"Cushion arm" moves to soon, intermittently. Cause unknown and damaging product.


Thread Starter

Matt Helm

OK, so I work in a paper factory and I have an issue with a mechanical cushion arm, which is just an arm that moves is a downward direction whenever a roll of paper is being moved from one conveyor to another.

The arm "catches the paper" in such a way that it slows the roll down, then stops it, so the paper doesn't become damaged. All the rolls are large compared to what we use in offices etc. But the problem only appears with very large rolls. The problem will appear once or twice then it will function normally for a few weeks or even a month recently.

Problem: the cushion arm moves too soon which means the paper hits a bar and since it hasn't been slowed down at all, it keeps going and bounces up into some venting shafts which damages the product. When watching, it functions exactly as it is supposed to. The problem is extremely intermittent. It only appears to us with the large rolls, but I have a hunch that it is happening with smaller rolls, but they are not tall enough to hit the venting shaft, and/or do not gain enough momentum.

Hardware/Setup: Allen & Bradley logix controllers utilizing the 1756 I/O modules. Controlled by Logix 5000 Ladder Logic. The Cushion itself is controlled with pneumatics, which are triggered by a solenoid.

Process: The cushion arm is the second arm in this short process. First there is a "kicker" which pushes the roll from the 1st conveyor belt to the next. When the paper leaves the kicker, it will hit a floor switch which triggers a 3 second timer, when the timer is done, that triggers a 0.1 second timer. If the second timer done bit is high, and "roll at cushion" is high, then the arm drops.

Any ideas or help on a programming fix would be greatly appreciated. The problem I'm having is coming up with a solution that may prevent the arm from ever coming down early, but will not mess up the timing when it is NOT malfunctioning. How do you fix an issue that rarely shows up and when it does show up, its not under common circumstances.