fanuc omd 4th axis randomly won't move 414 alarm excess error

lowCountryCamo · Mar 2, 2020

I have a Fanuc 0md Yang mill. And I found a Tsudakoma 4th from HGR minus a motor and internal wires. So I pieced together everything and got it running however after installing the motor cover it won't move and I get the 414 excess position error detected. With the cover off on the table with wires running through the case terminals it will run. I have been round and round with this thing. I nearly pulled it off today and gave up. Just then I think I narrowed it down. When the case is resting on the table grounded it runs. If I isolate it with card board underneath it wont move. How should the motor, case, wire connections be grounded?

Thanks,

Steve Austin

Vancbiker · Mar 2, 2020

It needs to be grounded for safety reasons. If it is an AC servomotor (red cap) there should be 3 power conductors and a ground conductor in the power cable. The encoder cable needs to have the shields from the pairs grounded on one end. For that I prefer it at the drive. The body of the 4th and any metal covers should be grounded. Best would be a separate ground wire in the cabling but in many instances that is accomplished through the servo motor power cable ground and the fact that the motor is bolted to the table.

lowCountryCamo · Mar 2, 2020

Hi VanC. I do have shields and the power cable appears to be correct. Can you think of anything else that would cause the motor to run sporadically with no alarm but the position error. That error comes from the control sensing the commanded movement did not happen. I measure 150v AC on all 3 power wires to ground.

Vancbiker · Mar 2, 2020

Yes, the 414 alarm is basically saying that the difference between the commanded move and the resulting feedback exceeds the error amount allowed. The majority of cases of this alarm are mechanical in origin. Your case does not sound like that so I need some more info the kick around.

Can you better describe what you mean by "the motor to run sporadically". Does that mean it is not rotating smoothly or sometimes it rotates and other times not?

Further describe the combination of parts you put together to make this 4th axis. Mainly interested in servo motor and encoder and drive. Also, is this a full closed loop setup?

lowCountryCamo · Mar 3, 2020

I have a Fanuc Alpha servo machine which was prewired for a 4th. I ordered the same Alpha motor/drive that would have come with the machine. I got the part numbers from the parts book. This has an incremental encoder in the red cap. I think this is considered a semi closed loop. This is a full 4th with a brake. I can see the bit for the break working but I guess it is possible the brake is not actually releasing. The servo will sometimes rotate and other times not. I have also seen it start to rotate and then quit. I checked power voltages and I see 150v from all three legs to ground.

Vancbiker · Mar 3, 2020

So new motor and drive? Did you make the cables or purchased? I'm just trying to narrow the possible areas of concern.

If there is any question that there is a mechanical issue it should be pretty easy to pull the motor and run it by itself for testing.

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fanuc omd 4th axis randomly won't move 414 alarm excess error

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