When choosing a PLC suitable for flour mill equipment, the following aspects can be considered:
Reliability and Stability
Brand Reputation: Select a well-known brand of PLC, such as Siemens, Mitsubishi, Omron, etc. These brands usually have long-term applications and a good reputation in the industrial field, and the product quality and stability are more guaranteed
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Environmental Adaptability: The working environment of the flour mill is harsh, so it is necessary to choose a PLC with good dustproof, moisture-proof, shockproof, and anti-interference capabilities. For example, the Siemens S7-1200 series has a high protection level and is suitable for harsh industrial environments.
Redundancy Design: For the key parts of the flour mill equipment, a PLC system with redundancy functions, such as CPU redundancy, power supply redundancy, and communication redundancy, can be selected to ensure that the system can still operate normally when a fault occurs.
Control Functions
Basic Logic Control: The start and stop of the flour mill, the switch control of material conveying, etc. belong to the basic logic control. Generally, a small PLC such as the Mitsubishi FX series can meet the requirements.
Analog Quantity Control: If accurate control of analog quantities such as material flow, temperature, and humidity is required, a PLC with analog input and output modules and PID control function needs to be selected. For example, the Siemens S7-300 series can achieve high-precision control of analog quantities.
Communication Function: If the flour mill equipment needs to exchange data with other equipment, perform remote monitoring, or form an automated production line, a PLC with corresponding communication interfaces and communication protocols needs to be selected. For example, the Omron CJ series PLC supports multiple field buses and industrial Ethernet communications.
Input and Output Points
Point Counting: According to the control requirements of the flour mill equipment, carefully count the number of sensors, switches, etc. that need to be connected to the PLC input port, as well as the number of controlled devices such as motors, solenoid valves, and indicator lights that need to be connected to the PLC output port.
Reserved Margin: In order to adapt to possible future equipment expansion or process adjustment, usually add a margin of 10% - 20% on the basis of the counted I/O points.
Storage Capacity
Program Capacity Estimation: There is no fixed formula for estimating the memory capacity. Generally, it is 10 - 15 times the number of digital I/O points, plus 100 times the number of analog I/O points. This number is taken as the total number of words in the memory (16 bits is a word), and an additional 25% margin is considered.
Data Storage Requirement Consideration: In addition to the program capacity, the data storage requirements generated during the operation of the flour mill equipment also need to be considered, such as production data records and fault alarm records.
Ease of Use and Maintainability
Programming Convenience: Select a PLC that is easy to program, such as a PLC that supports intuitive programming languages such as ladder diagrams and function block diagrams, which is convenient for technicians to write, debug, and modify programs. For example, the Rockwell AB series PLC has a user-friendly programming software interface and a rich instruction set.
Fault Diagnosis Function: The PLC should have a complete hardware and software diagnosis function to quickly and accurately locate the fault point and shorten the maintenance time. For example, the Schneider M340 series PLC has a powerful diagnosis function and can monitor the system running status in real time.
Maintenance Cost: Consider factors such as the service life of the PLC, the supply of spare parts, technical support, and after-sales service, and choose a PLC product with low maintenance cost.
Cost and Cost-Effectiveness
Budget Limitation: Clarify the budget range of the enterprise. Under the premise of meeting the control function and performance requirements of the flour mill equipment, choose a reasonably priced PLC product to avoid unnecessary function waste.
Long-Term Benefits: Comprehensively consider factors such as the quality, reliability, and expandability of the PLC. Although the initial investment may be relatively high, from the perspective of long-term operation and maintenance costs, it may bring higher benefits.
