喜歡就充值下載吧。資源目錄里展示的全都有，下載后全都有，CAD圖紙均為可自行編輯，有疑問(wèn)咨詢QQ:1304139763
================
喜歡就充值下載吧。資源目錄里展示的全都有，下載后全都有，CAD圖紙均為可自行編輯，有疑問(wèn)咨詢QQ:1304139763
================
本科生畢業(yè)設(shè)計(jì)（論文）翻譯
英文原文名 SOME ASPECTS OF USING STL FILE FORMAT IN CAE SYSTEMS
中文譯名 應(yīng)用抽芯機(jī)構(gòu)在注塑模具的設(shè)計(jì)
學(xué) 院
專業(yè)班級(jí)
學(xué)生姓名
學(xué)生學(xué)號(hào)
指導(dǎo)教師
填表日期
二〇一 年 月
英文原文版出處： International Workshop CAE Systems And Technologies
譯文成績(jī)： 指導(dǎo)教師（導(dǎo)師組長(zhǎng)）簽名：
譯文：
STL文件格式在CAE系統(tǒng)某些方面的使用
彼特
科希策總部設(shè)在該技術(shù)大學(xué)的制造技術(shù)學(xué)院
摘要:
所謂的“STL”格式 ，涉及到“立體成型”，這是該法制造發(fā)明層狀的三維系統(tǒng)? 。產(chǎn)品的設(shè)計(jì)發(fā)展過(guò)程中，主要是電腦制作及電腦輔助設(shè)計(jì)（ CAD ）。電腦是用來(lái)繪制三維模型的物體的幾何形狀。同時(shí)，各種機(jī)能檢查，技術(shù)和其他屬性可以指出該模型作為信息交流的一部分。從CAD到物理設(shè)計(jì)要求建立在物理原型的基礎(chǔ)上，使得計(jì)算機(jī)模型驗(yàn)證的形式，配合和功能有了進(jìn)展。STL文件格式的快速成型方法，才使得CAD模型數(shù)據(jù)翻譯成檔案格式，也可以被解釋為快速成型機(jī)械，因而物理樣機(jī)才可以被創(chuàng)造。
關(guān)鍵詞：STL文件格式，三角網(wǎng)格化
由STL文件創(chuàng)造輸出記錄地?cái)?shù)據(jù)
大多數(shù)真正的和表面上的CAD軟件，以STL文件格式使設(shè)備的自動(dòng)化輸出自己的模式。大部分的這些CAD系統(tǒng)中，以STL文件為背景的輸出依賴于以下參數(shù)：
弦公差：弦偏差數(shù)值描述的是實(shí)際零件表面最大距離和鑲嵌表面的STL文件，如圖1所示。
角控制：定角控制會(huì)影響到鑲嵌曲線比較小的半徑以及CAD模型的總體規(guī)模。
STL文件格式的類型：STL文件中只包含相互銜接的三角形面片節(jié)點(diǎn)坐標(biāo)及其外法矢量，它有ASCLL碼和二進(jìn)制碼兩種形式。二進(jìn)制碼輸出形式所占用的空間比ASCLL碼輸出形式的小得多（6:1比例），而ASCLL碼輸出形式可以閱讀并能進(jìn)行直觀檢查。
圖1 STL的三角
隨著一系列的三角化數(shù)量增加及相對(duì)的三角形面積減小，開(kāi)始以更準(zhǔn)確地將形狀朝某個(gè)解析方面定義。部分構(gòu)造快速成型可能需要額外整理或措施，來(lái)規(guī)范尺寸的準(zhǔn)確性。如果面的解析過(guò)于低。操作者必須要衡量精度問(wèn)題與銼刀的尺寸。很多時(shí)候，操作者過(guò)度嵌入式的輸出設(shè)計(jì)，但是快速成型技術(shù)會(huì)限制特征點(diǎn)的大小，所以一個(gè)光斑大小的尺寸就可以包括許多方面與信息。
STL文件相當(dāng)于CAD模型的多面化，作為一種三角網(wǎng)絡(luò)化。三角化的數(shù)量和規(guī)模確定如何準(zhǔn)確地從表面網(wǎng)格化來(lái)描述成品，如圖2所示。
一）理想的形狀 二）在質(zhì)量不高的網(wǎng)格
三）中等質(zhì)量網(wǎng)格 四）高質(zhì)量的網(wǎng)格
圖2 STL-嚙合質(zhì)量
精度問(wèn)題，使輸出的模式在CAD到STL ，顯然是為導(dǎo)出兩個(gè)可能的原因。直接利用STL文件的快速成型方法和使用STL文件作為交換格式所要求的一些CAE軟件。無(wú)論是在開(kāi)發(fā)領(lǐng)域中，還是必須要考慮到以STL文件格式輸出模式，可能出現(xiàn)的幾種錯(cuò)誤類型：
棋盤形鑲嵌形成的錯(cuò)誤：在一些生成的三角形的模型中，位離是起始點(diǎn)表面和鑲嵌表面之間的更弦寬允許誤差。這種類型的錯(cuò)誤結(jié)果表明如圖3 a所示。
