WMBA 6040 Week 5 Lean Waste Analysis Example

Fifty-Eight Remakes a Day, 5,400 Trays in Waiting and 46 Days of Lens Blanks: A Waste Analysis of an Optical Lab, Each Category Pinned to a Mapped Step and Priced in Units the Lab Already Tracks

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Walden University

WMBA 6040: Improving Business Performance

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Month Day, Year

Fifty-Eight Remakes a Day, 5,400 Trays in Waiting and 46 Days of Lens Blanks: A Waste Analysis of an Optical Lab, Each Category Pinned to a Mapped Step and Priced in Units the Lab Already Tracks

Approach

This analysis applies the lean idea of waste to one operation, Clearwater, the lab whose coated-lens flow was mapped in Week 2. Womack and Jones (2003) built lean thinking on two moves: define value as the customer would, then strip out work that uses resources without adding to it. For a practice ordering glasses, value is a correct pair of lenses, mounted, delivered when promised. Every category of waste claimed below is pinned to a step on the Week 2 map, given a quantity from the lab's scans or records and priced in a unit the lab already tracks: minutes per job, remakes per day, dollars of stock or square feet.

The analysis does not claim every category. A category is included only if it can be measured at a specific step.

Waste by Category

Table 1

Wastes Pinned to Mapped Steps, With Quantities and Prices

Quantities come from tray scans, stockroom counts and a two-shift observation; prices use the lab's standard costs. All figures are composite.

The Wastes That Matter Most

Waiting is the largest waste by time. The coating queue and the edging wave it creates hold coated jobs for 3.8 business days, nearly half the total. Because the lab ships about 650 jobs a day, a delay of that length leaves roughly 5,400 trays somewhere in process. Waiting is not priced here in dollars, because its main cost falls on practices and patients, but the lab tracks it in days, and it draws more complaints from practices than any other issue.

Defects are the largest waste by cost. Each remake consumes new lens blanks, coating material and about 35 minutes of labor across surfacing, coating, edging and inspection, about $42 at standard cost. At 58 remakes a day, defects cost roughly $2,400 a day, or about $600,000 over a year of 250 working days. The Week 4 analysis found that coating defects, the largest category, are concentrated among lenses that waited longest for coating, so waiting and defects are partly the same problem.

Overproduction is the link between them. Surfacing, which runs two full shifts, finishes more coated lenses each day than the coating schedule can absorb, so the queue at coating grows through the week and is cleared on weekends with overtime. In lean terms, surfacing is producing ahead of what the next step can use. Working surfacing faster would make the lab's main problem worse.

The Smaller Wastes

Inventory is the largest waste by money tied up. The stockroom holds about 46 days of lens blanks against a target of 20, roughly $260,000 more than needed and about 900 square feet of space the lab has considered leasing elsewhere. Much of the excess comes from discounted bulk purchases that looked like savings when they were made.

Motion, transportation and overprocessing are smaller but easy to fix. Surfacing technicians walk to the stockroom for blanks about 140 times a shift, losing around 3.5 labor hours. Carts move from surfacing to coating only when full, adding about two hours of waiting to each tray. Paper tickets are reprinted at each department because trays lose them, costing about 20 seconds each time and contributing nothing a scan does not already provide.

What Lean Research Suggests About Fixing Them

Shah and Ward (2003), studying a large sample of manufacturing plants, found that plants using lean practices tended to perform better operationally, especially when the practices were adopted together rather than one at a time. That finding argues against attacking each waste separately. Holweg (2007), tracing the history of lean production, emphasized that its practices grew from a focus on flow through the whole system. For the lab, both points lead to the same priority: reduce the wait at coating, which would shrink waiting, defects and the overproduction feeding the queue at once.

What Would Be Mistaken

Two tempting moves would be mistakes. One is buying a second coating chamber before changing the schedule; the Week 2 map shows the chamber's capacity is adequate on average, and the problem is how runs are scheduled across three formulations. The other is cutting the stockroom quickly by halting blank orders, which could leave surfacing without the blanks it needs while the queue problem remains. Waste removal should follow the constraint, not the easiest number to cut.

Pricing Waiting Itself

Waiting was not priced in dollars above, but it has a cost the lab can estimate. Practices that receive late coated lenses sometimes cancel orders or send future coated work to competitors. The lab's sales team estimates that four practices reduced their orders last year after repeated delays, losing roughly $180,000 a year in revenue. The figure is uncertain and partly anecdotal, but it is the right order of magnitude to set beside the $600,000 annual cost of remakes. Together they show that the two largest wastes, waiting and defects, cost the lab far more than the small wastes that are easiest to fix, which is a further reason to start with the coating schedule.

References

Holweg, M. (2007). The genealogy of lean production. Journal of Operations Management, 25(2), 420-437. https://doi.org/10.1016/j.jom.2006.04.001

Shah, R., & Ward, P. T. (2003). Lean manufacturing: Context, practice bundles, and performance. Journal of Operations Management, 21(2), 129-149. https://doi.org/10.1016/S0272-6963(02)00108-0

Womack, J. P., & Jones, D. T. (2003). Lean thinking: Banish waste and create wealth in your corporation (Rev. ed.). Free Press.