基于FDM技术的3D打印机的重建与开发外文文献翻译、中英文翻译、外文翻译.doc
基于FDM技术的3D打印机的重建与开发外文文献翻译、中英文翻译、外文翻译
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International Conference on Manufacturing Engineering and Materials, ICMEM 2016,6-10 June 2016, Nov Smokovec, SlovakiaReconstruction and development of a 3D printer using FDM technologyKrisztin Kuna* a Kecskemt College Faculty of Mechanical Engineering and Automation Department of Vehicle Technology, 10 Izski st., Kecskemt 6000, HungaryAbstract This study, we detail the constructional selection of a machine, which operates with FDM technology. We outline the milestones of the reconstruction of the printer, the restoration of the technical documentations (Reverse Engineering), and then the calibrations and the measurement results. Based on what we have learned from the construction, we started to design our own FDM printer, which is a compact, user demand-driven device. 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the organizing committee of ICMEM 2016 Keywords: FDM; design; 3D printing; RE-RP; reconstruction;1. Introduction of the FDM technology 1, 3, 4 3D printing is additive, which means it creates the desired form with a built-up manner. This means, that the body is built up as a thin layer without a preform. The applied materials are usually some kind of plastics. There are several methods of the 3D printing technologies depending on the layer creation manner. The FDM (Fused Deposition Modeling) 3D printing technology (Figure. 1.) works on an additive principle by laying down material in layers; a plastic filament is unwound from a coil to produce a part. The technology was developed by Scott Crump in the late 1980s. The FDM technology needs software which processes an STL file (stereolithography file format). After that we have to slicing the model with another program for the build process. If required, support structures may be generated. The model is produced by extruding thermoplastic material to form layers as the material hardens after extrusion from the nozzle. A plastic filament is unwound from a coil and an extrusion nozzle turn the flow on and off. There is a worm-drive that pushes the filament into the nozzle at a controlled rate. The nozzle is heated to melt the material. It can be moved in both horizontal and vertical directions by a numerically controlled mechanism. The nozzle controlled by a computer-aided manufacturing (CAM) software package, and the part is built from the bottom up, one layer at a time. The stepper motors are employed to move the extrusion head. The mechanism uses an X-Y-Z rectilinear movement. 1.1. Advantages-Disadvantages of the technology The FDM printing technology is very flexible, and it is can handle with the small overhangs on the lower layers. The FDM generally has some restrictions and cannot produce undercuts without support material. Many materials are available, such as ABS and PLA among many others, with different trade-offs between strength and temperature properties. We picked the most advantageous technology from the 3D printing methods, while considering the printing quality and the level of difficulty of the building process. This technology is the FDM, i.e. the 3D extrusion. Thereafter, the next main concern was the structure of the 3D printer, more specifically: what structure we want to conform to.Fig.Conceptual sketch of FDM2. Constructional selection 1 The most important premise is the mobility, in order to ensure a simple and fast usage of the 3D printer. Because of the mobility, it is essential to have a massive frame to prevent the printer for any kind of damage during the transportation. It was intented to make the printer out of simple parts to facilitate easy assembly and fast maintenance. Furthermore, it was an expection to make the printer compatible with electronic parts, such as standardized limit switches and to be able to print PLA and ABS. The selected construction from the founded printers was the FELIX 2.0. This printer satisfied our premises the