Voron PID Tuning Deep Dive — Perfect Temperature Control

Calibration Klipper Tuning

What Is PID Control and Why It Matters on a Voron

PID (Proportional-Integral-Derivative) control is a feedback loop that keeps your hotend and bed at the target temperature. On a Voron printer, the PID controller adjusts heater power hundreds of times per second to maintain a stable temperature. Imperfect PID tuning causes:

• Temperature oscillation — The temperature swings above and below the target (e.g., 240℃ ± 5℃). This causes inconsistent extrusion, visible layer lines, and poor part strength.
• Overshoot on heating — The hotend shoots past the target by 10-20℃ before stabilizing. This can degrade filament or cause stringing.
• Slow response to cooling — When the part fan turns on, the hotend temperature drops and takes too long to recover, causing under-extrusion on overhangs.
• Thermal runaway risk — A poorly tuned PID combined with a failing heater or thermistor can delay detection of actual temperature problems.

PID Theory in Simple Terms

The PID controller combines three terms to determine heater power:

• P (Proportional) — Responds to the current error (how far the temperature is from the target). A high P value applies more power when the temperature is far from the target. Too high causes oscillation. Too low causes slow heating.
• I (Integral) — Accounts for past error over time. It eliminates steady-state error (the temperature settling slightly below the target). Too high causes overshoot and slow oscillation.
• D (Derivative) — Predicts future error based on the rate of temperature change. It dampens oscillation and improves stability. Too high causes noise amplification and jittery power output.

The classic analogy: P is how hard you push a swing based on how far it is from center. I is based on how long it has been off-center. D is based on how fast it is moving away from center.

Hotend vs Bed PID — Key Differences

Hotend PID

The hotend has low thermal mass (20-40 grams of metal) and responds rapidly to power changes. Key characteristics:

• PID cycle time is typically 0.1-0.5 seconds (100-500 ms).
• The D term is important because the hotend temperature changes quickly when the part fan turns on.
• The hotend is affected by: part fan speed, print cooling fan speed, ambient (chamber) temperature, and air flow across the heater block (e.g., from a CPAP fan mod).
• Hotend PID should be tuned with the part fan at the speed you typically use while printing (e.g., 30% for ABS, 100% for PLA).

Bed PID

The bed has high thermal mass (1-15 kg depending on Voron model and bed size). Key characteristics:

• PID cycle time is typically 1-4 seconds (1000-4000 ms). Klipper defaults to 2 seconds.
• The D term can often be set to 0 (disabled) for the bed, because the temperature changes so slowly that derivative control is unnecessary and can introduce noise.
• The bed is affected by: ambient temperature, enclosure temperature, drafts from enclosure fans, and the thermal mass of the build plate material (aluminum vs cast aluminum vs mic6).
• Bed PID should be tuned at the temperature you normally print at, with the enclosure at normal operating temperature.

Klipper PID Calibration Procedure

Step 1: Find the Default Values

Before running calibration, check what your current PID values are:

# In the terminal or Mainsail console:
# For hotend:
PID_CALIBRATE HEATER=extruder TARGET=240
# For bed:
PID_CALIBRATE HEATER=heater_bed TARGET=110

Note: Replace TARGET with your typical printing temperature (240℃ for ABS, 220℃ for PLA on hotend; 110℃ for ABS, 60℃ for PLA on bed).

Step 2: Run PID Calibration

The calibration process takes 10-15 minutes for the hotend and 15-25 minutes for the bed. During calibration:

• The printer will heat, cool, and reheat the component in cycles (typically 5 cycles).
• Do not touch the printer. Do not turn fans on/off. Do not open the enclosure.
• Monitor the temperature graph in Mainsail/Fluidd — you want to see the temperature oscillating less with each cycle.

Step 3: Save the Values

After calibration completes, Klipper outputs new PID values. Save them to printer.cfg:

# Klipper output looks like:
# PID parameters: pid_Kp=22.356 pid_Ki=1.080 pid_Kd=115.602
# Use SAVE_CONFIG to save, or manually update printer.cfg

[extruder]
# ... other settings ...
control = pid
pid_Kp = 22.356
pid_Ki = 1.080
pid_Kd = 115.602

Use SAVE_CONFIG in the Klipper terminal to automatically update printer.cfg. Alternatively, edit printer.cfg manually and restart Klipper.

Understanding Your PID Values

The specific PID values depend on your hotend and bed hardware. Here are typical ranges for Voron printers:

Hotend PID Values (by Hotend Type)

Bed PID Values (by Voron Model)

Note: The D term for the bed is often set to 0 in Voron builds. If you see bed temperature oscillation, a small D value (200-500 for 250mm beds) can help. Do not set D too high on the bed — it will cause the heater power to fluctuate wildly and can damage the SSR (solid state relay).

