Welcome to my column where I will share best practices for Flexo Wash technology and common flexo challenges. I want to answer your real world questions, so be sure to send them to me at: firstname.lastname@example.org and we will feature them in an upcoming column. As your partner, I look forward to handling all your issues as soon as possible and offer lessons learned.
Question: Why is High Pressure Rinse and Air Dry not working?
Have you ever been in the situation where the high pressure rinse and air dry passes are not working on your anilox unit? We have run into this situation a number of times over the years. Let’s take a look on what might be causing the issue.
First of all, it is important to remember that the HP rinse and Air Dry do not actually come on until the drain cycle is complete . An anilox cleaning unit functions in the following order: wash, drain, HP rinse and then air dry. So, when you hit start, the unit goes into the wash cycle and the high pressure pump is not supposed to come on.
If your HP rinse does not come on after the drain cycle, the number one culprit is that the return proximity sensor is stuck on. This sensor is sending a signal to the circuit board, microcontroller or PLC when it should not be.
Here’s what’s going on:
When the spray head is in the home position, the home proximity sensor is illuminated. This tells the programming that “I’m at home, so I can start the high pressure rinse after the drain cycle.” If the return proximity sensor is also on, that tells the programming “I’m at the end and I need to go back to home”.
What we have here is two sensor inputs at the same time. This causes the programming to shut down and then there is no HP rinse or air dry passes. The cycle shuts off and then the unit is ready to start again.
One quick way to check this is to look at the return proximity sensor when the spray head is at home. If it is illuminated, then it is on and sending a false signal. However, it is important to note that the return proximity sensor does not have to be illuminated to be sending that false signal. The light on the sensor may be burned out or there may be a hole in the sensor cord which is causing that signal to jump across wires and go to the programming.
If the return sensor is not illuminated, you can check the input screen on narrow web circuit board units and wide web units. On narrow web circuit board units, the return sensor will say “on”. With wide web units, the circle on the screen will be green. On older narrow web units with a microcontroller, you will see an input on #7 when the lid is closed. On older wide web units, you will have to check the wiring diagram to see what input the return sensor is on and then look at the module to see if that particular input is lit up (unfortunately, the inputs vary from year to year). We recommend that the sensor and the sensor cable be replaced at the same time.
If your return sensor is good and the unit is going into the rinse cycle but the spray arm isn’t moving or you don’t see any rinse water, then something else is wrong — possibly a bad traverse motor, traverse coupling, broken timing belt/pulley, dropped output, water inlet solenoid valve, etc. that might be causing the problem.
Give us a call at the shop and we can help you troubleshoot the problem.
As always, if you need immediate assistance, call us at Toll Free: 888-493-5396 | F: 888-543-5396
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