6.3 Dual Feeds for One Axis (Only A-axis)

Some machines require two sets of servomotors to drive the same axis, for example: Long-span gantry cutters. The INCON-M84/M86/M86R CNC controller provides excellent dual-axis drive functionality. The dual axis drive uses the A axis (4th axis) to drive the X/Y/Z axis synchronously to achieve the dual axis drive.

Note: Only the A axis (4th axis) can be set to move with the X/Y/Z axis.

In the PLC, the synchronous drive status is read with the plc.vto3.bit.ddmt0 and plc.vto3.bit.ddmt1 signals:

Signal	None	A axis and X axis move together	A axis and Y axis move together	A axis and Z axis move together
plc.vto3.bit.ddmt1	0	0	1	1
plc.vto3.bit.ddmt0	0	1	0	1

If the A axis and the Y axis are to be driven synchronously, the mechanical manufacturer must use two servos of the same brand, model, and characteristics to push the Y axis. The parameter setting of the A axis in the controller must also be the same as the Y axis. And in the PLC, it is also necessary to move the A-axis definition with the Y-axis.

The PLC example is as follows:

#include "plc.h"

#define iDualDriveSafeUmount (plc.gdi[1].bit.bit01)

#define pDualDriveMount (plcData[50])

...

void plcRun(Status &sts, PlcBlock &plc)

{

...

if( pDualDriveMount == 0 ) {

plc.vto3.bit.ddmt0 = 0; plc.vto3.bit.ddmt1 = 0; // no mount

} else if( sts.state0.bManual && sts.state0.bManualMode == 0 && // manual INC

iDualDriveSafeUmount ) {

plc.vto3.bit.ddmt0 = 0; plc.vto3.bit.ddmt1 = 0; // no mount

} else {

plc.vto3.bit.ddmt0 = 0; plc.vto3.bit.ddmt1 = 1; // A mount to Y, A Y sync

}...

}

The CNC controller also provides a phase correction zero return mode so that the phases of the motor rotation angles of the Y-axis and A-axis are maintained in the just-adjusted position. The relevant parameters are set as follows:

1.	"Machine Parameter Menu → A-axis → Forward Index": Choose to use this phase alignment to zero, [√] Check this item.
2.	"Machine Parameter Menu → Y-axis → Zero Index Offset": The home reset index offset setting is the same as the single Y axis.
3.	"Machine Parameter Menu → A-axis → Zero Index Offset": Sets the relative position of the cnc controller's Y axis to the A axis.

The detailed setting procedure is as follows:

1.	The phase angles of the Y axis and A axis are adjusted and the verticality is adjusted.
2.	Turn on A axis "Forward index", set A axis "Zero index offset" to zero.
3.	Doing Y axis home return, this process will take time to finish find out Y axis and A axis index.
4.	Press ALT+F8 after completing the home return, and then press ALT+F3 to enter the mechanical page of the second page. Take the position of the locator of Yi and Ai and its absolute value of -500, set them to the Y axis and A axis respectively. The offset can be found.
5.	If Yi or Ai has a smaller absolute position than 500, change or (Ai + feed lead -500).
6.	After setting, the dual axis drive is adjusted.

After setting, the CNC controller will compensate properly in the process of zeroing so that the relative position of the Y axis and the A axis remains the same as the angle at the time of calibration. In addition, the first homing at power-on will take a long time in order to get accurate phase correction.

After entering the single-acting mode in the manual mode, when a certain external security button is pressed, the synchronous drive of the Y axis and the A axis will be released. At this time, the machine manufacturer can manually adjust the motor of the Y axis and the A axis. The phase of the corners allows the two sets of guides to be positioned in a suitable, synchronously pushable position and to make their verticality with the X axis accurate.