Operator Selectable Priority

Hi all,
I have a bit of a mental block in regards to some programming i need to do....
The factory cuts large sheets via a saw into various size stacks of melamine boards that then get loaded onto one of three storage conveyors. The packs of board travel down the conveyors then are transferred by a trolley setup to one of 7 stations that then edge them / bore them ect. The issue i have is that they wish (via a scada) to change which of the seven stations gets priority over the others, when their type/shape board is present on the storage Conveyors.
How would i do this elegantly?? without lots of if x is greater than y then do z code??
any ideas would be much appreciated
Simon

Will the operator choose which one gets priority manually? (Easy!)

or

Will the machine automatically choose priority based on what is stored and what is on the conveyor? (Not as easy...)

The operator will select via the scada, which i'll then have to translate into the slc5/05 coding, the scada part is easy, they will just prioritise the stations 1 through 7, but how do you then translate this into ladder logic??

Your handling machine (A robot? I'll call it a robot for this example) will check for material present on the top priority spot. Say you assign the spots a number 1 through 7.

Make an integer file. ie. N7.

N7:0 = First Priority
N7:1 = Second Priority
N7:2 = Third Priority

You get the idea.

The robot comes to it's home position, and it starts going through the priority list. N7:0 has a 5 in it. It looks first at position 5, if there is material present, it will do it's service routine. If there is no material present, it will move on to the second priority.

Once it finds a filled spot and services the material, it moves back to it's home position and begins to check the list again. You can either have it start at the top of the list or move on to the next in line. It depends on your needs.

We use similar methods to have a single robot load and unload numerous machines. It keeps checking until one is finished, and it goes to that one. Then it goes back to the beginning and repeats.

doh! your right that is easy


Just shows you what happens when you haven't programmed for a few years(your brain goes to mush!!!)
Thanks a lot for the quick response Tharon it's much appreciated

Simon