凸邊界誤差：在這種情況下，鑲嵌結(jié)果在一個(gè)較小的物體的地方，兩處左邊部分被刪除并第三部分效果在補(bǔ)充材料。這種類型的錯(cuò)誤結(jié)果表明如圖3 b所示。
翻轉(zhuǎn)的標(biāo)準(zhǔn)：要點(diǎn)是從一個(gè)三角形成未列入正確順序時(shí)，即通常有如下一些慣例（右手定則），結(jié)果要通過(guò)三點(diǎn)來(lái)使產(chǎn)品的兩個(gè)載體形成。有時(shí)候，正常的計(jì)算是在相反方向或者是不存在或無(wú)格式的錯(cuò)誤。必須予以糾正，這個(gè)錯(cuò)誤通常是很容易消除的。
兩個(gè)以上的三角形的每條邊（中間線節(jié)點(diǎn)）：基本的規(guī)則用來(lái)檢查對(duì)STL文件的有效性以確保一個(gè)三角形的每邊被認(rèn)同，只有兩個(gè)三角形的是沒(méi)有保存。這種類型的錯(cuò)誤是如圖3c所示。
封閉（孔）：鑲嵌執(zhí)行的是去尾的錯(cuò)誤，這個(gè)原因是同一時(shí)間在多個(gè)地點(diǎn)造成的這點(diǎn)。因此，三角形的形成，和目前在成品模型薄洞的。這種類型的錯(cuò)誤會(huì)經(jīng)常產(chǎn)生的，如果使用者選擇一個(gè)很小的弦偏差會(huì)出現(xiàn)這種類型的錯(cuò)誤，如圖3d所示。
截?cái)嗾`差：這些由電腦進(jìn)行預(yù)處理數(shù)據(jù)是錯(cuò)誤的補(bǔ)充。每次這些機(jī)器在不同的平臺(tái)上只有一定的精度，并且結(jié)果會(huì)造成的讀寫數(shù)據(jù)失誤。這些錯(cuò)誤通常是微不足道的。
其他錯(cuò)誤：這些錯(cuò)誤顯然是由于單純的CAD到STL轉(zhuǎn)換器因各種形式而造成的。
a）在一些生成的三角形的楷模，距離誤差
b）在凸邊界錯(cuò)誤
c）在中間線節(jié)點(diǎn)誤差
d）關(guān)閉錯(cuò)誤
圖3 STL的軟件輸出錯(cuò)誤
上述描述的錯(cuò)誤是軟件輸出模式所造成的。如果用一些快速成型機(jī)，有必要考慮其他類型的錯(cuò)誤，例如：
不當(dāng)矢量：矢量是轉(zhuǎn)型的曲線變成一系列的載體。在目前大多數(shù)快速成型制造過(guò)程中，鑲嵌轉(zhuǎn)換成非平面表面變成網(wǎng)格的三角形。相交的這些三角形與平行平面在z高度增量結(jié)果在載體驅(qū)動(dòng)激光或建立頭部控制器。不正當(dāng)方法矢量可導(dǎo)致的問(wèn)題，以快速成型機(jī)來(lái)移交檔案。
激光束或噴射厚度誤差：大多數(shù)進(jìn)程，無(wú)論是基于激光打印機(jī)或頭部為本必須以補(bǔ)償厚度的釋放系統(tǒng)為主。激光束厚度在航天器-登月艙適配器通常直徑是0.25毫米。
z效果：如果切片是由不斷層厚度和一個(gè)復(fù)雜的曲率的表面誤差造成的。切片過(guò)程中，在不斷的z高度遞增，可能導(dǎo)致丟失的平面或邊緣頂部表面的部分的失蹤。這是解決適應(yīng)分層過(guò)程中，以曲率的設(shè)計(jì)同層高度變化的根據(jù)。采用自適應(yīng)分層，表面光潔度質(zhì)量顯著上升。
在CAE系統(tǒng)應(yīng)用STL文件格式
STL文件格式開(kāi)發(fā)快速成型技術(shù)，但有些CAE軟件器件采用這種形式輸口的模式及預(yù)處理，然后再作分析。圖4表明，塑料封面上的電壓測(cè)試儀在設(shè)計(jì)Pro/E上，然后再分析了在三維模型速填助手軟件設(shè)備。參數(shù)的輸出表現(xiàn)在圖4 b ，c ，d如表1 所示。
表1 ：塑料罩-輸出到STL
名稱
弦高度
角度控制
構(gòu)造三角化的數(shù)量
二進(jìn)制文件大?。ㄇё止?jié)）
Stl1 (圖 4b)
0,5
0,5
1492
74,684
Stl2 (圖 4c)
0,05
0,5
7676
383,884
Stl3 (圖 4d)
0,01
0,5
25018
1,250,984
a ）設(shè)計(jì)模型（Pro/E）
b ）在STL文件（弦偏差=0.5）
c） STL文件（弦偏差=0.05）
d ）在STL文件（弦偏差=0.01）
圖4生成STL文件在Pro/E系統(tǒng)
三維模型速填助手允許研究的生產(chǎn)參數(shù)包括如：熔體前沿推進(jìn)，注射壓力所需的正確填充，鉗力，壓跡，樹(shù)脂溫度填充過(guò)程中，等待一時(shí)間以冷卻后澆注，氣泡，熔接線的定位等?；诟鶕?jù)這個(gè)分析，可以作出結(jié)論，對(duì)設(shè)計(jì)性能的塑料蓋技術(shù)。生成STL文件，為使分析在三維模型要求：
