Flexible TPU Filament - No bonding of perimeters on vase??

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09-20-2015, 07:32 AM
cassetti

Flexible TPU Filament - No bonding of perimeters on vase??
Greetings! I've been running several Flashforge 3D printers for over a year now, and I'm starting to play with flexible filaments. In 2013 I had a lot of success using a Makerbot Replicator 1 with a modified extruder upgrade to print (slowly) a huge 4inch to 2 inch Vacuum Adapter for a friend out of Ninjaflex filament - it was a pain in the butt, although it did print successfully.

Now I am trying to print flexible objects using Sainsmart TPU filament and noticing a major issue - my perimeters are not bonding well enough! I've been playing with every various slic3r setting I know to adjust and tweak the settings. I'm getting very close - my prints are coming out very nice - except when I flex them - the sidewalls delaminate completely. When printing an object like a vase, I can literally pull apart these layers by hand. (The layers are well bonded, but it's the damn perimeters I can't get to bond).

Please note I am using this extruder upgrade - http://www.thingiverse.com/thing:989965 and found it works pretty good, as long as I don't mess with my print settings too much.

Here are some key settings on my Slic3r Configuration:
- Diameter: 1.70mm
- Extrusion Multiplier: 1.15 (trying to mess with this to increase wall thickness - doesn't seem to help much with flexible filaments)
- Print temperature: 220C (was printing at 235C, testing lower temps to see if it affected print quality - doesn't seem to)
- Bed Temperature: 45C (using PrintInZ Zebra Plate bed - no problems with bed adhesion - it's perfect!)
- Extruder Retraction - 2mm
- Retraction Speed - 15mm/s
- Wipe on retract: Enabled
- Perimeters: 3
- 20% infill
- Speed
  - Perimeters: 25mm/s
  - Small Perimeters: 20mm/s
  - Infill: 10mm/s
  - Solid Infill: 10mm/s
  - Travel: 65mm/s
As you can see - print speeds seem to be ok, temperatures are ok. In fact the printer seems to be doing ok, it can print objects beautifully. Except when they are a vase or other tall hallow object. The layers will all bond to the base, but the sidewalls immediately break apart when I "crush" the print.

I suspect my Filament diameter and Extrusion Multiplier could be the key to fixing my print issues, but every time I crank up the multiplier past 1.25, my printer jams around the 6th print layer (10+ minutes into the print).

Please help! I really need to reliably print flexible filaments consistently (I'd even consider purchasing an upgraded extruder design if that would fix my problem)
09-20-2015, 10:06 AM
jimc

Ok so its not seperating along layer lines right? Each perimeter is seperating from the on next to it so its seperating vertically? If thats the case then your underextruding. Each perimeter isnt bonded to the one next to it because they are not touching or touching enough. Check filament dia and ext multiplier.
09-20-2015, 12:03 PM
cassetti

Quote:

Originally Posted by jimc

Ok so its not seperating along layer lines right? Each perimeter is seperating from the on next to it so its seperating vertically? If thats the case then your underextruding. Each perimeter isnt bonded to the one next to it because they are not touching or touching enough. Check filament dia and ext multiplier.

Yes, correct. I had the same thoughts as you, those are currently the two parameters I've been attempting to tweak. I have used calipers to measure the filament which had been measuring at around 1.70 a month ago, however it's flexible filament, so I don't know how much I can trust that reading (currently I measure 1.5mm? is that possible? Or do I need a new measuring device?)

Additionally I have been playing with the Multiplier setting with some success, although when I set the multiplier above 1.23, the printer will jam on the 6th or 7th layer (when the solid infill is finished, and the perimeter section of the vase begins). However when I turn the ext multiplier down below 1.23, the print finishes and looks perfect, except the shells/perimeter are not bonded together sufficiently

I am currently measuring 1.5mm diameter on the filament, is it possible that setting the filament diameter to that low of a setting will fix my issues? I've slowed down print speeds to less than 5mm/s and still encountering issues, so I don't think print speeds is my issue, moreover I have a feeling printing at high temperatures would be easier on the extruder, correct?

Side note - I recently upgraded my extruder teeth gears. After running more than 9000 meters of filament through each, I replaced the printer's extruder stepper gears with a fresh pair of sharp teeth, so that shouldn't be an issue (soooo much grip - it runs like a brand new printer again).
09-20-2015, 07:25 PM
jimc

well i dont have any definite answers for you since i dont use slic3r and i have not printed that brand of filament. i have printed a boat load of ninjaflex though. enough that i have one printer just dedicated to it that runs about 12hrs a day. for the ninjaflex i run that at 250deg. hotter is def better. i makes it thinner so it extrudes better. i would turn the multiplier up, temp up and the speed down a little for the perimeters. i also found retraction to be almost useless for ninjaflex. it just stretches it like a rubber band. i found it causes problems but i also never tried slower retractions like your doing
10-09-2015, 03:42 PM
cassetti

Well after a bunch of messing around. I discovered what the problem has been for me - the extruder drive gear!!

My original Flashforge included this iron extruder stepper gear:
http://ep.yimg.com/ay/yhst-136641646...ive-gear-3.gif

However prints would keep jamming, and I couldn't even print with Ninjaflex due to jammed extruders. TPU was better, but not by much.

Then I discovered my brand new Flashforge had a different style Aluminum extruder drive gear (similar to this picture, but silver color)
https://www.bilby3d.com.au/ImgProd/ptFildriveFFD.jpg

As soon as I swapped drive gears, my printer worked flawlessly. I can print Ninjaflex perfectly!!!! Phew!

Thanks for the Help JimC
10-18-2015, 12:10 PM
bonzo

I'm sorry, but which filament gear works for you?
The newer aluminum one or the older steel one?
10-18-2015, 01:19 PM
cassetti

Quote:

Originally Posted by bonzo

I'm sorry, but which filament gear works for you?
The newer aluminum one or the older steel one?

Sorry I wasn't clear - the newer aluminum gear is working

Since switching to the newer aluminum gear, I've been printing perfectly with Black Ninjaflex
10-18-2015, 03:46 PM
EagleSeven

Quote:

Originally Posted by cassetti

Since switching to the newer aluminum gear, I've been printing perfectly with Black Ninjaflex

Curious, is the aluminum gear Larger diameter than the steel one, ?
It appears to be, but it may not be larger where the Teeth are ?
If it is larger diameter at teeth, that may explain why it works better ?

Or was the steel-tooth gear clogged with filament, making it slip ?
(I normally clean that gear after about 25 prints, to remove residue,
and Flex-filament would require it be cleaned more often)
10-18-2015, 09:54 PM
bonzo

Thanks for the response. I have the alum one as well, I am betting the sharper pointed steel one was cutting in and grabbing the TPU, then pulling it around...