photo eye usage

I've attached a little model in which there's a short conveyor with a photo eye almost at the end. The conveyor can only contain 1 box.
1. If the conveyor is accumulating the photo-eye turns green based on the speed of the conveyor and the size of product when it leaves the conveyor
2. If the conveyor is NON accumulation the photo-eye nevery turns green anymore

Is this a bug or what is the intented behaviour?

Could you say that you can only use a photo eye at least one product length away from the end of the conveyor?

Martijn

Martijn,
I opened your model and I didn't find what I thought I would. I couldn't really understand what you wanted to happen and what wasn't happening. You mentioned a small conveyor with a photoeye at the end, I saw a default size conveyor with a photoeye at the beginning. You also said that the content of the conveyor could only be 1, I saw no attempt to regulate this however. Can they both only have 1 or just a specific conveyor? Is it not functioning properly for you or is the color of the photoeye just not what you are wanting?

Brenton,

Then you surprise me. I've opened my attachment to be sure, but it is definitely a default conveyor, followed by a conveyor of 1 unit with capacity 1 and then again a default size conveyor. This is just an example which I encountered in a model partly made by a customer. Indeed the changing of the photo-eye surprises me. It doesn't turn to green when it is uncovered when a new flowitem is already on the small conveyor (although the front is far from the photo-eye).

So to sum up what happens in order:

The first flowitem has left the small conveyor, but it's back still coveres the photo-eye on the previous conveyor.
The second flowitem can enter the small conveyor because the previous has left it.
The photo eye is uncovered. The back of the first flowitem has passed it. (It probably takes the speed of the small conveyor to determine when the photo eye is uncovered).
The second flowitem is not at the photo eye yet, but the photo eye stays yellow and turns red eventually.

Hope it's more clear now.

Martijn

Hi Martijn,

I tested your model and also get the same behaviour, the photo eye will not turn green.
I also tried different values on the position for the photo eye and found that if the position is 0.6 or bigger the problem occur. If the position is less then 0.6
the photo eye will turn green.

One more thing I found and that is the trigger UnCover is not fired when the position is >=0.6.

It looks like a bug, but I can be wrong.

Lars-Olof

I just post this message to get this post under the attention of Flexsim again. Is it a bug and is the assumption right?

Steven

Thanks for the bump Steven.

Yes, it is a bug, but it is a set of circumstances that never has to be used.

The assumption is not correct though. It is only in this specific set of circumstances that the photoeye doesn't work:
1) It is a non-accumulating conveyor
AND 2) It has a maximum content of 1 and is waiting for another flowitem to enter. (If you distance the flowitems in the given model so that only 1 is on that conveyor section at a time, it fixes the problem. Or if you set the maximum content to more than 1, it fixes the problem.)
AND 3) The photoeye is less than a product-length away from the end of the conveyor.

The assumption should be: if you have conveyors with a maximum content of 1, leave "Accumulating" checked (as it is by default).

**You can have photoeyes less than one product length away from the end of the conveyor just fine. The above exception is very rare and never necessary.**