質(zhì)量嚙合時(shí)的水平，保持起始位置的設(shè)計(jì)部分。
最佳人數(shù)三角形形成過(guò)程中嚙合。
設(shè)計(jì)模型是網(wǎng)狀沒(méi)有錯(cuò)誤。
清楚的由圖4所示，STL的輸出如圖4b所示不符合標(biāo)準(zhǔn)，用數(shù)據(jù)分析。由于設(shè)計(jì)出的一部沒(méi)有跟上，所以選擇可以從輸出口表現(xiàn)在數(shù)字第4 c ，d在這種情況下，無(wú)論外觀設(shè)計(jì)進(jìn)行了測(cè)試，在軟件DeskArtes ，即專門工作與STL文件。它提供了一部份很多有用的選項(xiàng)是不常見(jiàn)的標(biāo)準(zhǔn)的CAD系統(tǒng)。打開(kāi)DeskArtes例如：手動(dòng)和自動(dòng)更正 STL文件，自動(dòng)核對(duì)，生成STL文件對(duì)可能出現(xiàn)的其他錯(cuò)誤。
DeskArtes是一個(gè)以快速成型用于橋梁，民航處的軟件并且是芬蘭軟件，包括文件格式轉(zhuǎn)換，更正的STL ，分層算法和支距測(cè)法 。其他類似的工具，可用來(lái)彌補(bǔ)CAD與快速成型技術(shù)是眾多的漏洞，如CIDES，Bridgeworks ， ADMesh ，形狀SolidView ， Brockware ， Majics ，Surfacer ，調(diào)整STL及其他。輸出STL文件顯示如圖4c ，d所示進(jìn)行檢查 DeskArtes作出結(jié)論，其中的設(shè)計(jì)更適合用在三維模型軟件。 DeskArtes界面如圖5 所示。
圖5 DeskArtes軟件設(shè)備
在分析的基礎(chǔ)上執(zhí)行的DeskArtes軟件設(shè)備，它分析說(shuō)，STL輸出表現(xiàn)在圖4d超額 ，既考慮輸出含有一些細(xì)微的輸出錯(cuò)誤，這是有可能加以調(diào)整，這是決定直接在DeskArtes由自動(dòng)更正選項(xiàng)。由于這一事實(shí)上，STL的輸出表現(xiàn)在圖4c是最好的，所有產(chǎn)生的STL輸出檔案將用于在三維模型快速填補(bǔ)。由分析這個(gè)例子的結(jié)果，在三維模型顯示如圖6 。
圖6a顯示的結(jié)果，熔體前沿的推進(jìn)，這是重點(diǎn)考慮的因素，如圖6b所示樹(shù)脂溫度冷卻后澆注。圖6c表明可能位置有氣泡，并圖6d顯示的位置可能有熔接線，分析后重要的誤差在最后一部充模，即必須加以考慮，設(shè)計(jì)模具的部分才真正組成。此分析的基礎(chǔ)上，操作者還可以在現(xiàn)實(shí)條件作決定對(duì)可用性設(shè)計(jì)模型做測(cè)試。
a）熔體前沿推進(jìn)
b）在溫度
c）有氣泡
d）熔接線
圖6架C -模具分析
STL文件格式是常用的文件格式，CAE技術(shù)的應(yīng)用完全取決于塑料的分析，因?yàn)榻Y(jié)構(gòu)的STL嚙合是適合的數(shù)學(xué)描述模具潤(rùn)滑油問(wèn)題的分析。利用這種文件格式，有幾個(gè)明顯的優(yōu)勢(shì)，為塑料設(shè)計(jì)師和模具制造商，因?yàn)镾TL的一個(gè)標(biāo)準(zhǔn)格式，當(dāng)它需要由設(shè)計(jì)過(guò)程快速制作成型的情況下可用快速成型方法。
工作與數(shù)據(jù)，然后將其用于快速成型系統(tǒng)。這一部分是建立在CAD程序，然后再輸入到STL文件格式。CAD系統(tǒng)往往支持，也與快速成型設(shè)備，但人們普遍更適合使用專門的軟件，其中配備了快速成型機(jī)。 STL文件處理通過(guò)分層處理程序產(chǎn)生一個(gè)填充輪廓稱為一個(gè)SLI文件。那么支持和SLI的部分合并形成一個(gè)V文件，它可以用來(lái)與其他三個(gè)具體過(guò)程文件（俄，林巨成）來(lái)驅(qū)動(dòng)的SLA （立體成型設(shè)備） ，并建立了原型。
結(jié)論
