Printing errors with Mini Kossel

Hello,
I'm experiencing some print problems with my Mini Kossel...it looks like the Z is affected in some way but I really don't know where the problem is.You can find 3 files attached:
print defect 1: a groove extending from the bottom to the top of the printed part.
print defect 2: a "hump" on one side.
print defect 3: layers of wrong diameter in different point of the printed part.

Any suggestion really welcome!!!!

Cheers

Albert

Additional info:
Printed with Pla at 197/200 °C and Gcode created with Slicer version 1.2.9
Printer:
Mini Kossel (Think3dPrint3d version 2) with RAMPS and Mega 2560.

Edited 1 time(s). Last edit at 11/11/2015 01:03PM by Albert MKossel.

One of the problems you often get with tall thin prints is that one layer doesn't cool sufficiently before the next layer starts. Try printing 2 of them at once, or one + a sacrificial tower.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks for the suggestion! Do You think that the heat was the only responsible? (hump and uneven layers,photos 2 and 3).I was thinking about a not great quality (not perfect diameter) filament or not perfect extrusion rate or dirty extruder hole (in this case I've not yet finished my first spool of pla)...

Looks like a cooling problem. Play with the fan(s) and printing two of these objects together.

ok thanks!