DECISION-MAKING SYSTEMS IN PRODUCTION SCHEDULING
6. EXAMPLES
This section presents examples of representing production scheduling systems with swimlanes models.
6.1 CAD/PAD production scheduling
The Naval Surface Warfare Center, Indian Head Division (NSWC/IHD) serves the armed forces by developing, manufacturing, and supporting energetics products, including cartridge-actuated devices (CADs) and propellant-actuated devices (PADs) that are t3^ically found in aircrew escape systems and in other aircraft systems. The CAD/PAD assembly facility assembles devices using cartridges, primers, and other hardware that are made in other NSWC/IHD facilities and at contractors.
Workorders arrive from the acquisitions organization that is responsible for purchasing devices for the armed services. The branch manager logs the workorder. The production controller adds it to the long-range schedule.
The production engineer determines if the key hardware will be ready on time and informs the branch manager if the required delivery date is feasible.
The branch manager accepts the workorder and informs the acquisitions organization.
The production system operates with two schedules: a long-range schedule (discussed below) and a weekly schedule. The weekly schedule records the status of about 24 operations (for 13 workorders) that are currently in process or ready to start.
At the end of each week, the shop foreman tells the production controller how many hours were worked on which workorders. The production controller updates the weekly schedule (the one created at the beginning of the week) with this information and brings this interim schedule to the weekly meeting.
The primary communication mechanism in the production scheduling system is a weekly meeting (first thing Monday morning) of all the participants. The primary objective of the meeting is to create an accurate picture of which workorders are ready for production and which have priority so that the shop foreman can determine what the shop will do. The participants discuss the workorders scheduled for that week, the work performed the previous week, new workorders that are ready for production, and any other updates. For example, a workorder may be ready to be shipped to the X-ray facility, hardware may have been moved from storage to the production building, or a piece of necessary equipment may be unavailable. Based on information from a monthly meeting with the acquisitions organization, the branch manager identifies the workorders that have priority that week. After the meeting, the production controller updates the schedule accordingly, signs it, and distributes it to all personnel that day.
The shop foreman makes decisions about which operators will work on which activities, and when during the week tasks will be done. The shop foreman records the hours worked. When changes occur during the week (to
the status of equipment, hardware, or workorders), the production engineers, production controller, and shop foreman react appropriately without changing the weekly schedule. These events are discussed at the next weekly meeting, and the schedule is updated accordingly then.
The long-range schedule lists approximately 80 workorders and, for each one, the number of production labor hours scheduled in each of the next 12 months. Once a month the weekly meeting also discusses the long-range schedule. The group discusses each workorder on the long-range schedule and its status. The production controller updates the long-range schedule accordingly and distributes this to personnel in the branch and elsewhere.
Figures 4-3 and 4-4 illustrate the production scheduling process using swimlanes. Each horizontal bar corresponds to a particular person and shows the activities in which that person participates. The links between the activities show the flow of information. Figure 4-3 represents the activities that receive workorders and update the long-range schedule. Figure 4-4 represents the activities that update the weekly schedule.
Acquisition
Branch manager Production
controller Production Engineer
Shop foreman
Send workorder
I f*
rrt
u
Log workorder Add w/o to long-range sch.
Check w/o hardware J
r> workorder Accept
J Receive [ acceptance
1 Long-range schedule
^
Report w/o status I
Report shop status 1
[ ^
Discuss long-range
schedule
Update long-range sch.
Figure 4-3. Long-range production scheduling.
Acquisition manager
Branch manager Production
controller Production Engineer
Shop foreman
Monthly meeting
r — 1 J Supervise 1 production -W
Update weekly schedule
Report lOurs worked
Report w/o priorities
Report w/o status
Report shop status
Discuss weekly schedule
Finish and sign weekly schedule!
1 • production Schedule
Figure 4-4. Weekly scheduling of CAD/PAD production.
6.2 Conservatory assembly
Tanglewood Conservatories is a conservatory builder that designs, fabricates, and constructs custom conservatories (rooms with wood frames and glass panels typically used for dining, entertaining, or recreation). The firm completely constructs the conservatory at their facility and then (usually) disassembles the structure, ships the components to the site, and re- assembles the conservatory. Each conservatory project involves nearly 300 tasks and takes months to complete. The firm usually has four to six projects in process at one time.
The firm has many types of resources, including engineers, sales personnel, shop associates, woodworkers, a glass shop, and painters.
The firm has recently implemented a new scheduling system to give the owner better information about the status of each customer order and to create better schedules. The key personnel in the scheduling system are the owner and the administrative assistant. The foreman and the lead engineer also participate. The scheduling system uses standard office applications enhanced with customized data processing and scheduling macros (see Figure 4-5 for a representation of this system).
When a customer agrees to order a conservatory, the owner creates a new project using a template in his project management software. He then emails the new project file to the assistant, who saves it in the scheduling system folder on her computer.
The production scheduling routine occurs weekly. On Wednesday the assistant walks around the shops and talks to the foreman about the status of tasks that were supposed to be done that week. The assistant also talks to vendors who are supposed to deliver material that week and to the lead engineer about his tasks.
Based on this information, on Thursday the assistant updates the project files for each customer order, which specify the task information. The assistant also maintains a file that specifies the resources available (the
"resource pool"). Each one of the customer order files is linked to the resource pool file. The assistant runs resource leveling routines that resolve scheduling conflicts and produce a detailed production schedule. The schedule is exported from the project scheduling software and into an electronic spreadsheet that lists the tasks that need to be done. If a customer order is projected to be tardy, the assistant reviews the tasks on the critical path to locate the problems. The spreadsheet, which contains all of the unfinished tasks that have already begun and the tasks that need to start in the next two weeks, is the production schedule. For each task, it specifies when the task should begin and which resource group should perform it.
O w n e r
Admin, assistant
Shop foreman
Lead engineer Vendors
Create and 1 send new project J
Report task status
Report task status
Report order status
Save project Record status
Tourjob sites
Revise schedule
Discuss production
schedule (Friday)
Revise schedule Identify problems
f •" •• "s
Discuss production
schedule (Monday)
Figure 4-5. Swimlanes diagram for production scheduling at Tanglewood Conservatories.
On Friday morning the owner and the assistant meet to discuss this schedule. The owner brings additional information about new orders and other updates from his visits to job sites. If necessary, the assistant updates the project files and creates a new schedule later that day. If the schedule shows that a customer order will be tardy, the assistant reviews the tasks on the critical path to identify the problem.
On Monday morning, the owner, the assistant, the foreman, and the lead engineer meet to discuss the schedule and any issues that have not been considered. The foreman and the lead engineer then know what they and their staff need to do that week. The foreman has the freedom to make small adjustments and to expedite tasks when possible to work ahead and improve resource utilization. (Note that, because installation operations at the job sites are independent of the fabrication and assembly operations at the shop, they are managed locally by a supervisor at each site.)