reprap-granule-extruder-tudelft1

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2 Ṫhe RepRap project In the beginning of this project, a literature review was carried out. The goal of this review was to gain some insight in the RepRap project and to determine a goal for the project. After the review, the subject of creating a recycling add-on for the printer was determined. An extract of the review, with a focus on the parts about the RepRap project, can be found in this chapter. The RepRap 3D printer project is, according to their creators, “a project to save the world… or at least to improve it”. The project is initiated by Adrian Bowyer, member of the Department of Mechanical Engineering at the University of Bath, United Kingdom 1 . The first RepRap machine was the Darwin, completed in October 2008 2 , see figure 2.1. Recently a new version, the Mendel, was released, having various improvements like a bigger print area, simpler assembly and a higher efficiency 3 . At Delft University of Technology, a Darwin printer created from a Bits from Bytes kit, is assembled by a previous project group. Bits from Bytes is an online reseller, selling complete RepRap kits made from plexiglass 4 . The available printer is a RepMan version 3.1. Building a complete printer costs about $400 when producing all the parts at home, while commercial kits are available starting from $1200. 2.1 RepRap philosophy No current engineering manufacturing process is capable of exponentially expanding production, because none use self-replication. John von Neumann was the first person to propose self-replicating machines back in the 1960s 5 . The RepRap is built on the idea that anyone could manufacture products, anywhere in the world. It is an open-source project, with the goal to enable relatively low-cost 3d printing. This is realized by engineering a printer, using mostly simple standard components and of course the fact that both soft- and hardware are open-source. The hardware blueprints are available for free, so parts for the pinter can be produced at home. This leads to the next characteristic of the RepRap. Its name stands for REPlicating RAPid-prototyper: this means that the machine should be able to print the parts for a new printer. At this moment the RepRap can fabricate up to 50% of its own components 2 . To create the first RepRap of a family one can use a so called RepStrap 6 . Figure 2.1 - The Darwin RepRap The RepStrap project has been set-up to help people build there own RepRap machine without using an already existing RepRap machine. The goal of RepStrap is that anyone (no matter what education) can build his own complete RepRap only using tool and materials commonly available. Once someone has built his own RepRap machine, the printer is able to replicate itself and produce other useful parts. In this philosophy, the number of RepRap printer should be able to grow exponentially. 2.2 Working principle The machine is composed of a frame, built out of standard thread rods and printed parts. A platform, where the parts are meant to be built on, can move in the frame along the vertical axis. A stepper motor drives this platform up and down by using movement threads. On top of the frame rests the print head, which extrudes a thin layer of molten plastic to form a layer on the base platform. The extruder is moved along the horizontal axes by two stepper motors and toothed belts. 6 | Prototyping Lab (IO3028) - RepRap Recycle Add-on
2 | The RepRap project Fused deposition modeling The object that is printed is built up layer by layer, with the platform moving down as each layer is finished 7 . This form of rapid prototyping is also known as fused deposition modelling. From studies, factors that influence the strength of a sample part, created with fused deposition modelling, appeared. Layer thickness, sample orientation, raster angle raster width and the air gap were of significant influence 8 . Assembly To collect all the parts necessary for building a RepRap, the Bill of Materials (BOM) can be accessed through the project’s official website. The BOM divides the RepRap into different subassemblies, based on function. The main frame with the XYZ movement is called the Cartesian Robot; other subassemblies are the Thermoplastic Extruder and different drivers and controllers for the RepRap and its motors. For all parts that cannot be build by a RepRap, detailed specifications and professional suppliers are listed. With the stepper motor, for example, two online suppliers are provided. For all the other parts, parts that a RepRap can print itself, both online suppliers and digital files are provided. Although there is a ‘standard’ version of the RepRap Darwin, the open source approach of the project initiated the possibility of creating add-ons to the printer, what is also the goal of this research project. This has resulted in the release of an alternative tool head, as a replacement of the thermoplastic extruder head. This ‘Paste extruder’ can not