Efficiency

Both Activities and Conveyors can simulate situations were equipment or people work with less then 100% efficiency.

Note that Efficiency relates to machine breakdown rates, not loss of product in process in the from of scrap. This should be dealt with using a Routing Out option in the Activity. Typically a percent rule is appropriate.

Click the Efficiency button in either the Conveyor or Activity dialog to specify the efficiency rate.

Simply set the efficiency value (in % terms).

If you wish you can also specify a typical time it takes to repair the stoppage. If you leave this field as a ? then Simul8 will automatically “repair” the Activity at a speed that appears compatible with the rate at that it is working.

With efficiency set to “AUTO” Simul8 calculates automatically mean-time-between-failure figures and uses negative exponential distributions for mean-time-between-failure and Erlang 2 distributions for repair time.

Allows you to set a distribution for the frequency of breakdowns. This can be based on:

• MTBF: Mean Time Between Failures. By default based on clock time this option stops a machine working at intervals based on the distributions used. The default in Simul8 is to breakdown an Activity based on the elapsed time since the end of repair for the previous breakdown. This means that machines can breakdown even if they have not been working. Only Count Busy Time restricts the time since the last breakdown to count only to machine running time.
• MCBF: Mean Cycles Between Failure. The number of machine cycles, or items processed, between the end of repair and the next breakdown.

Allows you to set a distribution for the time taken to repair the object after a breakdown occurs. You can also set a Resource be required to complete the repair.

To create a new Breakdown type, first click the More » button, then press the New button and type a name for the Breakdown. Next set the Time between Failure and Time to Repair for the breakdown.

Press New to create a second Breakdown type. This second Breakdown type allows a different Time Between Breakdowns and Time to Repair to be set.

The purpose of this structure is to allow different types of Breakdown to affect each machine. In the above example there is a Breakdown event used for scheduled repairs to the machine a different Breakdown event for random breakdowns.

It can also be used to Simul8 the reliability of a number of components within the machine, each with their own breakdown characteristics.

Sometimes a stoppage (or breakdown) occurs in such a way that the Activity concerned will finish work on the items that are currently waiting at the Activity.

At checkouts in a food store customers select the Queue to enter, but if the checkout operator's lunch break time comes up while customers are in the Queue, these people are still served before the operator leaves the till.

To simulate this situation switch off the “stop work immediately” check box in the breakdowns / efficiency dialog and switch on the “close feeding Queues” check box. This stops customers entering the Queue until the “breakdown” is over, but lets the Activity continue working on remaining items.

You cannot have both check boxes off at the same time (because then the breakdown would have no effect!).

A Queue will not be closed if it feeds more than one object in your simulation.

In cases where the length of the breakdown is typically short compared to the time it takes to finish processing the Queue, you may want to have the breakdown timed from the moment the last Work Item leaves the Activity (rather than the time the Queue was closed). To achieve this select “Extend Breakdown time by time to process Queue”.

Select the Work Items option to control the action on the current Work Item during a breakdown.

Visual Logic can be triggered at the start of Breakdown, at the start of Repair time and at the end of Repair time.

• Break Downs from Visual Logic
• Breakdown_Type
• Breakdown Using Break Type