Z-axis Linear Rod and Leadscrew Stabilizer for Geeetech i3 Pro B printer with 8mm acrylic frame

thingiverse

In 2015 I bought a Geeetech i3 Pro B printer kit with an 8mm Acrylic frame. Every time I tried to use this printer as it was originally designed, the vertical walls came out very rough due to poor mechanical tolerance between the Z-axis threaded rods. This caused significant problems printing any part that required tight tolerances, such as parts with integrated print-in-place hinges. I tried several 'solutions' that I found here on Thingiverse and other internet sources, including common parts that attempt to physically decouple the Z-axis threaded rod from the X-assembly; these helped a bit, but did not solve the root cause of the problem. The parts you find here are what I finally came up with to truly fix the problem. The XYZ calibration cubes photo above shows the before and after results up close. Print Settings Printer: Geeetech i3 Pro B printer with 8mm acrylic frame Rafts: No Supports: No Resolution: 0.2mm Infill: 100% Notes: Material type, infill density and resolution is up to your personal preference. I printed mine using ABS plastic and 100% infill to maximize the part strength and allow me to drill holes in it wherever I want to later. Post-Printing You may want to lightly file all exterior edges when done, for aesthetics and fit. Avoid filing the inside of the printed holes where possible; the fit for the linear rod and 608 bearings should be somewhat tight. How I Designed This I used a digital caliper (accurate to 0.02mm) to measure the top-most acrylic part on my printer, and then re-created that part in Sketchup before modifying it to suit my design. First, I made sure to get accurate key measurements for Linear Rod center to Lead Screw center, both of those centers to the acrylic motor mount, and then ensure the Linear Rod goes into the receiving hole in the unchanged acrylic motor mount. This will be used to align your positioning of the newly printed bottom plastic piece, so make sure it is straight and true. Steps to use: 1] Replace the threaded rod with a proper Lead Screw. I used an inexpensive 8mm diameter 2-start stainless steel Lead Screw with a 2mm pitch and a 4mm lead (a TR8*4-2P Lead Screw). This change required me to reprogram the Z-axis steps per mm setting in the printer's Marlin firmware. 2] Print these four parts I designed, either individually or in pairs using the included files. 3] Remove the X-assembly, Z-axis rods, and Z-axis flexible couplers from the printer, and replace the top acrylic parts with these new printed ones. Also remove the 40mm fan from the lower left side, if you have one installed (it can be re-installed later, using only 2 screws, if needed). 4] Insert the 8mm Linear Rod into the 8mm hole in the newly printed top part, and then run it through the 8mm hole in the newly printed bottom part, and finally ensure the Linear Rod goes into the receiving hole in the unchanged acrylic motor mount. This will be used to align your positioning of the newly printed bottom plastic piece, so make sure it is straight and true. 5] Get a cordless drill, and a drill bit which fits loosely into the holes in the newly printed bottom part (these holes are for M4 screws). 6] With the 8mm Linear Rod now in place as a secured vertical guide from top to bottom, carefully position the bottom plastic piece so that it is both flush with the acrylic frame and is pressed down against the acrylic motor mount, then use at least two holes of your choice in the bottom plastic piece as guides to drill new holes into the acrylic frame (using the drill and drill bit from step 5) to use as mounting holes for this part. 7] Now tightly secure the bottom plastic piece in place against the acrylic frame using M4 screws. 8] Remove the 8mm Linear Rod, position/re-mount the X-assembly, and then replace the Linear Rod ensuring it goes through the linear bearings in the X-assembly. 9] Replace the 5mm to 8mm coupler on to the motor shaft, and press a 608 bearing into the large hole on both the bottom and top plastic pieces and gently secure them with a M3 screw (if needed) to stop gravity from pulling the bearing out of the hole. 10] Slide the 8mm Lead Screw through the top 608 bearing, thread it through the Lead Screw nut in the X-assembly, slide it through the lower 608 bearing, and secure it into the coupler on the motor shaft.