BU 421 Unit 2 process flow documentation example

Twenty-Three Minutes of Work in Ten Working Days: Process Flow Documentation for One Shaker Door at a Composite Cabinet Plant, From Lumber Rack to Dispatch

Student Name

Business, Herzing University

BU 421: Operations Management

Instructor Name

January 28, 2026

Twenty-Three Minutes of Work in Ten Working Days: Process Flow Documentation for One Shaker Door at a Composite Cabinet Plant, From Lumber Rack to Dispatch

Boundary and Unit Followed

This document maps the flow of a single five-piece shaker door, 15 by 30 inches in maple with a painted finish, through the Omaha plant of Tallgrass Cabinet Works, the composite cabinet maker used throughout this course. The mapped process starts when rough maple lumber is received at the dock and placed in the lumber rack. It stops when the finished door has been hung on its cabinet box and the box is packed at dispatch. The door's center panel, cut from medium-density fiberboard, joins the flow at panel cutting. Everything upstream of the dock, such as the sawmill and the lumber distributor, and everything after dispatch, such as delivery to the dealer, is outside the boundary.

Times were gathered over two weeks in January 2026. Operation times are the average of 20 timed cycles per step, converted to minutes per door. Queue and storage times were estimated by tagging 30 doors with their start time and recording when each tag reached the next step. The plant runs two eight-hour shifts, so one working day is 960 minutes, and all elapsed times below are in working minutes. All figures belong to the composite case.

Symbol Key

The chart uses the five process chart symbols that go back to Gilbreth and Gilbreth (1921): a circle for an operation that changes the door, an arrow for transport, a square for inspection, a D shape for a delay while the door waits for the next step and a triangle for storage, where the door is held and controlled. In the table below the symbols are written as letters: O, T, I, D and S. Rework is shown as a loop from finish inspection back to scuff sanding, and the one decision point, pass or fail at finish inspection, appears where it occurs.

The Step Table

The table carries every step in order with its type, time, distance moved and the number of people involved. The chart drawn from it has the same 25 steps, so every figure on the chart can be checked here.

Which Steps Add Value

Each step was classified by asking whether a dealer would pay for it if it were itemized on the invoice. The eleven operations, from ripping through hanging and packing, change the door's shape, surface or condition and add value; together they take 22.7 minutes. The two inspections, 1.8 minutes, add no value to the door but protect the dealer from defects; they are necessary for now, and the waste work in a later unit asks whether the need for them can be reduced. The five transports, 14.0 minutes over 940 feet, add no value. The clamp cure, primer dry and topcoat cure, 345 minutes, are necessary because glue and coatings must harden, but a dealer would not pay extra for them, so they are classed as necessary waiting rather than value. The three other delays, 2,160 minutes, and the two storage steps, 7,680 minutes, add no value at all.

Rework adds to these figures. About 6 percent of doors fail finish inspection, mostly for dust in the topcoat or thin coverage on an edge, and loop back through scuff sanding, topcoat, cure and a second inspection, usually after waiting about a shift for booth time. Across all doors that loop adds an average of about 43 minutes per door, which is not included in the totals below.

The Two Totals

Elapsed time from rack to dispatch totals 10,223.5 working minutes, or about 10.6 working days. The value-added time within it is 22.7 minutes. The ratio, 22.7 divided by 10,223.5, is about 0.22 percent: for every minute the door is being worked on, it spends roughly 450 minutes waiting, moving or being held.

The totals were checked a second way. On the days of the study the plant held about 4,300 doors between the rip saw and packing and completed about 420 doors a day. Little (1961) proved that average time in a system equals the average number of items in it divided by the rate at which they leave, so 4,300 divided by 420 gives about 10.2 days, close to the 10.6 days built up from the step table. The small gap is consistent with the lumber rack, which was below its usual level during the study.

Rother and Shook (1999) recommend comparing value-added time with total lead time as the first measure of a flow, because it shows where improvement effort belongs. Here the answer is plain: two storage steps and the wait at the spray booth account for about 89 percent of the elapsed time, while the operations themselves could be made twice as fast without shortening the door's trip through the plant by even a working hour.

What the Map Points To

Three findings follow for the units ahead. The six-day lumber rack holds far more stock than the door line needs and is a question for the inventory policy work. The day and a half each door spends waiting at the spray booth confirms the booth as the plant's constraint, which the capacity worksheet will size. The two days each finished door waits for its box show that doors and boxes are scheduled separately, so a door can be finished long before the box it belongs on; matching the two schedules is a candidate for the waste reduction proposal. Heizer et al. (2020) note that process analysis is most valuable when it directs attention to delays, since those rarely appear on any cost report. Tallgrass Cabinet Works, its door line and its times are composites created for this course.

References

Gilbreth, F. B., & Gilbreth, L. M. (1921). Process charts: First steps in finding the one best way to do work. Transactions of the American Society of Mechanical Engineers, 43, 1029-1050. https://doi.org/10.1115/1.4058133

Heizer, J., Render, B., & Munson, C. (2020). Operations management: Sustainability and supply chain management (13th ed.). Pearson.

Little, J. D. C. (1961). A proof for the queuing formula: L = λW. Operations Research, 9(3), 383-387. https://doi.org/10.1287/opre.9.3.383

Rother, M., & Shook, J. (1999). Learning to see: Value stream mapping to add value and eliminate muda. Lean Enterprise Institute.