so let's see I've done a couple of changes one is I went to a 6x6 grid so instead of doing just one
two three by three it does six by six and let's say I downloaded a calibration model here for
bed leveling I stopped the print after one layer I think some of these got to yeah I was starting to
print a second layer over there I think I still have the sensor a little too close or actually
I have it I need to raise it a little bit more because these are facing they're sticking pretty
solid this this was probably the first one so it might not have been extruding all the way
this was probably the second one yeah these are still hair like they're really stuck down yeah I
think it's I'm still a little bit close to the bed so what I may want to do here is I'm gonna
turn the sensor probably another eighth of a turn clockwise got a check to my instructions here so
it says if the filament is smooshed rotate one quarter turn clockwise I did about an eighth of
a turn last night I may go another eight to get that quarter turn is what that's gonna do if you
do that quarter turn clockwise lowers the sensor which means it's gonna detect the bed earlier and
that raises the nozzle so I think that'll be my next step here because all of these are these are
stuck down quite well okay it tried a second print here I changed the height a little bit
I think I might have gone too far you can see I'm getting a problem sticking there yeah I might have
to go back counterclockwise a little bit let's see what some of these look like here there's like the
front yeah that that peels up a little too easy yeah the that's a little too much so it looks
like I'm getting pretty close yeah you can see how those are really almost not sticking they're
just barely barely held down and that back one boy that wasn't even stuck so I guess I went too far
okay here's the third try I lowered the no it's a little bit it sticks pretty good and it looks
fairly full try one of these back here yeah that's looking pretty good sticking down pretty good ones
a little rough surface but I guess the bottoms look pretty good the tops are feel a little bit
rough but it I think they're okay they're definitely stuck down well but not insanely
hard like sometimes it's definitely adhered to the bed yeah just a few little holes like right down
right in there yeah I think everything's pretty uniform they're either completely filled in like
that one well there's like just a slight slight void right there around the edge but all of them
are very similar you wouldn't be able to tell which one came from where yeah I think that's
a pretty good setup right there yeah it took about three or four adjustments so we'll wrap
this up for now so I'm doing the auto bed leveling bilinear feature and I've programmed in a six by
six test array so that's actuated when you do the g29 g-code command that's in the start g-code in
the cure slicer so there's already Agito in there which basically says do the auto bed leveling and
so the only thing I do beforehand is I turn on the bed heat turn that on leave it on for about
10 minutes to make sure everything warms up and any thermal expansion is going to happen and I do
notice a difference I'll show you in Excel I put the cold and hot correction meshes into Excel and
then I have a spreadsheet and a chart that shows the cold the hot and then also the difference so
let's go take a look at that and see what that looks like ok let's take a look at this bilinear
bed leveling mesh data that's quite a mouthful so I showed you in the previous video where I
captured this data out of the octoprint terminal window after running the g29 bed leveling command
so what I had done first was I used a cold bed and ran the g29 command captured this data and
then I showed you capturing the data off of the hot bed so this bed was warmed up to 90 degrees
C for about 15 minutes and produced this mesh and you can see there's a difference between
the two things definitely moved around a bit so this was the first trial with bilinear bed
leveling using the default 3x3 mesh which gives you nine samples so then I changed the mesh size
from 3 by 3 up to a 6 by 6 mash which gives you 36 height samples here and then I repeated that
same test here I did a cold bed then the second array was again with the bed heated up to 90 C
and then what I did for this third array I did an array difference so I took the hot data minus
the cold data and computed a third array so here is the difference so I had hot - cold and that's
that's the difference and that's how much the bed moves once you heat it up and again this was 290
C definitely moves around so one lesson learned there is definitely if you're using bed leveling
and you're using a heated bed heat the bed up for a good 10 to 15 minutes anyway this was with the
6x6 bilinear and that's what I was using earlier in this video and then there's one other option
down in that section of the configuration dot H file they call it by linear subdivision and you
can see with the six by six points you've got 36 grid points that leaves five rows and five
columns of meshes and then that subdivision then takes each one of these mesh sections here and
divides it into a further three by three sections you start with a five by five mash or six by six
points and you end up with a 15 by 15 mash or 16 by 16 points so these points here are all
computed these points here are measured and you can see here some of the original data is still
there here's a point three four point three four here's a point to one point to one so what they do
when you turn on that subdivision option is they the comment mentions that they do this
Catmull ROM spline interpolation and that was a technique developed in the mid-70s by Edwin
Catmull and Raphael ROM and what it does this shows a 2d representation of that is you you
get your control points those are your measured mesh points that you sample with the proximity
sensor and then you fit a spline curve to those points and as it mentions here the spline passes
through the control points and then the spline is continuous and a c1 I think means it's continuous
at the first derivative which means there are no discontinuities in the tangent direction and
magnitude so if we look at that here you can see here we came up this slope here and then
there's a hard Bend and there's all these bumps and points and folds in the surface so the idea
is with this interpolation you smooth all those out and I think this is about as far as you can
go I tried bumping the code up to a 7x7 grid and the Arduino IDE gave me a linker time warning that
the program memory was dangerously low and the program might become unstable so I went back to
the 6x6 bilinear with the 3x3 subdivision and I think that's a reasonable compromise going
from the 3x3 to the 6x6 you're going from 9 sample points to 36 so this process here takes four times
as long to do because you're probing 36 points instead of 9 but then you you're computing 256
points from that original 36 points so it's likely that you could actually do a 16 by 16 sampling
without doing the subdivision you could just go and and probe that but that's going to take
forever because you're you're doing 16 rows and 16 columns of probing so this way you're you're
only doing four times as much sampling as you did in the 3x3 case and then you're computing
this 16 by 16 array of points and this this has been working very well I've had really excellent
bad adhesion and if you have any questions about that post up in the comment section below and I'll
put some follow-up videos over here on the left side and as always thanks for watching