extrude plastics, but all sorts of paste, from icing sugar to filler, and is still under development. Also, lots of other ideas for tool heads exist: from milling heads to a soldering tool 9 . Because of the number of subassemblies and the wish to be able to improve subassemblies without affecting the rest of the machine, the initiators of the RepRap project chose a modular approach. This means every component or assembly that is operated by electronics works complete separate of other components. The main controller is an Arduino, an open source microcontroller that is easy programmable 10 . One big disadvantage of the RepRap is that it needs to be assembled by people with technical knowledge. Since the whole philosophy of the project is to create a self-replicating device, current assembly is too hard for ‘normal’ people in their domestic environment. Further research is needed to get closer to that goal. CAD approach The digital files for the parts that are available on the RepRap website are so called STL (Stereo lithography) files, a widely used format for computeraided manufacturing 11 , although stereo lithography is not the technology used by RepRap. Many widely used CAD applications support importing and exporting STL, including AutoCAD, ProE, Rhino and Solid Works 12 . STL files only describe the surface geometry of a model, not colour, texture or any other attributes. The application that RepRap supports as CAD tool for part design is a programme called Art of Illusion (AoI). This programme is open-source and available for free. Although it is not created as a CAD programme more for assisting in animation, it was chosen because of its minimalistic and intuitive interface 13 . When sending a file to the RepRap trough USB and the serial connection on the Arduino, the file is converted to G-code, a programming language that can operate machine tools by sending the wanted position and movement of the various components. For this, a special piece of RepRap software, written in Java, is needed. Materials Many of the materials that are suitable for use with the RepRap are filed under the thermoplastic category. These materials change phase with temperature and return to their original state after cooling. Examples of thermoplastic materials that can be processed are ABS, PP, HDPE and PLA. Interesting is that PLA is a bio-degradable material, fermented from maize crops. Duroplastics, plastics that cannot be molten again once hardened, are less suitable for use with the RepRap. The most common way to obtain Duroplastics is to take a specific Resin and polymerizing it by initiating it with, for example, a catalyst. Also, fillers like wood saw-dust and glass can be applied 14 . 2.3 Crowdsourcing Since the RepRap project is open-source, everyone that wants to help should be able to share thoughts and knowledge about the process. This happens trough various channels. The official website, RepRap.org, contains extensive user forums and a wiki about all developments. Next to that, various projects keep track of their progress on their own weblogs. To incorporate this means of crowd-sourcing in this project, an online weblog was set up at WordPress.com. It is available at http://reprapdelft. wordpress.com. This weblog was updated regularly with updates on the progress and results of the process. Comments were posted by other RepRap enthusiasts, which varied from encouragements to fresh ideas to serious feedback on the progression. All questions were answered and discussed, to accentuate that the message was read and processed. At the end of this project, this report will be put online on the weblog, to ensure it is available for everyone that is willing to further investigate the subject and to emphasise on the open-source character of it. 7 | Prototyping Lab (IO3028) - RepRap Recycle Add-on
Page 1 and 2: Developing a plastics recycling add
Page 3 and 4: Table of Contents 1. Introduction 5
Page 5: 1 İntroduction The RepRap is a 3D
Page 9 and 10: 3 | From product to granule Possibl
Page 11 and 12: 3 | From product to granule Figure
Page 13 and 14: 3 | From product to granule As for
Page 15 and 16: 4 | From granule to extrusion decre
Page 17 and 18: 4 | From granule to extrusion threa
Page 19 and 20: 4 | From granule to extrusion screw
Page 21 and 22: 4 | From granule to extrusion Figur
Page 23 and 24: 5 Ȧdapting the prototype to the Re
Page 25 and 26: 6 Ċonclusion and discussion The ma
Page 27 and 28: 7 Ṙecommendations for further dev
Page 29 and 30: 8 Ṙeferences 1 - Bowyer, A. 1992.
Page 31 and 32: Appendix A Blender granule tests 1.
Page 33 and 34: A | Blender granule tests 5. Blendi
Page 35 and 36: - Granule still bounces up without
Page 37 and 38: A | Blender granule tests 13. Blend
Page 39 and 40: Appendix B. Technical drawings of t
Page 41 and 42: 50 5 5 10 25 50 50 10 R8 5 25 1 10
Page 43 and 44: M16 20 25 14 2 30° 7 nozzle benami
Page 45 and 46: Appendix C. Extrusion screw manufac

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