Proper rewind?
Yesterday I had another case of a print getting stuck because the thread got tied up on the spool. I had it before with a spool of (very) budget PLA filament but this time it was a spool of Fiberlogy ASA, which is not exactly budget. It irked me from the start how dodgy the winding was and now there is the result. I'm happy the spool was in a drybox and tubed to the Nextruder so the forces were contained within the system and the blockade did not make the things topple over.
So, I'm thinking building/buying a rewinder, but one that yields a proper, say Prusament like, winding.
Most designs I see do some spreading but give no proper filament guidance.
Do you know of any good proven products/designs?
RE: Proper rewind?
This issue is usually caused when you change filament and the free end of the filament springs back on the roll and ends up underneath another section of filament. You have to be careful to not let go of the free end of the filament or this can happen.
It can't physically be wound that way from the factory.
RE:
Thanks. I do not know what they did at the factory, but as I said I keep my ASA in a drybox with a tube connection. The tube stays on the box permanently and the filament stays in the tube. When unloading I just let the filament stay 10 mm out of the tube and seal it with some tape. On load I pull filament out a few cm, clip off the end that was exposed to the tape and then feed it in and lock the tube onto the Nextruder. Thus there was no filament change with a free end or springing back. Also the block happened 3 m of filament down this print, which was the 3rd since I started using this filament this time.
By the way it is physically perfectly possible to wind wire on a spool such that it is dug under wire that was laid before. This happens when spooling is done at too low tension.
Re-spooling also is a good occasion to dry the filament.
RE: Proper rewind?
It is also possible, especially with the MMU there is a very great danger, but also if you have very lightly running filament bearings (with the MK4 (s), due to the sensitivity of the load cells and the associated problems with the calibration and first layer, since the electronics cannot distinguish whether it is now being pushed upwards from the bed, or pulled upwards by the ever tighter filament thread, against the downward movement)...Smooth-running bobbins lead to the reel being strongly accelerated with fast pressure, but suddenly there is no more “material requirement” during retraction, but the mass pushes even further, so that it loosens. This loosening can cause a small loop to form, which then “slips” under the neighboring loop. If the printer now wants to feed material again, the large winding tightens again and the small loop is practically securely fixed under the resulting “strain relief” - it tightens more and more the more you pull on the thread - the “Chinese finger trap” principle... That's why too smooth-running is not really a good idea...
RE: Proper rewind?
I agree on the danger of spool support running too lightly. I use friction bearings PLA to PLA, but admittedly only 12 mm radius. Note I use a tube between the drybox and the Nextruder. An X or Z move of the Nextruder does not pull any filament. It just bends the tube.
RE: Proper rewind?
Just stating from experience, I've probably used 500 rolls of material and this has only ever happend 1 time to me exactly how I explained it.
You've had it happen 2x in a relatively short period of time (or so I assume) and was trying to point out how it most likely happened. It could've happened when loading it into the drybox.
Good luck solving your problem.
RE: Proper rewind?
Logically, in the vast majority of times this problem is user's mishandling, but not in the 100% of cases. That would be against the laws of Murphy. Unlike Prusament s and other brands, that always comes nicely winded, I received now and then spools in such messy looking condition that it seemed impossible they were winded in a machine. I won't mention names. Most of the times, these rough looking spools have no internal knots, but because of the extra friction the extruder needs to pull harder. If the filament path from spool to extruder is a bit convoluted that extra friction may cause stutter and irregular layers.