The motor determines whether it is in a state of lock-up by monitoring the current change when the motor is rotating. When the motor is lock-up, the current will increase instantaneously. The TMC driver will monitor the current change of the motor in real time through the internal current sensor. Thus avoiding motor overload and damage.
Using this feature, the non-inductive homing function of the 3D printer can be realized, that is, the motor is blocked by hitting the frame and stopped after being detected by the drive. The advantage is to reduce the wiring and increase the mobile range; The disadvantage is that it is necessary to adjust the appropriate locked-rotor detection threshold, and this threshold is affected by the return speed, motor running current and temperature, of which the first two are controllable, and the temperature needs to be observed.
Source: https://www.klipper3d.org/TMC_Drivers.html#_2
1. The belt is loose, causing the impact force of the print head to Auto home to change, and the print head cannot be triggered or the trigger is not sensitive during Auto home, resulting in a collision of the nozzle.
2. When the print head is triggered, it will move 150mm in the opposite direction and stop. If the driver_sgthrs value is too high, the print head will be triggered in advance, and the travel distance of 150mm in the opposite direction will be insufficient, resulting in a collision.
If the driver_sgthrs value is set too low, there will be a slight collision sound when the print head is Auto home.
1. Check and adjust the A/B belts. You can change the tightness of the timing belt by adjusting the belt tensioner. Make sure the belt is within the appropriate range. If the belt is severely worn or deformed, it is recommended to replace it with a new one.
WIKI tutorial: http://wiki.sovol3d.com/en/SV08-AB-axis-belt-replacement-and-adjustment-tutorial
Video tutorial:https://youtu.be/7n_p33_o6dQ?si=0R7_zr_fYEcHiLg2
2. Enter the Mainsail interface via WIFI or network cable, click "Machine", find the "Print.cfg" file and open it, search for "driver_sgthrs", and modify the X or Y driver according to the direction in which the printer hits. Under normal circumstances, the order of zeroing the printer is to move backwards until it is triggered, then move to the right of the X axis to hit and trigger, and after triggering, the X and Y directions move 150mm in the opposite direction at the same time (the print head returns to the center of the hot bed, and the zeroing steps of the XY aixs are completed)
(1) If the print head hits to the left (X-), it can be confirmed that the zeroing of the print head X axis is triggered in advance, and the travel of the reverse direction is insufficient. Please modify the driver_sgthrs of the X axis. The default value is 65. You can try to lower it to 60, 55, 50... Save and restart the printer until the print head hits the right and then moves 150mm in the opposite direction and no longer hits.
(2) If the print head hits the right (X+), it can be confirmed that the driver_sgthrs value is too low, resulting in failure to trigger or inaccurate triggering. Please gradually increase the driver_sgthrs value in Print.cfg and save and restart until the print head hits the right lightly.
(3) If the print head hits the forward (Y-), because the order of zeroing is to move backwards first until it is triggered, if there is a collision when moving forward, it means that the zeroing of the Y axis of the print head is triggered in advance, and the travel of the reverse direction is insufficient. Please modify the driver_sgthrs of the Y axis. The default value is 65. You can try to reduce it to 60, 55, 50... Save and restart the printer until the print head is triggered by hitting backwards and rightwards, and then moves 150mm in the opposite direction (forward) and no longer hits.
(4) If the print head hits backwards (Y+), it means that the driver sgthrs value of the Y axis is too low, resulting in the Y axis direction not being triggered normally. Please gradually increase the driver_sgthrs value until the print head hits backwards lightly and is triggered.