Gantry Homing Example
This example covers one method for gantry homing while using the HSReverseZPulse home type.
Homing parameters should be set as follows:
Home Type - HSReverseZPulse for the master axis.
Gantry Homing Use Slave HS - TRUE for the master axis.
Gantry Homing Use Slave Z-Pulse - TRUE for the master axis.
Often, the Z-pulses of the master and slave axes are not located parallel to each other. As such, if the Z-pulses are set as the home positions without any modification, the gantry will twist. To prevent this, the distance between the Z-pulses of the master and slave axes must be found.
To find the distance between the Z-pulses of the master and slave axes, homing is executed without breaking synchronization. The Gantry Homing Retain Sync Offset parameter is set to enabled for the master axis. Then, synchronization control is started at a position where the master and slave axes are perfectly parallel to each other. It is important that the master and slave axes are parallel to each other at this point, because if any warping exists, it will affect the calculation of the distance between the Z-pulses, and will reappear after future homing operations.
The following diagram shows the example setup before homing.
After starting homing, the slave home switch is found.
Then, the master home switch is found. Because both home switches have been found, the synchronized axes will reverse direction and search for the first Z-pulse (index pulse) before the home switch.
The master Z-pulse is found. A slave Z-pulse also exists, but it is ignored because it is located after the slave home switch.
The slave Z-pulse is found. Because both Z-pulses have been found, the axes will move to the home positions.
Normally, the master axis would move to the position where the master axis Z-pulse was found, and the slave axis would move to the position where the slave axis Z-pulse was found. However, because the Gantry Homing Retain Sync Offset parameter is enabled, the slave axis will follow the master axis to the home position of the master axis without breaking synchronization.
After the homing routine is complete, the Dist Z-Pulse To Master Z-Pulse status will contain the distance between the Z-pulse positions of the master and slave axes. In this example, the distance is -5000.
After the distance between the Z-pulse positions has been obtained and entered into the Home Shift Distance parameter, homing can be performed with Gantry Homing Retain Sync Offset disabled. Because of this, it is no longer necessary to ascertain that the master and slave axes are perfectly parallel before starting synchronization and homing.
The value of Home Shift Distance must be set so that the home position of the slave axis is shifted by the correct amount. In this example, the Home Direction is in the negative direction, so the negative value of the Dist Z-Pulse To Master Z-Pulse is copied to Home Shift Distance.
The following diagram shows a homing operation with Gantry Homing Retain Sync Offset disabled. In addition, the master and slave axes are slightly warped when the homing operation is started. This warping will be corrected by the homing operation.
The slave home switch is found first.
Then, the master home switch is found. The synchronized axes will reverse direction to search for the first Z-pulse before the home switch.
The master Z-pulse is found. This becomes the home position of the master axis.
The slave Z-pulse is found. This position, shifted by the Home Shift Distance, becomes the home position of the slave axis.
The master and slave axes break synchronization and independently move to the home positions. The warping of the gantry is corrected in this step. To prevent the gantry from temporarily warping more during this step, the Home Shift Velocity, Home Shift Acc, and Home Shift Dec parameters should be set to the same values for the master and slave axes.
