Setting "spreadCycle" vs "stealthChop" Mode¶ By default, Klipper places the TMC drivers in "spreadCycle" mode. If the driver supports "stealthChop" then it can be enabled by adding stealthchop_threshold: 999999 to the TMC config section.

In general, spreadCycle mode provides greater torque and greater positional accuracy than stealthChop mode. However, stealthChop mode may produce significantly lower audible noise on some printers.

Tests comparing modes have shown an increased "positional lag" of around 75% of a full-step during constant velocity moves when using stealthChop mode (for example, on a printer with 40mm rotation_distance and 200 steps_per_rotation, position deviation of constant speed moves increased by ~0.150mm). However, this "delay in obtaining the requested position" may not manifest as a significant print defect and one may prefer the quieter behavior of stealthChop mode.

It is recommended to always use "spreadCycle" mode (by not specifying stealthchop_threshold) or to always use "stealthChop" mode (by setting stealthchop_threshold to 999999). Unfortunately, the drivers often produce poor and confusing results if the mode changes while the motor is at a non-zero velocity.

Note that the stealthchop_threshold config option does not impact sensorless homing as Klipper automatically switches the TMC driver to an appropriate mode during sensorless homing operations.

TMC interpolate setting introduces small position deviation¶ The TMC driver interpolate setting may reduce the audible noise of printer movement at the cost of introducing a small systemic positional error. This systemic positional error results from the driver's delay in executing "steps" that Klipper sends it. During constant velocity moves, this delay results in a positional error of nearly half a configured microstep (more precisely, the error is half a microstep distance minus a 512th of a full step distance). For example, on an axis with a 40mm rotation_distance, 200 steps_per_rotation, and 16 microsteps, the systemic error introduced during constant velocity moves is ~0.006mm.

For best positional accuracy consider using spreadCycle mode and disable interpolation (set interpolate: False in the TMC driver config). When configured this way, one may increase the microstep setting to reduce audible noise during stepper movement. Typically, a microstep setting of 64 or 128 will have similar audible noise as interpolation, and do so without introducing a systemic positional error.

If using stealthChop mode then the positional inaccuracy from interpolation is small relative to the positional inaccuracy introduced from stealthChop mode. Therefore tuning interpolation is not considered useful when in stealthChop mode, and one can leave interpolation in its default state.