Print going bad at higher layers - Mono Mendel

Hi,
I have built an Mono Mendel, but struggling to get quality prints. First layer sticks good on to heated / non heated bed (masking tape applied to bed).
First few layers are fine, but after a few layers it goes haywire. Things i've checked are,
- Extruder calibration - Changed default steps/mm value to around 100. This extrudes around 31mm filament instead of 30mm.
- Motor Currents - All NEMA17 motors used, pots set for voltage of 0.75V
- X/Y/Z axis calibration - With default steps/mm values, movements are fine.

Setup that I have is, standard Mono Mendel built with following modifications,
E3D-V5 Hotend - 1.75mm Bowden
Kossel Mini Extruder - Direct Feed hobbed nut extruder.
PC SMPS for power

Attached snap is that of 2 prints i've been trying (50mm calibration tower - Thingiverse) , the right one (shorter one) is when motor current pot was set to 0.6V & the left part (taller one) is when motor current potset to 0.75V

One observation that i have is, while printing or even offline extruding filament, my extruder, frequently makes clicking noise, something like slipping hobbed nut. Its most probably motor trying to push filament, but hotend is not in a position to accept it.
I had also tried printing another object having larger surface area (Geometric box - Thingiverse), here the print went bad immediately after say 10 -15 layers.

Hope attached snap helps in debugging this issue.
Really appreciate any inputs on this.

Hi,
What speed you printing at, do you use slic3r what retraction set at.

Yes, I'm using Slic3r .. these values are from gcode generated after slicing,

layer_height = 0.25
; perimeters = 2
; top_solid_layers = 5
; bottom_solid_layers = 5
; fill_density = 0.4
; perimeter_speed = 30
; infill_speed = 50
; travel_speed = 130
; nozzle_diameter = 0.5
; filament_diameter = 1.75
; extrusion_multiplier = 1
; perimeters extrusion width = 0.84mm
; infill extrusion width = 0.84mm
; solid infill extrusion width = 0.84mm
; top infill extrusion width = 0.84mm

Speed not the issue , still no retraction setting " hiding under the extruder setting" alter that to .1 for now.while testing set the speeds to 20mm/s infill and perimeters.

Edited 1 time(s). Last edit at 03/20/2014 04:07AM by jinx.

I changed retraction to 0.1 , 0.2 but, prints were still bad .. were even worst than default retraction value (filament stopped oozing after 5-8 layers), all the axis movement seemed to be fine. Is there any method to calibrate that value ?
What is the required ampere rating for power supply ? (With all NEMA17 motors, heated bed off )
I highly doubt the hotend / extruder because even during dummy extrusion its not consistent. Sometimes it works sometimes have to struggle a lot to get it start extruding (have to retract then extrude )