STL的是一個(gè)標(biāo)準(zhǔn)的輸出文件格式，CAD軟件以及多個(gè)三角化網(wǎng)格用戶可自定義。有必要校準(zhǔn)之間的準(zhǔn)確性和文件大小的設(shè)計(jì)型號(hào)。測(cè)繪任何曲面與平面三角形（面）的意思是很多小面需要有一個(gè)良好的配合，以得到完整的曲線，但另一方面又有非常龐大的文件很難處理其他CAE軟件或快速成型。常見(jiàn)的翻譯從建模格式到STL子節(jié)點(diǎn)的缺陷，因此，完整的STL三角化數(shù)據(jù)模型通常利用特殊的軟件檢查之前，檔案是用在其他軟件或建立一個(gè)快速原型物體。小錯(cuò)誤可以自動(dòng)更正，但大斷層需手工操作加以修整。軟件錯(cuò)誤，影響使用STL文件格式很多，由于多方面因素影響，許多嘗試控制這些錯(cuò)誤已被公布或有效的被共有，但有一點(diǎn)為了保持程序的控制，很好的了解各種錯(cuò)誤和其來(lái)源是需要。
參考文獻(xiàn)：
[1] Barton, S.: Coin Acceptors Combines C-Mold Advanced Mesh Express and Productivity Solutions to Make Big Impact. In: C-Mold News, Vol.12, No.3, 10/1999
[2] Marcincin, J.N.: Tendencie vo vyvoji ?pickovych CAD/CAM/CAE systémov. Strojárstvo. Roc.3, c.11, 1999, str.36-37
[3] Marcincin, J.N.: Problematic of Rapid Prototyping from the CAD/CAM system connection point of view. In: Proceedings of the International Conference TOOLS′99, Zlín, 1999, pp. 135-138
SOME ASPECTS OF USING STL FILE FORMAT IN CAE SYSTEMS
Petík
Faculty of Manufacturing Technologies of the Technical University Ko?ice
with headquarters in Pre?ov
Introduction
The format called "STL", relates to "stereolithography" which is the method of layered manufacturing invented by 3D Systems?. Process of product design development is mainly performed using the computers and computer-aided-design (CAD). Computers are used to create 3D models of object’s geometry. Also, various physical, technological and other properties can benoted as an information part of the model. The progression from CAD to physical design requires building physical prototypes based on the computer model for validation of form, fit, and function.STL is file format of rapid prototyping method that allows translating the CAD model data into afile format that could be interpreted by rapid prototyping machinery, and thus physical prototype can be created.
Key Words : the STL file , the triangles
Notes to creating STL file output
Most of solid and surface CAD software devices enable automated export of their models to STL file format. In most of these CAD systems, the settings of STL export depend on following parameters:
Chordal Tolerance: Chordal tolerance numerically describes the maximum distance between the actual part surface and the tessellated surface of the STL file, as it is shown in Figure1.
Angle Control: Setting the angle control influences the tessellation of curves with relatively small radii in comparison to the overall size of the CAD model.
Type of exported STL file: In most systems, two types of exported STL files are allowed, binary and ASCII. The binary format is compressed and allows smaller file size, (6:1 ratio) whereas the ASCII format can be read and visually checked.
Figure 1 STL triangle
As the number of triangle increase and the relative triangle size decreases, the shape begins to be more accurate what is defined as facet resolution. Parts constructed by rapid prototyping may require additional finishing or may not measure to accurate dimensions if the facet resolution is too low. The user has to balance the accuracy issue with the file size. Often, the users over-tessellate exported design, but rapid prototyping technologies have limited feature spot sizes, so one spot size may include facets with useless information.
STL file represents surfaces of CAD model, as a mesh of triangles. The quantity and size of the triangles determines how accurately the surface mesh represents the product, as shown in Figure2.
a) Desired Shape b) Low Quality Mesh
c) Medium Quality Mesh d) High Quality Mesh
Figure 2 STL - quality of meshing
Accuracy issues, making the export of model created in CAD to STL is obviously performed for two possible reasons, direct use of STL file for rapid prototyping method and use of STL file as exchange format required by some CAE software. For both exploitation areas, it is necessary to take into account that exporting the models to STL file formats can be influenced by several types of errors:
Tessellation generation error: In some of the generated triangles of the model, the distance between origin surface and tessellated surface is more that chordal tolerance. This type of error is shown in Figure 3a.