most. We introduce the building of this printer in the following phase. Before we started building the printer itself, we made a sketch of which parts should be bought and which parts could be manufactured by us. Thanks to the manufacturer, building kits were available, so the project could be more cost-efficient, than we had bought the complete printer. By using the above mentioned, 3D printed parts and the own made ones, we created the FDM printer based on the construction of Felix Ltd., which is shown on Figure 2.Fig.2 The built FDM 3D printerWe wanted to make the 3D printer in a virtual version. The purpose of this was to measure the parameters of the printer in a 3D model form, while simulating digital manufacturing. Since we bought the printed parts from the official dealer, their documentations were missing. If there would be accurate models of every part, those could be used for manufacturing spare parts or even a second 3D printer. In order to implement this, we had to use Reverse Engineering, which helped us to get the original documentation and dimensions. The essence of the manner is detailed in the next phase.3. Reverse Engineering 1, 2, 5 Reverse Engineering is an engineering labour process, where we define the CAD geometry of a physically existing object with 3D digitalization. Reverse Engineering uses the end product to start off. Its purpose is reconstruction. Reverse Engineering is applied in the following cases: l If the new design is based on an existing part, l Hand-made master pattern, l Outdated” plans (no computer data, CAD drawing), l Part, tool reproduction, l Rapid prototype making. We could not have measure workpieces with complicated geometries with conventional measuring tools, since the caliper is not able to define complex geometries. In our case, the parts were only physical and the virtual documentations were missing. In order to make these parts re-manufacturable, we had to apply Reverse Engineering. Steps of Reverse Engineering: 1. Scanning, 2. Making a point cloud, 3. Coating, surface fitting, 4. Inspection, correction, 5. Manufacturing 3.1. Scanning Initially, we had to perform spatial scanning, alias 3D digitalization. The result of the scanning process was a point cloud, placed into a coordinate system. The CCD camera process was given for us, which is a non-contact technology. We did the measurement with a Steinbichler Optotechnik VarioZoom 200-400 3D scanner. With this manner, we were able to reproduce the virtual documentations of the existing parts. The technology is shown on the extrusion head holder unit (Figure 3.), but the other printed geometries are also made by the same manner.Fig.3 Extrusion head holder unitThe projector of the scanning device capable for accurate surface scanning projects black and white, parallel light strips onto the surface of the object, which are deformed there. The scanners CCD camera initializes the breakage of the reflected light strips. The computer evaluation system calculates the attitude of the lined-up strips and then makes a point cloud. 3.2. Preliminary processing of the point cloud after scanning For the final version of the cloud, we needed 34 photographs (Figure 4.), which were combined together by finding their corresponding points. When the point cloud has been completed, it was necessary to remove the parts which did not connect to the object. (clamping elements, workbench, risers, etc.)Fig.4 Matching the recordings: The first recording is on the left,while on the right we can see the assembly of the 34 pictures.3.3. Final processing of the point cloud The most commonly used manner of reproduction is the triangle STL file format coating, since it creates a simple and universal file format for every designing software. We approach the points of the point cloud with triangles (Figure 5.). The smaller the triangles, the more accurate the shape analysis. Fig. 5. Approximation of the points with trianglesOn the picture, we can see grey and blue surfaces at the same time. The grey surfaces give us an accurate picture of the surfaces of the part, while the blue ones refer to surface discontinuity. Here the scanning was unsuccessful, since the camera didnt get a proper view into these areas. 