The below question is regarding a siemens 317T CPU, CU320 S120, encoder: 6SL3055-0AA00-5Mxx, motor: 1FK7 synchronous motor
I am looking at the possibility of backing up the positions of a set of axes we currently have installed in the case of a CPU failure whilst the axes are loaded with parts. There are several axes which are synchronous and when loaded with parts need to be moved in sync, therefore the axis cannot be driven to their home position independently. I need to be able to swap out the CPU and restore the position (at the point instantly before CPU failure) of each axis without moving them.
Does anyone know the most effective way of doing so?
The encoders are configured as 'absolute encoder, absolute cyclic' which means i cannot use the siemens approved method of reading drive parameter 4010, writing it to the load memory and then reading it back to the working memory upon CPU replacement. The reason given for this in the S7Tech manual is:
For the "Absolute encoder, cyclic absolute" encoder type, in addition to the adjustment value,
the value of the cyclic counter must be backed up. This is only possible using the Backup
and Restore feature in S7T Config.
This cannot be done when the CPU is dead so doesn't help me
My other theory was to constantly write the live 'actual unscaled position' of each axis whilst it is moving to the an unlinked DB on the MMC. Swap the CPU and MMC, then use these positions stored on the MMC and the 'home' technology function to reteach the axis positions. The problem with this is that the MMC has a limitation of 100,000 read/write cycles according to Siemens documentation.
Cheers
I am looking at the possibility of backing up the positions of a set of axes we currently have installed in the case of a CPU failure whilst the axes are loaded with parts. There are several axes which are synchronous and when loaded with parts need to be moved in sync, therefore the axis cannot be driven to their home position independently. I need to be able to swap out the CPU and restore the position (at the point instantly before CPU failure) of each axis without moving them.
Does anyone know the most effective way of doing so?
The encoders are configured as 'absolute encoder, absolute cyclic' which means i cannot use the siemens approved method of reading drive parameter 4010, writing it to the load memory and then reading it back to the working memory upon CPU replacement. The reason given for this in the S7Tech manual is:
For the "Absolute encoder, cyclic absolute" encoder type, in addition to the adjustment value,
the value of the cyclic counter must be backed up. This is only possible using the Backup
and Restore feature in S7T Config.
This cannot be done when the CPU is dead so doesn't help me
My other theory was to constantly write the live 'actual unscaled position' of each axis whilst it is moving to the an unlinked DB on the MMC. Swap the CPU and MMC, then use these positions stored on the MMC and the 'home' technology function to reteach the axis positions. The problem with this is that the MMC has a limitation of 100,000 read/write cycles according to Siemens documentation.
Cheers