Convex boundary error: In this case, the tessellation results in a smaller object where the two left segments are removed and the third segment results in added material. This type of error is shown in Figure 3b.
Flipped normal: The points that form a triangle are not listed in the correct order, that typically follows some convention (right hand rule) which results in the cross product of the two vectors formed by the three points. Occasionally, the computed normal is in the opposite direction or is non-existent or plains wrong, and must be corrected. This error is typically easy to correct.
More than two triangles per edge (mid-line nodes): The basic rule used to check the validity of the STL file to ensure that each edge of a triangle is shared by only two triangles is not kept. This type of error is shown in Figure 3c.
Closure (holes): The tessellation is performed with round-off errors and this causes one point to be at multiple locations at the same time. Thus, triangles are formed, and a thin hole is present in the finished model. This type of error if often generated if user selects a very small chordal tolerance and it is shown in Figure 3d.
Truncation errors: These are the errors added by the computers that preprocess the files. Each of these machines has only certain accuracy, and errors can result from reading and writing the files on different platforms. These errors are usually negligible.
Other errors: These errors are obviously caused as a result of pure CAD to STL converter and can have various forms.
a) tessellation generation error
b) convex boundary error
c) mid-line nodes error
d) closure error
Figure 3 STL software export errors
The above-described errors are the errors caused by software export modules. If using some of the rapid prototyping machine, it is necessary to consider other types of errors, such as:
Improper vectorization: Vectorization is the transformation of curves into series of vectors. In most current rapid prototyping processes, the tessellation converts non-planar surfaces into a mesh of triangles. The intersection of these triangles with parallel planes at z height increment results in the vectors that drive the laser or build head controllers. Improper method of vectorization can result in problems with transferring the file to rapid prototyping machine.
Laser beam or jet thickness error: Most processes, whether laser based or printer head-based have to compensate the thickness of the delivery system. Laser beams thickness used in the SLA is typically 0.25 mm in diameter.
Z effect: The error is caused if the slicing is performed by constant layer thickness and the curvature of the surface is complicated. Slicing process at constant z height increments may lead to missing planes or missing edges on top surfaces of parts. This is solved by adaptive layering process, with slice height changing in accordance to curvature of design. Using adaptive slicing, surface finish quality increases significantly.
Application of STL file format in CAE systems
STL file format was developed for rapid prototyping technology, but some CAE software devices use this format for import of models and their preprocessing before making the analysis. Figure4 shows plastic cover of voltage tester that was designed in Pro/Engineer system and then analyzed in C-Mold 3D QuickFill software device. Parameters of exports shown in Figure 4b,c,d are noted in Table1.
Table 1: Plastic cover - export to STL
Name
Chord Height
Angle Control
Number of triangles created
Binary file size
(kB)
Stl1(Figure 4b)
0,5
0,5
1492
74,684
Stl2(Figure 4c)
0,05
0,5
7676
383,884
Stl3(Figure 4d)
0,01
0,5
25018
1,250,984
a) Design model (Pro/E)
b) STL file (chordal tolerance = 0.5)
c) STL file (chordal tolerance = 0.05)
d) STL file (chordal tolerance = 0.01)
Figure 4 Generating STL files in Pro/Engineer system
C-Mold 3D QuickFill allows to study the parameters of cover production such as: melt front advancement, injection pressure required for correct filling, clamp force, pressure trace, temperature of resin during filling, time to cool after filling, air traps, orientation of weld lines and other. Based on this analysis, it is possible to make conclusions about the design properties of plastic cover in relation to its technology. Generating STL file for making the analysis in C-Mold requires:
Quality of meshing at level that keeps origin design of the part.
Optimal number of triangles created during meshing.
Design model is meshed without errors.