3.4. The usage of RapidForm XOR for creating a model The previously created model is not yet useable directly on CNC machining or 3D printing, since the triangles have not fit perfectly onto the point clouds during the coating process, which caused dimensional errors. The software of the scanning device analyzed these errors during the triangle-coating process according to Figure 6.Fig.6 The amount of errors occured during the triangle coating processWe imported the .STL file generated by the software of the scanner device to Reverse Engineering software (specialized on these purposes). The name of the software is: RapidForm XOR. We picked the base planes of the model. It is necessary to recognize during the usage of the software, that which steps did the previous designer follow to create the entire model. Thereafter, we used the Mesh Sketch command, which provided us cross-sectional sketches of the surface. We round drawed these sketches with approximate lines, then the real mesh size of the sketch has become definable after dimensioning them. We reconstructed the 3D CAD model with the help of the sketches (Figure 7.). We used the usual basic commands of a 3D modeling software, namely the Extrude and the Cut commands. By the result of these processes, we got the CAD model, which dimensions are changeable and measurable on every surface Fig. 7. CAD model of the extrusion head unit holder3.5. Virtual prototype After using the manner presented in the 3.4. subsection we had complete 3D models of every printed part. After this, we created the virtual construction of the printer in an assembly environment (Figure 8.) by using Autodesk Inventor. In this way, we were able to measure the parameters of the printer in 3D model format as well, and we also found it capable for a digital manufacturing simulation.Fig.8 3D assembly of Felix 2.04. Constructional design of a parameterized workspace printing unit 1 The biggest disadvantage of the built construction emerged from the dimension of the printing area. The area of the tempered, heated workbench is not isolated from the environment, so there is no chance of increasing the dimensions of the printing area, because of the increased heat loss. Further problem was the transverse movement (Y) of the bench based on the below mentioned reasons: l A bench, bigger than a certain size, and the movement of a printed object would overwhelm the stepper motor of the shaft. l Further problem can be, that the overall dimension of a closed constructional frame would be increased in both directions by a formation like this. By keeping this perspectives in mind, we started to design an own printing unit. Our goal was to create a structure, where the extrusion head unit does the X-Y movement at the same time. The way of printing without a supporter unit also highly restricted the feasible geometries, since the undercut surfaces collapsed after the printing process. That is why we wanted to make the designed printing unit out of two extrusion head units. 4.1. Design of the extrusion head unit Important requirement is the running on linear bearings as well as the holding of the two extruders. The easy strain adjustment of the leading belt is an advantageous attribution as well as the adjustment of the grip during the retortion done by the motor. The diameter of the string is 1,75 mm. 4.1.1. The retortion unit We started the design with the retortion unit, because it was relevant to know what is the distance between the output shafts of the two motors, when placing them next to each other. The mesh size of the retortion unit is based on this dimension, where we took into consideration the dimensions of the output PTOs (5), the standardized bearing dimensions (8), and also the thickness of the string (1,75). By placing the