PLC-CNC Cyclic Data Retention for Missed Operation Timing
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Solution Overview
Problem
In CNC systems, the PLC faces challenges in acquiring operation information at expected timings due to CNC unresponsiveness during machining or loading status issues, leading to disrupted intervals for data retrieval.
Innovation Solution
The PLC sets a cyclic time for the CNC to periodically acquire and retain operation information when unresponsive, allowing for continuous data collection and transmission once responsiveness is restored.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PLC transmits the special instruction WINDR to the CNC at the desired timing, then the PLC can acquire operation information from the CNC, but the PLC cannot acquire the operation information at the expected timing when the CNC is unable to respond due to machining timing or loading status
Solution Approach 1:
The CNC performs preliminary action by periodically acquiring and retaining operation information in advance even when unable to respond to PLC requests. The information acquiring unit continuously collects operation information and stores it in the information retaining unit before the PLC needs it, so that when the PLC requests data, the CNC can immediately provide the most recent retained information without delay.
2Measurement precision
If the PLC waits for the CNC to become able to respond before transmitting the next special instruction, then the PLC can receive accurate operation information, but the interval for acquiring operation information corresponding to periodic PLC operation is disturbed
Solution Approach 1:
The CNC continuously performs preliminary acquisition of operation information at predetermined intervals independent of PLC request timing. This allows the information to be ready when needed, maintaining both timing precision and acquisition productivity without the PLC needing to wait for CNC availability.
Solution Approach 2:
The information acquiring unit continuously acquires operation information at regular intervals regardless of whether the PLC has requested data. This continuous useful action ensures that operation information is always up-to-date and available, eliminating gaps in the acquisition process and maintaining steady productivity while preserving timing precision.
3Adaptability or versatility
If the CNC overwrites the data for each control cycle, then the CNC maintains current operation state, but the data to be originally returned cannot be returned when the PLC requests it later
Solution Approach 1:
The CNC performs preliminary retention of operation information in the information retaining unit before the PLC requests it. Instead of immediately overwriting data with each control cycle, the system preliminarily stores multiple instances of operation information, ensuring that when the PLC requests data at any timing, the appropriate historical information is still available and can be returned.
Data Source
AI summary
To enable acquisition of operation information of CNC corresponding to periodic operation of PLC, even when the CNC is unable to respond due to the timing of machining, the loading status, etc. The PLC device includes: a special instruction control unit that sets, to a special instruction for acquiring operation information indicating an operation state of a control device from the control device controlling an industrial machine, a cyclic time for causing the control device to periodically acquire and retain the operation information in a case in which the control device is unable to respond, and transmits to the control device the special instruction in which the cyclic time is set; and an acquisition unit that acquires the operation information acquired on the basis of the cyclic time from the control device.