Soft Flex  

RE:

I am able to print Coex Flex 60A with decent success but it did require a lot of patience and tinkering.  For me it, it was all about adjusting the tension on my Bontech extruder.   

RE:

Update - the M3 x 45mm long screws came today so I put one in ro replace the 40mm and tried the Fiberology Fiberflex 40D. 

I set the bond tech wheel tension set very very low.  (1/2 turn after it touched  the filament)  I am happy to report I just had my first successful print with the material! 

I will try the fiberflex 30 in a couple of minutes.  I am not going to get my hopes too high on that one though.  It is very soft.

Joe

RE: Soft Flex

The fiberflex 30d was a fail.  I was at least able to get it to extrude manually, but the print fails horribly underextruded.

RE: Soft Flex

I have played a lot with slicer settings and drive wheel tension.  If you want to print flex reliably, get a 45mm drive wheel screw adjust it to about 1/4 turn tighter than the minimum needed to get it to feed.  (I would preheat, then manually actuate the extruder axis until the filament could feed through the nozzle, than add 1/4 turn) 

FlexFill TPU 98A = Prints no problem and fairly fast.  I just used the settings in the Prusa Slicer for it and it works.  No need to have the longer screw.  I really like this material for parts that need to be tough / durable and can be a little flexible (think vise jaw inserts etc)  I have given some parts I made out of it to buddies and asked them to try to break them.  Hammers, Vises, and pliers couldn't do it.  Scissors and other cutting devices did.  It is a really good material.  I wish they made it even stiffer so I could use it for any structural part.    

FlexFill TPU 92A = Prints pretty reliably.  The settings in Prusa Slicer work for this, but to get reliable prints, I had to loosen the drive wheel tension further than possible with the 40mm bolt that comes with the MK3S+.  I went to a 45mm bolt and that enabled me to loosen it enough to reliably print.  This is a pretty flexible material and it prints fairly easily.  I made some antique car door bumpers out of it.

FiberFlex 40D = It took some tweaking, but I can get it to print slowly with the 45mm screw set loose.  I don't like this stuff.  The standard settings for it in the Prusa slicer did not work for me.  If I "tuned" the speed down to 60% I got reliable prints.  The end product is slightly stiffer than the FlexFill TPU 92A parts.  The Flexfill stuff is really strong and just as flexible.  I see no advantage to the FiberFlex 40D.  It is a pain to print and with no softer finished product than the much easier Flexfill TPU 92A.  I will probably give my roll of FiberFlex 40D to someone I don't like.

Fiber Flex 30D = I can't get a print out of this stuff.  It just doesn't feed through the extruder.  I have made a few way under extruded parts that came out like crap, but I cannot get anything close to a decent print, even at comically low print speeds.  I went down to 40% of the speed setting for this in the Prusa Slicer and was able to get some under extruded parts out of it that were useless.

NinjaFex TPU = I ordered a roll since I saw some people has success with it.  I tried the settings found here but the part was a little stringy.  I then went to the Prusa slicer settings for FlexFill TPU 92A but slowed it down via the "tune" function on the printer to 60% speed.  It printed perfectly.  I think I can speed it up a little, but am really happy with it.  The part came out softer than any of the other materials I tired and am on my way to 3 successful prints in a row with these settings.  I think this will be my go to stuff for parts that need to be very flexible.

If anyone gets FiberFlex 30D or something even softer than Ninja Flex TPU to print successfully, please let me know.

Thanks!

-Joe

RE: Soft Flex

I appreciate all the insight on this thread, these are exactly the issues I'm currently tackling.

My only question, is how do you tell when the drive tech wheel has been loosened enough? I have no gauge as to what point to loosen it too - nor what amount it has to be tightened to be applicable for PLA again. Is there an easy way to test if I have approximately the right looseness (for something like 92-95A), or is it just trial an error with seeing if that jams?

