Few new FDM printers appear and arouse our interest now, but [Kralyn]of Positron Managed to do it. (Video, embedded below.) It can be printed upside down and loaded into a filament box while still having a print volume of 175 mm x 176 mm x 125 mm.
Unlike most 3D printers, the hot end and XY rack are installed under the build plate, directly on the base. You may think that the printer needs to use gravity to squeeze the plastic to work properly, but the real function is to flatten the plastic layer. It seems that it can even improve bridging because the hot end supports the plastic as it is being extruded. Use transparent glass to construct the board, the same as the heating strips on most car rear windows. This also allows the user to still see the parts and provides the added advantage of being able to quickly spot flatness and adhesion problems on the bed surface.
Another interesting side effect of this arrangement is rigidity. There is no need to directly install the heavy-duty hot end suspended XY gantry on the thick aluminum substrate. It uses H-bot type gantry and uses Synchromesh synchronization cable to replace the belt, eliminating the problem of belt distortion. In order to obtain the best print volume within the size of the filament box, the gantry shafts are arranged diagonally on the bottom plate. The Z axis can be disconnected and placed flat on top of the printer, and use linear guides to keep it perfectly straight and vertical during installation.
To reduce the height of the hot end to fit the available space, the filament enters from the side and the molten plastic is rotated 90 degrees before extrusion.it took [Kralyn] Some modifications were made to make it work properly, but the large volume of the melting zone allows for increased flow. However, we suspect that it may also make the hot-end maintenance slightly more difficult. Our only other concerns are the reduced visibility of printed parts and the possibility that plastic fragments may fall into the gantry mechanism and jam it. As far as a compact folding printer is concerned, this may be the best design we have seen so far.The design has been licensed CC BY-NC, And all design files are linked in the video description.
thank you for your hint [IraqiGeek] and [Jasper Jans]!