算臨界轉速……………………………………………………234.3.16 效率驗算………………………………………………………23第 5 章 導軌的選定…………………………………………………………255.1 主要要求及種類…………………………………………………………255.1.1 對導軌的基本要求………………………………………………255.1.2 導軌的技術要求…………………………………………………255.1.3 分類及特點………………………………………………………255.2 導軌的選用………………………………………………………………26第 6 章 步進電機及其傳動機構的確定…………………………………286.1 步進電機的選用………………………………………………………286.1.1 脈沖當量和步距角………………………………………………286.1.2 步進電機上起動力矩的近似計算………………………………286.1.3 確定步進電機最高工作頻率……………………………………296.2 齒輪傳動機構的確定…………………………………………………296.2.1 傳動比的確定……………………………………………………296.2.2 齒輪結構主要參數(shù)的確定………………………………………306.3 步進電機慣性負載的計算……………………………………………30第 7 章 傳動系統(tǒng)剛度分析…………………………………………………337.1 根據(jù)工作臺不出現(xiàn)爬行的條件來確定傳動系統(tǒng)剛度………………337.2 根據(jù)微量進給的靈敏度來確定傳動系統(tǒng)的剛度……………………33第 8 章 消隙方法與預緊……………………………………………………358.1 消隙方法………………………………………………………………358.1.1 偏心軸套調(diào)整法…………………………………………………358.1.2 錐度齒輪調(diào)整法…………………………………………………35v8.1.3 雙片齒輪錯齒調(diào)整法……………………………………………368.2 預緊……………………………………………………………………37第 9 章 結論……………………………………………………………………38參考文獻…………………………………………………………………………39致謝…………………………………………………………………………………40 VSS motion control for a laser-cutting machineAbstractAn advanced position-tracking control algorithm has been developed and applied to a CNC motion controller in a laser-cutting machine. The drive trains of the laser-cutting machine are composed of belt-drives. The elastic servomechanism can be described by a two-mass system interconnected by a spring. Owing to the presence of elasticity, friction and disturbances, the closed-loop performance using a conventional control approach is limited. Therefore, the motion control algorithm is derived using the variable system structure control theory. It is shown that the proposed control e!ectively suppresses the mechanical vibrations and ensures compensation of the system uncertainties. Thus, accurate position tracking is guaranteed.1. Introduction For many industrial drives, the performance of motion control is of particular importance. Rapid dynamic behaviour and accurate position trajectory tracking are of the highest interest. Applications such as machine tools have to satisfy these high demands. Rapid movement with high accuracy at high speed is demanded for laser cutting machines too. This paper describes motion control algorithm for a low-cost laser-cutting machine that has been built on the base of a planar Cartesian table with two degrees-of-freedom (Fig. 1). The drive trains of the laser-cutting machine are composed of belt-drives with a timing belt. The use of timing belts in the drive system is attractive because of their high speed, high efficiency, long travel lengths and low-cost (Haus, 1996). On the other hand, they yield more uncertain dynamics and a higher transmission error ( Kagotani, Koyama ● the laser-beam source, which generates the laser beam (the laser-generator);●the laser-head, which directs the laser beam onto the desired position in the cutting plane.The table has to move and position the laser head in a horizontal plane. This is achieved by the means of a drive system with two independent motion axes. They provide movement along the Cartesians' XY axes of 2 and 1m, respectively. The X-drive provides the motion of the laser-head in X-direction. The drive and the laser-head as well as the laser-generator are placed on the bridge to ensure a high-quality optical path for the laser-beam. The movement of the bridge along the Y-axis is provided by the Y-drive. The laser-head represents the X-drive load, while the Y-drive is loaded by the bridge, which carries the complete X-drive system, the laser-head, and the laser-generator. The loads slide over the frictionless slide surface.The positioning system consists of the motion controller, the amplifiers, the DC-motors and the drive trains. The X-drive train is composed of a gearbox and a belt-drive (Fig. 2). The gearbox reduces the motor speed, while the belt-drive converts rotary motion into linear motion. The belt-drive consists of a timing belt and of two pulleys: a driving pulley and a driven pulley that stretch the belt. The Y-drive train is more complex. The heavy bridge is driven by two parallel belt-drives; each bridge-side is connected to one of the belt-drives. The driving pulleys of the belt-drives are linked to the driving axis, which is driven via the additional belt-drive and the gearbox is used to reduce the speed of the motor.2.2. AssumptionsThe machine drives represent a complex non-linear distributed parameter system. The high-order system possesses several resonant frequencies that can be observed by the drives' step response (see Section 4). From a control design perspective, difficulties arise from mechanical vibrations that are met in the desired control bandwidth (~10 Hz). On the other hand, the design objective is to have a high-performance control system while simultaneously reducing the complexity of the controller. Therefore, a simple mathematical model would only consider the first-order resonance and neglect high-order dynamics. In other words, the design model of the control plant will closely match the frequency response of the real system up to the first resonance. Next, the controller should be adequately designed to cope with the higher-order resonance in such a way that the resonance peaks drop significantly to maintain the system stability. Thus, according to the signal analysis and the drives' features, the following assumptions could be made:●the DC-servos operating in the current control mode ensure a high-dynamic torque response on the motor axis with a negligible time constant;●the small backlash