Different acceleration and jerk for X and Y

[petronel 0]

Most printers have a slinging bed where X axis allows a much higher speed than Y axis.

Marlin has separate values for X and Y yet i can't seem to find any way to set this in Cura.

Maybe some plugin can do this?

Editing the gcode is not really an option since the values are set a few times per layer.

[ahoeben 1,431]

28 minutes ago, petronel said:

Most printers have a slinging bed where X axis allows a much higher speed than Y axis.

Ultimaker printers don't though. So implementing your request has no benefit for Ultimaker. So it would likely come down to community members or manufacturers of bed slinging printers to come foreward and contribute this.

[GregValiant 548]

Speed is one thing, Acceleration is another.  This may be a workaround that will work for you.  I don't know if this is firmware specific or not.  It works with my Ender 3 Pro running Marlin 1.1.8.

 

Cura varies the Accel values in a gcode file according to things like travel accel, or different accel values for infill, outer wall, whatever.  When those numbers are different by "TYPE" then that means changes in Accel throughout a file.

 

When Cura changes the accel number in gcode it does so with M204.  However, the Maximum Acceleration rates are stored in M201 in the printer so they are not affected by Cura changing the Print/Travel accelerations.  M201 remains the limit.

 

If you put something like M201 X500 Y50 in your StartUp G-Code, and then in your settings for a model put all the acceleration settings at 3000 then when the printer sees M204 S3000 it will use 500mm/sec² for the X and 50mm/sec² for the Y because those are the limits stored in M201.  If you were to print a large flat with a 200 x 200 footprint you would see that the X appears to be faster than the Y (although top speed is the same).  When the skin is put down at 45° acceleration would be limited by the Y number.

 

You cannot do the same trick with Jerk because M205 (which holds the Jerk values) is a Setting and not a Maximum.  Cura will always make the values of X and Y Jerk equal to each other as it uses M205 to change them.

 

So that is the workaround - add M201 X500 Y250 (use your preferred numbers for Accel) to your StartUp G-Code.  It will not effect the current E and Z accel numbers but will limit your acceleration values regardless of what Cura says in an M204 line.  You could do the same sort of thing with speed, but it's the acceleration that is the problem, not the top speed.

 

[petronel 0]

Thanks a lot for the info!

I incorrectly assumed M204 overrides M201, but now that i think of it, it didn't make much sense.

 

I'm testing this on an Ender 3 as well, and get occasional layer shifts on Y-axis at 5000 accel and 50 jerk. I hope lower acceleration would fix this, although as you said, it's not that big of an advantage since infill and top/bottom is limited to Y acceleration.

[GregValiant 548]

I've written a little program to calibrate Accel and Jerk.  On long runs the printer handles up to about 3000 pretty well at under 150mm/sec.  Above that it really hits the end stops hard.  Circles are a different story.  Above 500 and 8 (which are the defaults in the definition file) circles get herky-jerky do to stuttering.

I run my E3Pro at X=600, Y=450.  It's a fair compromise that gives me good corner definition and smooth circles on the prints while allowing me to speed along (75 anyway) on the straight runs.

Regarding Greg's Accel, Jerk, and Print Tool you can download it and install it.  It's for Windows only (VB doesn't port to others).  It does require a USB connection to the printer in order to function.

Edited September 6, 2021 by GregValiant

[petronel 0]

Great, i'll make sure to try your tool, at the moment i don't have the printer next to my pc.

 

Why are you running the settings so low? You use the same settings for everything? I mean i use low values for outer walls and high values for everything else and i cut down the print time to 60-80% with little to no quality loss, maybe a bit of extra ghosting bleeding from internal walls.

[GregValiant 548]

I do a lot of round things and it matters.  On something like a big cube or a bracket it doesn't.  On something like these I found it does as not stuttering is a key since everything is curved.

 

 

[petronel 0]

Ah, i assume you have an 8-bit board and you mean stuttering because of the board being unable to process that many lines on round geometry, not that there's any mechanical issue with it.