In many organizations, managers need to be aware of resources that perform more than one operation in a process or are shared across processes. For example, a receptionist in a doctor’s office not only greets patients but also collects payment and schedules future appointments.
Similarly, a product designer may design more than one type of merchandise in a given time period for different brands. Analyzing these situations requires special care because they affect process performance metrics.
Assignment of a resource to more than one operation
Assigning a resource to more than one operation in a process can be a smart way to help balance the line so that each person or machine has approximately the same work content. Work content is the total time a resource spends working on one flow unit, or one part that goes through the entire process.
This structure can increase resource utilization without creating an overproduction dilemma. But when assigning resources to multiple operations, you want to be sure to avoid resource conflicts.
When calculating a resource’s cycle time — the time a resource takes to process one flow unit — you must account for everything that each resource does in the process. Often, this includes multiple operations. Considering each resource’s total work time is important when identifying bottlenecks.
Consider a situation in which individual clerks perform multiple operations:
Clerk 1 performs OP1 and OP5; his cycle time is 18 minutes (6 + 12).
Clerk 2 performs OP2 and OP4; her cycle time is 15 minutes (10 + 5).
Clerks 3 and 4 both perform OP3, and each has a cycle time of 20 minutes.
Clerk 5 performs OP6 with a cycle time of 15 minutes.
If you analyze the process without noticing that operations share resources, you may conclude that the bottleneck is Clerk 5 performing OP6 with a cycle time of 15 minutes.
Or maybe you’d peg Clerks 3 and 4 at OP3 as the bottleneck; but they don’t represent the smallest capacity or the longest cycle time because the cycle time for the resources at OP3 is really 10 minutes — you have two resources in parallel. The actual bottleneck of the process is Clerk 1 because he performs both OP1 and OP5 and has the longest cycle time of 18 minutes.
When assigning resources, you need to verify that, given current demand, you aren’t creating any resource conflicts. Resource conflicts arise when a resource must do two or more operations on different flow units at the same time. For example, a receptionist at a doctor’s office can’t check in one patient at the same time he is scheduling a future appointment for another; this is a resource conflict.
A resource conflict would exist if Clerk 1 has to perform OP1 on a new customer at the same time he needs to perform OP5 on a different customer. Because of the potential for resource conflicts, sharing resources often increases the time a flow unit spends in the process.
Allocate resources to more than one process
A single resource may be assigned to perform one or more operations in more than one process. When this happens, analyzing the performance of a particular process becomes tricky. Here are some important questions to ask when you’re evaluating a process that uses a resource that also works on other processes:
Is the resource a bottleneck in any of the individual processes in which it performs? If the resource is the bottleneck in an individual process even if the resource was dedicated exclusively to that individual process, then you have a serious issue. The resource is limiting production in a process, so any additional activities it performs in other processes further limits the capacity of that first process.
How much total work content does the resource perform across all the processes? The resource may not be the bottleneck in any individual process but may actually be a bottleneck given its activities across all processes in which it performs. If this occurs, then the resource may make one process wait while it performs an activity in another process.
Do you need to adjust your material release policy? If a resource becomes a bottleneck because of its shared activities, then you may need to adjust the material release policy of all processes the resource works in to reflect the new bottleneck. Scheduling is critical when resources are shared among processes. You must schedule the processes in a way that doesn’t create resource conflicts.
