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<article class="guide-article">
<header>
<h1>Voron Klipper StealthChop vs SpreadCycle Guide</h1>
<p class="lead">Master TMC driver mode selection for your Voron — balance silence, torque, and print quality.</p>
</header>
<section>
<h2>Understanding Driver Modes</h2>
<p>
TMC2209, TMC5160, and TMC2240 stepper drivers on Voron control boards support two main operating modes: StealthChop and SpreadCycle. Each offers distinct trade-offs that significantly affect printer behavior.
</p>
<ul>
<li><strong>StealthChop2:</strong> Voltage-mode PWM control that runs motors nearly silently. Excellent for noise-sensitive environments but reduces high-speed torque and can introduce position jitter at certain speeds.</li>
<li><strong>SpreadCycle:</strong> Current-mode control with higher torque output, especially at medium to high speeds. The trade-off is audible motor whine and a more aggressive electrical signature.</li>
</ul>
<p>
Klipper also supports `hybrid` mode, which automatically switches between StealthChop at low speeds and SpreadCycle at high speeds using a configurable threshold.
</p>
</section>
<section>
<h2>StealthChop: The Silent Choice</h2>
<h3>Benefits</h3>
<ul>
<li>Near-silent operation — ideal for office or bedroom environments</li>
<li>Smoother low-speed movement for the first layer</li>
<li>Reduces audible resonance from the printer frame</li>
</ul>
<h3>Drawbacks</h3>
<ul>
<li>Torque drops off significantly above 60-80 mm/s — risk of skipped steps on fast travel moves</li>
<li>Can cause visible artifacts on print surfaces at certain speeds (VFA / surface ringing)</li>
<li>Generates more heat in the driver IC at the same current setting compared to SpreadCycle</li>
<li>Position error accumulates at higher velocities due to the voltage-mode control scheme</li>
</ul>
<h3>When to Use StealthChop</h3>
<p>
Use StealthChop on Z axes, extruder, and X/Y at low speeds (below 80 mm/s). It's also the default for many Voron configurations out of the box. If you print mostly at moderate speeds and value silence, StealthChop on all axes is a reasonable starting point.
</p>
</section>
<section>
<h2>SpreadCycle: The Torque Choice</h2>
<h3>Benefits</h3>
<ul>
<li>Higher torque at all speeds — lower risk of skipped steps</li>
<li>Better high-speed performance for travel moves (200+ mm/s)</li>
<li>Reduces VFA (Vertical Fine Artifacts) on print surfaces at high acceleration</li>
<li>Cooler driver operation compared to StealthChop at same current</li>
</ul>
<h3>Drawbacks</h3>
<ul>
<li>Audible motor whine at all speeds — can be annoying in quiet environments</li>
<li>More electrical noise on the power rail</li>
<li>Can sound harsh at low speeds (below 20 mm/s)</li>
</ul>
<h3>When to Use SpreadCycle</h3>
<p>
Use SpreadCycle on X and Y axes for high-speed printing (150+ mm/s), especially on Voron 2.4 350mm builds where the gantry mass requires more torque. Also preferred on heavy toolheads with direct-drive extruders.
</p>
</section>
<section>
<h2>Hybrid Mode: Best of Both Worlds</h2>
<p>
Hybrid mode uses StealthChop below a velocity threshold and SpreadCycle above it. This gives silent low-speed operation (first layer, probing) with high-speed torque.
</p>
<pre><code>[tmc2209 stepper_x]
run_current: 0.8
hold_current: 0.5
stealthchop_threshold: 999999 # Disabled by default
# Enable hybrid mode with a threshold:
stealthchop_threshold: 30 # Switch at 30 mm/s
</code></pre>
<p>
With `stealthchop_threshold: 30`, the driver runs in StealthChop below 30 mm/s and SpreadCycle above 30 mm/s. The transition is seamless and happens mid-move.
