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---
title: Tutorial 20 Acceleration & Jerk Tuning
description: Understanding the physics of printer movement.
---

Tutorial 20 Acceleration & Jerk Tuning

1. Lesson Header

2. Concept Introduction

Speed vs. Acceleration vs. Jerk.
- Speed (F): How fast we want to go (mm/min).
- Acceleration (M204): How quickly we reach that speed (mm/s²).
- Jerk (M205): The instantaneous speed change allowed at a corner (mm/s).

Imagine driving a car:
- Speed: 60mph.
- Acceleration: 0-60 in 5 seconds.
- Jerk: Turning a 90-degree corner without slowing down completely.

If Acceleration is too high: The printer shakes violently, causing "Ringing" (echoes of features on the surface).
If Acceleration is too low: Prints take forever, corners bulge.

3. Machine State Explanation

M204 (Set Acceleration)
- M204 P500 R1000 T500
- P: Printing Acceleration (moves with E).
- R: Retract Acceleration (E-only moves).
- T: Travel Acceleration (moves without E).

M205 (Set Jerk)
- M205 X10 Y10
- X/Y: Max instantaneous speed change (mm/s).

4. Command Breakdown

5. Minimal Working Example

The Fast Corner.
We print a square.
Pass 1: Low Accel (500).
Pass 2: High Accel (3000).

G28
G1 Z0.2
; Pass 1 (Smooth)
M204 S500
G1 X100 Y100 F3000 ; Takes time to ramp up/down
; Pass 2 (Aggressive)
M204 S3000
G1 X0 Y0 F3000 ; Almost instant start/stop

6. Visual Representation

Interactive preview is available in the interactive reader.

Artifact:
High Accel causes "Ghosting" -> faint ripples after a sharp corner.

7. Build Exercise

Task: Build a Ringing Tower.
A simple box (Vase Mode again).
Every 10mm, increase Acceleration.
- 0-10mm: 500 mm/s²
- 10-20mm: 1000 mm/s²
- 20-30mm: 1500 mm/s²
- 30-40mm: 3000 mm/s²

Why?
To find the maximum acceleration your printer can handle before quality degrades.

8. Deep Insight Section

Jerk is not "Jerk".
In Physics, Jerk is the derivative of Acceleration (change in acceleration).
In 3D Printing (Marlin), "Jerk" is actually Instantaneous Velocity Change.
It's a threshold. If the corner angle requires a speed change less than the Jerk setting, the printer doesn't slow down at all. It just "bangs" through the corner.
If the change is greater, it decelerates to the Jerk speed, turns, and accelerates again.

Junction Deviation (Newer Marlin/Klipper):
Replaces Jerk with a smarter algorithm based on centripetal force.
If your firmware uses Junction Deviation, M205 might use J instead of X/Y.

9. Common Failure Modes

  1. Layer Shift: If Acceleration is too high (e.g., 5000+ on a heavy bed), the motor might skip steps. The entire print will shift sideways.
  2. No Difference: If your M201 (Max Accel) is set low in firmware (e.g., 500), sending M204 S3000 does nothing. The safety limit overrides it.

10. Real-World Application

High-Speed Printing (SpeedBenchy).
To print a Benchy in 5 minutes, you need Accel > 10,000 mm/s².
Normal printers use 500-1000.
High-end CoreXY printers (Voron, Bambu) use 20,000+.

11. Final Clean Version

; Lesson 20 - Ringing Tower
G21
G90
M83
G28
G1 Z0.2 F3000

; --- Layer 1 (Accel 500) ---
M204 S500
G1 X50 Y50 E2
G1 X100 Y50 E5
G1 X100 Y100 E5
G1 X50 Y100 E5
G1 X50 Y50 E5

; --- Layer 2 (Raise Z) ---
G1 Z0.4
; Still 500
G1 X100 Y50 E5
G1 X100 Y100 E5
G1 X50 Y100 E5
G1 X50 Y50 E5

; --- Layer 3 (Accel 1500) ---
M204 S1500
G1 Z0.6
; Now faster starts/stops
G1 X100 Y50 E5
G1 X100 Y100 E5
G1 X50 Y100 E5
G1 X50 Y50 E5

; --- Layer 4 (Accel 3000) ---
M204 S3000
G1 Z0.8
; Very aggressive
G1 X100 Y50 E5
G1 X100 Y100 E5
G1 X50 Y100 E5
G1 X50 Y50 E5

; Reset
M204 S500 ; Always be polite and reset to safe defaults
G28 X0 Y0

12. Stretch Challenge

Challenge: Write a G-code file that tests Jerk instead of Acceleration.
Keep Acceleration constant (e.g., 1000).
Change M205 X... Y... every 10mm.
Values: 5, 10, 20, 40.
Observe the corners.
Note: High Jerk makes corners sharper but induces more ringing. Low Jerk makes corners bulge but reduces ringing.