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fuh

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Everything posted by fuh

  1. fuh

    Old PLA

    Same here (though not with every PLA brand). Seems systematic, very strange. Does anyone have an explanation for it? Maybe fumes of lactic acid (depolymerized PLA)?
  2. Updated the ring design. New in version 8 (vs. version 5): Now easier to assemble.
  3. Update: I was a bit unhappy with the "just hanging" idea because occasionally, the ring slipped off and fell down. So I made a guide thingy for the ring. Updated on Youmagine.
  4. Update: I have a suspicion that it becomes (more) brittle while staying in the bowden tube for a longer time. No idea why. Now I unload the filament whenever I won't print for, say, one day, and I think it's better now. Maybe an idea for you, too.
  5. Soon I will have four empty Ultimaker.com filament spools. Wouldn't it be a waste to throw them away? Any ideas for repurposing/upcycling of the spools? Preferably printable ideas, of course.
  6. Thank you! Looking forward to hearing about your results...
  7. Just hanging. It is held by the filament loop itself, while spreading it. It leans lightly against the feeder.
  8. I found a very simple solution to reverse the bend: Flip the filament spool winding direction and guide the filament around a ring. Like this: Although the image shows a modified spool holder, I tested it with the original spool holder and I reached 10mm^3/s no problem. (PLA, 210°C, original feeder, 0.4mm nozzle) Get the ring here: https://www.youmagine.com/designs/spreading-ring-for-reverse-bend-filament-feed-for-ultimaker-2
  9. Same problem here with PLA (white) from GermanRepRap.com .
  10. I use my old laptop computer, having a camera, and run Skype on it, with an extra Skype account just for that purpose and set up to accept a call without asking. That's all - very easy, works from anywhere.
  11. I noticed that the infill left not only a little ridge where it overlaps with the shell, but also little droplets now and then. First I thought this doesn't matter because it is inside the obect. But then I noticed that on the following layer, these droplets are sometimes dragged to the surface when the shell is plotted, and there they remain as bumps. I simply reduced the infill overlap (in the experts menu in Cura) from 15% to 8% and the bumps were gone. Maybe it's helpful to someone.
  12. I never noticed any improvement with glue stick. I'm printing PLA directly on the glass at 75°C. I found it sticking noticeably better than at 60°C.
  13. And I remember a case (with an UM orig.) where the filament was completely stuck, it could even almost no more be pulled out by hand. All because the printing speed had been set far too high whereby the feeder had caused a lot of deformation and abrasion. Thus the friction was extremely high. I stay with my theory that friction forces after the feeder are the central problem, and those before the feeder are neglectable, compared. Why: The brake effect of pressing material through the nozzle must be by far higher than the brake effect of spool unwinding, and these brake forces are the cause for the friction forces. Just normal engineering logic. How much is the deformation by the knurled wheel, anyway? Could it happen that it increases the maximum filament diameter to more than the tube inner diameter? Then the friction would increase overproportionally. If the increased counterforce of the feeder wheel in turn causes deeper filament deformations (just a possibility, not an observation) then we have an escalating problem!
  14. I'm not sure if everybody has noticed my findings about filament friction which allowed me to at least double the extrusion rate before underextrusion occurs. http://umforum.ultimaker.com/index.php?/topic/5454-ultimaker2-reduce-filament-friction-in-the-bowden-tube/&do=findComment&comment=52713. It might help.
  15. It may also have been the reason why some people have had success with putting the spool on the floor and some have not. It's all dependent on the orientation of the spool whether the rough side of the filament moves to the side of the tube where it causes increased friction.
  16. I noticed that the filament scars make an approximate quarter twist in the bowden hose, so they move to the outside of the bend. This is pretty obvious because the filament wants to keep its bend and adapts to the hose bend. So I put the spool on the other side of the feeder, outside the printer, in order to have the scars on the bend inside. The quarter twist would reverse its direction. But I had to help it a little to do so because the last decimeters of the filament had already a screw shape in the wrong direction. So I deformed the filament end, using hot water, from left-hand thread to right-hand thread, before inserting it. The result confirms my initial assumption. Here it is:
  17. As far as I remember from university lessons long ago, friction is, astonishingly, only dependent on the materials of the objects that have contact and the accumulated bend angle, but not on the contact area amount. So my idea was actually not supported by that theory, but I think it does not consider possible elastic deformation of the tube walls (by the filament surface scars in this case). I could imagine that the friction will be increased thereby. But my intuition may be wrong....
  18. I would expect that it's also much dependent on whether the bend orientation of the filament matches the bend orientation of the tube. But I don't know how to separate the two effects. Straighten the filament somehow maybe?
  19. Yes, obviously both work on the same principle. You could say, I'm misusing support as raft. Hmm, trying to remember why I thought it would be better than a raft... I think a thin raft can absorb much less contraction than a support structure. And it is my experience that a raft is hard to remove, but maybe that has changed? For parts without a flat bottom there is no transition from raft to support. I found an almost flat bottom is not easy to print without my trick. Or is it? But support generation strategies change all the time, and my experiences become worthless, I need to keep experimenting. So I could imagine an integrated support/raft structure with adjustable minimum height could be best. All this is just meant to be brainstorming.
  20. I managed to print some critical shapes by letting them "hover". That is, not letting them touch the platform level anywhere but having support structure under the whole part. That way, the support structure elasticity is used to absorb the tiny shrinkage movements that would else lift the corners or edges, sometimes invisibly at first but causing a bend that would escalate in the next couple of layers. So I may still get some slight distortion but it will not substantially bend a layer, and thus not escalate. For example I have applied this to nylon material which has severe warping problems else. In order to not let the part be automatically adjusted by the slicing program to begin at z = 0, I use to place some additional, tiny "dummy part" a bit below the needed part in my design. Maybe a nice feature candidate for Cura that a model can be shifted interactively in z direction, too, to achieve the same effect?
  21. I tried to print a pretty much "precision part" with ultimaker.com's black PLA. So I sliced with 0.1 mm and printed with just 25mm/s – but failed! This material, though molten, seems to be much less fluid than others, for example the light blue one, at the same temperature. The effect was that it seemed to disintegrate to droplets when it left the extruder, resulting in an ugly, "torn" structure. I aborted the print job. Then the idea came to my mind that there might be some kind of minimum flow, so I tried again with 0.2 mm and 50 mm/s. The problem is gone, the result looks perfecty even! My conclusion: Fine slicing or slow speed doesn't guarantee a better result!
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