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譯文題目：CATIA逆向工程技術(shù)在注塑模具設(shè)計中的應(yīng)用
學(xué)生姓名：
This paper introduces the concept of reverse engineering in the modern manufacturing industry and the general method of reverse engineering and reverse function module of CATIA software, by car dashboard injection mould as an example, shows that using CATIA specific process of reverse engineering technology design of injection mould, including the point cloud filter, paving grid and grid surface repair, to create boundary characteristic curve, curved surface reconstruction and curved surface quality analysis and CAD model is set up.
In the process of injection mold development and manufacturing, the general process is to design personnel according to product drawing 3 d model, and according to the requirements of the properties of component materials, equipment, process modification, after computer software treatment to generate NC machining equipment NC file, this design pattern known as scheduled. In practical production, the only real samples, without a reference drawings, due to the injection mold is often used between the surface smooth transition, the appearance of some products is composed of multiple complex can be connected with the different spatial curvature of surface, with the traditional method is difficult to measure, cannot be ordered mode is adopted to improve the design. If there is no CAD digital model, can't use CAD/CAM, multi-axis machining center and other advanced processing means. Therefore, designers need to through certain ways of measuring physical information and translated into CAD digital model, it is applied to the reverse engineering technology. For car dashboard injection mould as an example, the author introduces the CATIA reverse engineering technology in the application of the injection mould design.
Reverse engineering is to point to in certain measurements to measure physical or model, according to the measured data reconstruction by using the method of 3 d geometric modeling physical process of CAD model.
Reverse engineering requirements shall be established in accordance with the product measurement data with the existing CAD/CAM system is fully compatible with the digital model, which is the ultimate goal of reverse engineering. Measurement data is the first step in reverse engineering, is the foundation of data processing, model reconstruction. By far the most commonly used point data acquisition device has three coordinate measuring machine, three-dimensional laser scanner, such as joint type robot arm.
Point cloud, after get the quality of the reconstructed surface objectively depends on the use of reverse engineering software functions. Reverse engineering software is mainly to complete the point cloud processing, curve processing and surface processing three functions, the commonly used professional point cloud processing software Imageware with EDS, RaindropGeomagic Studio, DelCAM company Copy - CAD, PTC company ICEMSurf, Pro/Designer (CDRS), Pro/Scantools, etc.
Imageware and other professional software work speed, when dealing with point cloud data fitting method for line/face can be more easily, but curve and curved surface creation tools provided by the software itself is less, so the fitting line and also need to get in general such as UG further changes in the 3 d CAD/CAM software. And the use of Pro/E, UG software to read alone, dealing with point cloud data, fast read hundreds of thousands or even millions of point data is difficult. Therefore, in the concrete engineering design, often using professional software to point cloud data processing, get basic control curve, and then import the UG and Pro/E 3 d software to construct the surface, creating entity.
Using CATIA software is the French dassault company with the United States developed by IBM has the industry leading level of CAD/CAE/CAM software packages. It has unique advantages in the aspect of curve and surface modeling, such as its unique high times (15) can achieve the Bezier curve surface function, can satisfy the special industry to the strict requirement of the surface smoothness. Point cloud with CATIA software, entity modeling, surface modeling and nc machining module, can completely in a software to delete point cloud, filtering, create characteristic line, paving, repair, surface quality analysis, such as operation, with high quality surface, and converts surface entity, and then generate a knife road path for nc machining.
Reverse engineering using CATIA digital surface editor (DigitizedShapeEditor DSE arithmetic), chuang cheng type design (GeneraiveShapeDesign, GSD), rapid surface reconstruction (QuickSurfaceReconstruction, QSR), free surface modeling (FreestyleShaper, FSS) module for reverse operation.
DSE arithmetic module can be used to process the point cloud file, the module can be an analysis of the import and export, point cloud filtering, grid, paving, drawing intersecting lines and so on. For large parts of partitioned scanning of the division of DSE arithmetic splicing function can be a basis of the point cloud files on the ball (dots, measurement point cloud data be set to two parts as the following point cloud aligned benchmark) for joining together, each piece of point cloud data into parts of a whole point cloud. USES DSE arithmetic module is the most main purpose is through to the parts of point cloud data analysis and processing, so as to get the point cloud surface grid feature line, this is the basis of the fitting surface.
