Operator always loads and waits

Hi all

I have a simple question that I cant figure it out.
In the attached flexsim file, you will see that a batch of 10 items goes into queue2, which will then be processed one by one in the processor, downstream. Processor's capacity is 1. My problem is that, when the operator takes an item from queue2 and unloads it to the processor, it will stay near the processor and waits there. This is NOT what I want.

What I want is:
1. Operator loads one item from queue2 --> travel to processor --> unloads the item to processor
2. While the processor is processing, the operator will go back to queue2 and loads one item again in queue2 --> travel to processor --> waiting for the processor.

I want the operator always prepares one item on his hand and wait for the processor.

Please guide me. Thank you!!

Best regards
Hendry

Hi hendry,

You can (for example) put trigger OnEntry in processor. So everytime one box entries the processor, it will send message to the operator. Then set the trigger OnMessage in operator and create some codes with tasksequence like codes below:

/**Custom Code*/
treenode current = ownerobject(c);
treenode queue_loading = centerobject(current,1); //reference for Queue2
treenode Processor = centerobject(current,2); //reference for Processor
treenode box = rank(queue_loading,1); //reference for box in queue
//create task sequence for operator
treenode ts = createemptytasksequence(current,1,0);
inserttask(ts,TASKTYPE_TRAVEL,queue_loading, NULL);
inserttask(ts,TASKTYPE_FRLOAD,box, queue_loading,1);
inserttask(ts,TASKTYPE_TRAVEL,Processor,NULL);
inserttask(ts,TASKTYPE_BREAK,NULL,NULL);
dispatchtasksequence(ts);

I hope it helps

Hi Rahel,

Firstly, thanks to your reply and help.

From the code that you have generated, I think there is still some issue, which I believe it is due to the reference of flowitem. I did as what you have suggested, and found out that, the so-called 'buffer box' (the flowitem which is in operator's hand), is not released to the processor. Any idea to solve this? Thank you again!

Best regards
Hendry

Hi hendry,

I think you are looking for at least 2 things.

1. you should set the Position of the item on the Processor. There some ways for it. One would be to just turn off the "Convey items across processors lenght", another one could be to use "setloc()" for this.

2. Write Tasksequences to the Operator to send him back and collect the next item.
You can send the Operator back to the Queue just by picking "Travel to a home Location" in his "OnRessourceAvailable Trigger". If it arrives you have to check if there is an item and if so then you can load it and travel back to the processor. The best way would be, to use some Networknodes. This way you can use the Triggers on it to check, if the Operator arrived at the Destinations.
This all will need some more logic to resist all deadlogs ;-)

For example you have to unload the item (I think the missing part on the solution of Rahel is the Unload Task) but only if Operator has reached the Processor, and really loaded an item, an Processor has finished the Process (is empty).

Hi Sebastian

Thank you for your suggestion, but I still think something is missing.

"check if there is an item and if so then you can load it and travel back to the processor."
It is true that if there is NO item in the queue, operator does not have to load it and travel back to the processor. However, if there IS item in the queue, operator has to load it and travel back to the processor, which is true also, but this does not mean the operator could unload the item to the processor until the processor has done processing.

If I were to use your method (correct me if I am wrong), the operator would only wait near to the queue while the processor is doing its job. Nothing on the operator's hand while he is waiting.

For me, I want the operator to collect an item in the queue and travel back to the processor. Hold the item on hand while waiting for the processor. Only when the processor is done, he will release the item to the processor.

Yes, I agree with you that the missing part on the Rahel solution is the unload task. But if I insert in another unload task to the operator, then, he will NOT wait for the processor regardless it is still processing.

Any ideas? Thank you so much!

Best regards
Hendry

I would take a look at a callsubtask. If it arrives at the processor it does a call subtask and in the code that you then call, check if the processor is busy. If it is busy you return a utilize task if not you simply return and let him continue with unload task. When the product leaves the processor you check if the operator is utilized and then you free him to continue with the unload task.

The callsubtask is specifically designed to handle these kind of situations where a taskexecuter arrives somewhere and only when he is there you know what to do.

Hi Steven

I thought of using call subtask before. However, I have never used that command before. Can you please guide me?

I have passed the secondary task sequence to the "Break To" in the TaskExecuter, e.g.
inserttask(ts, TASKTYPE_CALLSUBTASK,NULL,NULL);
right??

Then in the "Break To" of the task executer, I also write another new task sequence:

treenode Processor = centerobject(current,2);
if (getstatenum(centerobject(current, 2)) == STATE_IDLE){
treenode dispatcher = current; // the dispatcher or task executer
double priority = getvarnum(current,"transportpriority"); // read the Priority value on the GUI
int preempting = getvarnum(current,"preempttransport"); // read the Preemption mode on the GUI

treenode ts = createemptytasksequence(dispatcher,priority,preemp ting);
inserttask(ts,TASKTYPE_FRUNLOAD,item,Processor);
return tonum(ts);
} else {
treenode dispatcher = current; // the dispatcher or task executer
double priority = getvarnum(current,"transportpriority"); // read the Priority value on the GUI
int preempting = getvarnum(current,"preempttransport"); // read the Preemption mode on the GUI

treenode ts = createemptytasksequence(dispatcher,priority,preemp ting);
inserttask(ts,TASKTYPE_UTILIZE,item,Processor);
inserttask(ts,TASKTYPE_FRUNLOAD,item,Processor);
return tonum(ts);
}


What is wrong? and,
I do not know how to refer to the flowitem on the operator's hand. Please help! Thank you!!

Hendry

I have rewritten your code a bit for better understanding on my part
treenode Processor = centerobject(current,2);
treenode item = first( current );
treenode ts = NULL;
treenode dispatcher = current; // the dispatcher or task executer
double priority = getvarnum(current,"transportpriority"); // read the Priority value on the GUI
int preempting = getvarnum(current,"preempttransport"); // read the Preemption mode on the GUI

if( getstatenum( Processor ) == STATE_IDLE)
{
ts = createemptytasksequence(dispatcher,priority,preemp ting);
inserttask(ts,TASKTYPE_FRUNLOAD,item,Processor);
return tonum(ts);
}
else
{
ts = createemptytasksequence(dispatcher,priority,preemp ting);
inserttask(ts,TASKTYPE_UTILIZE,item,Processor);
inserttask(ts,TASKTYPE_FRUNLOAD,item,Processor);
return tonum(ts);
}

So the item can simply be referenced by using first( current) because when you call this function the item is in the operator.

If you have this build in and it doesn't work please post the model

Hi Steven

I am not sure what is wrong with my task sequence. Please check this for me. I will try to familiarize with the code after that. Thank you

Note: I have customized the task sequence in Queue3's "Use Transport", and also Operator's "Break To". That's all. Thank you very much!

Hendry

Your tasksequence was mostly fine. There was one small issue when you create the Utilize task it is easier to specify both reference parameters with NULL because then if you call freeoperators you don't have to specify a matching parameter.

The other problem you had was the capacity of the processor was 1, which means that the next tasksequence from the queue is not generated. That will only generate if the product can leave the object if there is capacity on the receiving object. So if you put the max content on the processor on 2, change your Utilize task to have to NULL parameters and write:
treenode operator = centerobject( current, 1 );
if( getstatenum(operator) == STATE_UTILIZE )
{
freeoperators( operator, NULL );
}

On the exit trigger of the processor you are done.

Btw are we now doing your homework?

Hi Steven

Haha. It works perfectly fine now, exactly like what I want it to be. Really many thanks to your explanation, time, and effort to help me.

Best regards
Hendry