PLC programming example - Paint Spray
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The document outlines a 5-step process for developing a PLC program for a paint spray application system. The steps are: 1) define the task, 2) define inputs and outputs, 3) develop a logical sequence of operation using a flowchart, 4) develop the PLC program, and 5) test the program. It then provides details for each step as applied to a conveyor system that feeds boxes through a spray nozzle, with inputs like start/stop buttons and outputs like conveyor motor and spray valve control.
PLC programming example - Paint Spray
- 1. Five Steps to PLC Program Development Paint Spray Application
- 2. 1. Define the task: What has to happen?
- 3. 1. Define the task: Paint spraying system where boxes are fed by gravity through a feeder magazine one at a time on to a moving conveyor belt. Upon the start signal, boxes are pushed towards the conveyor by cylinder A which extend and retract operation is controlled by switch S1 and S2. A spraying nozzle paints each box as it passes by and a detector D1 counts each box being sprayed. When 20 boxes have been painted the valve V2 shuts off and cylinder A stops operating. Eight seconds later the conveyor stops moving and the hopper with its load now moves to the B+ position where it is emptied. Thirty seconds later the hopper returns to the original B- position. End of cycle of operation.
- 4. 2. Define the Inputs and Outputs: Inputs: Start Pushbutton – Normally Open – On/Off Stop Pushbutton – Normally Closed – On/Off S1 – Valve 1 (cylinder retract) On/Off - NO S2 – Valve 1 (cylinder extend) On/Off – NO S3 – Box Detected- On/Off - NO Outputs: Motor – On/Off (Conveyor Run) Valve 1- Cylinder to feed boxes – On/Off Valve 2- Paint Spray – On/Off Valve 3- Cylinder to move hopper – On/Off
- 5. 3. Develop a logical sequence of operation: Use a flow chart or sequence table. Fully understanding the logic before starting to program can save you time and frustration. What happens when electrical power and/or pneumatic air is lost? What happens when the input / output devices fail? Do we need redundancy?
- 6. 3. Develop a logical sequence of operation:
- 7. 3. Develop a logical sequence of operation: Review this sequence with the person with the most knowledge of the machine. This can be the designer and / or the machine operator.
- 8. 4. Develop the PLC program:
- 9. 4. Develop the PLC program:
- 10. 4. Develop the PLC program:
- 11. 4. Develop the PLC program:
- 12. 4. Develop the PLC program:
- 13. 4. Develop the PLC program:
- 14. 4. Develop the PLC program:
- 15. 4. Develop the PLC program: Document, Document, Document! This save you time and money when you have to return to the program years later.
- 16. 5. Test the program:
- 17. 5. Test the program: Test the program with a simulator or actual machine. Make modifications as necessary.
- 18. 5. Test the program: Check with the people most knowledgeable on the machine, to see if it is doing what they expect.
- 19. 5. Test the program: Follow up after a time frame to see if any problems arise that need to be addressed in the PLC program.
- 20. PLC Program Development The five steps form the basis of all PLC development. You will notice that the actual programming does not occur until the second last step. Usually more time is spent on clearly understanding the task and sequence of operation.
- 21. ACC Automation Practical Tips and Techniques Spray Paint Application – More information can be found on our website More PLC Programming Examples