in the gearboxes and the backlash of the belt-drives due to the applied pre-tension of the timing belts is negligible;●a rigid link between a motor shaft and a driving pulley of the belt-drive could be adopted;●the inertia of the belt-drives' driven pulleys is negligible in comparison to other components of the drive system.Using the assumptions above, dynamic modeling could be reduced to a two-mass model of the belt-drives that only includes the first resonance. In the control design, the uncertain positioning of the load due to the low repeatability and accuracy of the belt-drive has to be considered as well.Note, that no attention is paid to the coupled dynamics of the Y-drive due to the parallel driving, thus, the double belt-drive is considered as an equivalent single belt-drive.3. The motion control algorithmThe erroneous control model with structured and unstructured uncertainties demands a robust control law. VSS control ensures robust stability for the systems with a non-accurate model, namely, it has been proven in the VSS theory that the closed-loop behavior is determined by selection of a sliding manifold. The goal of the VSS control design is to find a control input so that the motion of the system states is restricted to the sliding manifold. If the system states are restricted to the sliding manifold then the sliding mode occurs. The conventional approach utilises discontinuous switching control to guarantee a sliding motion in the sliding mode. The sliding motion is governed by the reduced order system, which is not affected by system uncertainties. Consequently, the sliding motion is insensitive to disturbance and parameter variations (Utkin, 1992).The essential part of VSS control is its discontinuous control action. In the control of electrical motor drives power switching is normal. In this case, the conventional continuous-time/discontinuous VSS control approach can be successfully applied. However, in many control applications the discontinuous VSS control fails, and chattering arises (S[abanovicH, Jezernik, Young, Utkin Kawamura, Itoh & Sakamoto, 1994). Jezernik has developed a control algorithm for a rigid robot mechanism by combining conventional VSS theory and the disturbance estimation approach. However, the rigid body assumption, which neglects the presence of distributed or concentrated elasticity, can make that control input frequencies of the switcher excite neglected resonant modes. Furthermore, in discrete-time systems discontinuous control fails to ensure the sliding mode and has to be replaced by continuous control (Young et al., 1999). Avoiding discontinuous-feedback control issues associated with unmodelled dynamics and related chattering are no longer critical. Chattering becomes a non-issue.In plants where control actuators have limited bandwidth there are two possibilities: actuator bandwidth is outside the required closed-loop bandwidth, or, the desired closed-loop bandwidth is beyond the actuator bandwidth. In the fist case, the actuator dynamics are to be considered as the non-modelled dynamics. Consequently, the sliding mode using discontinuous VSS control cannot occur, because the control plant input is continuous. Therefore, the disturbance estimation approach is preferred rather than VSS disturbance rejection. In the second case, the actuator dynamics are to be lumped together with the plant. The matching conditions (Draz\enovicH, 1969) for disturbance rejection and insensitivity to parameter variations in the sliding mode are violated. This results from having dominant dynamics inserted between the physical input to the plant and the controller output. When unmatched disturbances exist the VSS control cannot guarantee the invariant sliding motion. This restriction may be relaxed by introducing a high-order sliding mode control in which the sliding manifold is chosen so that the associated transfer function has a relative degree larger than one (Fridman& Levant, 1996). Such a control scheme has been used in a number of recently developed VSS control designs, e.g. in Bartolini, Ferrara and Usai (1998). In the latter, the second-order sliding mode control is invoked to create a dynamical controller that eliminates the chattering problem by passing discontinuous control action onto a derivative of the control input.The system to be controlled is given by Eqs. (1) ―(5) and the system output is the load position. The control objective is the position trajectory tracking. The control algorithm that is proposed in this paper has been developed following the idea of the VSS motion control presented by Jezernik. Since the elastic belt-drive behaves as a low bandwidth actuator, the conventional VSS control algorithm failed to achieve the prescribed control objective. Thus, the robust position trajectory tracking control algorithm presented in the paper has been derived using second-order sliding mode control. In order to eliminate the chattering problem and preserve robustness, the control algorithm uses the continuous control law. Following the VSS disturbance estimation approach, it will be shown that the disturbance estimation feature of the proposed motion control algorithm is similar to the control approach of Jezernik (Jezernik et al., 1994). Additionally, the proposed control algorithm considers the actuator dynamics in order to reshape the poorly damped actuator bandwidth. Consequently, the proposed motion controller consists of a robust position-tracking controller in the outer loop and a vibration controller in the inner loop .