Gantry Homing - Stratasys FORTUS 360mc Service Manual

Gantry Homing

1.
The Motion Control System detects home position by driving each axis into its negative
hard travel limit - the hard travel limit is recorded.
• There are no mechanical homing switches mounted on the gantry.
• Servo amplifiers have software controlled torque adjustment capability
• During the homing process, the current to the X and Y servomotors is
• A following error from the motor encoders accumulate quickly when the
• Detection of the increase in following error is used to establish the home
2.
The X and Y axes are homed simultaneously.
• Zero-zero position for XY is front, left corner of gantry.
3.
Current (torque) of the servo amplifier is lowered to approximately 50ma.
4.
The axis motor is commanded to move incrementally in a negative direction (Y-axis -
toward the front of the system; X-axis - toward left of the system) as the Motion Control
board monitors encoder feedback following error.
5.
When the hard limit is reached, the increase in following error is detected and axis
movement is stopped by the Motion Control board.
6.
A positive direction motion command is applied in increments of 0.0005 inches (0.127
mm).
7.
Following error decreases with each incremental move.
8.
When following error reads zero, the hard stop has been found.
9.
Both the X and Y-axis are moved in a positive distance of 0.5 inches (12.7mm). This
position becomes the Global Zero position of the axis.
10.
The homing process is completed by moving the head to the park position.
FORTUS 360mc/400mc Service Manual
that allow the system to vary the amount of current to the servomotors.
reduced to approximately 50ma (normal operation is 4 amps).
axis hits the travel limit. (Following error is the location the axis is
expected to be - somewhere past the hard stop in this case - versus its
actual location. With time, the expected location continues to advance,
while the axis does not, increasing the following error.) In essence, the
motor is commanded to move and there is no response from the encoder
confirming the move.
position.
The success of the gantry homing process is dependent on there
being no mechanical binding in the gantry. If, during the homing
process, an axis develops a bind, excessive following error may
develop and cause an erroneous home position.
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