The whole point of the new guide tube block is to see if a larger ID tube will reduce the force required to pull the filament through it; long after Dan suggested simply using a larger tube, I got around to picking up a lifetime supply of 1/4 inch OD polyethylene tubing: 25 feet for $3. The ID is about 0.17 inch = 4.3 mm, large enough to let the 1.75 mm filament move smoothly, and the inside clearance provides a few millimeters of free motion so that retraction moves don’t require pushing the guide tube around.
The new filament guide + wire cover anchors the spool end of the tube:
On the other end, I blobbed a piece of 1/4 inch ID tubing to anchor the guide tube. It’s nicer than the twist of cardboard I used before, but nothing to get excited about:
There exists a printed tubing anchor that attaches to the bolt that adjusts the force pressing the filament against the drive gear, but:
- It’s just an STL model
- That fits the original guide tube
- So I’d have to reverse engineer it
- And I don’t want to fiddle with the extruder
This will suffice for a while.
As I hoped, the larger guide tube reduces the force required to pull the filament into the extruder under 1 pound. Most of that force comes from persuading the filament spool to drag-rotate around the plastic support arm, so some simple improvements should help there, as well. I foresee some bearings in its future.
Fine tuning of the tubing length is also in order, but that’ll require more printing sessions.