Spline travel settings
If "Spline travel" button is down, all travel moves are going to be replaced by smooth ones. The travel path is a 3rd-order Bezier curve, constructed so as to match exit and enter speeds, and not exceeding acceleration setting.
The move as the Bezier curve is traced with time put as its parameter. This means that the speed is changing throughout the curve. If required, the speed is artificially limited to not exceed the speed limit setting (thus, speed limit does not affect the shape of the curve).
In case the spline (generated only taking acceleration limit into acound) has pieces with the speed that exceeds this value, the speed will be limited on these pieces.
Sets the smoothness of the spline. The higher the acceleration, the closer the spline is to a straight-line move. High acceleration values require finer tessellation of the curve, so decreasing it can solve communication choke.
Sets how finely the spline is approximated with line segments (tessellated). The value sets the maximum speed vector change between adjacent segments. The smaller the value, the more line segments are generated for a spline.
It is recommended to set this to a value slightly below the jerk value in firmware. If the speed change between adjacent line segments is larger than jerk in firmware, it is likely that firmware will decelerate at the joint.
This value controls the amount of [Z-hopping](SplineTravel glossary#z-hopping). Enter and exit speeds will be modified (Z component specified here will be added). This will raise the middle of the curve by some amount, which depends on the speeds and the length of the spline.
Direct Z hopping is impossible to combine with spline travel, because it requires to come to a complete stop before raising Z.
Set this to a value smaller than Z jerk setting in firmware. Otherwise, the printer will likely decelerate at enter and exit points.
Retraction and unretraction process is injected into the travel process, so that the printer doesn't have to stop to do a retract/unretract. Retraction is a five-step process:
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accelerate E motor until half of retract distance is covered
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decelerate E motor, completing the full retract distance in the process
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rest until time comes to start unretract
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accelerate E motor until half of unretract distance is covered
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decelerate E motor, completing the full unretract distance in the process
todo: picture
If retract/unretract doesn't fit into travel time, retraction distance is reduced. If only retract or only unretract is needed (happens when seam concealment is on), and the process doesn't fit in travel time, E acceleration will be increased for that particular move.
This value sets the acceleration of retraction. Note that because E curve tessellation and spline travel tessellation are shared, high E acceleration will cause a finer tessellation of travel near enter and exit. This can cause communication choke. On the other hand, higher E acceleration makes retract/unretract quicker, which can reduce the amount of ooze, thus improving print quality.
This value sets the tessellation of retract/unretract curve, just like "Curve tessellation (jerk)" parameter sets the tessellation of travel move. Note that because E curve tessellation and spline travel tessellation are shared, low E jerk will cause a finer tessellation of travel near enter and exit. Yet, for the same tessellation sharing reasons, very high jerk setting may not influence anything, because the tessellation will never be reduced below one required by travel tessellation settings.
It is recommended to set this to a value slightly below the corresponding jerk value in firmware. If the speed change between adjacent line segments is larger than jerk in firmware, it is likely that firmware will decelerate at the joint.