July 22, 2018
Description
The goal was to create a printer using 500mm 2020 extrusions and to use linear rails for the axes. To minimize the impact on the build volume I tried to minimize the components used within the frame. I also wanted to mount the Nema17 motors only behind the printer, where I plan to store have all the electronics, so when later on an enclosure will be added, the electronics will reside outside of the heat chamber and can even be cooled properly. 4 additional 540mm 2020 extrusions are used for the vertical edges to cover the corners.
The rails are 450mm size. The left out 50mm are divided by two and used on the inside of each frame to place the corner brackets.
A very important task for me was to ensure the Y rails are on the same level as the X-rail, which implies that the X beam must be on the same level as the outer frame of the printer. This resulted in a quite strange shape of the XYCarriage (aka. xy joiner), but it turned out to be possible and works very well. The main reason was the tool changing and parking system I had in mind.
As another self set limitation of my design I wanted the XY pulley and the XY joiner section to only use one axle, which in the result causes the timing belts to get quite narrow towards the XY joiner. On the Nema17 block this wasn´t a big issue. As I did not want to mount the Nema17 steppers as overhang to the sides, but at the back, I needed to design a 90° belt angle and an additional pulley to get the belt around.
The desired build volume will probably be 395mm x 335mm x 430mm. This is due to several things that cannot be changed easily. Like the linear rail block and the hotend dimensions eat alot of space. Due to the corner brackets I already lost 50mm on each axis, since the linear rail block would collide. I probably could get rid of them and use longer rails, but at the cost of stability. That is also one reason I did not use 400mm or even 300mm extrusions as a starting point as the result should be far bigger then the build volume of my AnetA8. The tool changer mechanism eats additional 50mm of the Y-axis anyway. That is the reason why we get around only about 335mm in reachable size there. As a bonus I will be able to park four (!!) tool heads. Not counting modules that can be easy stored externally like a laser engraver. Tool changing is more or less impossible with a preset system like the Anet A8 or my TronXY X5. It is also far easier to modify and fix things on a big printer compared to fiddling around on some small one. Even simple experiments are impossible due size limits. Especially the TronXY X5 (the one with real rods and not the junky plastic wheel edition) is by default so packed that it is hard to even get the hands in to add fixation clamps for the glass surface. The GeitPrinter is using a dual lead screw driven z axis. Two 60 teeth driver pulleys create enough torque to lift about 4.7Kg additional weight with a single Nema17 stepper. At least the crappy prototype parts did manage that. Also keep in mind the aluminium bed and the 2020 extrusions used for the bed are not included in this calculation, so the total amount of weight the construction was already able to lift was around 7Kg in total. The bed frame has three mount points with very nice bed level adjustment wheels. These work great. The 300x300 heat bed is currently not mounted, as I want to finish the electronics casing first, to avoid messing around with mains power and low voltage loosely mixed together and risking to break something or someone. I also got new longer ribbon cables for the display. Now I am able to move and mount the Ramps board behind the printer as planed. I currently mounted only two extruders. They came with corner brackets and I needed to enlarge the slot holes from M4 to M5, to make it fit (M5 T-Nuts). I could have printed the part, but in my experience extruder motors gets quite hot and the heat must be transferred away from the filament, which a metal frame is perfect for. I had much trouble with my Bowden Anet in this department and only an additional fan on the extruder helped to fix filament jams. Since the ANet extruder is basically PLA mounted on Acryl, there is no other way to transfer the head away from the Nema17. I hope the metal bracket, as well as the printer frame, will act like a huge heat sink. Since the Nema17s are getting quiet hot in general I also have one part less to reprint in ABS when the design has been finalized. The first prototype version of my printer used optical end stops for the X and y axis. It worked fine, but in the end the moving wires from the x carriage around the printer to the electronic was a real show stopper. So I adapted my design and replaced the old stepper drivers. The new TMC2209 drivers allow sensor less homing without any additional wiring needed. This works surprisingly well. The only end stop left is for the z axis as we don't want to crash into our tools when homing. The new X-Carriage with belt tensioner and a magnetic tool holder is working like a charm. This way the printer can swap the tools on demand. And guess what? It works perfect. I used three 10mm neodymium magnet balls on the holder and M6 washers on the tool mounts. There is no active component and no additional wiring. Many thanks to Frank Herrmann for inventing this mechanism in the first place. Check out his YouTube profile for additional information, but be aware that both systems only share the basic mechanism and not the actual measurements. The tool mount is basically a bracket which the tool gets mounted on. Hence the naming. :D I designed a fully enclosed E3DV6 mount, with two separate air flow channels for part and heat break cooling. A third channel guides the wires from the hot end to a Sub-D9 connector, so the tool block can be removed by simply unplugging the Sub-D cable and the PTFE-Tube. This will make replacing and cleaning tools so much easier. Here the basic design in action: https://youtu.be/fZJShQEbW1U The most recent addition to the printer was the ATX power supply mount, which I modified, so it can be controlled by the Raspberry Pis gpio using OctoPrint. The Pi itself now gets powered by the 5V standby, so for the first time the GeitPrinter is portable and save again, as there are no open high voltage lines and no loose components below the Z axis belt, which is a nice progress. And only one power supply for printer and pi. Now we have 2020 an the GeitPrinter is still not finished. Well, we are close. I did most of the software fixes. ToolChange is now build in and the Sensorless Homing is 100% accurate. One thing I noticed missing were the antennas. Well, they are not really antennas, but sticks that got straight up between the extruders and prevent the cables from getting tangled during tool changing. I know. They cannot really tangle, but there weight make them tilt sideways and two extruder cables may laying ontop of each other. The Zip-tie or plastic wrap around the cables my cause them to interlock, which is a bad thing, when the print head drives away with the extruder and the wire is somehow attached to the other wire by interlocking. This simple antenna like solution is fixing this odd behaviour and also gives the printer proper height dimensions, so nothing can accidentally rip of cables while parked. 30.Jul-2020 ---------------- Added reworked lead screw mount with integrated z adjustment knob. 04.Aug-2020 ----------------- Added Nema17 mount bracket. 09.Aug-2020 ----------------- Marlin firmware containing all changes required to get the GeitPrinter up and running is available here: https://github.com/Geitde/Marlin/tree/bugfix-2.0.x
The included files are not ment to be used yet. I just added them for documentation purposes and they will update frequently. When I finished my design I will include the FreeCAD source files.
When left/right/front/back is used in naming of the parts, the direction is to be seen from the front of the printer and not from the side the part gets mounted on.
Of course this may look like overkill as there is the LCD Controller right next to it, but sometimes the ipad is more handy and you can easily take it off, when working on the side. Especially when re/starting a print via OctoPrint you need additional help. I also have a spare ipad1 which is perfect for the job. While assembling I used the empty mount as "this is the front" indicator. It will probably be mounted above the LCD display anyway.
The ipad Idea probably killed itself as I am not able to log into OctoPrint with the old ipad anymore. That´s a bummer. :( The display mount: https://www.thingiverse.com/thing:1975439 The display case: https://www.thingiverse.com/thing:213852 Case handles: https://www.thingiverse.com/thing:754938
Here the original magnetic tool changer my design is based on. The XHTC was designed by Frank Herrmann (xpix): https://www.thingiverse.com/thing:3036622 Please note that the original XHTC and the GeitPrinter only share the basic docking mechanism and not the measurements. The systems are not compatible to each other as my printer is intended to have the x axis (2020 beam) on the same level as the y axis.
License:
Creative Commons - Attribution
geit_de