As it is clear from Figure4, STL export shown in Figure4b does not meet the criteria for using it for analysis, since the design of origin part is not kept. The selection can be performed from exports shown in Figures 4c,d. In this case both designs were tested in software DeskArtes, that is specialized for work with STL files. It provides many useful options that are commonly not a part of standard CAD systems. DeskArtes enables for example: manual and automatic corrections of STL files, automated check of generated STL files on possible errors and other.
DeskArtes is one of the available software that bridges the CAD to rapid prototyping machines, it is Finnish software that includes file format conversion, correction of STL, slicing, and offsetting. Other similar tools available to bridging between CAD and rapid prototyping are numerous, such as CIDES, Bridgeworks, ADMesh, Shapes, SolidView, Brockware, Majics, Surfacer, STL-Manager and other. Exported STL files shown in Figures4c,d were checked in DeskArtes to make conclusion which of the designs is more suitable for using in C-Mold software.
DeskArtes environment is shown in Figure5.
Figure5 DeskArtes software device
Based on the analysis performed in DeskArtes software device, it was analyzed that, STL export shown in Figure4d is over-tessellated, both considered exports contain some minor export errors, that are possible to be corrected directly in DeskArtes by AutoCorrect option. Due to this fact, it was decided that, the STL export shown in Figure4c is best of all generated STL export files to be used in C-Mold 3D Quick Fill. The examples of the results performed by analysis in C-Mold are shown in Figure6.
Figure6a shows the results of melt front advancement, which are important for considering the time of form filling. Figure6b shows resin temperature after filling. Figure6c shows possible location of air traps and Figure6d shows possible location of weld lines, what are important kinds of error in final part after mold filling, that have to be considered, before real design of mold components. Based on this analysis, the user can make the decision about usability of tested design model in real conditions.
a) melt front advancement
b) temperature
c) air traps
d) weld lines
Figure 6 C-Mold analysis
STL file format is often used file format in CAE applications that are determined for analysis of plastics, since the structure of STL meshing is suitable for mathematical description of the mold filling problem analysis. Using this file format has several advantages for plastic designers and mold-makers, since STL as a standard format for rapid prototyping methods can be used for quick making of prototypes in cases, when it is required by design process.
The work with data before their use in rapid prototyping systems . The part is built in the CAD program, and then exported into STL file format. CAD systems often support also work with rapid prototyping equipment, but it is generally more suitable to use specialized software by which is equipped the rapid prototyping machine. STL file is processed through a slicing program that produces a list of filled contours known as an SLI file. Then the support and part SLI are merged to form a V file, which is used with three other process specific files (.r, .l, .prm) to drive the SLA (stereolithography device) and build the prototype.
Conclusions
STL is a standard output format from most CAD software, and the number of triangles used can be user-defined. There is necessary to calibrate between accuracy and file size for most design models. Mapping any curved surface with flat triangles (facets) means that a lot of small facets are needed for a good match to a smooth curve, but on the other hand very large files are difficult to handle by other CAE software or by rapid prototyping machine. Commonly the translation from the modeling format to STL leaves a few flaws, and so the integrity of STL files is usually checked using special software before the files are used in other software or to build a rapid prototyped object. Small errors can be corrected automatically, but big faults have to be repaired manually. Software errors affecting using the STL file format are numerous due to a multiplicity of influencing factors. Many attempts at controlling these errors have been published or are available to the user community, but a good understanding of the various errors and their source is needed in order to maintain control of the process.
References:
[1] Barton, S.: Coin Acceptors Combines C-Mold Advanced Mesh Express and Productivity Solutions to Make Big Impact. In: C-Mold News, Vol.12, No.3, 10/1999
[2] Marcincin, J.N.: Tendencie vo vyvoji ?pickovych CAD/CAM/CAE systémov. Strojárstvo. Roc.3, c.11, 1999, str.36-37
[3] Marcincin, J.N.: Problematic of Rapid Prototyping from the CAD/CAM system connection point of view. In: Proceedings of the International Conference TOOLS′99, Zlín, 1999, pp. 135-138