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<article class="guide-article">
<header>
<h1>Voron Klipper Chamber Fan Control</h1>
<p class="lead">Configure temperature-activated chamber fans to maintain optimal enclosure conditions for ABS and engineering materials.</p>
</header>
<section>
<h2>Why Control Chamber Fans?</h2>
<p>
Voron printers are enclosed to maintain chamber temperatures around 50-65°C for ABS, ASA, and polycarbonate printing. A chamber fan serves two purposes:
</p>
<ul>
<li><strong>Temperature equalization:</strong> Circulates air to prevent hot spots and cold spots inside the enclosure</li>
<li><strong>Exhaust ventilation:</strong> Vents fumes and excess heat to the outside when the chamber gets too hot (above 70°C)</li>
</ul>
<p>
Without active fan control, the enclosure can overheat during long prints, causing skipped steps on the Z motors, heat creep into the extruder heat sink, or degraded print quality from inconsistent chamber temperatures.
</p>
</section>
<section>
<h2>Hardware Setup</h2>
<h3>Chamber Thermistor</h3>
<p>
Place a 100k NTC thermistor (type: generic 3950) on the top panel or rear wall, away from the bed and hot end. Wire it to any free thermistor port on your MCU board (TH0, TH1 on Octopus, or THERM1 on Spider).
</p>
<h3>Fan Configuration</h3>
<p>
Use a 120mm or 140mm axial fan (Noctua, Sunon) for circulation. For exhaust, a 60mm fan mounted in the top or rear panel works well. Wire the fan to a MOSFET-controlled fan port (FAN0, FAN1) on your controller board.
</p>
</section>
<section>
<h2>Klipper Configuration</h2>
<h3>Step 1: Define the Chamber Temperature Sensor</h3>
<pre><code>[temperature_sensor chamber_temp]
sensor_type: Generic 3950
sensor_pin: PC5
min_temp: 0
max_temp: 120
</code></pre>
<h3>Step 2: Temperature-Triggered Fan (Bang-Bang Control)</h3>
<p>The simplest method — the fan turns on at a setpoint and off below it:</p>
<pre><code>[temperature_fan chamber_circulation]
pin: FAN2
max_power: 1.0
shutdown_speed: 0.0
cycle_time: 0.5
hardware_pwm: true
sensor_type: temperature_mcu
target_temp: 45.0
max_temp: 60.0
min_temp: 0.0
control: watermark
</code></pre>
<p>
This defines a circulation fan that activates at 45°C and deactivates below 45°C using watermark (bang-bang) control. The fan speed is always at max_power when active.
</p>
<h3>Step 3: PID-Controlled Variable Speed Fan</h3>
<p>For smoother control that ramps fan speed gradually:</p>
<pre><code>[temperature_fan chamber_circulation]
pin: FAN2
max_power: 1.0
shutdown_speed: 0.0
cycle_time: 0.5
hardware_pwm: true
sensor_type: temperature_mcu
target_temp: 50.0
max_temp: 65.0
min_temp: 0.0
control: pid
pid_Kp: 20.0
pid_Ki: 0.5
pid_Kd: 100.0
</code></pre>
<p>
PID control adjusts fan speed proportionally to the temperature error. This maintains tighter chamber temperature control but requires tuning the PID values for your specific enclosure size and fan.
</p>
</section>
<section>
<h2>Exhaust Fan Setup</h2>
<p>
Many Voron builders add an exhaust fan to vent excess heat and fumes outside. Configure it with a higher target temperature to avoid exhausting warm air during normal printing:
</p>
<pre><code>[temperature_fan chamber_exhaust]
pin: FAN3
max_power: 1.0
shutdown_speed: 0.0
cycle_time: 1.0
hardware_pwm: true
sensor_type: temperature_mcu
target_temp: 60.0
max_temp: 75.0
min_temp: 0.0
control: watermark
</code></pre>
<p>
When the chamber exceeds 60°C (e.g., during a high-temp polycarbonate print), the exhaust fan activates to pull in fresh air. Below 60°C the enclosure stays sealed to retain heat.
</p>
</section>
<section>
<h2>Macro-Controlled Fan Override</h2>
<p>
You can add a macro to manually override fan behavior during specific print phases:
</p>
<pre><code>[gcode_macro SET_CHAMBER_FAN]
gcode:
{% if params.SPEED|default(1.0) > 0 %}
SET_FAN_SPEED FAN=chamber_circulation SPEED={params.SPEED}
{% else %}
SET_FAN_SPEED FAN=chamber_circulation SPEED=0
{% endif %}
</code></pre>
<p>
Call it with `SET_CHAMBER_FAN SPEED=0.8` in your start gcode to run the fan during bed soak, then disable it for the print.
</p>
</section>
<section>
<h2>Troubleshooting</h2>
<h3>Fan Never Turns On</h3>
<p>
Check that the `sensor_pin` is reading correctly with `QUERY_ADC` in the Klipper console. Verify the fan pin is not shared with another function and that `max_power` is not set to 0.
</p>
<h3>Fan Oscillates On and Off Rapidly</h3>
<p>
Increase `cycle_time` or switch from PID to watermark control. PID parameters may be too aggressive — reduce Kp and Kd.
</p>
<h3>Chamber Temperature Too High Despite Fan</h3>
<p>
Your fan may be undersized. Consider a higher CFM fan or adding a second exhaust fan. Also check that the fan isn't blocked by the electronics compartment partition.
</p>
</section>
<section class="summary">
<h2>Summary</h2>
<p>
Chamber fan control in Klipper can be as simple as a bang-bang thermostat or as precise as a PID-controlled variable speed fan. Use `temperature_fan` sections in printer.cfg to define circulation and exhaust fans with separate temperature targets. A chamber thermistor is required, and hardware PWM is recommended for silent fan operation. With proper tuning, your Voron's enclosure stays at 45-60°C for optimal ABS printing while preventing overheating.
</p>
</section>
</article>