motor housing next to each other demanded the need of guide cylinders (20,55) on each of the shafts. The mesh size is shown on Figure 9. These dimensions also directly affected the distance between the extruders. . Fig. 9. Mesh size structure Fig.9 Mesh size structureIt is also relevant to ensure an easy removal of the string at the retortion unit. We managed to solve this by clenching the string with the guide cylinder and the bearings both can be found at the end of the motor. In this way we ensure the holding. We designed the retortion unit according to these perpectives, which model is shown on Figure 10.Fig.10 Model of the retortion unit4.1.2. Structure of the extrusion head unit Since the distance between the extruders axes has been defined during the evolving of the retortion unit, we started building the holder unit by using these dimensions. Important perspectives were: l Minimalization of the dimensions, l Placement of the linear bearings, l Ensurance of the cooling for the protection of the elements connected to the heated units, l The slight adjustment of the strain on the leading belt. We kept in mind all requirements during the design of the extrusion head unit (Figure 11.). The head units design ensures the accurate guidance, fast material flow as well as cooling. Fig. 11. The extrusion head unitWe displaced the axes of the leading linear bearings in order to maintain an accurate guidance and the carrying capacity of the parts, so while it carries the weight of one motor, the other two prevent the transverse axial movement. We actualized the cooling in the following ways: l We used standardized fans l We separated the heated unit with porcelain sleeves l We created heatsinks on the stem of the extrusion unit l We created surfaces on the extrusion head holder unit for deflecting the air to the required place. l We designed an air control surface onto the workbench for instant cooling of the freshly printed material.Fig.12 Cooling around the heated area4.2. Implementation of the X-Y movement with the new extrusion head unit The biggest challenge of the construction was to maintain two-axis movement of the head unit. Our goal was to create a paremetrized workspace, which replaces the movement of the bench and with a few modifications of certain values, it is possible to make an adequate printing area according to the desired demands. We achieved this by replacing the linear elements with beam (grinded) guided linear bearings on the X axis as well. We designed an assembly of the model (Figure 13.) in Inventor 2016 Pro software, where the entire construction refreshes itself when we modify a dimension on it, so everyone can adjust the coverage of the printing area on their own preferences. Fig. 13. The Assembly of the printing unitThe dimension driven parametrization works both on X and Y axes by changing the dimensions of the appropriate beam. The shafts are moved by separate electric motors on both sides along the X axis. The motors are connected in series. In this way the path that can be done is controlled by only one limit switch. (Figure 14.)Fig.14 The Assembly of the printing unit4.3. Belt tension We had to introduce the belt drive applied to the moving unit which ensures an accurate positioning. It is essential to keep the belt in the adequate tension in order to maintain the accurate guidance. For this, it is indispens able to strain the belt in the easiest way. The designed method oversimplifies the maintenance as well as the calibration. Figure 15. also shows the essence of the system in 3D. Fig. 15. Demonstration of the belt tensioning5. Summary We detailed the building process and the Reverse Engineering of a machine which operates with FDM technology. After the experiences, gained on the builded printer, we started to design an experimental printer unit, which correct the earliers deficiencies. The designed printing unit is a compact, user-friendly jog unit and a head-holder console. Our goal was to create a structure, where the extrusion head unit does the X-Y movement at the same time, and to be able to print support material. That is why we designed the printing unit with two extrusion head. In conclusion, we have designed a unit to be a great assembly of an existing or a whole new machine. References 1. K. Kun, I. Miskolczi. A. Fodor. 