When to Re-Tune PID

PID values are not static — they change when your hardware changes. Re-tune PID after:

• Changing the hotend (different thermal mass, different heater cartridge wattage).
• Changing the heater cartridge (e.g., 40W to 50W, or standard to high-watt).
• Changing the thermistor or thermistor position.
• Adding or removing enclosure insulation.
• Changing the build plate (e.g., PEI sheet vs glass vs G10).
• Changing the bed heater (e.g., AC vs DC, or different wattage).
• Changing the part cooling fan to a higher-flow model (e.g., 5015 dual fans vs stock).
• Changing the ambient printing environment significantly (moving the printer to a colder/hotter room, changing seasons).

Troubleshooting Temperature Oscillations

Oscillation Pattern: Fast, Small (±1-3℃, 2-5 second cycle)

Cause: P value too high. The controller applies too much power, overshoots, cuts power too much, undershoots, and repeats.

Fix: Reduce pid_Kp by 10-20%. Run PID_CALIBRATE again. Alternatively, manually reduce P and re-run calibration.

Oscillation Pattern: Slow, Large (±5-15℃, 10-30 second cycle)

Cause: I value too high. The integral term accumulates error and pushes power too high, causing large overshoot and recovery cycles.

Fix: Reduce pid_Ki by 20-30%. This is most common on beds with oversized heaters and low thermal mass.

Oscillation Pattern: Random Spikes or Drops

Cause: D value too high amplifying noise. The derivative term reacts to thermistor noise, causing erratic power output.

Fix: Reduce pid_Kd by 50% or set it to 0. If using a bed, set Kd to 0 and rely on PI control.

Symptom: Temperature Drops When Part Fan Turns On

Cause: The PID controller cannot respond fast enough to the sudden cooling from the part fan. This is normal to some degree but should not drop more than 5℃.

Fix: Tune the hotend PID WITH the part fan running at your typical printing speed. Add this macro to your START_PRINT:

# In your START_PRINT macro, after reaching printing temperature:
M106 S{ part_fan_speed }  # Turn on part fan
G4 P10000                    # Wait 10 seconds for stabilization
# Then start the actual print

Symptom: Temperature Oscillates Only at High Temperatures (250+℃)

Cause: Radiative heat loss changes the system dynamics at higher temperatures. PID tuned at 220℃ may not work well at 280℃.

Fix: Run PID calibration at the highest temperature you print. If you print across a wide range (PLA at 220℃ and PC at 290℃), consider saving two sets of PID values and applying them via macros.

Multiple PID Profiles via Macros

If you print materials with very different temperature ranges, you can store and apply PID profiles in Klipper:

[gcode_macro SET_PID_PLA]
gcode:
  SET_HEATER_PID HEATER=extruder
      Kp=22.0 Ki=1.1 Kd=100.0
  SET_HEATER_PID HEATER=heater_bed
      Kp=150.0 Ki=10.0 Kd=0
  { response('PID set to PLA profile') }

[gcode_macro SET_PID_ABS]
gcode:
  SET_HEATER_PID HEATER=extruder
      Kp=26.0 Ki=1.3 Kd=120.0
  SET_HEATER_PID HEATER=heater_bed
      Kp=200.0 Ki=14.0 Kd=0
  { response('PID set to ABS profile') }

Call these macros in your START_PRINT before heating, or use them in the slicer's start G-code. Note that SET_HEATER_PID values are temporary and reset after Klipper restart or SAVE_CONFIG. To make them permanent, edit printer.cfg.

Environmental Factors Affecting PID

• Chamber temperature — A Voron with a heated chamber (40-60℃) changes the heat transfer dynamics. The hotend loses less heat to the environment, so the PID needs less power to maintain temperature. PID tune with the chamber at normal printing temperature.
• Enclosure drafts — Fans (exhaust fans, Nevermore filter fans, enclosure cooling fans) create air currents that cool the hotend and bed. If you run these fans during prints, run them during PID calibration too.
• Ambient room temperature — Seasonal changes matter. If you PID-tuned in summer (30℃ room temp) and are now printing in winter (10℃ room temp), run PID calibration again.
• Build plate material — A tool steel plate has lower thermal mass and higher emissivity than an aluminum plate. Different plates require different PID values for the bed heater.
• Insulation — Adding insulation under the bed (e.g., 3mm cork sheet or silicone mat) changes the thermal dynamics significantly. Always re-tune bed PID after adding or removing insulation.

Verifying PID Performance

After tuning, verify stability with these tests:

• Hotend stability test — Heat to 240℃, let it sit for 10 minutes. The temperature should stay within ±0.5℃ of the target. In Mainsail/Fluidd, the temperature graph line should look almost perfectly flat.
• Part fan test — With the hotend at 240℃, turn the part fan on to 100%. The temperature should drop no more than 3-5℃ and recover to the target within 15-30 seconds.
• Bed stability test — Heat bed to 110℃, let it sit for 20 minutes. The temperature should stay within ±1℃ of the target. Longer convergence time is normal for the bed (5-10 minutes).
• Print test — Print a single-wall cube at 60mm/s. Measure extrusion width with calipers — it should be consistent within ±0.02mm through the entire height of the print.