Would like to "ramp up" equipment to full speed after breakdown or idle time

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Joseph B asked Jul 05 2017 at 2:23 PM Joseph B commented Sep 24 2019 at 10:07 PM

Would like to "ramp up" equipment to full speed after breakdown or idle time

I've created a small line simulation for a packaging (liquid bottle filling) line in order to figure out optimum buffer sizes between equipment. I'm trying to add a function for each piece of equipment which simulates ramping up their speed after a stoppage (due to a breakdown, or idle time because of lack of materials upstream or downstream stoppage). I'd like to add 5 seconds of setup time to simulate this ramp-up time for an equipment stop. starstruck.fsm

Software Version:

FlexSim 17.0.2

setuptime

starstruck.fsm (121.0 KiB)

Answer 1 · 2017-07-06T13:10:12Z

Sam Stubbs answered Jul 06 2017 at 1:10 PM Joseph B commented Sep 24 2019 at 10:07 PM

The idle time after a lack of materials will be simulated by the flow of items, you don't need to incorporate that into your MTBF table. I'm a bit confused by what you mean by "full speed," do you want to decrease the processing time for each station? And if so, how long are the processors at "full speed" after a break down before they go back to "normal speed?" And your 5 second set up time, I assume you want this as a single time setup, just to get the processors at "full speed?"

I think your best bet is to see if you can control the logic of your model using a process flow, I think this might give you a little more direct control over the model. Incidentally, we actually have a bottling station that uses Process Flow to simulate break-downs and maintenance. Perhaps it can give you some ideas on how to approach this.

bottlestationexample.fsm

As a side note, I noticed that you had a few things in your MTBF tables that you should be aware of. First I noticed that the MTBF tables are duplicates of each other, instead of creating a table for each processor, you can just attach each processor to the same table, and have them utilize the same logic. Also I noticed that in your down and up functions you are using a percentage, but you aren't using a full 100 percent. In your up time you say that for 90 percent of the time you want the uptime to be 1, but how long do you want the other 10 percent of the time to be? Same with the down time. I think you are confusing the two, and you are saying that you want the up time to be 90 percent of the time and down to be 10 percent of the time, but instead, these two values should be actual times or random distributions. (IE how long are the machines up for, and then how long are they down for when the break down.)

bottlestationexample.fsm (50.0 KiB)

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Joseph B commented · Jul 06 2017 at 1:37 PM

Sam, thank you for taking the time to answer my question! This is my first time trying to use flex sim, I'm really just trying to learn what the heck I'm doing.

First, for my MTBF tables, I created separate tables for every machine center as I wanted to be able to input a different value for every machine. What I'm trying to depict is that the machine, when it is not idle do to upstream shortage or downstream blockage, will be running at X% efficiency (I think I n the model I sent, most equipment was set to 90%. I would like to depict a random distribution of breakdowns so that the machine shows that it is 90% efficient. I thought that my 90% uptime and 10% downtime would show that. Is that not correct? I'm not sure how do to what you are saying...

For my original question, I'll try to describe a little better what I was trying to do. Lets say that my filler runs at 400 bottles per minute when it is running "steady state". When it encounters a breakdown or has to stop due to an upstream lack of materials or downstream blockage, it goes to a rate of 0 bottles per minute. Upon each individual restart, there is a "ramp-up" period where it has to change its rate from 0 bottles/min back to 400 bottles per minute. I'd like to say that this "start-up" period is 5 seconds. I'd like to do this for every equipment center.

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Joerg Vogel Joseph B commented · Jun 30 2018 at 6:23 AM

@Joseph B, have you thought about to exchange the dimension which is responsible for the flow. You can substitute the speed and in this the amount per time by the spacing of the items on the conveyor. Of course there will be a small statistical error for the first two or three bottles.

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