The Record Table integrated into the Festo CMMT-AS and CMMT-ST servo drives is a powerful tool that simplifies the PLC programming needed to execute a sequence of moves or commands. By offloading the logic to the servo drive, this approach allows easy replication across multiple devices. Fundamentally, each record in the Record Table can perform a specific function such as executing a move, writing a parameter, or engaging/disengaging a gear. This can then trigger a transition to another record based on conditions like a time delay, move completion, or evaluation of a parameter.
In its simplest application, a PLC can issue a single command to initiate a series of moves, for example moving through three distinct positions. This works the best for applications where the motion profile (velocity/acceleration/deceleration) does not need to change between iterations. The PLC specifies the starting record, and the drive then carries out the sequence autonomously.
For more complex scenarios, decisions may be required such as determining which end position to move to or waiting for sensor confirmation before proceeding. The Record Table supports two digital inputs that can be evaluated to add this flexibility. For instance, one digital input might start a loop where the actuator oscillates between two positions, while the other input stops the motion. This use case is further demonstrated in this YouTube video: https://www.youtube.com/watch?v=2o6tXRwfmm8&t=2s
While this example relies on two boolean inputs for decision-making, it can be limiting. Some applications require comparing more detailed values to enable more advanced functionality, such as bytes, integers, or real numbers. For example, an actuator might loop between two positions, but the second position could vary depending on the product being processed. If there are more than four product recipes, relying solely on two digital inputs becomes insufficient.
The approach outlined next explains how to write to a real or floating-point value that can be utilized within a record transition to address these more complex requirements.
There is not explicitly a parameter defined for this type of transition in Festo Automation Suite. But, there is a parameter that has read/write access that is no longer used in the most recent software and firmware versions. This parameter is P1.102441.0.0 and is labeled as 'unused'. This value is no longer, at the time of the firmware versions listed above, used for calculations and can therefore be written to without affecting any functions.
This post is provided solely for the purpose of offering setup assistance and general guidance. It is important to note that the ultimate responsibility for ensuring the overall safety and proper functionality of the machine lies with the System Integrator / End User. It is crucial to exercise caution, adhere to proper safety protocols, and consult relevant experts or professionals when necessary.
Although Festo employees will be contributing to this blog, please note this is not the official Festo support channel. For more timely technical support please reach out to your regional Festo support channel and/or consult user manuals and relevant documentation.