Making Standard Work Work
Without a stable, repeatable process that syncs with customer demand (takt) it is impossible to have Just in Time and variability will lead to variable quality. Standardized work is the foundation of stability. But there is often confusion about how to deal with variability. Can you really have standardize work practices if your work isn’t standard? The answer is Yes.
Zingerman’s mail order (ZMO) of Ann Arbor, Michigan sells traditionally made food products all over America. Their basic process is picking items for orders, inspection, assembly, pack and load the truck. They have huge numbers of items, many perishable, and extreme seasonality with over 60% of sales between October and Christmas. Seems like a nightmare for standardized work, right? Not so.
Here are the issues ZMO faces and how they solve the problem of making the variable become standard:
1. Demand Variability. The starting point for standardized work is to load the work at each process as close as possible to the demand. But what if demand varies daily? ZMO solves this problem by defining standardized work for a number of different demand levels.The standard demand selected for that day is the one closest to that day’s actual demand. Daily staffing depends on the daily demand as well.
2. Cycle Time Variability: ZMO’s products are assembled like so: A Picker selects the items ordered from their respective locations, sends that collection in a bin to Inspectors, who pass the bins to an assemblers who assembles any gift packages before the final step where a Packers packs it in a box and loads boxes on a truck. The number of items, the amount of inspection time required and the size of the box needed can all vary.
This variation is managed by giving each job its own approach to standardized work. The picking, inspection, and final packing jobs are quite routine and can be leveled to suit daily demand within a reasonable range of variability. Assembly is the most complex. Standard gift boxes have standardized work on a computer screen showing the layout in the box and a countdown timer for how long the job should take. Non-standard gift boxes require judgment so only experienced team members work in assembly.
3. Leveling the Load (heijunka): Leveling at ZMO is done at the beginning of the process—picking of items. They use a kanban system to replenish the standard items located in flow racks close to the conveyor. Sets of racks are assigned to different zones and a computer system levels the orders across zones so different pickers pick a similar volume of orders. If picked bins are backed up to a visually labeled point on the conveyor pickers will stop and help inspection get caught up. Inspectors will help pickers if they are starved for product. Variability in assembly is handled by a buffer between assembly and packing. This is not perfect leveling, but the warehouse ships with high quality and reliably on time, even same day for orders before 5pm.
4. Improving on Standard Work: There are chiefs for each zone who are longer-term experienced workers and lead improvement activities. There is also a daily auditing system. Workers who do not follow the standard work can be retrained to follow the standard work or can explain their deviation. Often the deviation leads to improvements in standardized work. The auditing system greatly increased useful suggestions for improvement.
5. Training to the Standard work: One of the biggest problems faced by ZMO was the extreme seasonality and the need to hire large numbers of temporary workers in the peak Fall period. As the standardized work has been refined with a sequence of steps and keypoints on a computer screen by each job it is almost possible to self-train. The chiefs do the training using the job-instruction-training method that is a central part of lean. There are experienced people in all areas training and watching to help those who need it. The standard processes and training have also enabled a rigorous hiring process where recruits’ skills are judged by how they perform actual jobs based on the standardized work.
This all works because of the leadership and culture of ZMO. The owner who manages production, with an IT background, learned from a lean coach the value of managing from the gemba. Zingerman’s as a company has strong values for treating employees as team members and creating an open environment based on trust. Commitment to developing employees, creative thinking about applying lean tools, leading from the gemba, creating an atmosphere of trust, auditing and improving the standardized work are all preconditions to a stable process that gives the customer what they need when they need it.
Dr. Jeffrey Liker is professor of industrial and operations engineering at the University of Michigan and author of The Toyota Way. He leads Liker Lean Advisors, LLC and his latest book (with Gary Convis) is The Toyota Way to Lean Leadership.