In terms of the “static retraction” you mentioned. Simplify3D may be your culprit here. Try turning off “Force retraction between Layers” under the advanced tab although IMO this feature doesn’t necessarily work.
Other settings that may help with over extrusion are “Coasting Distance”, “Wipe Nozzle”, “Extra restart distance (use with caution – especially for prints with lots of retraction)” and when you’ve got a full weekend purely for firstly understanding the subject and repetiers implementation – Linear advance which must be enabled in firmware configuration.h file “#define USE_ADVANCE 1” before it can be used.
In regards to linear advance, despite what many have said about bowden systems, I was able to get excellent results with long bowden tubes and Linear advance. My figures and settings will be of limited use to you as I used Marlin firmware which uses different settings. For what its worth – as a yard stick though my settings in Marlin were LIN_ADVANCE_K = .95 for a 700mm bowden tube with 1.75mm filament. FYI if it helps marlins default for a direct drive is .22 – meaning my setting was roughly 4.3x that.
From what I can gather from Reps limited documentation on the subject its useful to know that Repetiers “ADVANCE_L” appears to be the equivalent of Marlins “LIN_ADVANCE_K”. Also that Marlins M900 is Repetiers M233. The scale of this factor is also different between the systems. In Marlin 2.0 a typical scale would be 0.0 – 1.8. In repetier, the advance L range would be more like 0-200 from what I can see. (Ref
The only way to know what works for your system is to run some specific test prints where the range increases line by line, looking at the result and making a judgement as to which line is best, then translating that lines position into your “advance L” in eeprom.
Some useful reading on Linear Advance (this is made for an older Marlin implementation v 1.x, however the test code can be easily converted for repetier by opening the test code in Notepad++ and doing a search and replace to replace “M900 K” with “M233 Y”) :
If all of this is a bit advanced for you at the moment, seriously, leave it. There are other ways of controlling flow without resulting in as much hair loss. Saying that, im happy to help wherever possible.
Needless to say. using a .8mm nozzle, you’re amplifying just about every unwanted artifact 3D printers can produce. Large nozzles always require significantly more tuning that small ones.
One final thing. Don’t be afraid to try Slic3r. (use advanced mode). It gives you much more granular control of different parts of the print – and preventing unwanted retraction actually works. I personally prefer it over Simplify3D (which IMO is buggy, poorly supported and rubbish – god knows why so many people love it).