Parametric Horizontal Spool Roller (for rostock-mini, Octave, MakerGear, othes)
by summetj, published
This is a parametric horizontal spool roller. I created it to hold a spool of filament above the top frame of my (slightly modified) rostock-mini, but it can be used to hold a spool horizontally above any flat surface.
The STL files provided work with spools that have 31mm and 51mm holes (Octave and MakerGear). If your spool(s) have different sized holes, you will need to modify the SCAD file and re-generate the STL files. (You can also make the arms longer or shorter, and make the base/shield a different height). The smaller spool hole size is built into the parts, and the larger hole size is accomodated by an "expansion ring" that is held by the shield piece at the base until it is needed.
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I recommend that you print the testPrint.stl file first to make sure that everything will fit your spools, 608 bearings, and that the expansion ring will fit snugly, but not too tight, over the inner ring. If anything doesn't fit, adjust the "calib" setting (or the small/large spool radius) in the SCAD file and re-print. Read the comments in the SCAD file to figure out which ring should fit over what other rings/parts.
In adition to the printed parts, you will need two 608 (roller skate) bearings, a M8 (or 5/16) bolt of the appropriate length, with 4 nuts and optionally 4 washers.
With the provided STL files, I mounted my spool holder such that a NEMA 17 stepper could fit under it horizontally, and bolted it to a 0.25 inch (6.35mm) thick sheet of acrylic, and I used a 100 mm bolt (4 inches) but could have gotten away with a 90mm bolt. If you want to mount it closer to the mounting surface, either omit the shield piece, or edit the .SCAD file and re-create the STL files after shortening the shield. (and use a shorter bolt unless you don't mind that it pokes out the bottom).
Use two nuts tightened against each other under the bottom bearing to hold the head up. Then use a nut and washer above the mounting plate, and a washer and nut under the mounting plate. (You will have to drill an 8mm or 5/16 hole in whatever is your mounting plate.)
My specific order of assembly is:
- Insert the two 608 bearings, one into the piece with arms, and the other into the "sr bottom" (which may actually go on the top!)
- Stick your bolt through the "sr bottom" piece with the bolt head against the plastic part, through the 608 bearing and out the top.
- Thread the bolt through the part with the arms, leaving the bearing at the bottom visible.
- Place a washer next to the bearing.
- Thread two nuts down to the washer, barely finger tight.
- Tighten the two nuts against each other to keep the "head" of the spool roller from moving down the bolt (when it spins it may want to loosen a single nut). DO NOT APPLY PRESSURE between the two bearings! The head should have a 0.1mm "gap" so that it spins easily. If it starts to be hard to turn you've tighetened it too much! Tighten the two nuts against each other, not up towards the bolt head.
- Place a nut and washer farther down the bolt, at the appropriate location for how high you want your "head" to be above the mounting plate, taking into account the thickness of the shield (if you are using it.)
- (optionally) Place the shield piece on the bolt, then push the bolt against your mounting plate. Make sure you are happy with the location, and drill a hole in your mounting plate. Push the bolt through the hole and afix it with a washer/nut on the other side.
Possible Modifications: You probably don't even need the washers if your nuts are the right size.
You can of course reverse the bolt so that the head is under the bottom mounting plate and the extra threads stick out of a nut on the top. You can also turn the entire "head" of the spool roller upside down, such that the SR_bottom piece is actually upside down below the arm piece, hiding the double nut arrangement. But you'll need a socket to tighten them up, and tightening them against each other is harder. This is actually how I had originally designed the part to work (hence the SR Bottom name), but then I realized that my sense of aesthetics was upside down and it looked better if I fliped it....go figure.