How to Calibrate Input Shaper and Pressure Advance in Klipper

Introduction

Input Shaper and Pressure Advance are Klipper's two most powerful features for print quality. Input Shaper compensates for mechanical resonances — the vibrations that cause ringing (ghosting) on sharp corners and curved surfaces. Pressure Advance compensates for the delay between extruder motion and nozzle flow — eliminating corner blobs, improving dimensional accuracy, and allowing faster print speeds. Together, they can transform a mediocre printer into one that produces commercial-quality results. This guide explains the physics behind each feature, provides step-by-step calibration procedures, and shows you how to tune both to perfection for your specific machine.

What You Need

• Klipper firmware installed and running
• Accelerometer (ADXL345, MPU9250, or LIS2DW12) for Input Shaper OR use Klipper's resonance tester
• Calipers for measuring test prints
• Filament in good condition (dry, consistent diameter)

Part 1: Input Shaper

How It Works

Every mechanical system has resonant frequencies where vibrations amplify. When a printer's nozzle changes direction, the frame and belts ring at these frequencies, creating visible artifacts on the print surface. Input Shaper modifies the motion command signal to cancel out these resonances before they reach the mechanical system — similar to noise-canceling headphones. It does this by splitting motion commands into multiple smaller moves timed to destructively interfere with the resonant frequency.

Shaper Types

• ZV (Zero Vibration): Cancels one frequency, minimal speed penalty
• ZVD (Zero Vibration Derivative): Cancels one frequency with better robustness, slightly more smoothing
• EI (Extra-Insensitive): Cancels a range of frequencies, more smoothing, good for unknown/multiple resonances
• MZV (Modified ZV): Compromise between ZV and ZVD
• MVZV: Multi-frequency variant for complex resonances

Method A: Automatic Calibration with Accelerometer

Wiring the ADXL345

• VCC → 3.3V (NOT 5V — ADXL345 is 3.3V only)
• GND → GND
• SCL → Raspberry Pi GPIO 3 (SCL)
• SDA → Raspberry Pi GPIO 2 (SDA)
• CS → 3.3V (SPI disabled, I2C mode)

Install Dependencies

cd ~/klipper sudo apt install python3-numpy python3-matplotlib ~/klipper/scripts/install-klipper.sh

Configure the Accelerometer

[adxl345] axes_map: x,y,z [resonance_tester] accel_chip: adxl345 probe_points: 117.5, 117.5, 20

Run Calibration

RESONANCE_TESTER_ACCEL_CHIP=adxl345 TEST_RESONANCES AXIS=X TEST_RESONANCES AXIS=Y

Klipper moves the toolhead back and forth at increasing frequencies while the accelerometer records vibrations. It generates:

• resonances_x.png — vibration spectrum for X axis
• resonances_y.png — vibration spectrum for Y axis

Calculate Optimal Shaper

SHAPER_CALIBRATE AXIS=X SHAPER_CALIBRATE AXIS=Y

Klipper recommends the best shaper type and frequency. The output looks like:

Recommended shaper_type_x = mzv, shaper_freq_x = 48.4 Hz

Update Config and Save

[input_shaper] shaper_type_x: mzv shaper_freq_x: 48.4 shaper_type_y: mzv shaper_freq_y: 42.1

Then: SAVE_CONFIG

Method B: Manual Calibration (No Accelerometer)

If you do not have an accelerometer, use the ringing tower test:

1. Download the ringing_tower.stl from Klipper's docs
2. Print it at 100mm/s with acceleration at your normal setting
3. Examine the ringing patterns on X and Y faces
4. Measure the distance between ringing lines with calipers
5. Calculate frequency: freq = speed (mm/s) / distance (mm)
6. Example: 100mm/s speed, 2.1mm ring spacing → 47.6 Hz
7. Start with shaper_type = mzv and calculated frequency
8. Print another test and fine-tune

Testing Results

1. Print a sharp-corner test cube (40x40x20mm)
2. Compare with Input Shaper on vs off
3. Ringing should be dramatically reduced or eliminated
4. If corners look rounded, the shaper is too aggressive — try ZV or lower frequency

Part 2: Pressure Advance

How It Works

When the extruder pushes filament, the molten plastic in the nozzle behaves like a spring — it compresses under pressure and decompression takes time. When the print head decelerates for a corner, the extruder slows, but the nozzle keeps extruding due to this stored pressure. This creates a blob at the corner. When accelerating out of the corner, the opposite happens — a slight under-extrusion. Pressure Advance compensates by advancing (or retarding) the extruder position relative to the toolhead motion, keeping nozzle pressure constant.