RE: Soft Flex

FocusOnTheSun, If you still have the 40mm tension screw that came with the unit, set it as loose as you can.  I had mine only threaded 1/4 turn after it grabbed.  Unfortunately that might still be too tight for some of the softer filaments.  If you want to print the particularly soft stuff, put a 45 mm screw in.  Here are some tips to set tension with a 45mm screw.

Insert the filament by hand with the screw backed out all the way.  Make sure you get it inserted far enough to be between the drive wheels.  From there I tightened until the both wheels just touched the filament.  To find that spot, I would put my thumb on the head of the screw and my pointer finger on the door and gently try to move it side to side.  It I felt play, I tightened a little more.  You can also find this spot if you have a very soft touch on the shaft of the Allen key and tighten slowly and gently.  You will feel a very small torque increase to turn the Allen key once all the slop is taken out.  It is subtle, but if you tighten with a very soft hand, you can distinctly feel once the slop is gone.

Once I got all the slop out, I heated my nozzle to 240F and went into settings and manually moved the extruder axis.  You have to move it far enough that it is in the hot end trying to liquify.  As you feed it in, very gently hold the filament just above the inlet with two fingers.  You don’t want to add any resistance, just feel if it is moving.  Get a feel for how far it moves in one extruder step.  Do this slowly, like one step pause a second, one step.  When it gets to the hot end, the filament may not advance.  If that is the case, turn the screw in 1/4 turn and repeat.   Each filament was a little different, but I did not have to go very far at all once I got the slop out.

If the wheels are too tight you will have 2 issues - The filament can wrap and jam around them, or it can under extrude.  If they are too loose, the filament will either under extrude or not extrude at all.  You basically want them only as tight as necessary to get the filament to feed.  I checked this by manually advancing the extruder and feeling the filament move.

For the really soft stuff I would make sure I waited 5 seconds or so between extruder steps to give time for everything to liquify.  You have to feed that stuff very slowly to not have back pressure...

-Joe

RE: Soft Flex

Wow thanks very much for the insight! I've already put what you've said into action and I can say that it's made a huge difference!
The filamentum 98A filament works perfectly now with no issue!

Weird that I have a 95A filament, but occasionally it just stops extruding quite far into a print, even with the screw untightened all the way. I would've thought from what I've heard I wouldn't need to buy the 45mm screw for 95A - but I guess I'll have to give it a try. From what I could tell, the filament did not slip out of the side of the extruder assembly, it just for some reason wouldn't go into the nozzle any further - so I assume it got squashed again, but if there was any squashing, it's incredibly subtle...

From experience do you need the larger screw to reduce the tension even at the level of hardness I'm working at?

RE: Soft Flex

At 95A, you might need the longer screw.  The tension seems to depend not just on the filament hardness, but the actual filament.  With Filamentum I was able to print their 98A stuff 100% of the time with a 40mm screw loosened to 1/4 - 1/2 turn from all the way out.  When I switched to the Fillamentum 92A, I could print with about a 75% success rate for prints that took an hour or so.  When I switched to a 3 hour print I had 0% success with the 40mm screw.  Once I switched to the 45mm, and adjusted it, I had 100% success with the 92A.    I have even had 100% success with Ninjatek 85A after tuning the 45mm screw tension and that is really soft stuff.

As a point of note, I just went from Ninjatek Ninjaflex (85A) to Ninjatek Armadillo (70D) and did not change the screw tension.  It was too low for the Armadillo.  It would skip now and then.  Point I am making, is you may need to tune it as you switch materials.  I tightened it 1 full turn from the ninjaflex to the armadillo and now it is printing perfect.

I don't know why Prusa doesn't use a 45mm bolt and / or a softer rate spring from the factory.  It would basically add zero cost and increase the range of materials the user can print with out of the box.  

I was ordering some other stuff from McMaster and ended up adding 92290A764 in my cart for that order.  There are likely cheaper options of you search around.  You need a M3x0.5 pitch 45mm long.  As a bonus if you get a SHCS with a 2.5mm internal hex you can use the same Allen key that came with the machine.  

-Joe