The first thing we had to do was print a "filament guide" piece for our Printrbot Simple Metal. Without it, the softer filament would bunch up before it even got to the extruder.
The first problem was that the design must be for an older version or our printer because the bottom "bridge" piece would not go over the "hump" where the filament enters the extruder.
So I had to brake it off and see if that would work. It fit and then it was time to adjust the tension. Getting the right about of pressure took a little time. Too loose and the filament wouldn't be pushed through the extruder, too tight and it would start to bunch up around the wheels.
Finally the pressure was correct and we started to print. I started out with the suggested settings from the NinjaFlex website (http://www.ninjaflex3d.com/). It worked OK but as I did more research, I realized that different people used different settings...sometimes for the same machines.
Five different settings and 5 different caps. The best one (the one on the far right) was the most consistent print with the least amount of "whiskers" (it had a travel speed of 100mm). I realized that lower the "travel" time the more "whiskers" you got. I have a few more test to run, but it seems like it's going to be somewhere between 100mm and 130mm. At the end of this post, I'll have all the settings I am using.
The next printing was with a travel speed of 130mm. I still got whiskers but not as many.
The castle with the slow travel time is on the left and the faster travel time is on the right. You can even see the door on the right one...the left castle's is filled in.