Step 14.15 — Save the shaper and set the real max_accel¶
Step 15 of 36 · Chapter 14 — Calibration and tuning
(no image — see text)
Parts: none.
Do: If the recommendations look sane, SAVE_CONFIG. That writes [input_shaper] with shaper_type_x/y and shaper_freq_x/y. It does not touch max_accel; Klipper says so explicitly, and this is the step everyone skips. The LDO config ships:
[printer]
max_velocity: 300
max_accel: 10000 # placeholder — must come down
max_z_velocity: 15
max_z_accel: 350
square_corner_velocity: 5.0
Check
printer.cfg's bottom block has [input_shaper] with four values and [printer] max_accel is no longer 10000.
What you're looking at
SAVE_CONFIG writes the shaper's four values into the auto-generated block at the bottom of the config. It deliberately does not touch max_accel, which the stock file leaves at a 10000 placeholder, so setting that by hand is the half of this step everyone forgets.
Set max_accel to at or below the lower of the two per-axis suggested values, with margin — if the run suggested ≤4000 for X and ≤3500 for Y, use 3000–3500. Leave square_corner_velocity at 5.0.
Why the suggested number is a ceiling, not a setting — and the post-run walk
Klipper is blunt that the suggested figure "is by no means a recommendation to set
this acceleration for printing"; it is only the ceiling at which that shaper stops
smoothing badly, and your real ceiling is also limited by motor torque. Leave
square_corner_velocity at 5.0 because the calibration script assumed it — changing
it invalidates the max_accel numbers.
Re-print the Voron cube and compare the corners to the first one; that is your before/after. Then walk the machine and check nothing has unscrewed itself — Klipper warns that resonance testing loosens fasteners.
Good stopping point · ~25 min since the last one
SHAPER_CALIBRATE run, graphs read, [input_shaper] saved and max_accel brought down from the 10000 placeholder. Never stop between running the calibration and saving it; the CSVs live in /tmp and a reboot loses them.
Source: Klipper docs § Input shaper auto-calibration · Klipper docs § input_shaper · leviathan-printer-rev-d-sbv2.cfg · Video: Extras! @2:00:00