Arena Simulation Software; randomly stop processing entities

[alexduque89]

Dear all,

My name is Alejandro, I am doing an MSc in Engineering Management. I am writing to you because currently I am writing my dissertation and I have to model and simulate the maintenance procedures in a factory, however there is a SMALL detail that I haven’t figured out how to model in Arena Simulation Software. I saw on the RAM Professionals Group that you might have some advanced insight on this software, thus I ask you to please help me with this, if you have the time to:

Let me explain:

In the factory they have 40 machines. All of these machines are of the same type of machines (same MTTF and MTTR) and the maintenance technicians perform both preventive (scheduled) and corrective (when something fails) maintenance for these machines. They aim to perform one preventive maintenance task per day; this means, ideally, they should be able to perform preventive maintenance for all of the machines within 40 days (1 machine per day). However, this is not the case, because, when any other machine fails, the maintenance technicians have to postpone (and abandon) the preventive maintenance task they are performing for one of the machines and go to see what happened to the machine that just failed.

Thus, as you can see, they usually postpone the preventive maintenance tasks because of random episodes (other machines failing). The company, then, wants me to determine how many technicians they should hire to have all the preventive and corrective maintenance tasks covered, since they have experienced an increase in the failure rates for their machines because they haven’t been able to perform enough preventive maintenance operations for them.

I have been trying to model this in Arena; however I haven’t managed to figure out how to model a STOP in the process. This is: in my model, the entities are of two types: either preventive maintenance or corrective maintenance. The creation of these two types of entities along time has been determined by having a look at data provided by the company. In a process block, I have located the technicians (there are 3 technicians available). Also, it was determined statistically the time it takes for a technician to process these two type of entities. Thus, both preventive and corrective maintenance tasks are created and go to be processed by the technicians.

The logic followed to model the above scenario is: imagine that there is one preventive maintenance task (the one scheduled for that day) being processed and, as well, two corrective maintenance being processed (this means, all the three technicians are busy). However, if another machine suddenly fails, the technician who is processing the preventive maintenance has to leave the machine (postponing the preventive maintenance task) and goes to see what caused the failure in the other machine that failed. Thus, as you can see, I would have to suddanly and radomnly STOP the processing of the preventive maintenance entity in the model, maybe dispose it and start the processing of the new entity (corrective maintenance). Is it possible to do this in ARENA? I am using basic and advanced process blocks only.

Thank you for your help and excuse me for the length of the message.
Waiting for your response,
Best regards,
Alejandro.

[Kelly_Bramble]

The Arena Simulation Software website does have a software usage forum and help center.. This is where I would go for your answers.