The print is now much better than before after I tighten the belts again. But I notice these horizontal lines. It is less visible in other color but white kindda accentuate this problem. My initial research shows that this is related to over-extrusion. Is it? What am I missing here?
Don’t worry about the pimples. I have my slicer with random starting point for each layer.
Your object is showing facets. Is that intentional or the result of exporting the model at a low resolution?
It looks, to me, that eliminating those facets would also eliminate the blobs on their edges.
I got this from thingiverse. The author includes the scad file so I will try reexporting.
@Dat_Chu lower the values for $fa and $fs to get more facets. I usually use 1 on both for draft, and 0.3 for final renders.
http://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Other_Language_Features#.24fa.2C_.24fs_and_.24fn
Edit: And those blobs should not be there regardless. One potential cause is over extrusion.
Those blobs are indeed strange. I believe they are related to the starting position. I am testing dialing down the flow rate to 90%. I have measured the filament and it is indeed 1.75mm. Either the motor is rolling faster than it should or the tip needs replacement.
@Dat_Chu any other signs of over extrusion? If the blob is only at the start of each layer you could try to vary the retraction.
More or less retraction? The corner doesn’t look smooth either, it has lines sticking out a bit.
May need more retraction or possibly less prime/extra feed after a retraction for a move, but there are calibration objects on thingiverse and youmagine that can help you verify that better
Cool, I will try some of them out. There are just too many calibration objects on these repo :(. If you have one that you recommend, please let me know. Thanks.
If you haven’t before, run through this bad boy: http://reprap.org/wiki/Triffid_Hunter’s_Calibration_Guide
This is a decent one for retraction and ooze: http://reprap.org/wiki/Calibration#Oozebane
Also, if you find you’re having to adjust your extrusion % after calibration, its best to recalibrate your extruder steps to compensate. Much healthier to fix issues in firmware and hardware than to customize your slicer to do so in the long run.
Pump up $fn value in the cylinders in the source code for more facets.
@Miguel_Sanchez $fn is to define a fixed number of facets. $fa and $fs, minimum angle and minimum size, is generally speaking a better choice as the arcs keep their “resolution” if dimensions are changed.
See the section Interlude: a technical note about the precision of the facets in @Jeremie_Francois excellent blog post here;
(Just had to mention this since I was using $fn fo so long, for the wrong reasons 
)
@korpx indeed, we probably all did this at the beginning 
By the way, setting both $fa and $fs to less than 0.5 is probably overkill. It generates a huge amount of gcode (where the segments are often smaller than what the printer is capable of). More importantly, if you use a serial link (USB tethered printer), small pauses may happen as the link is overflown (or the arduino fails to keep up with the conversion, e.g. on delta printers). This in turn impacts quite badly the print!
updated: added this warning to my tutorial
