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Sudden change in material flow scale?

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I've been experimenting Flex PLA by Ultimaker over the past couple of days. This material requires quite high material flow factor - I have used 130% with quite OK results. Suddenly, when starting a new print, I realized the material flow was not nearly enough. First I didn't touch the material flow factor as I thought there must be some other problem... Just a few days back I took into use IRobertI's feeder - but that seemed to be in good condition. I double-checked all printing parameters (the gcode was the same as I had used already before). I aborted the print and started all over - the same poor result. This time I checked the leveling of the bed, cleaned the nozzle, restarted the whole printer, went through the material changing process - nothing helped, a newly started print showed the same symptoms as before.

Then, I made the (kind of) obvious move: I started to increase the material flow factor - and it helped, above the level of 300% (!). 260% (doubling the original) was not enough, but here's the difference going from 130% to 320%:



WT...? So far haven't noticed any fluctuation in the material flow. If I have set it somewhere, there it has stayed. Now it feels I have switched on a new gear and the RPM figure translates into a different speed... I wonder what will happen if the gear changes back ...


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Where does all the extra material go? Does it turn into a gas? Is the diameter 2.85mm?

Maybe it is slipping? It must be slipping. Try printing slower? Some people say you have to print as slow as 10mm/sec with flex materials. Some people recommend a drop of oil inside the bowden but I don't know how to get it in there!


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Your print speed should improve drastically if you would move the feeder onto the extruder like here: http://umforum.ultimaker.com/index.php?/topic/3261-ultimaker-2-extrusion-problem/&do=findComment&comment=46577

I have seen how good flex materials are printable on machines with extruders that had their feeder directly built above them..... it limits your speed naturally but should improve overall speed with flex mats by a great deal.


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It took me some time to return to the topic - my claim that 3D printing is an old Easter tradition didn't sell well in my family.

I wonder what will happen if the gear changes back ...

Now I know:

back to full throttle


After my tests with Flex PLA I returned to "normal" printing. First printed objects were printed with sky-high material flow and the results were slightly off - but only slightly. However, the printed objects were quite small. Then, while printing the object above, something happened - obviously the nozzle got to full throttle again and my UM2 pushed filament through it as if there was no tomorrow. I reverted to normal material flow and continued printing. But, the problem - serious under-extrusion - returned for several times.


I'm still not sure if I have fully recovered from the problem, but obviously residue from Flex PLA plays a significant role here. After realizing the nozzle was partly clogged (having had cleaned it already), I took some time to clean it as well as I could. But it turned out to be very tricky. I really don't know where/how the particles of Flex PLA were hiding, but they were very good at it. After several changes of filament, dozens of meters of PLA and ABS filament consumed, I still could get the nozzle partly clogged every now and then. At this point I decided to wear my silk gloves I use for gentle wor, heated the printing head to 260C, removed the Bowden tube from it and rammed several meters of PLA filament through it. Still after a meter, this is what I got:


Flex PLA residue


So - it looks like Flex PLA particles are fairly die-hard, staying somewhere in the system and ready to delight at their convenience.


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Thank you for the hints... Feeder I had checked already; it's IRobertI's design and very easy to clean - also the tube was clean. I had tried to make an ABS cold pull, but the filament got seriously stuck to the nozzle and I didn't dare to use enough force to take it out. However, after giving it a second thought, I realized there must be a reason for the filament to get so stuck to the nozzle... This time, after warming up the nozzle and inserting white ABS filament into it, I injected there also some acetone - quite a cocktail :)

Here you can see the result:


I can't believe it... This is after quite rigorous cleaning, dozens of meters of different filaments consumed etc - and the black stuff was still there.

Flex PLA is certainly a nice material, but it also requires quite a lot of patience - not only during but also after printing with it.


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