QSR module DSE arithmetic can be processed to get the point cloud surface grid characteristic curve, and further into space using curved surface fitting commands, point cloud as reference, on the basis of the space curve fitting with high quality surface. Its with curve analysis tools can analyze the characteristics of grid space curve and the point cloud surface intersecting line between error.
GSD and CATIA FSS module is used for three dimensional surface design of the main working platform, the platform can be used in wire frame and surface features quickly built from simple to complex of the arbitrary shape curved surface, the two modules have a large number of design tools to create and edit surfaces. In reverse design, mainly application of the two modules fitting and joining together the function of the surface, the structure of form a complete shape; To hole, at the same time, positive reconstruction arc such as the details. FSS module of the surface analysis function can be used for all types of curve and surface analysis, to restore the fitting surface with point cloud or mesh surface to surface analysis, can get error analysis diagram, easy to verify the correctness of the reconstruction of curved surface.
A simple shape of parts do you usually use DSE arithmetic and QSR two modules can complete construction of curved surface; With complex appearance and are porous, more muscle complex parts, after DSE arithmetic and QSR processing whole surface structure, also need the GSD and FSS module in detail the structure of the reconstruction and modified, finally an entity in the FSS module generated surface quality analysis.
The instrument panel mold production provided by the demand side, there is no drawings or digital model. Due to the corrosion of injection molding materials, the use of a certain period of time after the mold cavity part size changes, causing out-of-tolerance products installation size. But the mold first acceptance test of the sample is still there, so the parts can use reverse engineering to reconstruct digital models.
The Taiwan company production of 3 d laser scanner point cloud data of samples are collected. In product appearance limit, the sample section scan, the point cloud file is divided into five parts. Based on the left side of the point cloud processing as an example for reverse operation instructions below.
In the reverse engineering, the user the number of point cloud data obtained from measuring instrument is very large, usually no explicit geometrical topology relation between data, including a large number of useless data, reducing the processing speed of the computer, need to process to reduce the number of point cloud data. Point cloud processing principle is the part of the changes in surface flat sparse density can be obtained, the larger curvature change parts and detail parts dense take, so need to deal with the number of points will be less. In CATIA, can use the delete and filtering approach to remove the excess noise.
On the surface of the grid size can be adjusted through the "Neighborhood" parameter, the value for the radius of a sphere, in a point cloud as long as three points within the scope of the radius of sphere, CATIA will be in 3 points as the vertices to create a triangular mesh surface. So the pavement is also called triangular mesh. Grid size should be based on principles of grid surface with holes but less, if the parameter selection is too big, can cause the loss of the grid on the surface detail structure, can't complete reconstruction surface. Hole can be used "grid surface repair" (FillHoles) command to repair. Point cloud becomes a "grid", but the rest Polygon another (Polygon) is made up of thousands of sizes triangle face, is not usually curved surface, cannot edit for other modules.
After the completion of the paving, into the workbench, QSR module delivered boundary line into characteristic curve. Characteristic curve should satisfy continuous and second-order geometric curvature change uniform requirements, and on the premise of guarantee the surface fitting curve and the grid, minimize the number of control points, to reduce the curve of the order, to ensure a uniform surface curve control points, consistent, and tidy, otherwise will appear the phenomenon of surface distortion.
According to the above operating characteristic curve can be used for "curved surface fitting in QSR module (Powerfit) command reconstruction surface, also can use GSD and for building a curved FSS in the module commands, such as Loft (Loft), scanning (Sweep), bridge surface (such as FreestyleBlendSurface) to realize the reconstruction of the surface.
Free surface modeling using CATIA (FreeStyle) module provides a variety of analysis tools of various qualities of the reconstructed surface can be analyzed, such as point cloud data and surface error analysis, such as illumination analysis, etc. The analysis result shows that surface with point cloud data error within + / - 0.2 mm, the error is distributed in the edge of the late after decorate beautification reduces; Uniform surface curvature, curvature change, conform to the requirements of the product.
Each point cloud processing respectively integral split after modification to get the final CAD model. Model the process modification, using CATIA own programming module to generate feed processing and NC code file, processed into the mold after a test is successful, the dashboard parts made by completely accord with the requirement of the upstream manufacturers.
