Y-axis rework for Anet A8

thingiverse

So finally I uploaded the OpenSCAD files so you guys can improve this design. Removed 2017-04-14: Removed old versions; now there are only files for the latest version. I changed the spec for threaded rods to 340 and 290 mm. Added 2017-03-23: I remade two endpoints by moving screws a little left to make more room for belt and belt mount. Also made cylinders where screws insert less deep for easier assembly into printer. Files have version number "2.1". Added 2017-02-19: I added lower profile belt tensioner that gives 8mm more Y space in front, file "Y-axis belt3.stl". I also added files for belt mount under heat bed, files "Y belt bedmount.stl" and "Y belt bedmount w offset.stl". Stock design for Y-axis on A8 printer is not good. Y-axis belt is clamped between front and back of printer. When belt is tensioned, front and back will be bent towards each other and Y Engine mount will rotate slightly. Also when Y-carriage makes direction changes, front and back move a little bit in relation to print head and frame. This can lead to imperfections on print. One solution is to print frame stabilizers to make front/back more stiff and resilient to bend. However, principle to have frame cope with belt tension is wrong. With this model I'm trying another approach, to decouple Y-axis belt tension from frame. Belt, roller, motor are contained in integrated module. Belt tension is balanced by two 6mm threaded bars and not by frame. This module is then only attached to back frame of printer. As bonus we get nice belt tensioner for Y. There are two files for belt mount under hot bed. One to use when hotbed H alu bracket is turned upside down (Y_belt_bedmount_w_offset.stl) and another when H bracket is mounted with middle section of H downwards (Y_belt_bedmount.stl). Printer Settings: Printer: Anet A8 Rafts: No Supports: Yes Resolution: 0.2 Infill: At least 40% and 95% on belt tensioner Notes: I would strongly recommend infill of 90% with belt tensioner to get it strong. You could also print motor part with motor mount down on heated (thank you naifa). Model needs to be placed 0.9mm beneath Z=0 in order to flatten out motor mount. Post-Printing Remove structures obviously. 6 mm holes for threaded rods might have to be drilled to dimension. Four "pins" that is supposed to fit in four holes of front may need some sanding to fit. Bill of Materials 1 pc. 6 mm stainless steel threaded rod, 340 mm long. 1 pc. 6 mm stainless steel threaded rod, 290 mm long. 6 pc. 6 mm stainless steel locknut. 6 pc. stainless steel washer for 6 mm screw. 1 pc. 3 mm axle or screw without nut, 60 mm long. Assembly Instructions Remove Y blank rods by pulling them through hole in front. Remove belt mount and remove bed. Remove stock Y motor mount. Insert assembled unit to its position in printer as in pictures. Place bed in place, wrap belt around motor axle pulley, and put belt roller in place with 3mm axle (with belt around it). Center 6mm rods between front and back mounts and turn back two nuts until they rest against back mount. Tension belt by moving belt roller carriage forward and turning nuts so that they help tensioning belt to desired tension. Fasten motor mount in back frame using original screw/nut that held stock motor mount. Turn frontmost two nuts on rod until they rest against front mount, do NOT tense so that front is pressed forward and bends. There is no need for tension here other than to prevent front mount from being loose. If printer is mounted on base plate: Fasten motor mount to base plate with screw in slotted hole on motor mount. You may need to check that belt is in parallel with blank bars; I had to move belt roller on Y motor axis a couple of mm away from motor