Tevo tarantula Z Stepper mount reinforcement.

thingiverse

This is a unique approach to making the Tevo Tarantula as rigid as possible. The only part that needs to be printed is a minimalist Z motor mount reinforcement, which can be printed twice without changes for a dual Z motor setup as well. Alone, this part won't make the tarantula rigid on its own. It simply transfers the forces away from the Z motor mount acrylic piece to the upper rail. We'll address that in the next steps. To make the tarantula as rigid as possible, grab a piece of Plywood at least 500x500mm by at least 15mm thick and mark a cross on the top side where the lower support beams will go. On the X axis of this cross, mark out the centers of each vertical support - there's an unused central shaft running through these extrusions. This is the only critical measurement you need to make, though there's some room for error as the shafts are quite large compared to the threaded rod we'll use. You can add other holes spaced out along the lines of the cross as you like. The base beams are double 20x20, so you can add more holes 20mm above the X axis line on the cross pattern. I recommend one in the dead center of the cross. First, drill through the plywood with a 3mm bit where you want the holes, keeping the bit as perpendicular as possible to the plywood, of course. Now flip the plywood over and using a 15mm Forstner bit, countersink to a depth of around 6mm, or enough that a fender washer and M4 locknut in the hole will be flush with the bottom surface of the plywood sheet. Now from the top, you can drill through again with a 4.5-5mm bit. You'll need to cut two 420mm lengths of M4 threaded rod. Put a 4.3mm inner, 12mm outer diameter fender washer and an M4 locknut on one end, then thread them up through the plywood and through the central shaft of each Tarantula's upright (Z) supports until they hit the top beam. Secure it with a t-nut in the lower slot of the top beam. Tightening these from below makes the frame of the tarantula as rigid as possible by drawing the top beam down onto the two vertical supports. The added bonus is no more flex in the top extrusion when the Z height changes. All the forces get transferred down to the plywood base through the vertical supports, which are also now under lengthwise compression via the threaded rods. Similarly, you can insert 15mm M4 screws through a washer and any other holes along the marked cross and secure them the same way into the bottom rails using t-nuts. There's a bit of an art to getting them all lined up. It's best to start with the lower supports - the t-nuts will rotate into place as normal. The two threaded rods, that's another story. A combination of small magnets and Allen wrenches plus a lot of patience worked for me. You only have to do it once. Finish off by adding felt pads to the underside of the board - these will help quieten the printer by damping vibration. You can also screw the power supply to the board with a couple of 3mm screws. It takes up less space mounted sideways. A cable strap on the mains power cable is also a good idea. The result is incredibly rigid, and without having to waste printing time on loads of plastic parts just to get your printer to a point where it's rigid enough to do decent prints at reasonable speed. Update, 5 months later: Since doing this mod, adding the second Z axis motor and changing out the bed plate for an aluminum one, my printed parts have been close to perfect. The Z height is very consistent also, and I've been using original autolevelling sensors without having to ever re-level the bed. The sensor did need shortening, which I did on a milling machine, taking off around 3mm from the end so the sensor could not interfere with any printed plastic I kept milling off thin slices until I could just see the induction coil through the epoxy potting. This modified sensor works very well over a sheet of recycled scanner glass (2.8mm thick) with a 0.3mm sheet of stainless steel sandwiched between the glass and the heated bed. These other mods are well detailed in some YouTube videos. Since the levelling seemed consistent, I decided to upgrade to the dual extruder printhead and this works well too. I have another thing for mounting the autolevelling sensor to the back of the dual extruder heatsink here on Thingiverse.