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Você está aqui: Página Inicial Bulletins 2012 fall LulzBot AO-100 3D printer is certifiably fun

LulzBot AO-100 3D printer is certifiably fun

por Libby Reinish Published on 27/11/2012 10h40

by Nico Cesar, Peter (Peabo) Olson, and Ward Vandewege, System Administration Team

We already covered the importance of having a free hardware certification in previous articles in this bulletin. The good thing about doing a hardware certification of a 3D printer is that you get to play with one of them!1 The LulzBot AO-100 3D printer melts plastic filament and builds up a three dimensional object out of thin extruded layers. Two commonly used plastics are ABS and PLA.2 When I first read about these kinds of printers I got really excited about the possibilities, but I thought it would be a challenge to get it working. Luckily, I was proven wrong. The LulzBot makes it quite easy to materialize creations in 3D.

The setup and software

The printer has 2 thermal components: the heater and the bed. The heater needs to reach 230 Celsius (446 Fahrenheit) for ABS plastic to melt. The bed needs to heat up to 110 Celsius (230 Fahrenheit). It takes about 10 minutes for the bed to be heated up sufficiently to start printing - the heater warms up more quickly. The heated bed prevents distortion of the object which might otherwise occur if it cools down too quickly. The extruder contains a mechanism which pulls the plastic filament into the melting area, and pushes it out through a small diameter nozzle, allowing for very fine features to be printed. As it extrudes each layer, the extrusion head moves to the right and left, and the bed moves forward and backward. When each layer is finished, the extruder moves a little higher to position itself for the next layer.

Objects to be printed are described by StereoLithography (STL) files that can be imported/exported from free software such as Blender or FreeCAD. There are also repositories of STL files available online. The file has to be translated to code that the printer will execute, or GCode. The STL to GCode conversion is done by Slic3r. In this transformation there are many parameters to tweak, like the width of the filament, printing speed, and the fill pattern. It is also possible to merge several STL files into one GCode file. This allows for printing multiple copies of an object in one batch. When Slic3r has done its conversion, it prints out an estimate of the amount of raw material the print job will take. It also estimates the time required for the job. The GCode file needs to be sent to the printer. Pronterface is the software that handles the physical controls of the printer. It has X/Y/Z axis buttons that can be used to move the print head around. It shows the head and bed temperature. It also has a "Load" button to load the GCode file. With the "Print" button, GCode can bring your creations to (static) life. Pronterface also allows exploring of the layers of the GCode file, where the quality of the print may vary according to what direction the print head is moving, especially close to the edges of the object. Also, the printer generally uses an open cross-hatch pattern for interior sections of the object, to minimize the amount of plastic used (and hence optimize the print time) without impairing the structural stability of the object.

The hardware and the project

One of the most impressive aspects of 3D printers is that many of the parts can be produced by a 3D printer. If a part of a 3D printer breaks, it is often possible to print out a replacement part to fix the printer. The LulzBot AO-100 seems very robust. The heated extruder is responsible for the X and Z axis movement. The bed provides the Y axis movement. About the electronics you can read in their homepage: "The Tosduino MEGA 2560 micro-controller board is an Arduino MEGA clone made by Tinyos.3 The Mega is used in the RepRap community with RAMPS electronics and also widely used in the hacker and DIY community."

If you are buying a 3D printer, you probably have a project in mind. At the FSF we have a messy server room (who doesn't?). We have many cables that need to be organized better. Using the Lulzbot, we are printing cable holders and cable wrappers so that we can get the cables to fit into boxes and shelves.4 5 There is an ongoing effort done by the MediaGoblin crew to provide a federated repository of 3D creations ready to print.6 You can donate to MediaGoblin at mediagoblin.org to support this project.

Problems and solutions

Early on, we saw some glitches on the first printed layer. This was due to the slightly slippery bed surface. We used acetone mixed with some ABS to make the bed stickier, spreading it out on the bed as it heated up. Once started, the printing process should not be left unattended, because if the filament gets stuck it will mess up the printing. Luckily, the printing process is fun to look at and the stepper motors make almost musical tones as they work. There are some design limitations to keep in mind when printing 3D objects as well. It is important not to make overhangs which might sag while the plastic is still soft. This may require an object to be printed in more than one section and then glued together, or might require some extra supporting struts to be printed which are later cut away. A mixture of acetone and ABS makes a very good glue for ABS objects, since the bonds it makes are like welds that are as strong as the rest of the object. This mixture can also be used to refine the surface appearance of the object, so that the layers are less visible.

The low-cost 3D printing revolution is just beginning. For sure, there is a lot of room for improvement on the technical level, but the current results are quite impressive for a low budget start. As users we have to make sure that we are on the right path and that our freedom is guaranteed. The LulzBot AO-100 3D printer allows us to generate 3D objects in freedom. Recommended!

Footnotes:


1ur1.ca/aiix2

2www.lulzbot.com/en/3d-printer/153-ao-100.html

3http://www.lulzbot.com/en/83-arduino-mega-2560.html

4www.thingiverse.com/thing:28696

5www.thingiverse.com/thing:10219

6mediagoblin.org/news/3d-support

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