Tronxy Zonestar P802M Multi-Axis Overhaul Pack Bear Exxa 1.0 MK3S Optional Bowden Upcycled Extruder by JBieri

Last crawled date: 3 years, 3 months ago

This is an overhaul pack for the Tronxy, Zonestar, and other P802M cheap Shenzhen export 3D printers focused to accept the BEAR Extruder and X-Axis (Bear Exxa 1.0) assembly from the 2020 Prusa MK3S. There are three extruder options including: Bear 1.0 direct drive extruder using Bondtech gears, a Bear Bowden extruder (using a special lid), or you can up-cycle the P802M's stock extruder.
Features
-Complete Y Axis Overhaul
-New Z Top Plates
-Fixated Z-Endstop Height with Fine Adjustment Screw
-Bear 1.0 X-Axis
-Bear 1.0 Direct Drive Extruder (Option)
-Bowden Bear Extruder Lid (Option)
-Recycle P802M Stock Extruder w/ Remixed Bear Cooling Fan Duct (Option)
GOAL
Take the cheap P802M and update it to 2020 standards, while removing as many design flaws as possible on a super strict pandemic budget.
This overhaul is not for the faint of heart. You will have to cannibalize your P802M for parts, visit the hardware or parts bin, drill/rig things for endstops, and likely re-flash the firmware. I replaced Melzi with RAMPS 1.4 because I don't like repetier. Do not tear your P802M apart until you have all printed parts and or a secondary printer.
Y-AXIS
The Y axis on the P802M isn't the best; the motor mount drifts out of horizontal orientation, causing belt alignment, and other issues that may ultimately break the acrylic front and or rear plate of the machine. The end stop mount also sucks; mine is currently screwed into a block of wood, super glued to the original mount.
The original Prusa i3 Y axis is cheap, strong, adjustable, and adaptable at minimal cost compared to aluminum extrusions. The frame of the P802M also already accepts the threaded rod design, which saves time and avoids replacing the center frame plate, which would require a full tear down. Also, completely replacing the Y axis, avoids having to print the massive reinforcement brackets that many people install into Anet A8 machines.
I remixed some the Thingiverse's favorites into the Y axis to make it easier to square, screw/bolt down to retain alignment, and keep upgrade costs under $20. I designed it for mild abuse. The motor mount is available at the remixed design and I've remixed and reinforced the Y Belt Tensioner which is available in this thing.
Current Y Belt Holderhttps://www.thingiverse.com/thing:1669305
I cut a paint stick as wide as the carriage where the belt fits. Cut a second. Layered them and used the belt holder above. I also had to cut a notch in the frame so the lower belt would not rub on the central frame of the printer as the pulley is lower than the frame.
Z TOP PLATES
I redesigned the top plates, replacing the odd rear outer edges with sweeping curves to improve strength, avoid catch points, and ensure the smooth rods align with the new BEAR Exxa Z motor mounts. At present, the lead screws on the test platform are unconstrained without issue. Possible update will be added in the future.
*Z-ENDSTOP FIXATION**
The Z endstop height adjustment on the P802M sucks and isn't reliable. I've redesigned it fixating it and adding a fine adjustment screw. You'll have to drill the holes for your specific endstop; same 1mm drill bit. See thing for more details if needed. See 'remixed' design for files, the link below, or find the lid included in the files for this thing as well for convenience.
Bear Exxa Z Axis Endstop Fixated with Fine Adjustment Screwhttps://www.thingiverse.com/thing:4592796
X-AXIS
The Bear Exxa is awesome! Cheers to Grégoire Saunier for his elegant design and the subsequent remix/es.
Bear Exxa 1.0 is available here:https://www.thingiverse.com/thing:4362586
IMPORTANT: The Bear X axis will currently limit you to what alternative extruder/tool options you can mount without creating an adapter plate as it is different than previous Prusa models. Be sure to read through the documentation to ensure you know what you're getting into. There are good assembly videos on youtube for Bear Exxa. I spent about $15 in hardware on the X-axis and extruder.
I printed the X-axis components, cannibalizing the P802M for components. The MK3S does not use endstops, so I mounted my endstop to the lower X-carriage cap by drilling two holes for screws with a 1mm drill and then mounted a block on the X-Motor End for it to run into. Be careful while setting it, better to give up some X movement than risk slamming your fan unit or carriage into the X motor end (use images with red X-carriage mount for guidance). Importing the carriage cap file into sketchup breaks it. I gave up after trying a few other programs with no success.
EXTRUDER
There are three options for the extruder set up.
(1) BEAR DIRECT EXTRUDER: Print the Bear extruder, use the parts from the P802M to complete it, purchase Bondtech gears, and follow standard assembly instructions.
(2) BEAR BOWDEN EXTRUDER: Print the Bear extruder, hone the filament hole with a 2mm drill bit (or larger if you plan to line it with PTFE, print the Bear Bowden lid that I've designed, get yourself one of those Creality Metal Bowden kits with a Capricorn tube, and go from there. See 'remixed' design for files, the link below, or find the lid included in the files for this thing as well for convenience.
Bear Bowden Extruder Lid:https://www.thingiverse.com/thing:4582453
(3) RECYCLE P802M DIRECT EXTRUDER: Take the P802M extruder apart, so all you have is the metal bracket, take the mounting plate for the Bear X-Carriage, clamp it together carefully, making sure it's level/square, and drill three holes in it. Bolt it together, reassemble the extruder, mount it and run the wires through the carriage/follow standard assembly after that for the Bear X axis.
The P802M's stock cooling duct is a bit dated, so I remixed the Bear extruder's cooling fan duct by adding 10mm to get near the P802M's nozzle height. See 'remixed' design for files, the link below, or find the lid included in the files for this thing as well for convenience.
Bear Extruder Hot End Part Cooling Fan Duct Dropped 10MM for P802Mhttps://www.thingiverse.com/thing:4592771
Final Notes
During final testing I was able to reach micron level output resolution (EG: 20.00XXX mm) on all axes. Reliability testing while printing LowRider2 CNC is underway. The heat bed could be insulated and a co-planar bed leveling system would be nice additions beyond this upgrade pack.