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How to select the right level of detail

Valued Contributor
Valued Contributor

I have thought to build a simulation model of a factory with several different types of processes. Processes that have different processtimes and process steps. between the processes there are bufferts of diffrent sizes. What I want to build is a general model of the factory that is moore in a "black box" type than a modell where every singel processstep och conveyor, elevetor etc is included in the modell. Soo far i have used parallelproc where i have set the X value to represent the number of products that process contains and the Y value is set to 1 becose the process is a singel flow process. The processtime i have set to be comparable with the time it take for one part to travel through the process. I whant to know if this approach is okej and if others have experience.

Br Joakim

6 REPLIES

Re: How to select the right level of detail

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello Joakim,

 

from my point of view, using the ParallelProc is a good idea for a rough simulation of the production line you are describing.

In the ParallelProc you can define the processing time for each part separately by defining the processing time before the part enters the ParalleProc. This can be done in an entrance control where you mark the check box 'Before action'.

On the other hand side, normally every processing station in your production line has a typically availability. This means, the parts have different throughput times. As mentioned above this can be achieved as described before by using a random processing time for the ParallelProc.

If you are more interested in the typically buffer size of your production line, you have to simulate each production step and the buffers in between each step.

 

I hope this answer will help you a little bit.

 

Regards

 

GG

Regards
GG

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Re: How to select the right level of detail

Valued Contributor
Valued Contributor
Hello

* If you set the processtime with a entrance control will units/product have the same order that they enter the parallelproc when they exit the proc? Independent of ther individual process time?

* One problem I have is that the technical stop time that have been logged is not on individual process equipment level but on the hole process department level. Soo when I model I try to put all technical stoptime/availability on the key process and the rest have 100% availability.



Jfinnberg

Re: How to select the right level of detail

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello Joakim,

 

when setting the processing time with an entrance control, this may disturb the sequence of the products, because there may be one product with a short processing time which overtakes a product with a long processing time.

 

So the sequence of products at the entrance may not be the same sequence at the exit.

 

Regards

 

GG

Regards
GG

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Re: How to select the right level of detail

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

Hi Joakim,

 

The XDim and YDim attributes do not specify the behavior of the ParallelProc, as you seem to assume. Basically, you control the exit sequence by means of the processing time (exit time = entry time + processing time). So, yes, MUs can take over each other inside a ParallelProc.

 

There may be an alternative, although you would need to split up your model a little more (digging one level deeper). For instance, if you have a sequential production line, you can model it as a buffer with a CycleTime (which represents the takt-time) and a Capacity (number of stations). You find these attributes on the Times tab and Attributes tab. On the Statistics tab you should change the Resource type to Production if you want the right kind of statistics.

 

Your dilemma is one that all of us face in every simulation project. Your choice for the level of detail should amongst others depend on the time and data that is available to you.

 

Regards,

Gert Nomden


Gert Nomden
Senior Consultant | Tecnomatix Product Manager
cardsplmsolutions.com

Re: How to select the right level of detail

Valued Contributor
Valued Contributor
Thanks!
Yes you are correct I assumed that the XDIM and YDIM affected behavior of ParallelProc.
So moving forward I shuld use bufferts and singelproc instead. Is the placebuffer to prefer over buffer when modeling sequential production line?

Br
Jfinnberg

Re: How to select the right level of detail

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

Maybe this is a behaviour that Siemens should consider to implement!

 

Anyway, yes, I think the PlaceBuffer is a better choice for a production line if you want the best statistics. Good question!


Gert Nomden
Senior Consultant | Tecnomatix Product Manager
cardsplmsolutions.com