Quick Tension Knobs for Deltaprintr

thingiverse

What is this? This is an easy, toolless spectra line tensioning system for the Deltaprintr. It replaces the plywood pulley mounts at the top of each tower. With this design, just home the carriages, pluck the lines, and give each knob a quick twist so they're nice and tight. No more tools, no more feats of strength required, no more worrying about lines loosening. I've been using this design for a couple of years, and I'm pleased as punch. I started a thread on the Deltaprintr forum if you want to chat over there. Why do I want it? The original plywood slot has flaws: Adjustment requires tools. Adjustment is awkward. You need two hands to loosen the pulley and a third hand to pry up on the machine to draw the line tight. Then, while prying, you need to tighten it all down again. The only thing keeping the pulley from sliding loose is the friction between the plywood and the hardware. Parametric, source included. The OpenSCAD source is included so you can modify the design to suit your printing ability or your tastes. Pulley carrier gets stuck? Increase carrier_tolerance. Bigger knob? Change knob_dia or knob_height. Different size pulley mounting hardware? Tweak mount_screw_dia. Need it taller for more adjustment? Increase worm_length. But I like using tools for adjustment! Check out kietcallies's remix that uses M5 bolts instead of printed knobs. Print Settings SUGGESTED SETTINGS FOR ALL PARTS Layer height: 0.2 mm Print speed: 30 mm/s (60 if using patched firmware) Bottom layer speed: 15 mm/s Outer shell speed: 20 mm/s Inner shell speed: 30 mm/s (40 if using patched firmware) Bottom/top thickness: 1.2 mm Fill: 35% Combing (expert): No Skin MOUNT (tall U-shaped piece) Shell thickness: 1.2 mm (3 shells) Retraction: on Support: Touching Buildplate Support fill amount: 30% PULLEY CARRIER (smallest piece) Shell thickness: 2.4 mm (6 shells) Retraction: off Support: none KNOB (should be knobvious) Shell thickness: 2.4 mm (6 shells, very important for durability!) Retraction: off Support: none FULL PLATE (if printing all parts at once) Shell thickness: 2.4 mm (6 shells) Retraction: on Support: Touching buildplate Support fill amount: 30% Instructions Print Parts Each tensioner is made of three (3) parts: knob, mount, and pulley carrier. You need a set of those parts for each tower on the printer. In total: 3x dp_tensioner_knob (or _nologo)3x dp_tensioner_mount3x dp_tensioner_carrier OR 3x dp_tensioner_all_parts I suggest printing and installing a single set of knob, mount, and pulley carrier first to check fitment. I've spent a lot of time tuning fitment, but your printer may have different tolerances from mine. Remove Old Tensioner (see printer diagram for definition of terms) On the tower you want to swap, slide the carriage down the aluminum extrusion a few inches. Tape the fishing lines to the extrusion above the carriage. Loosen the pulley axle screw and relax line tension. Unhook the loop of fishing line, fold it flat, and tape it to the printer's upper platform. Remove the two T-slot mounting screws on the face of the small plywood pulley carrier, then remove the carrier assembly. Remove the pulley axle screw and nut from the carrier, then remove the pulley and washer. Set the hardware aside for the next section. Assemble New Tensioner Insert the pulley axle screw into the small printed pulley carrier with the head on the side with the threads. You may have to screw it into the plastic. Add the washer, pulley, and nut to the other end of the screw and tighten the nut. Insert the carrier assembly into the slot in the tall U-shaped mount. You don't have to slide it all the way down and it's okay if it's tight. If you haven't installed the fishing line yet, put the pulley toward the bottom of the mount to provide the shortest path when tying the lines. If the lines are already installed, put the pulley toward the top to take up more slack. Screw the knob partway into the top of the mount. Push on the knob to slide the carrier to the bottom of the mount. It may be tight. If this takes more than hand strength, you may want to edit the source to increase carrier_tolerance and reprint. See photos if you need help understanding how the parts fit together. Install Slide the tensioner assembly into place so that the mounting ears fit where the old part was. Make sure the endstop wiring fits into the channel on the bottom of the mount. Install the T-slot mounting screws and nuts. Tighten firmly but gently. Untape the loop of fishing line and loop it over the pulley (or install new line now). Twist the tensioner knob clockwise to draw the pulley up and pre-tension the line. Untape the line from the extrusion above the carriage. Twist the tensioner knob to tension the lines. They should go "plink" when you strum them. You're ready to go! Now repeat for the other two towers. Tips If you have trouble printing the knob threads, make sure you have enough cooling. Try any or all of the following: turn on your part cooling fan, add a desk fan blowing over the build, reduce your print temperature, increase minimum layer time in your slicer, make sure you're not overextruding. If you can't get enough travel out of the tensioner to tighten the lines, try flipping the carrier over so the pulley is oriented closer to the top. You'll gain a few millimeters of adjustment. If you still can't tighten the lines far enough, you may want to replace your fishing line and make it tighter to begin with. Or, you can edit the source for this assembly in OpenSCAD (download both dp_quick_tension_knob.scad and ISOthreadUM2.scad) and increase worm_length. This will make the whole assembly taller. You can verify that the knobs aren't loosening over time by adding a conspicuous tape flag or sharpie mark. Or you can take my word for it. The only loosening I've seen is after a head crash or when a line was about to break, and I've since revised the design to make slipping even less likely. Origin Story On the Deltaprintr forums, Colin posted his lasercut design for a tensioner that used a hex cap screw, and Costfu adapted it into a 3D-printable design. I wanted to make something that looked better, didn't need additional hardware, and didn't require tools to adjust. The idea for a worm gear rack came to me in the car one day. Worm gear systems are great for low-lash "only move when I say so" situations. The knobs are inspired by the ones on Koni's adjustable sport shocks for cars.