Baby step during a long linear move? Baby step other Axes?

jml

I read in another post that:
"The baby stepping is implemented in near real time, normally after the end of the current move or after 0.5 seconds, whichever is greater"

I'm wondering if that is still the case.

I was planning on doing the baby stepping during a slow, but long G1 command while the extruder was near the front of the printer. But if the above is true, then the baby stepping won't occur until that long move is finished! Perhaps I will have to program a sine wave or sawtooth pattern instead of a straight line movement.

jml

And can you do babystepping for other axes? For example, X or Y? Or U or V?

T3P3Tony

@jml as it is currently implemented it is for Z only:

https://duet3d.dozuki.com/Wiki/GCode#Section_M290_Baby_stepping

what use case do you see for another axis?

jml

@t3p3tony in case I have mounted a tool imperfectly.

fma

Or to correct a layer shift... Would be nice!

dc42

@jml said in Baby step during a long linear move? Baby step other Axes?:

I read in another post that:
"The baby stepping is implemented in near real time, normally after the end of the current move or after 0.5 seconds, whichever is greater"

I'm wondering if that is still the case.

I was planning on doing the baby stepping during a slow, but long G1 command while the extruder was near the front of the printer. But if the above is true, then the baby stepping won't occur until that long move is finished! Perhaps I will have to program a sine wave or sawtooth pattern instead of a straight line movement.

If you have mesh bed compensation enabled (even with a flat height map) then long straight moves are broken up into segments with lengths approximately equal to the mesh spacing. So in this case, babystepping will take effect faster.

jml

@dc42 Thanks, will that work even if I don't have a z-probe? That is, can I just use M557 and have it still work?

dc42

@jml said in Baby step during a long linear move? Baby step other Axes?:

@dc42 Thanks, will that work even if I don't have a z-probe? That is, can I just use M557 and have it still work?

You will need to generate a dummy height map file and load it using G29 S2 S1.

jml

@dc42 Will do, thanks!

jml

@dc42 Wait, G29 S2 clears the bed height map. I assume you meant G29 S1? First I would make the heightmap.csv file manually.

Could I instead use M557 X0:20 Y0:20 S1 to set the mesh spacing to 1mm?

dc42

@jml said in Baby step during a long linear move? Baby step other Axes?:

@dc42 Wait, G29 S2 clears the bed height map. I assume you meant G29 S1? First I would make the heightmap.csv file manually.

I'm sorry, I did mean S1.

Could I instead use M557 X0:20 Y0:20 S1 to set the mesh spacing to 1mm?

Instead of what?

jml

@dc42 Instead of manually creating a dummy .csv height map in excel. I thought when you said "You'll need to generate a dummy height map file" I thought that meant manually create it in Excel or TextEdit. But maybe I mis-assumed!

dc42

If you create a tiny height map, then outside the bounds of that height map it will extrapolate, which is likely to give poor results.

jml

@dc42 can you clarify whether I should make the height map manually in excel, or if I should make it using M557?

Phaedrux

@jml I think either way you do it, don't make it very small.

jml

Ok I wasn't sure if one way was the wrong way.

jml

Well I'm not sure if M557 X0:200 Y0:200 S1 will actually create the height map with zeros everywhere, or if there is an extra step after that to populate it with zeros.

Phaedrux

I think you would have to either run an actual g29 to get it to output a height map you could edit or you'd have to just create your own height map from scratch.

jml

This post is deleted!

jml

Just playing with baby stepping, I have made a short g-code file to move back and forth slowly in the x dimensions (80mm back and forth).

I see that if a G4 command is 5 lines away from the current move, then the baby steps will not execute until after the G4 command has passed.

Normally they will execute after the current move (or "after 500ms is passed, whichever is greater").

I also see that the z axis doesn't just move up right away ... it spreads out the height adjustment across the next move.

This is all without the height map file, so now I will test with the heightmap file (if I can create it successfully. Can someone post their heightmap.csv file so I can base mine off that?

Phaedrux

@jml 0_1536647204948_heightmap.csv.txt

M557 X10:280 Y35:270 S15

jml

Adding the heightmap.csv file into the /sys folder didn't change anything - probably I made the file incorrectly or config is wrong.

In config.g I put this near the beginning of the file:
M557 X-100:300 Y-100:300 S1
G29 S1 ; load heightmap.csv

And then in heightmap.csv, I have what I think is correct based off what I see others do online. But it didn't seem to change the behavior at all - I'm still not able to babystep the height during long moves.

Phaedrux

I'm not sure about using negative values in M557 unless you intend it for areas off the bed? Do you have negative values for your axis minima?

jml

@phaedrux No negative values, but I assumed the map could extend beyond the actual print bed boundaries.

I'll change it to M557 X0:200 Y0:200 S1
But then in the csv file, should xnum and ynum be 200, or should it be 201? xspacing and yspacing should be 1, and xmin/ymin and xmax/ymax should be 0 and 200 respectively, right?

Phaedrux

For it to work it also has to have a grid spacing that generates only as many probe points as it can handle. I think the limit is around ~~4000~~ 441? So spacing of 1mm is probably way too low. Try 20 or 30mm.