Feb 11, 2019 | By Cameron

For makers like Daniel Harari at Harari Projects who store their filament spools on a rod above their 3D printers, sometimes printing from a distant spool can create so much tension that the extruder on the 3D printer can’t pull the filament in, causing prints to have gaps or to fail. The same tension can also cause the spools to unspool and then tangle, again causing print failures. It’s a popular setup because feeding down into a 3D printer is most ideal, but the lateral tension issue is bothersome. Daniel had had enough and came up with a solution: a “buffer” device that detects tension and pre-extrudes the filament directly at the spool.

Daniel’s invention is brilliant due to its high level of practicality and low cost, being constructed of 3D printed parts, components from an old paper printer, and a couple of 555 timer circuits.

He 3D printed a cone, wrapped it in aluminum foil, and then positioned it on a base printed with flexible filament within a copper ring.

The filament is fed from the 3D printer through the cone; when tension is applied, the cone bends and makes contact with the copper ring, completing the circuit that instructs a motor to extrude a bit of filament.

Daniel was kind enough to share all of his schematics and design files on Thingiverse, which we all appreciate.



Posted in 3D Printing Application



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Techbunny2000 wrote at 6/9/2019 3:01:06 PM:

This is really not new. The original UP printer from PP3DP used a tension based filament feeder to relieve tension on the print extruder. This was done more then 5 years ago.

Bill Pealer wrote at 2/12/2019 4:58:00 PM:

the cone with no motor provides most of the strain relief. you could simply slide the cone feeder horn in front of the selected spool, and it would provide enough reduction in friction to buffer the feeder. How is that additional feeder going to react to a 215mm travel at 150mm/s? That is why a spool must be free to unspool as fast as the printer can take it.

Chris wrote at 2/12/2019 8:16:55 AM:

In the automated welding industry, we'd call this a wire feed assist. There's so much overlap between welding and 3D printing, I'm continually watching hobbyists reinventing the wheel.

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