A spool holder upgrade to lower the incidents of filament cross-threading during a 3D print job
A variety of manufacturers provide filament which is reasonably suitable for the average 3D printer. The biggest problem I've found is that—during the process to extrude that plastic and to place it onto those spools—the plastic is often too hot to be spooled. This results in filament that doesn't easily want to de-spool from the holder during a print job. The proper way to spool freshly-extruded filament during the manufacturing process is to cool it below the "plastic" point and this fact seems to be lost on the people who are making the stuff.
The second biggest problem appears to be the cheap/simple filament spool's shape which is a simple cylinder. This shape promotes a condition called cross-threading which results in a catastrophic loss of filament during a print job. Typically, you'll come back hours later to see the printer "air printing" inches above the part and something like this behind the printer:
And so, you've lost another part to a common condition. I decided (finally) to deal with the problem and to recreate the standard filament spool itself with the introduction of a spool guide.
The solution is a spool guide which is inserted into an empty spool holder and which changes the inner volume for the re-spooled filament. The cross shape is now an optimal parabola instead of a rectangle, delivering filament in a straight path to the filament sensor itself.
Given the reusable nature of the spool guide as combined with the print volume on the Robo C2 printer, it was necessary to split the project into eight parts. Each half (bottom/top) is held together with four aluminum hex-head 6-32 5/8" bolts and this threading is incorporated into the design.
Each piece printed in about four hours so it took a total of 32 hours overall. Assembly was fast but it was necessary to keep tabs on part identification during that process.
The task to re-spool was made easy by temporarily re-purposing a rock tumbler base for this activity. I was able to control the tension by using my hand in between the two spools, which worked fine. (The base on the right is one of my filament holders which work smoothly since they include four bearings into their design.)
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