Calibration Procedure

Step 1: Prepare

• Use a single-wall test model (e.g., calibration cube with no infill, 2 perimeters)
• Ensure your extruder e-steps are calibrated first
• Use your standard printing temperature and speed

Step 2: Print the PA Test

1. Use Klipper's built-in pressure advance tower:

Pressure Advance Calibration: Set VELOCITY=100, use SET_PRESSURE_ADVANCE ADVANCE=0.0 and increase by 0.02 every 10mm

1. Or manually slice a tower with PA values labeled in G-code:

; Layer change — set PA to 0.02 SET_PRESSURE_ADVANCE ADVANCE=0.02

1. Print at your normal outer wall speed (30-50mm/s)

Step 3: Analyze the Print

Examine the corners of the test print:

• Too low PA (0.00-0.02): Bulging corners, over-extrusion at deceleration points
• Optimal PA: Sharp, clean corners with no bulge or gap
• Too high PA (0.08+): Under-extrusion at corners, gaps, weak walls

Step 4: Fine-Tuning

1. Find the section with the best corners
2. Note the PA value
3. Print a finer-resolution test around that value (steps of 0.005)
4. Select the best value

Step 5: Update Configuration

[extruder] pressure_advance: 0.04 pressure_advance_smooth_time: 0.04

SAVE_CONFIG and restart Klipper.

Pressure Advance by Filament Type

• PLA: 0.02 — 0.06
• PETG: 0.04 — 0.08
• ABS/ASA: 0.03 — 0.06
• TPU: 0.08 — 0.15 (flexible filaments need much more PA)

Part 3: Combined Testing

With both features enabled, print a comprehensive test:

1. 40x40x20mm hollow cube (2 walls, no infill, no top)
2. 50mm/s print speed
3. 3000mm/s² acceleration

Inspect for:

• Corner sharpness (PA check)
• Wall surface quality (Input Shaper check)
• Consistent wall thickness (both)

Advanced: Tuning for Speed

Once calibrated, you can increase acceleration without ringing:

1. Start with your current acceleration (e.g., 1500mm/s²)
2. Print the test cube
3. Increase acceleration by 500mm/s²
4. Reprint and check quality
5. Continue until quality degrades
6. Back off 20% for reliable daily printing

Typical results after tuning:

• Cartesian printers: 3000-5000mm/s² acceleration
• CoreXY printers: 5000-10000mm/s² acceleration

Troubleshooting

Input Shaper Issues

• Rounding of corners: Shaper too aggressive — use ZV or lower frequency by 5-10%
• Still seeing ringing: Frequency may have changed — re-run calibration
• Shaking/vibration: Normal during resonance test — keep hands clear
• Accelerometer not detected: Check wiring (3.3V not 5V), I2C address

Pressure Advance Issues

• Retraction problems after PA: You may need to reduce retraction distance (PA reduces needed retraction)
• Gaps at seams: PA too high — reduce by 0.01
• Blobs at seams: PA too low — increase by 0.01
• Thin walls: Check extruder calibration first — PA cannot fix under-extrusion

Pro Tips

• Recalibrate when you change hardware: New belts, different hotend, modified toolhead — all change resonances
• Store PA per filament: Use Klipper's SAVE_VARIABLE to store optimal PA for each filament type
• Run at lower accel for first layer: High acceleration can cause first layer issues
• Input Shaper reduces ringing but does not increase rigidity: Loose belts still need tightening
• Pressure Advance works with any speed: The PA value is speed-independent in Klipper
• Use a macro to toggle IS and PA for testing:

[gcode_macro TEST_QUALITY] gcode: SET_INPUT_SHAPER SHAPER_TYPE=none SET_PRESSURE_ADVANCE ADVANCE=0.0 M104 S200 M140 S60

Conclusion

Input Shaper and Pressure Advance are the two calibration steps that separate average prints from exceptional ones. Input Shaper eliminates ringing artifacts by compensating for mechanical resonances, letting you run higher accelerations without surface degradation. Pressure Advance eliminates corner blobs and gaps by synchronizing extruder pressure with toolhead motion. Both calibrate in under an hour and the results are permanent until hardware changes. A properly tuned Klipper printer with IS and PA enabled can print at 2-3x the speed of an untuned Marlin machine while producing cleaner surfaces and sharper corners.