armstrongracer
Member
Hi, after 30 years involved with automation I'm actually writing my first PLC program and am struggling a fair bit. My background is mechanical but have been involved for years with special purpose machine building, equipment maintenance, install and commissioning. So although I've probably programmed in excess of 50 robots over the years and can fault find at PLC level the PLC's have always been programmed by someone else, up to now that is.
I'm modifying a special purpose leak testing machine by adding extra clamping and sequencing. The system originally came from the vendor with some existing on-board I/O capability but what I need to do exceeds the capability of that non-expandable I/O. The easiest option is to let the tester do what its good at and add an Omron Zen plc to handle part clamping sequence and to initiate the testing. The hardware part is completed and by simulating the I/O I've verified that everything works as it should. I just need to convert that to an automated program.
Essentially the Zen will just have to deal with with 4 inputs (external start button, Light curtain OK from safety relay, Test Pass from tester, Test Fail from tester) and drive seven outputs (6 x pneumatic solenoids, 1 x Start-Test signal to Tester). The pneumatic cylinders are actuated by 5/2 solenoids such that they are fully retracted the un-energised state. So a held-on output drives cylinders forward, removing the output sends them back. I also want to improve the safety of the system. As delivered the system only inhibited start if the light curtain was broken, it didn't stop a sequence once initiated. I've hard wired the "clear" signal from the safety relay through a normally close solenoid that dumps pneumatic air supply if the curtain is broken. In addition I want to monitor that output in the PLC such that any output that drives a cylinder is conditional of the light curtain being clear.
I'm modifying a special purpose leak testing machine by adding extra clamping and sequencing. The system originally came from the vendor with some existing on-board I/O capability but what I need to do exceeds the capability of that non-expandable I/O. The easiest option is to let the tester do what its good at and add an Omron Zen plc to handle part clamping sequence and to initiate the testing. The hardware part is completed and by simulating the I/O I've verified that everything works as it should. I just need to convert that to an automated program.
Essentially the Zen will just have to deal with with 4 inputs (external start button, Light curtain OK from safety relay, Test Pass from tester, Test Fail from tester) and drive seven outputs (6 x pneumatic solenoids, 1 x Start-Test signal to Tester). The pneumatic cylinders are actuated by 5/2 solenoids such that they are fully retracted the un-energised state. So a held-on output drives cylinders forward, removing the output sends them back. I also want to improve the safety of the system. As delivered the system only inhibited start if the light curtain was broken, it didn't stop a sequence once initiated. I've hard wired the "clear" signal from the safety relay through a normally close solenoid that dumps pneumatic air supply if the curtain is broken. In addition I want to monitor that output in the PLC such that any output that drives a cylinder is conditional of the light curtain being clear.
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