Flexible filament Expanding spool holder

thingiverse

Nov 13, 2019 New Design https://www.thingiverse.com/thing:3975184 Any filament feed friction causes flexible and other filaments to behave like stretched rubber bands, varying the amount of filament extruded and visible in the finished print surface if you're lucky or the print fails completely. I improvised longer than necessary before designing this, but the moral is make it before you need it. The toggle action release lever allows single-handed operation with a cantilever-mounted configuration, which creates the mounting for you. I used a threaded rod as the axle that supports two ball bearings in turn supporting the spool assembly. I drilled and tapped a 1/4"-20 thread hole horizontally into 2020 aluminum extrusion to mount the threaded rod, which could be replaced with a larger hole and two nuts if you don't have taps or a long bolt with one nut. I also added an extra nut on the lever end of the thread to prevent the ball bearing threaded PLA sleeve from moving. The expanding spool holder has an adjustment range from 50 to 60 mm in diameter, and the toggle lever action alters the diameter by about 2mm. Flip over the lever and print with the flat face down. The design uses thin 0.8mm walls or two nozzle widths thick walls that need to fuse together for strength, making under extruding a problem. The design also uses 1mm pitch printed threads, which is another problem caused by over extruding. Extruder Printer Test: https://www.thingiverse.com/thing:3390910 I printed with a 0.1mm layer, 0.4mm nozzle, and 0.4mm line (paving) width using fine Cetus print settings. The model took about 7 hours to print, requiring good cooling to print the 9-flexure spring connecting struts strongly. I included supports only for the three arms as part of the printed model, and the slicer needs to generate support for the collar. After printing, cut off the bottom of the arms along with the radial support to the flexure to prevent interference with the release lever action or nut rotation. Additionally, 18 small horizontal stability tabs between the arms and struts need to be cut before use. If you use a slicer that has nozzle Z hop, enable it to prevent rapid horizontal nozzle moves from dragging across and grabbing the flexure struts. Rotating the model 10 degrees or so around the vertical axis reduced the nozzle contact problem for me with the Tiertime slicer (no Z hop). The PLA collar is printed closely around but not touching the threaded area of the main tube, moving freely as the nut is turned if it's printed correctly. You need two 8x16x5mm 688-ZZ ball bearings for the lowest rotating friction or 688-2RS rubber sealed ball bearings if you have a dusty area and can tolerate or want a small amount of friction from the rubber seal. Filament spools are reasonably balanced, but adding a small weight to the rim makes the balance perfect. Friction Averaging PTFE Mount: https://www.thingiverse.com/thing:3815678 Designed in Fusion 360 and printed on a Cetus MK2 extended. Quick Tip: If you have a postal scale and write the weight of new spools on the side, you can weigh how much filament remains on a partially used spool. Have Fun! -Peter