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docs: Update Kinematics.md with regards to stepper torque limits 

It is not necessary to limit stepper acceleration - only the limiting
of stepper torque is important.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
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Kevin O'Connor 2017-07-19 19:09:14 -04:00
parent 17a3e25036
commit 2ee42997e4
1 changed files with 10 additions and 10 deletions
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@ -18,12 +18,12 @@ rapid jerking of the head can cause disruption of recently deposited
filament. Limiting speed changes of the print head (relative to the filament. Limiting speed changes of the print head (relative to the
print) reduces risks of disrupting the print. print) reduces risks of disrupting the print.
It is also important to enforce a maximum acceleration of the stepper It is also important to limit acceleration so that the stepper motors
motors to ensure they do not skip or put excessive stress on the do not skip or put excessive stress on the machine. Klipper limits the
machine. Klipper limits the acceleration of each stepper by virtue of torque on each stepper by virtue of limiting the acceleration of the
limiting the acceleration of the print head. Enforcing acceleration at print head. Enforcing acceleration at the print head naturally also
the print head naturally also enforces acceleration at the steppers limits the torque of the steppers that move the print head (the
that control that print head (the inverse is not always true). inverse is not always true).
Klipper implements constant acceleration. The key formula for constant Klipper implements constant acceleration. The key formula for constant
acceleration is: acceleration is:
@ -213,10 +213,10 @@ motor greater than the move's acceleration. This can occur when a
stepper arm is more horizontal than vertical and the line of movement stepper arm is more horizontal than vertical and the line of movement
passes near that stepper's tower. Although these moves could require a passes near that stepper's tower. Although these moves could require a
stepper motor acceleration greater than the printer's maximum stepper motor acceleration greater than the printer's maximum
configured move acceleration, this would only occur when the stepper configured move acceleration, the effective mass moved by that stepper
is moving a small amount of mass. (The stepper would essentially only would be smaller. Thus the higher stepper acceleration does not result
be moving the mass of the tower carriage.) Therefore, these brief in significantly higher stepper torque and it is therefore considered
periods of high acceleration are considered harmless. harmless.
However, to avoid extreme cases, Klipper enforces a maximum ceiling on However, to avoid extreme cases, Klipper enforces a maximum ceiling on
stepper acceleration of three times the printer's configured maximum stepper acceleration of three times the printer's configured maximum