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08-19-2015, 02:44 PM #1
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- Feb 2015
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Help me understand the Acceleration settings
There are two different spots in Marlin that I see for acceleration.
#define DEFAULT_MAX_ACCELERATION
#define DEFAULT_ACCELERATION
What is the difference? What does each do/control?
I'd like to have my Y a little slower since it is a bit more massive than the X axis.
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08-19-2015, 02:58 PM #2
That starts to be obvious by comparing the parameters for the two. DEFAULT_MAX_ACCELERATION has parameters for each axis (X, Y, Z, extruder). DEFAULT_ACCELERATION only has a single term.
For a given axis, the acceleration value Marlin will apply is whatever is the lowest value between the two settings. DEFAULT_ACCELERATION will have no effect unless its value is less than one of the axis settings in DEFAULT_MAX_ACCELERATION.
Why are there two? IDK, but note that there are two gcode commands related to this. M201 can be used to set the four terms associated with DEFAULT_MAX_ACCELERATION. M204 can be used to set the value associated with DEFAULT_ACCELERATION. I could see DEFAULT_ACCELERATION being used more on a delta printer where there'd be less of a reason for x, y, and z acceleration values to differ. In your case, you'd set the Y value in DEFAULT_MAX_ACCELERATION to something lower than the X value.Last edited by printbus; 08-19-2015 at 03:50 PM.
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08-19-2015, 05:54 PM #3
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- Feb 2015
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So it will always default to the lowest value? So if my DEFAULT_ACCELERATION is less than whatever I put in for the four value for the DEFAULT_MAX_ACCELERATION it will use the lowest one?
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08-19-2015, 07:05 PM #4
Yep. If you want to experiment, I'll offer the gcode snippets in the LINEAR CONCENTRIC SQUARES TEST post in the Marlin Motion Related Configuration.h Settings for MakerFarm i3v thread. They provide non-extrusion movements that can be used to observe the printer over a range of distances at both printing and movement speeds. I provide gcode there for both the 2014-era MakerFarm defaults and the tweaked values I settled on via testing. Use a text editor or an integrated gcode editor like that in Repetier Host to tailor values in the gcode commands as you wish.
I found the concentric squares approach very instrumental in learning how different acceleration settings affects the movement speeds achieved over various distances.
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