Plotches on first layer. not z calibration issue?

Dear team,
please help.
For the first layer using CUra slicer, I encounter the following plotches. (see image in link below):
the cube is 1x1x1 cm.

so the skirt is 2x2 cm “brim” for the first layer.

https://www.dropbox.com/s/0e9j02ur11wvduo/IMG_3375.JPG?dl=0

NOTE: the plotches at the turns at every corner. the nozzle touches these spots each time it gets to the corner, melts the plastic, and drags it around.

I played with three variables:

1. z- calibration.
[ul] a. 0.35 mm (using the calibration method in the build instruction section 3)
b. variation of stage height (with thumbscrews, rotating quarter turns increments).
c. range of variation is 1/2 turn reduction of nozzle to stage height from factory setting. and FULL turn of thumb screw increase from factory setting.
d. when stage is closer to nozzle, i get ‘flatten’ lines during prints. and worst plotches. when stage is further from nozzle, i get lines of PLA. still plotches at the corner.[/ul]
2. fillament temperature
[ul] a. going from 210 C to 180 C range (in increments of 10 C) for each of the temperature. plotches does not go away
b. lowering temperature decreases amount of fillament deposited onto the stage. but does not remove plotches. it reduces them a little though.[/ul]
3. flow percentage
[ul] a. flowing from 70-90 % (in increments of 10%)
b. lower flow rate reduces plotches, but they still exists.
[/ul]
I changed one of the variables at a time above and ran a case for each of them. I think there may be something else at play here that I do not know. I am new to 3D printing. please help.
One thought may be that these plotches only occurs when the nozzle stops momentarily when it changes direction (transitioning between x and y movements). while materials are still being flowed onto the stage and thus causing materials to flow in excess. is there something to help with this in the slicer settings?

thank you for your time, any help is appreciated.

You didn’t tell the size of your object. Small objects are harder to print.

Your issue looks a lot like over-extrusion.
The correct settings for PLA are 190° and 70-75% flow. The best head-bed distance is 0.2mm. Also change retraction to 3mm/120mm/s.

Try various speeds : high speeds will prevent the head from staying too long at the same spot but will increase vibration.

Dear Raby,
Thank you so much for the hints.

the cube is 1x1x1 cm.

so the skirt is 2x2 cm “brim” for the first layer.

I will try out the hints and change the original post.

I have a follow up question:

[color=#FF0000]- at the turn, (corners) does the filament gets retracted as the x/y movement slows down?[/color]

thank you,
-Phi

[quote=“phicoi”]- at the turn, (corners) does the filament gets retracted as the x/y movement slows down?[/quote]No, only when the head is crossing a perimeter.