About this 3D model

Hi there, I made another RepRap style printer. Why? Because I wanted a 3D printer, and I wanted to roll my own design just for fun. Now that the printer is up and running, I would not only like to share the design with you, but also discuss some of the design decisions I made. Especially those that turned out to be the wrong decisions, after all the reader should be able to learn from my mistakes. But first some details about the printer. The frame was made using 30mm aluminum extrusions, resulting in a really sturdy, yet relatively light and inexpensive mechanical build. The two extrusions along the x axis are 500mm in length, all other extrusions are 400mm. The footprint of this design is quite large (about 580mm x 420 mm), but space was not an issue, so I am fine with being a bit on the huge side. The printing area is the standard 200mm x 200mm offered by the RepRap heated bed. The z direction also extends 200mm-ish (I have to get the exact amount of travel sometime...). The y axis was designed to be compatible with prusa mendel carriages (see the sources for the version I am using). This approach was quite convenient, but on the other hand designing a custom carriage should not be that hard if you would like to go custom here. I am also using a popular extruder that you can get of the shelf. My hotend is a handcrafted one-of, though. The design is close to the "All steel hot end for Makerbot" (again, see sources). Hotend/Extruder -------------------- This is the first design decision that I would like to talk about. Buying a complet hotend/extruder from ebay. Do not do that, except when you know that you buy a quality product. It looked good first, but turned out to be terrible! The barrel of the hot end was made from PTFE, which was in contact with the heater block without any additional mechanical support. I do not want to go too much into details when it comes to bad design decisions other people made, but do not buy such a hotend. Period. After a short period of frustration, which ended in the total destruction of said hot end, I decided to make one myself. First I have to say that making your own hot end is fun and quite educating. I had to go through a few iterations, gradually evolving towards a working version. On the other hand, you will need the appropriate tools for this. Without a drill press you might get lost. You should also be aware that printing PLA with a metal hot end is challenging due to the friction inside the barrel. I failed in my attempts so far. ABS works like a charm, as long as I cool the cooling fins of the hot end with a fan (try not to point the fan towards the build platform while printing, this may have side effects with a fan constantly running at max speed). I read about lubricating PLA with some WD40 before pushing it into a metal hot end for some reduced friction, but I have not tried that so far. I am really proud of my custom hot end, so I want to show you some printing action: http://www.youtube.com/watch?v=H8cVUjxpEn0 Ok, back to the topic: Bad design decisions. Z Axis ------- The first thing that I would have made differently today is the design of the z axis. I made a few mistakes there. I had the idea of supporting the z threaded rods with a ball bearing at the bottom, motors held on top. The expected wobble should be minimized with some kind of flexure bearing on the y ends (like in "Wobbless X Mounts for MakerGear Prusa"). Turns out that I designed that flexure bearing far too stiff, resulting in an enourmous amount of wobble. So, what to do if you encounter such a problem? Improvise! In my case the solution was quite easy. I moved the z motor ends a few mm higher. The lower end of the threaded rods is no longer supported by the ball bearing and hangs in mid air. In combination with the flexible shaft coupler, this results in a smoothly moving z axis guided along the smooth rods. The downside is that now the motors have to carry the weight of the whole y axis and the extruder, but so far i have not encountered any problems with that. Z Endstop ------------- I am using optical endstops. Although those can deliver a very precise position, my z axis was always a bit off (enough to prevent the first layer to print correctly). After a while I figured out what the problem was. The flag used to trigger the endstop was printed in light-blue ABS. As it seems, this material is not 100% opaque in the infrared used in the photoelectric sensor of the endstop. I immediately got more repeatable results after applying some duct tape on the surface of the flag. Nonetheless, a few days later my endstop position was off again. Seems like the tape is peeling off. I fixed that with more tape for now. More is better, right? In the long run I might replace the flag with one made of aluminum to fix that for good. X Ends --------- As already mentioned, the flexure bearing in the e ends was too stiff to absorb the z wobble, but there were more problems then that. The parts have some