MS1978

Servo Movement

7 posts in this topic

I have a machine that has been in operation for more than six years. It uses a Mitsubishi MR-J2S-350B servo amplifier and a Mitsubishi QD75M2 positioning module.

When the control power is turn off for more than 30 minutes the servo will move when power is restored to the amplifier. The unit moves down to position -30. Then you have to manually jog the servo to -29 before you are able to send the unit to home position.

This issue just started a couple of months ago. The machine is powered down each night for PMs and has to be homed every morning. I have changed the battery.

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In the amplifies its probably set that you have to pass the z-phase of the encoder before you can home. which means you have to jog one revolution of the drive so you are sure it has passed the Z-phase. 

This can be turned off.

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 Would this setting change after an encoder swap? There has been no changes to this machine except an encoder change in the last 5 years. This issue just started happening within the last couple of months.

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Posted (edited)

Well No not really but the description of your problem seems to suggest this.

So I would check the setting in the amplifier and change them if it this so you can rule this out.
Also I would check which homing is being used and check if all the homing signals like dog sensor etc are working correctly.

 

Edited by Gambit

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which exact homing method is used? how exactly it is setup? things could slip if there was a collision.

also what kind of motor is this? does it have a brake? it may be worn out so motor slips a bit when powered off.

as i recall these drives also have absolute encoder option (requires battery). did anyone ever change that battery?

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The first thing that I did was to change the battery. As far as I know there has been no crash in the last year or so. The encoder has been changed.

The Servo does not move while the power is off as far as I can tell. The machine stays in the home position until the servo amp power is restored. As soon as the power is restore the servo motor drives down to the lower over travel proximity switch and faults out. The encoder position reading is -30. You have to manually jog the servo to -29 by selecting the servo counter clockwise button on the HMI. Once the machine has moved away from the switch you can select the servo home button on the HMI. The servo then travels up to the original (home) position.

The maintenance group informed me that this issue occurred with the twin machine a few years back. The controls specialist changed the servo amp out to correct the problem. 

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Well I would still check the Z-phase issue, but other than that. Do you know which error the servo amplifier has when it faults out?
 

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