3D nyomtat ptse s fejlesztse. Gradus Vol 2, No 2 2015. p. 155-159. 2. J. Kodcsy, Zs. Pintr, P. Pokriva. Reverse Engineering mdszerrel ellltott felletek minsge. Kecskemt; 2003. p. 1-7. 3. J.G. Kovcs. Gyors prototpus eljrsok II. Gyakorlati megvalstsok. 2002. p. 103-107. 4. L. Morovic. Rapid technolgie. Rapid Technologies. In Automation and CA Systems in Technology Planning and Manufacturings. Pozna University of Technology, 2004, p. 177-183. ISBN 83-904877-8-0. 5. L. Morovic. A lzeres 3D szkennels. Fiatal mszakiak tudomnyos lsszaka. Kolozsvr; 2005. 185-188. p. ISBN 973-8231-44国际制造工程与材料会议，ICMEM 2016，2016年6月6日至10日，Nov斯莫科维奇，斯洛伐克基于FDM技术的3D打印机的重建与开发Krisztian库纳* a Kecskemt学院-机械工程和自动化学院-车辆技术系，10 Izski st.， Kecskemt 6000，匈牙利摘要在本研究中，我们详细介绍了使用FDM技术的机器的结构选择。我们概述了打印机重建、技术文档恢复(逆向工程)、校准和测量结果的里程碑。根据我们从建造设计中所学到的知识，我们开始设计我们自己的FDM打印机，这是一种紧凑的，用户需求驱动的设备。2016作者。关键词:FDM;设计;3 d打印;RE-RP;重建;1.FDM技术介绍3D打印是累加的，这意味着它以一种叠加的方式创建所需的形式。这意味着，打印体是没有预制的薄层。应用的材料通常是某种塑料。根据不同的图层创建方式，3D打印技术有多种方法。FDM(熔融沉积建模)3D打印技术(图1)通过将材料分层放置在“添加”原理上工作;将一根塑料灯丝从线圈上松开来制造一个零件。这项技术是斯科特克伦普(Scott Crump)在20世纪80年代末开发的。FDM技术需要处理STL文件(立体光刻文件格式)的软件。在此之后，我们必须使用另一个程序对构建过程中的模型进行分割。如果需要，可以生成支撑结构。该模型是通过将热塑性材料从喷嘴挤压后硬化而形成层状而制成的。塑料灯丝从线圈中解开，挤出喷嘴打开或关闭流量。有一个蜗杆驱动装置以可控的速度将灯丝推入喷嘴。喷嘴被加热以熔化材料。它可以在水平和垂直方向通过数控机构移动。喷嘴由一个计算机辅助制造(CAM)软件包控制，零件是自下而上的，一次一层。使用步进电机来移动挤出头。该机构采用X-Y-Z直线运动。1.1. FDM技术的优点与缺点该技术的优点-缺点FDM印刷技术非常灵活，可以处理下层的小悬垂。FDM通常有一些限制，并且不能在没有支持材料的情况下产生底价。许多材料是可用的，如ABS和PLA等，在强度和温度性能之间有不同的权衡。我们从3D打印方法中选择了最具优势的技术，同时考虑了打印质量和建筑过程的难度。这种技术就是FDM，即3D挤压。此后，下一个主要问题是3D打印机的结构，更具体地说:我们想遵循什么结构。图1 FDM概念示意图2.结构选择1最重要的前提是移动性，以保证3D打印机的简单快速使用。由于机动性，必须有一个巨大的框架，以防止打印机在运输过程中受到任何形式的损坏。它的目的是使打印机由简单的部件，方便组装和快速维护。此外，这是一个期望，使打印机兼容电子部件，如标准化的限制开关，并能够打印PLA和ABS。从创建的打印机中选择的构造是FELIX 2.0。这台打印机最符合我们的要求。我们将在下一个阶段介绍如何构建此打印机。在我们开始制造打印机之前，我们先画了一张草图，说明哪些零件应该买，哪些零件可以自己制造。多亏了制造商，建造工具是可用的，所以这个项目可能比我们买完整的打印机更划算。我们使用了上述的3D打印部件和自己制作的部件，在Felix Ltd.的基础上创建了FDM打印机，如图2所示。图2 FDM 3D打印机我们想在虚拟版本中制作3D打印机。其目的是在模拟数字化制造的同时，以3D模型的形式测量打印机的参数。因为我们从官方经销商那里买了印刷零件，他们的文件就不见了。如果每个零件都有精确的模型，这些模型就可以用来制造零部件，甚至可以用来制造第二台3D打印机。为了实现这一点，我们必须使用逆向工程，这帮助我们获得原始文档和尺寸。方式的本质将在下一阶段详细说明。3.逆向工程125逆向工程是一种工程劳动过程，我们通过三维数字化来定义一个物理存在对象的CAD几何形状。逆向工程以最终产品为起点，其目的是重建。逆向工程主要应用于以下几种情况:l l如果新的设计是基于现有的部分，l l手工制作主图案，l l“过时”的计划(没有计算机数据，CAD绘图)，l l零件，工具复制，l l快速原型制作。我们不能用传统的测量工具测量复杂几何形状的工件，因为卡尺不能定义复杂的几何形状。在我们的例子中，这些部件只是物理的，而虚拟的文档却丢失了。为了使这些部件可再制造，我们必须应用逆向工程。逆向工程步骤:1. 扫描2. 做点云3. 涂料、表面拟合4. 检查、调整5. 制造业3.1扫描首先，我们需要进行空间扫描，别名三维数字化。扫描过程的结果是一个点云，放置到一个坐标系统。给出了一种非接触式CCD摄像工艺。我们使用Steinbichler Optotechnik VarioZoom 200-400 3D扫描仪进行测量。通过这种方式，我们能够复制现有部分的虚拟文档。该技术显示在挤出头支架单元上(图3)，但其他打印几何图形也以同样的方式制作。图3 挤压头固定装置扫描设备的投影仪能够进行精确的表面扫描将黑白平行的光条投射到物体的表面，而物体的表面是变形的。扫描仪的CCD摄像机开始破坏反射光条。计算机评估系统计算出条形线的姿态，然后做出点云。3.2扫描后点云的初步处理对于云的最终版本，我们需要34张照片(图4)，通过找到它们对应的点将它们组合在一起。当点云已经完成，有必要删除那些没有连接到对象的部分。(卡紧元件、工作台、隔水管等)图4 匹配:第一张在左边，而在右边我们可以看到34张图片的组合。3.3最后处理点云最常用的复制方式是三角- STL文件格式-涂层，因为它为每个设计软件创建了一个简单而通用的文件格式。我们使用三角形来接近点云的点(图5)。三角形越小，形状分析越准确。图5 用三角形逼近这些点在这幅画上，我们可以同时看到灰色和蓝色的表面。灰色的表面给了我们一个准确的零件表面的图像，而蓝色的表面是指表面的不连续。这里的扫描是不成功的，因为相机没有得到一个适当的视野进入这些区域3.4使用RapidForm XOR创建模型之前创建的模型还不能直接用于数控加工或3D打印，因为在涂层过程中，三角形并没有完全贴合到点云上，导致了尺寸误差。扫描装置的软件根据图6分析了三角涂层过程中的这些误差。图6 三角涂层过程中出现的误差量我们导入了. stl文件-由扫描设备的软件生成-反向工程软件(专门针对这些目的)。软件名称为:RapidForm XOR。我们选择了模型的基本平面。在使用软件的过程中，有必要认识到之前的设计师在创建整个模型时遵循了哪些步骤。之后，我们使用了Mesh Sketch命令，它提供了我们表面的横截面草图。我们用近似的线条画出这些草图，然后在标注尺寸后，草图的实际网格尺寸就可以确定了。我们借助草图重建了3D CAD模型(图7)。我们使用了3D建模软件中常用的基本命令，即挤压和剪切命令。通过这些过程的结果，我们得到了CAD模型，该模型的尺寸是可变的，在每个表面上都是可测量的。挤压头单元支架的CAD模型图7 挤压头单元支架的CAD模型3.5虚拟样机在使用3.4中给出的方式之后。分段-我们有完整的3D模型的每个打印部分。在此之后，我们使用Autodesk Inventor在组装环境中创建打印机的虚拟构造(图8)。通过这种方式，我们能够测量3D模型格式的打印机的参数，我们也发现它能够进行数字化制造模拟。图8 Felix 2.0的3D装配4.参数化工作空间打印单元1的结构设计建筑结构的最大缺点是印刷区域的尺寸。回火、加热工作台的面积并没有与环境隔离，所以没有机会增加印刷面积的尺寸，因为增加了热损失。进一步的问题是工作台的横向移动(Y)，原因如下:l l一个工作台，大于一定的尺
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