My first request on the forum so be gentle with me.

Siemens 840di

Linear motor 1FN3450-3WB50-0AA1

I have recently moved a machine to a new location (it was working fine prior to the move). On powering the machine up at the new location, reseting the safety circuit and enabling the drives, the linear motor axis moves in a X+ or X- direction maybe 50mm and gives a 611 alarm. The only way I can get the axis to stay still at start up is to reduce P1019 from 40% down to 10%. I can then jog the axis but only for about +/-10mm before the current rises quickly and 608 occurs. It will then not continue in that direction without error but will travel in the opposite direction! So overall about 20mm slowly without error. This is the same wherever the motor is positioned along its working range.

There is no mechanical restriction on the axis and the axis brake is releasing correctly.

Motor power and encoder cables are free of damage.

Motor air gap is approx 0.9mm as per manual.

Axis plug in card and LT Module have been substituted.

Encoder has been substituted.

A backup of the parameters to the drive have been loaded.

I can't use P1017 to set commutation angle offset as the axis will not jog without error.

I have tried manually entering a value in P1016 from -360 to +360 with no luck.

I have run out of ideas. What should I be trying next?

I am by no means highly experienced on Simodrive and Simocomu but know my way around but I know nothing on fault finding on linear motors. This is my first problem on these in probably 15 years.

Thanks, Stuart

PISCEAN 2010

As stated in manual you can try by increasing mass on linear motor & try for rotor position identification, i.e. your linear axis should not move at 40% current setting. 

 I have increased P1076 from 0 to 75kg and now the axis does not alarm when enable is applied. When i then try to jog the axis i still get alarm 608. The axis will then move in the opposite direction when the alarm is reset or vibrates violently before alarming.

The axis was clamped in place for transport but has to be moved around with power off to reassemble the machine. I have all the original parts back on the machine and the original parameters loaded in the drive (these have not been changed since new).

Today I've removed the motor for check & test at a repair centre. If it's found to be faulty that is good news but delivery on a replacement is 6-8 weeks!!