Friday, May 11, 2012

Analyzing Human Resource Utilization

In the previous chapters, we have taken a detailed look at inventory related issues in our processes. The next big chunk of problems in any process is “Staff” or “Human Resources”. Go back to the call center example, what would happen if the number of people assigned to the call center is fixed and 2 people and does not change irrespective of the call volume? The wait time is going to increase and both customer & staff satisfaction is going to go down badly.

Thankfully, the good news here is that we have a number of Lean-type techniques at our disposal to analyze our resources and determine their optimum use. These include Ideal Manning Calculation, Workload Balance, and Standard Work Combinations. Lets take a look at them one by one.

Ideal Manning Calculation

Every process requiring humans has to be staffed with people who are capable of doing their respective jobs. But you never want to understaff or overstaff, so it pays to use a formula to determine your ideal manning levels. You determine your Ideal Manning Levels by dividing the sum of your manual cycle times (time required to perform a job) by your Takt Time (rate of customer demand).

Summing cycle times provides the total work content time, while Takt Time (customer demand rate) gives you the number of people required to produce to that demand rate. This is your Ideal Manning Level. The implication is that you can’t achieve or sustain your Ideal Manning Level without also addressing all causes of mura, or unevenness in Flow. A process must be approaching near zero downtime, zero rework, and zero defects to sustain ideal manning.

Workload Balance

Workload Balance is the distribution of total work cycle time, and the pacing of that work content to the customer demand rate. This process helps eliminate bottlenecks, unevenness in Flow (mura), and overburdening of people and machines (muri). Workload Balance is done through Cycle Time Bar Charts to identify imbalances in equipment, workers, and process times.
The chart on the left is without Workload Balance and the chart on the right is with Workload Balance.

You can see from the picture above that your goal is to engineer staffing levels to utilize people at their fullest capacity as close to Takt Time as you can.

Here’s how it works: you plot the manual cycle times for each operator (staff) on a bar chart against the upper limit of the Takt Time. In principle, you have cycle times at or below the Takt Time to assure you have the capacity to service the demand rate of the customer.

Let’s go back to our car manufacturing example. As vehicles move through an assembly line, workers have a fixed amount of time to complete their work at each step. Imagine the problems and amount of waste created if the windshield installation step takes 20 percent longer than the Takt Time. By the time you get to the sixth vehicle, you are one car behind schedule, and you are faced with a tough choice: stop the line, skip a car, or put the car in the parking lot with no windshield and work overtime to catch up every day.

Analyzing Standard Work Combinations

Standard Work Analysis breaks down process steps in small increments and compares performance to the Takt Time. By doing this you eliminate the overburdening of people (muri), and you identify worker variations that can be smoothed and made consistent. Such an analysis, an example shown following, helps you determine the best arrangement of work tasks for optimum performance.
Standard Work Analysis is useful for arranging work tasks and for keeping each worker’s responsibilities below the customer demand rate.

Prev: Kanban

Next: Analyzing Equipment Effectiveness

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