How hard does your printer fight its own spool? I measured it with marbles, then designed a bearing-based spool holder that cut the drag almost in half.
Editor's note (July 2026): From my 2017 journey on the now-discontinued Maker Select V2. The idea here, that a spool that spins freely on a bearing puts less strain on the extruder, applies to any printer. Many modern machines still ship with a plain spool holder, so this is a cheap upgrade worth doing on almost anything. If you are starting fresh, see the current-printer link at the end.
Every time your extruder tugs filament, it also has to overcome the spool's weight and friction. To measure that drag I hung a basket off the filament and added marbles until the spool broke free: 11 marbles on the stock holder. Then I designed a five-piece spool holder that rides on two ball bearings, so the spool spins with almost no resistance. It dropped the drag to 6 marbles, and the filament feeds noticeably smoother.
Let the spool spin freely. Ease the extruder.I wanted an actual number for how hard the feeder motor has to fight the spool, so I rigged up a simple test. I printed a little basket, hung it from the filament on an S-shaped hook, and dropped in steel marbles (about 8.5 grams each) until their weight was enough to make the spool rotate on its own. On the stock holder it took 11 marbles, roughly 93.5 grams or 3.3 ounces of pull, before the spool would turn freely. That constant fighting with the spool is not good for the printer, and over time that repeated stress can wear out the feeder motor.
A basic out-of-the-box holder forces the feeder motor to overcome both the spool's weight and the friction of it dragging on a fixed rod. I tried an existing modification (Thingiverse thing 1805457) that uses a wider sleeve to spread that friction, but in my test it was actually worse, needing 14 marbles to break free, and it shifted around unpredictably while printing. Clearly the answer was not more surface area, but less friction entirely.
My fix was a five-piece assembly, drawing on a few existing designs but with my own refinements. It has two cone-shaped holders that adjust to fit spool hubs from 35mm to 65mm, a spindle, a large and a small fastening nut, and the key ingredient: two deep-groove ball bearings. The cones sandwich the spool, and the small nut presses only against the bearing's inner race, so the whole spool turns on the bearings with almost nothing holding it back.
The bearing I used is a PGN 6204-2RS, a sealed and pre-lubricated deep-groove ball bearing: 20mm inner diameter, 47mm outer, 14mm wide, rated for a wildly overkill 2000 pounds. I picked up four for about ten dollars. It is far more bearing than a spool needs, but it was perfectly sized and cheap, which is exactly the right kind of overkill.
Grab the files: I shared this spool holder design on Thingiverse. It suits any printer where you can mount a spool on a spindle, not just the Maker Select.
Back to the marble test with the finished holder: it broke free at just 6 marbles, down from 11, so nearly half the resistance the stock setup put on the extruder. I ran the test several times to be sure, and it was consistent. In real printing the filament fed smoothly, without the little lurches the stock holder produced, and watching the filament guide roller you could see it making the constant tiny adjustments a print actually needs.
Because the extruder has to pull the filament, and a stiff spool adds weight and friction to fight against. That extra drag can cause tiny lurches in the feed and, over time, strain the feeder motor. A free-spinning spool lets the filament flow smoothly.
A sealed deep-groove ball bearing like the 6204-2RS (20mm inner, 47mm outer, 14mm wide) works well and is cheap. It is far stronger than a spool needs, but the size is convenient and it spins with almost no resistance.
Hang a small weight off the filament and add to it until the spool starts to rotate on its own. I used a printed basket and steel marbles: the number of marbles it takes to spin the spool is a simple, repeatable measure of the drag.
Yes. In my test a bearing-based holder cut the drag from 11 marbles to 6, nearly in half. In practice the filament fed noticeably smoother, without the lurching the stock holder caused, which is easier on both the print and the motor.
Off to the side, or at least off the top frame, is often better. A full 1kg spool is heavy, and on an open-frame printer that weight up top can add to gantry movement. Mounting the spool separately keeps that mass off the moving parts.
This turned into one of my favorite upgrades of the whole series. Measuring the drag with marbles made the problem tangible, and cutting it nearly in half with a couple of cheap bearings was deeply satisfying. If your printer still runs its spool on a bare rod, a bearing holder is one of the easiest wins there is.
That is the last of the build episodes for now. Next I step back and take stock: episode 8 is a two-years-later look at whether this printer was still worth it.
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