TPE on Printrbot LC

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TPE on Printrbot LC

Postby Richy_T » 2016-Dec-Sat-01-Dec

Is this at all possible? I have tried but it always jams up, even when I've put the temperature up to where it should just be plain runny. I have a standard LC head but I added the ptfe tube upgrade.
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TPE on Printrbot LC

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Re: TPE on Printrbot LC

Postby RetireeJay » 2016-Dec-Sat-07-Dec

There are several Thermo-Plastic Elastomers on the market. I have used NinjaFlex SemiFlex very successfully (it's a type of polyurethane - a plastic system which is almost infinitely "tunable" for different rigidity and other properties); there are other people on the forum who have used other brands of flexible filament.

Two major considerations are:

(1) Have the filament supported by tubing or close-fitting holes right up to the driving point. And I mean right up there - with the tube or machined hole nearly touching the driving gear and idler wheel. In my case, I had to reverse-engineer the exact geometry of my old Wade's extruder and print an insert out of nylon to get the required support. That shouldn't be necessary on newer extruders, but it illustrates the importance of good support. The flexible filament will "escape" out of the desired path and kink if there's a gap equal to the diameter of the filament.

Even if the filament can't escape and form a kink, it can bulge and create a blockage, so...

(2) Slow down the printing speed. Ideally, use a volumetric limit (i.e. the speed is determined by the volume of filament extruded per second, not the linear motion of the printhead in mm per second). This volumetric limit would also be dependent on the nozzle diameter. With a nozzle size of 0.8mm, I printed successfully at 235C and a volumetric rate of 10 cubic mm per second. The resulting print is flexible and extremely strong (i.e. inter-layer adhesion is perfect). With a nozzle size of 0.4mm, I printed successfully at 235C and a volumetric rate of 2.5 cubic mm per second. (The area of a 0.4mm nozzle is 1/4 the area of a 0.8mm nozzle - although fluid dynamics would lead to an even greater penalty for the smaller nozzle, this setting worked for me to print a cellphone case.)
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
"My next printer is..." Prusa i3 MK3
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Re: TPE on Printrbot LC

Postby Richy_T » 2016-Dec-Tue-02-Dec

Thanks. I'll give that a try. I have plenty of the ptfe tube left so I'll see if I can cut a new piece and get it snug up to the feed. I'd consider a newer feed but there are other issues with the printer that I really need to address first.
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