Looking for a little insight… My delta (a FolgerTech Kossel 2020) is generally printing ok. However, There are a few little things that are still bothering me. First, is the stringing. Printing with PLA at 204C and printing slow at 25mm/sec. I am using Matter Control and I have a bowden setup, with a retraction set to 6.5mm @ 65mm/sec , and Z lift, .08. Yet, I still get the stringing. I just lowered my temp to 200C and it is about the same. Any thoughts?
looks like cobwebs , cool effect. Probably not what you were looking for but still nice 
Keep going lower on temperature - I have some PLA that prints at 185C and others that print at 210C.
Try with pla that prints fine on another printer. Is there a cooling fan? What firmware on the printer. Check that when its retracting it actually retracts. If the hot end is different to the other printer it may need more retraction. Are you printing from pc or sd card?
Stringing can come from both sides of the temperature range. Too hot and you can get ooze-strings, too cold and backpressure strings. Too cold and the backpressure built up in a bowden system can continue to push out during a travel move because there continues to be filament spring pressure on the back side of the nozzle.
A few things to try:
try hotter, try more retract distance, try faster travel moves, try “coast to end” which stops extruding before the end of the path before the travel move.
z-lift makes stringing worse in my experience.
In case of heavily oozing filament i was sometimes able to reduce it by simply speeding up printing and even reducing retraction length (for speedup).
Thanks for the comments… Working down to 185C right now…
Keith, keep the temps high with PLA. You’ll have stronger and better parts (superior layer adhesion & better looking walls). Use jerk/junction deviation and high travel speeds to combat stringing.
Keep in mind retraction distance is only one piece of the puzzle, extruder acceleration & retract speed is generally more important than the length itself (although all of it matters).
Fan will help with stringing some, but even with high fan you’ll start to see tiny spiderweb looking strings, which aren’t a big deal, but if you’re neurotic like me they can get annoying too.
I had already reduced jerk settings and use a fan. 185C seems to have finer strings. I may just need to up my travel speeds. This PLA I am using is not my normal brand. I should have done a temp calibration tower to sort out its best temp.
Keith, you’d want to be increasing the jerk / accel to really snap of the potential string before it is a problem. PLA really always prints best > 200c, but not all thermistors are accurate so YMMV. Deltas handle higher acceleration just fine and in many cases it’ll actually improv
I run ~8000 accel, 0.05 junction deviation (probably similar forces to 10 jerk or so in marlin) along with 250-300mm/s travels on my deltas, and always print between 205-230c for PLA depending on speed/etc.
^ all prints there with settings mentioned above
Your prints are gorgeous. I think part of my problem is that I am using Matter Control, which I really like, but am kinda floundering in the dark about the settings to use to get the best from my printer, a Kossel 2020.
@Mike_C What software do you use to print?
I use S3D at the moment. It isn’t perfect but I’ve found it to produce better results than slic3r/cura for me at least.
As far as firmwares go, I’m currently using smoothieware but I’m considering moving to something like machinekit to get some proper pressure advance features.
I’m not sure if your delta is tall enough for it, but a great way to get around the whole bowden setup on a delta is going with a suspended extruder. Short tube makes it print nearly identical to direct drive. Here’s mine http://www.thingiverse.com/thing:991638
Is it possible that your retraction speed is too high? Mine is 3.2mm at the Slic3r default of 40mm/sec. Perhaps you should try starting from scratch to configure your retraction?
John-Paul Hopman, there’s no downside to retracting fast. You want to be retracting with the highest speed/accel you can do reliably without skipping steps 