At present, mould industry is more and more business needs according to customers samples produced mold, based on the prototype or physical way of reverse engineering because of its fast development, especially for parts not original geometry information, reverse engineering is an important means of finished parts precise geometric modelling, application of CATIA reverse engineering the advanced design method, can greatly improve the efficiency of injection mold design, production, reduce the manufacturing cost.
介紹了現(xiàn)代制造業(yè)中逆向工程的概念及逆向工程的一般方法和 CATIA軟件的逆向功能模塊, 以汽車儀表盤注塑模具為例, 說明利用 CATIA逆向工程技術(shù)設(shè)計注塑模具的具體過程, 包括點云濾除、網(wǎng)格鋪面及網(wǎng)格面修補(bǔ)、創(chuàng)建邊界特征曲線、重建曲面、曲面品質(zhì)分析和建立 CAD模型。
在注塑模具開發(fā)制造過程中, 通常的流程是設(shè)計人員依據(jù)產(chǎn)品圖紙繪制三維模型, 并根據(jù)零件材料的性質(zhì)、設(shè)備的要求進(jìn)行工藝修改 ,經(jīng)計算機(jī)軟件處理后生成數(shù)控加工設(shè)備的 NC文件 , 這種設(shè)計模式稱為預(yù)定模式 。實際生產(chǎn)中 ,在只有實物樣件、沒有可參考圖紙的情況下 , 由于注塑模具各面之間常采用圓滑過渡 ,部分制品的外形是由多個復(fù)雜的不同空間曲率的曲面連接而成, 用傳統(tǒng)的方法很難測量, 無法采用預(yù)定模式進(jìn)行設(shè)計。如果沒有 CAD數(shù)字模型,就無法使用 CAD/CAM、多軸加工中心等先進(jìn)的加工手段 。所以 , 設(shè)計人員需要通過一定的途徑測量實物信息并轉(zhuǎn)化為 CAD數(shù)字模型, 這就應(yīng)用到了逆向工程技術(shù) 。筆者以汽車儀表盤注塑模具為例, 介紹 CATIA逆向工程技術(shù)在注塑模具設(shè)計中的應(yīng)用 。
逆向工程是指用一定的測量手段對實物或模型進(jìn)行測量, 根據(jù)測量數(shù)據(jù)通過三維幾何建模的方法重構(gòu)實物 CAD模型的過程.
逆向工程要求按照產(chǎn)品的測量數(shù)據(jù)建立與現(xiàn)有CAD/CAM系統(tǒng)完全兼容的數(shù)字模型 , 這是逆向工程的最終目標(biāo)。測量數(shù)據(jù)是逆向工程的第一個步驟 ,是數(shù)據(jù)處理、模型重建的基礎(chǔ)。目前最常用的點數(shù)據(jù)的采集設(shè)備有三坐標(biāo)測量機(jī)、三維激光掃描機(jī) 、多軸關(guān)節(jié)式機(jī)械臂等。
點云獲取后,重構(gòu)曲面的品質(zhì)客觀上取決于所選用的逆向工程軟件的功能。逆向工程軟件主要完成點云處理、曲線處理和曲面處理 3項功能, 常用的專業(yè)點云處理軟件有 EDS公司的 Imageware, RaindropGeomagic公司的 Studio, DelCAM公司的 Copy-CAD, PTC公司的 ICEMSurf、Pro/Designer(CDRS)、Pro/Scantools等。
Imageware等專業(yè)軟件在處理點云數(shù)據(jù)時工作速度快,可以較容易地進(jìn)行線 /面的擬合, 然而軟件本身所提供的曲線 、曲面創(chuàng)建工具較少 ,因此擬合得到的線和面還需要在 UG等通用三維 CAD/CAM軟件中進(jìn)一步修改。而單獨使用 Pro/E、UG等軟件讀取、處理點云數(shù)據(jù)時 ,快速讀取幾十萬甚至上百萬個點的數(shù)據(jù)量是比較困難的 。因此 ,在具體工程設(shè)計中,往往采用專業(yè)軟件進(jìn)行點云數(shù)據(jù)處理,得到基本控制曲線 ,然后導(dǎo)入 UG或 Pro/E等三維軟件來構(gòu)造曲面、創(chuàng)建實體。
CATIA軟件是法國達(dá)索公司與美國 IBM公司共同開發(fā)的具有工業(yè)領(lǐng)先水平的 CAD/CAE/CAM軟件包。它在曲線 、曲面造型方面具有獨特的優(yōu)勢,比如其特有的高次 (能達(dá)到 15)Bezier曲線曲面功能,能滿足特殊行業(yè)對曲面光滑性的苛刻要求 。CATIA軟件包含點云處理、實體造型、曲面造型 、數(shù)控加工等模塊 ,完全可以在一個軟件里對點云進(jìn)行刪除 、過濾 、創(chuàng)建特征線、鋪面 、修補(bǔ) 、曲面品質(zhì)分析等操作,得到高質(zhì)量曲面 , 并將曲面轉(zhuǎn)換成實體 , 而后生成刀路軌跡用于數(shù)控加工 。
CATIA逆向工程使用數(shù)字曲面編輯器 (DigitizedShapeEditor, DSE)、創(chuàng)成式外形 設(shè)計(GeneraiveShapeDesign, GSD)、快速曲面重建 (QuickSurfaceReconstruction, QSR)、自由曲面造型 (FreestyleShaper, FSS)等模塊來進(jìn)行逆向操作。
DSE模塊可用來處理點云文件 ,該模塊可以對點云進(jìn)行導(dǎo)入導(dǎo)出、分析過濾、網(wǎng)格鋪面 、繪制交線等操作 。對于分塊掃描的大型零件, DSE的分割拼接功能可以對點云文件依據(jù)對準(zhǔn)球 (測量點云數(shù)據(jù)時人為設(shè)置的小圓點, 作為后續(xù)工作兩部分點云對齊的基準(zhǔn))進(jìn)行拼接 , 將各塊點云數(shù)據(jù)合并為一個整體的零件點云 。使用 DSE模塊的最主要目的是通過對零件點云數(shù)據(jù)的分析、處理,從而獲得點云網(wǎng)格面特征交線,這是正確擬合曲面的基礎(chǔ) 。
QSR模塊可以將 DSE處理后得到的點云網(wǎng)格面特征交線進(jìn)一步轉(zhuǎn)變?yōu)榭臻g曲線, 使用曲面擬合命令, 以點云為參考、以空間曲線為基礎(chǔ)擬合得到高質(zhì)量曲面。其帶有的曲線分析工具可以分析空間曲線與點云網(wǎng)格面特征交線之間的誤差 。
GSD和 FSS模塊是使用 CATIA進(jìn)行三維曲面設(shè)計的主要工作平臺, 在平臺中可使用線架和表面特征快速建立從簡單到復(fù)雜的任意形狀曲面 ,這兩個模塊有大量創(chuàng)建和編輯曲面的設(shè)計工具 。在逆向設(shè)計中 ,主要是應(yīng)用這兩個模塊擬合和拼接曲面的功能, 形成完整的結(jié)構(gòu)外形 ;同時對孔 、筋 、圓弧等細(xì)節(jié)部分正向重建 。 FSS模塊的曲面分析功能可用于所有類型的曲線 、曲面分析 ,將重建的擬合曲面與點云或網(wǎng)格面進(jìn)行曲面分析 ,可以得到誤差分析圖,便于驗證重建曲面的正確性 。
簡單外形的零件一般采用 DSE及 QSR兩個模塊即可完成曲面的構(gòu)建;具有復(fù)雜外觀及有多孔、多筋的復(fù)雜零件,在 DSE及 QSR處理得到整體曲面結(jié)構(gòu)后, 還需要在 GSD和 FSS等模塊里進(jìn)行細(xì)部結(jié)構(gòu)的重建與修飾,最后生成的實體在 FSS模塊里進(jìn)行曲面品質(zhì)分析。
