If you ever have an issue with the way simplify3d is slicing try to do the following which was recommended on reddit:
The way to fix this is to add 0.001mm to the primary layer height. i.e if you are using 0.2000mm, change it to 0.2001 and so on.
S3D has some weird bug where it can't always detect vertices properly, or something like that. I believe that the official line from the devs is that the model has problems, but that is BS.
Ever wonder how tight your belts should be on your printrbot or any 3d printer? Well thanks to redditor /RememberToBackupData, somebody posted a good way of doing this.
I use a guitar tuner app to help me get my belts consistently tight. I traverse the stage or arm so that it's furthest away from the belt tensioning screws, and then I strum the belt and ballpark the sound around 150 hz. Do note that I just picked 150 hz arbitrarily; I couldn't find any advice about how tight a belt should be except the eminently helpful, "Not too tight and not too loose." I think the design of the Simple makes perfect belt tightness unimportant, but I feel that having a benchmark for consistency is a good idea.
The guitar app "Chromatic Guitar Tuner" is on the apple store: https://itunes.apple.com/au/app/chromatic-guitar-tuner-tune/id662890455
Always use at least a minimum of 30% infill, the higher the better.
Print at a slow speed: 20-30mm/sec (1200-1800mm/min for simplify3d).
Extrude at a temperature between: 210-225°C.
Not really needed, but you can have the platform bed temperature set to: 20-50°C.
To reduce stringiness, set retraction for 1.75mm filament, to 2-3mm. Go with the lower amount if using an Ed3. Another option is to turn on the cooling fan.
When switching filaments (ABS or PLA) purge thoroughly before starting a print. Preheat, using a lower temperature 180-200°C.
If you need to glue ninjaflex, 3M trim adhesive and Gorilla Glue provide moderate bonding. The best way to connect NinjaFlex parts is with a hot knife welder.
Lastly, Never, Ever print on PEI, ninjaflex sticks like crazy glue. Use painters tape and make sure to wipe thoroughly with alcohol.
A nice site with some good info on printing with ninjaflex: