Under extrusion on start

Please help me!
For last 8 months i was trying to solve strange problem with my printer without any success.
My printer was running almost perfect for about 2 years at absolutely same configuration with no changes untill i noticed it first time.

About the problem:
It looks like in start of extrusion, doesn't matter was it retracting or not, printer underexrude some material. So first few cm of perimeters or infill are underextruded, then it comes back to normal. It causes delamination of internal perimeter from external ones. Also honeycomb infill looks messed up.






Unfortunately i haven't got photos of worst cases.
This underextrusion goes through all layers.

About printer:
Self builded prusa i3, 6mm aluminium frame, y axis on sc10uu, bowden extruder with mk8 gear directly on motor shaft, original E3D V6 hotend. Arduino mega + RAMPS 1.4 + a4988 on marlin, pronterface.

Things i've tried:
2 times fully reassemble the printer, inspected every part for cracks/wear/play, stretched belts, changed all not smoothly running linear bearings, z axis threaded rods, clean, grease, calibrate, etc.
New hotend heatbreak (my was slightly bended), nozzle, mk8 gear, PTFE tube, extruder stepper motor, arduino, RAMPS, a4988 drivers. Fillament passes through bowden system smoothly.
Tried run pronterface and slic3r on another machines and OS (problem happened after i updated my win7 laptop to win10), another versions of slic3r including Josef Prusa's builds and 1.30 dev.
Tried cura and simplify3d.
In slic3r played with extrusion width, tried compencate by extra length on restart, but it causes overextrusion in thin places of prints.
Tried another versions of marlin and some play with it's acceleration, speed and jerk setting.
And lots of another things.

Sorry for long post and my english, but i am in despair.

I don't use the slicers that you mention so I am not familiar with their settings. You say that you have a Bowden extruder, how long have you had it? I understand that with Bowden extruders the filament snakes from side to side in the feed tube. This means that the length of filament between the drive and the nozzle must be longer than the actual length before the pressure required to push the filament through the nozzle is generated. Could it be something to do with your retraction settings together with the Bowden extruder?

Mine does the same. I have to add material after a retract otherwise it runs about 20mm before it starts extruding after a retract. Its a setting in most slicers

Quote
Supermec
I don't use the slicers that you mention so I am not familiar with their settings. You say that you have a Bowden extruder, how long have you had it? I understand that with Bowden extruders the filament snakes from side to side in the feed tube. This means that the length of filament between the drive and the nozzle must be longer than the actual length before the pressure required to push the filament through the nozzle is generated. Could it be something to do with your retraction settings together with the Bowden extruder?

I switched to bowden more than year ago and it was running fine without pressure compensation and extra length on restart. Retraction speed and distance also was same.

Quote
Floyd
Mine does the same. I have to add material after a retract otherwise it runs about 20mm before it starts extruding after a retract. Its a setting in most slicers

If i pick value of extra length on restart in slic3r to compensate underextrusion it causes overextrusion in thin places of part with solid infill like walls of hole for smooth rod. Also i've played with pressure advance, but it not helped.

EDIT: nevermind..

Edited 2 time(s). Last edit at 12/13/2016 10:03AM by Veesta.