該儀表盤由需求方提供模具生產(chǎn), 沒有圖紙或數(shù)字化模型。由于注塑材料的腐蝕,使用一定時間后模具型腔部分尺寸發(fā)生變化,造成制品安裝尺寸超差。但該模具最初驗收時試模的樣件還在, 因此可以采用逆向工程重建零件數(shù)字化模型。
采用臺灣智泰公司生產(chǎn)的三維激光掃描機(jī)對樣件的點云數(shù)據(jù)進(jìn)行采集 。于產(chǎn)品外形限制, 將樣件分段掃描,整個點云文件分成 5部分。筆者以左側(cè)面的點云處理為例進(jìn)行逆向操作說明 。
在逆向工程中 ,用戶從測量儀器獲得的點云數(shù)據(jù)數(shù)量非常龐大,通常數(shù)據(jù)之間沒有顯式的幾何拓?fù)潢P(guān)系,包括大量無用數(shù)據(jù),這會降低電腦的處理速度,需要進(jìn)行處理來減少點云數(shù)據(jù)的數(shù)量。點云處理的原則是在曲面變化平緩的部位取點的密度可稀疏,在曲率變化較大的部位及細(xì)節(jié)部位密集取點 ,如此一來需處理的點的數(shù)量就會變少。在 CATIA中 ,可以使用刪除和濾除的方法去除的多余噪點。
網(wǎng)格面的大小可以通過對 “Neighborhood”參數(shù)進(jìn)行調(diào)節(jié) ,其數(shù)值為一個圓球半徑 ,在點云中只要某3個點在圓球半徑范圍內(nèi), CATIA就會以此 3點為頂點建立一個三角網(wǎng)格面。因此鋪面又稱為三角網(wǎng)格化 。網(wǎng)格的大小應(yīng)以網(wǎng)格面上有破洞但較少為原則,如果參數(shù)選取過大, 則會造成網(wǎng)格面上細(xì)部結(jié)構(gòu)的丟失 ,不能完整重建曲面。破洞可以應(yīng)用 “網(wǎng)格面修補(bǔ) ” (FillHoles)命令進(jìn)行修補(bǔ) 。點云鋪成了“網(wǎng)格面 ”,但這種多邊形面片(Polygon)是由成千上萬個大小不等的三角面構(gòu)成 ,并非通常意義上的曲面 ,不能為其它模塊直接編輯。
鋪面完成后 ,進(jìn)入 QSR模塊工作臺, 將邊界交線轉(zhuǎn)化為特征曲線。特征曲線應(yīng)滿足曲線二階幾何連續(xù)和曲率變化均勻的要求 ,并且在保證曲線與網(wǎng)格面擬合的前提下,最大程度地減少控制點的數(shù)量 、降低曲線的階次 ,以保證構(gòu)成曲面的曲線控制點的均勻、一致、整潔, 否則將會出現(xiàn)曲面扭曲的現(xiàn)象 。
根據(jù)以上操作獲得的特征曲線可以使用 QSR模塊中的 “曲面擬合 ”(Powerfit)命令重建曲面, 也可以使用 GSD和 FSS模塊中構(gòu)建曲面的各種命令 , 如放樣 (Loft)、掃掠 (Sweep)、橋接曲面(FreestyleBlendSurface)等來實現(xiàn)曲面的重建 。
利用 CATIA的自由曲面造型 (FreeStyle)模塊提供的多種分析工具可以分析重構(gòu)曲面的各種品質(zhì) ,如點云數(shù)據(jù)與重構(gòu)曲面誤差分析、等照度分析等 。由分析結(jié)果可知, 重構(gòu)曲面與點云數(shù)據(jù)誤差在 ±0.2 mm以內(nèi) , 大的誤差都分布在邊緣 , 后期修飾美化后可以減小 ;曲面曲率連續(xù) ,曲率變化均勻,符合產(chǎn)品要求。
各部分點云分別處理后整體拼合修飾得到圖最后 CAD模型。模型經(jīng)過工藝修改, 利用CATIA自帶的編程模塊生成走刀加工 NC代碼文件,加工成模具后一次試模成功,所制儀表盤零件完全符合上游廠家的要求。
目前 ,模具行業(yè)越來越多的業(yè)務(wù)是需要根據(jù)客戶提供的樣件制造出模具, 基于原型或?qū)嵨锏哪嫦蚬こ桃蚱淇旖莸拈_發(fā)方式, 特別是對于沒有原始幾何信息的零件 ,逆向工程是完成零件精確幾何造型的重要手段,應(yīng)用 CATIA逆向工程這一先進(jìn)的設(shè)計手段 ,可以大大提高注塑模具設(shè)計、生產(chǎn)效率, 降低制造成本 。