</p>
<h3>Tuning the Hybrid Threshold</h3>
<table>
<thead>
<tr><th>Axis</th><th>Recommended Threshold</th><th>Rationale</th></tr>
</thead>
<tbody>
<tr><td>X</td><td>30-50 mm/s</td><td>Low-speed first layer is silent; high-speed travels get torque</td></tr>
<tr><td>Y</td><td>30-50 mm/s</td><td>Heavier bed needs torque at speed; first layer still quiet</td></tr>
<tr><td>Z</td><td>999999 (always StealthChop)</td><td>Z moves are slow and need positional accuracy, not torque</td></tr>
<tr><td>Extruder</td><td>15-25 mm/s</td><td>Retractions are fast; low-speed extrusion stays quiet</td></tr>
</tbody>
</table>
</section>
<section>
<h2>VFA and Print Quality Impact</h2>
<p>
VFA (Vertical Fine Artifacts) are faint, evenly-spaced bands on print surfaces, often caused by stepper motor microstep positioning errors. StealthChop can exacerbate VFA because its voltage-mode control has less precise current regulation than SpreadCycle.
</p>
<p>To minimize VFA:</p>
<ul>
<li>Use SpreadCycle on X and Y for the outer perimeter of the print</li>
<li>Reduce acceleration slightly (3000-5000 mm/s² instead of 5000-10000)</li>
<li>Ensure your belt tension is even and within spec (100-120 Hz on the tension meter)</li>
<li>Use `driver_SGTHRS` tuning to reduce motor resonance at specific speeds</li>
</ul>
</section>
<section>
<h2>Klipper Configuration Examples</h2>
<h3>Pure StealthChop (Silent Build)</h3>
<pre><code>[tmc2209 stepper_x]
run_current: 0.8
stealthchop_threshold: 999999
</code></pre>
<h3>Pure SpreadCycle (Performance Build)</h3>
<pre><code>[tmc2209 stepper_x]
run_current: 0.8
stealthchop_threshold: 0
</code></pre>
<h3>Hybrid (Balanced)</h3>
<pre><code>[tmc2209 stepper_x]
run_current: 0.8
stealthchop_threshold: 40
driver_TBL: 2
driver_TOFF: 3
driver_HSTRT: 4
driver_HEND: 2
</code></pre>
<p>
The additional driver parameters (TBL, TOFF, HSTRT, HEND) tune the SpreadCycle chopper behavior for smoother transitions. These are defaults in many Voron configurations.
</p>
</section>
<section>
<h2>Run Current and Mode Interaction</h2>
<p>
Driver mode affects how run current translates to actual motor torque:
</p>
<ul>
<li>In StealthChop, set run_current 10-15% higher than you would for SpreadCycle to compensate for the lower torque-per-amp efficiency.</li>
<li>Never exceed the driver's rated RMS current: 1.2A for TMC2209 (with heatsink), 2.8A for TMC5160.</li>
<li>If you see OTPW (over-temperature pre-warning) flags, reduce run_current or switch to SpreadCycle rather than adding more heatsinking.</li>
</ul>
</section>
<section>
<h2>Testing Your Configuration</h2>
<ol>
<li>Set hybrid threshold and run a torture test: `G1 X0 Y0 F30000` (500 mm/s travel)</li>
<li>Check for skipped steps: measure position repeatability with a dial indicator</li>
<li>Print a 100mm hollow cube at 120 mm/s, 3000 mm/s² — inspect for VFA on the sides</li>
<li>Listen for driver whine: SpreadCycle is noticeable at low speeds; if it's too loud, increase the hybrid threshold</li>
</ol>
</section>
<section class="summary">
<h2>Summary</h2>
<p>
StealthChop and SpreadCycle offer a trade-off between noise and torque on Voron printers. StealthChop is silent but loses torque at high speeds and can introduce VFA. SpreadCycle provides full torque with audible motor whine. Hybrid mode with a velocity threshold of 30-50 mm/s on X/Y axes gives the best balance for most builds. Z axes and extruders should remain in StealthChop. Tune your driver mode choice based on your speed requirements, noise tolerance, and surface finish expectations.
</p>
</section>
</article>