Resource Availability

My employees have a primary activity but occasionally receive random interruptions that occupy their time. What is the best way to model this situation in SIMUL8?

This is a common situation. As a simple example, consider a receptionist whose primary duties are to answer phone calls and emails. Occasionally, the receptionist must also leave to fax a document or make copies. The best way to handle this depends upon how the employee should respond when an interruption occurs. Will the employee first complete the current task, then deal with the interruption or will the employee immediately drop the primary activity (even if in the middle of a task)?

The following SIMUL8 feature is very convenient method of randomly consuming a resource's time without needing to explicitly model the arrival and process times of the interruption.  If you are interested in the more detailed and complex method of modeling the interruption, please see Work Center Interruption.

The simplest approach is to use the availability feature of the resource in question.  Much the same as a work center's efficiency, availability randomly creates resource absences.  You can achieve this by either using the auto field by entering an availability % and  average absence time, or by using the detailed option.

The detailed option allows you to enter more accurate distribution parameters for time between absences and time to return.

Select Resource by Label

When SIMUL8's Select Resource by Label feature was introduced, I have to admit that I was initially skeptical about its potential for practical use. However, I recently came across a sticky situation where Select Resource by Label was indeed quite useful.

Here's how the feature works: You allow a work center to dynamically set its resource requirements by referencing a label on the work items bound for the work center. If the value of the label is 1, then the work center requires the first resource in the defined list of resources.  If the value of the label is 2 then the second resource would be required, and so on.

Because the Select Resource by Label feature does not support situations where multiple resources are required, such as a task that requires both a doctor and a nurse, I could not think of an immediate use for this new feature.

Last week, that changed. I had the pleasure of teaching SIMUL8 to a six sigma black belt from a major mortgage lending company. We found that the Select Resource by Label feature would nicely solve a staff allocation issue that would have previously required messy Visual Logic. 

In the situation that came up last week, a new mortgage application must be assigned to an individual mortgage 'specialist'. Once assigned, the 'file' belongs to the same specialist for the duration of the lenghtly application review process.  If we were to model the specialists as a single skill and set the number of resources available equal to the total number of specialists available, the total time in system would not be accurate as the 'pooling' would inaccurately portray capacity.  If Speciality A was not available, all of their files would sit and wait. Specialist B, C, D... would not be covering for them.

To solve this, we:

1. Created a specific resource for each specialist. 
2. Created one (replicated) work center for each manual task in the mortgage application process.
3. Assigned the 'file' to an individual Specialist via a label using a slighly complex 'circulate' assignment algorithm.
4. Used the Select Resource by Label feature to easily reflect which specialist was required by each file for each work center (task) in the process.

This approach offered a number of attractive advantages. It:

• Minimized the number of work centers in the simulation
• Minimized the amount of complex Visual Logic required
• Maintained a nice "Flow Chart" graphical layout of the simulation which enhanced the presentation value of the simulation
• Allowed for flexible and comprehensive staffing schedules
• Allowed for staff specific process times where warranted