Introduction

This procedure only applies to machines with PWM Drive Amplifiers shown below.

There are four potentiometer adjustments on the motor drive unit. These adjustments are preset at the factory and should not require field adjustment. However, if a motor drive unit is replaced or the performance needs to be modified, these pots function as follows:

P1 Loop gain CW increases gain

P2 Current limit CW increases current limit

P3 Reference gain CW increases gain

P4 Offset adjust N/A

Presets

Four DIP switches on the motor drive unit set the amplifier’s operating mode. Set all four switches to OFF position.  Set Current Limit potentiometer, P2, fully clockwise.  Check gain and balance adjustments for each axis. The gain adjustment affects the motor speed for a given drive signal. The balance adjustment affects the motor drift when there is no drive signal. Both adjustments can be made without any measuring devices and both use the CNC to provide speed feedback from the motors.

Gain Adjustment

Use the Speed Measurement display of Vision CNC to adjust gain of PWM amplifiers. This feature momentarily drives the motors and displays the resulting maximum drive speed. Adjust each axis to have the same maximum drive speed.

Crush hazard.

Machine starts automatically.

1. Before doing Speed Measurement Test, verify no personnel or equipment are in machine’s way.
2. Machine will move by itself in both axes.

Procedure

• Leave drives engaged.
• Press Shift-Data Window to select Startup Window.
• Startup Window appears.
• If Startup Window menu does not display all options shown here, press Shift-Rapid to access Service Mode
• A message indicates Service Mode is activated. Press F1 to clear message.
• In Startup Window, press F2 to select Speed Measurement Test.
• Speed Measurement screen appears.

• To start Speed Measurement, press F1 to select X-axis or F2 to select Y-axis.

During speed measurement, the function key for the selected axis is displayed in inverse video. When machine stops, it returns to normal.

The selected axis moves about 1" (25mm) in the positive direction, and then moves back about 1" (25mm) in the negative direction. Display shows calculated drive speed.

At this time, make adjustments to Speed Potentiometer, P3, on PWM drive board. Repeat test and check speed display. Continue making adjustments and repeat test until a speed of 250ipm (6,350 mm/min) is displayed.

When each drive is adjusted satisfactorily, press Backpage to exit Speed Measurement display. New speed values are recorded in Machine Constants.

Balance Adjustment

To adjust balance of PWM amplifiers, disconnect the drive signal outputs and use the Loop Error Display feature of the CNC. This display shows the position following the error of each axis. When an amplifier’s balance is out of adjustment, the loop error value climbs.

Procedure

Manually release the tension spring to disengage the drive pinions from drive rack. Use a block of wood to block out drives. Don’t disengage drives, but watch carefully in case they drift.  Open the CNC console. Disconnect the X8 connector from the Process I/O Board (PIO). This disconnects the CNC’s drive signal output. The PWM drive amplifiers should hold the motors still. Since actual motor output shaft cannot be seen, use the Loop Error Display to see if motors are drifting.

Press Shift-F1 to access Loop Error Display.

The loop error (position following distance) is displayed for each axis.

If the loop error is climbing for any of the axes, adjust Balance Potentiometer, P4, on the PWM drive board for that axis until loop error stops changing.

Response Adjustment

While still in Loop Error Display, adjust Response potentiometer, P1, on PWM drive unit. Turn potentiometer clockwise until drive makes a high- pitch squeal, then back off counterclockwise three full turns.

Repeat above steps until each axis is adjusted satisfactorily.

Turn OFF machine power

Reconnect X8 connector to Process I/O Board.

Attach tension spring to re-engage drive pinions.