"shark gills" printing ugh! creality cr-10s

hello. i was all excited to try the new mirror plate, it leveled pretty darn well as far as i can tell, using the paper method. so i started printing and things got worse and worse, turns out i had a clog. remove the nozzle and tube leading down into the nozzle, type clog. i cleared that up and leveled, then started printing. works pretty well now. BUT the last print i tried printing before the clog got worse and worse had shark gills like layer! i cleared the clog and no strings, seems like everything is sticking well to the mirror with hairspray on it, except when it come time to print the solid bottom layer, i got what looks like shark fins. the nozzle would lay down a few diagonal rows pretty well, then it looked like as soon as the filament made contact with the mirror, it arched upwards like the wake of a boat in water. i've attached pics.

i'm using cura 3.1 and
layer height 0.1mm
initial layer height of 0.2mm
line width of 0.4mm
shell wall thickness 0.8mm
top/bottom thickness of 0.6mm
Top/Bottom pattern - Lines
Bottom Pattern Initial Layer - Lines

my print speed for everything is 50mm/s

bed temp: 65deg (this is pretty dead on +/- 1 degree according to printer display and temp gun)
filament temp: 200deg (not sure if this is on or not, but all other prints (8 or so of them of varying sizes) up to this point printed OK even the little benchy boat which used 200/60deg)

i did try 62deg on the bed with no difference.

i'm pretty lost as to what it could be and what it would take to fix. the only thing i can come up with is that as the printer moves in the X Y axis it's not moving far enough in X and the nozzle kicks up the filament it is extruding? but - observing it, it simply looks like as soon as the filament hits the mirror, it is repelled up in an arch form. i checked just about all of the bolts and made sure they were tight - i did not tighten any. so maybe it's something in my settings for this particular print. or maybe it's over/under extruding (to me that means it's pushing too much filament into the nozzle?).

also, in 4 other attempts to print a similar model, it printed this layer very very well, the diagonal lines were perfect and uniform, stuck together very well. the only difference there was those prints failed in other areas - i think because of the clog getting worse and worse.

thanks!

Attachment 11319Attachment 11320

yeah I've had that.
It's one of those weird ones where you think moving the nozzle closer and smooshing it down a bit more will fix it - whereas in reality you need to adjust the z gap up slightly.
I do this in the slicer via gcode z offset.
Go up in 0.05 increments till you get a smoother layer.

nice thanks. i'll give that a try!

since i'm such noob i'll ask --> z gap adjusting up via the gcode, is more or less equivalent to manually lowering my mirror with the thumb screws... ie) re-leveling my bed? just that i'm doing it in the software now since all leveling seems good via the paper method though a little tight.

EDIT: and perhaps my printer has the ability to adjust an offset in the control menu...

Yes, sort of.

I only ever do it via simplify 3d - that way I can have different ffsets for different filaments. Might be a way to do from the printer comtrol panel.
Mine does have a menu to select what surface you are printing on. No clue what changes though, or indeed why you'd bother.

what slicer are you using ?

i'm using cura 3.1. i checked in my printer menu and there is an option under Prepare>Move>.01 or .1 or 10mm> z-axis. while it looks like that may add offset to the nozzle, seems like doing it in code is the better option.

i believe in cura, i just need to add the z offset in the code editor in the section under start settings.


EDIT: so in cura 3.1, there is an initial layer height option set to .2mm double my regular layer height .1mm

well, that didn't do it. cura doesn't have an adjustment for the offset, i couldn't find how to do it in the gcode, so i re-leveled the bed with a little bit bigger gap, a thicker piece of paper. that thicker piece was more like two pieces of paper that i used before to level the bed. i still got the gills. i'm trying a different type of top/bottom layer pattern right now, also lowered the bed temp down to 60 where i have had 4 or 5 successful prints including one wide one, 280mm wide, but it was narrow in the x direction.

ok wow. so looks like i fixed some of this.

1. i put the old bowed-in-the-middle glass plate back on - instead of using the mirror which i know to be flatter
2. i re-leveled the glass plate and as expected the center gap to the nozzle was very tight, so tight it scored the piece of paper when i tried to pull it out (yes, i put paper there and let nozzle settle down onto it when leveling moved to that location)
3. i lowered the two front corners of the bed so that i could get the piece of paper out from under the center point where the nozzle was
4. i made a mental note of how tight it was in the center
5. i loaded up Benchy3d boat gcode and printed

well guess what? that little thing dead center, printed just fine

6. i removed the glass plate and replaced it with the mirror
7. i re-leveled with the mirror in each of the corners, i really reduced the gap such that the paper had about the same amount of drag on it as it did with the glass plate in the center - which was a lot of drag! i mean, the paper had to be slid diagonally with two hands so it would fit under the nozzle, then there was a lot of vibration and drag
8. i updated my model in the slicer so that it would print the lines at 90 degree instead of 45 degrees as seen in the pictures above (this may or may not have contributed - i was willing to do more than one change at a time at this point!)
9. the center of the mirror has a lot less drag on the paper than the corners, but i can still kind of feel some "light scratchy" feeling in the center
10. so my mirror is obviously concave in the center - then i went ahead and printed the actual model above (i did not test the benchy3d boat because i wanted to get things going)
11. the print started and primed a little goofy on the first pass, then went to town printing my model and so far perfect! the lines are going the long way left/right. it's not lifting up or curving
additional info: i can see the nozzle head impression in the hair spray layered on my mirror in the four corners, that's how tight it is.
additional info 2: i put glue stick down on the glass plate print and on the hair spray covered mirror
additional info 3: my PLA temp is back to normal 200deg and the bed temp is back to normal 60deg

two take aways:

1. i will have to try the diagonal again
2. when people on the internet say "raise the bed just so that there is a little scratchy feeling on the paper" what they must really mean is: raise the bed so the frickin paper is held in place damn tight to the point where it scores about half-way into the paper when you pull it out ha!

i did see a video somewhere where someone did not use a piece of paper when leveling the bed, the person got a vibration when the nozzle hit the glass, then backed off a tiny bit.

so we will see. almost done with bottom layer at 47mins and no lifting etc...