BU 421 Unit 8 supply chain scheduling file example

Nine Days of Slack and a Port Hold Two Tiers Up: A Supply Chain Scheduling File for a Composite Cabinet Plant, From Maple and Hinge Suppliers to the Spray Booth Queue

Student Name

Business, Herzing University

BU 421: Operations Management

Instructor Name

April 22, 2026

Nine Days of Slack and a Port Hold Two Tiers Up: A Supply Chain Scheduling File for a Composite Cabinet Plant, From Maple and Hinge Suppliers to the Spray Booth Queue

Purpose of the File

This closing file joins three pieces of work on Tallgrass Cabinet Works, the Nebraska cabinet maker built as a composite for this course: a map of the supply chain behind one kitchen order, a scorecard for adding a second hinge distributor, and a sequencing decision at the spray booth, the plant's constrained work center. Each part answers a question the next one depends on. The map says how much time sits upstream of the booth, the scorecard says who should carry part of the hinge risk the map exposes, and the schedule says how the booth spends the slack the map leaves. A single disruption is then traced through all three, ending at the dates dealers were promised. All firms, suppliers, jobs and figures are invented for the case.

The Chain Behind One Kitchen Order

Two material paths feed every order. Maple for doors comes from a sawmill in northern Wisconsin, which cuts, kiln dries and grades the boards and ships them to a hardwood distributor in Des Moines, which trucks them to the Omaha dock. Concealed hinges come from an overseas hinge maker whose containers land at a Gulf Coast port and move by rail and truck to Prairie Hardware Supply, a regional distributor, which ships to Tallgrass on an eight-day lead time. Inside the plant, the door line, box assembly and packing come before freight to the dealer.

Lead times are listed below in working days, with the range seen in the 2025 composite records, and then summed along the maple path. Chopra and Meindl (2016) argue that the figure a customer promise rests on is the cumulative time along the longest path, not the time of any single link, and the sum shows why that matters here.

The full path takes 34 working days, yet Tallgrass promises delivery five weeks, or 25 working days, after an order is entered. The promise holds only because maple is bought to forecast and held in the lumber yard, so the customer's clock starts at the door line. From that point the internal path is one day of order entry and release plus 10, 3 and 2 days, a total of 16. The nine days between 16 and 25 are the plant's slack, and most of it is consumed in one place: the queue ahead of the finishing booth, where doors and face frames wait their turn for color. The sawmill link carries the widest range, but the lumber yard absorbs it. The hinge link has a narrow range and no yard of its own beyond the reorder point, which makes it the weaker link even though it looks steadier.

Choosing a Second Hinge Distributor

Because every cabinet ships with its doors hung, one distributor holding the only hinge supply is a single point of failure. Tallgrass will keep Prairie Hardware Supply and move about 20 percent of hinge volume to a second source. Two candidates quoted: a distributor in the Twin Cities and one in Kansas City. The criteria and weights below were fixed by the buyer, the plant manager and the controller before either quote was opened, following the long-standing finding that buyers rate delivery and quality above price when they state their priorities in advance (Dickson, 1966). Tallgrass rated both candidates on a five-point card, one line per criterion, and the incumbent is scored on the same card for comparison.

The Twin Cities distributor wins at 4.20 against 3.75 for Kansas City. The weighting decided it. Kansas City is cheaper and closer, and under a card that put 0.35 on price and 0.20 on delivery the two candidates would tie at 3.90. Tallgrass ranks delivery reliability as its main order winner, so a card that let price outweigh on-time performance would have contradicted its own strategy. The visibility criterion also earns its place: the Twin Cities firm reports the status of its inbound containers to customers each week, which is the information that would have warned Tallgrass of the disruption traced later in this file. The incumbent's low score on that criterion is a finding in itself.

Sequencing the Spray Booth

Six kitchen orders wait at the booth on a Monday morning. Processing times are booth hours, including the 25-minute purge for each change of finish, and due times are the hours by which each job must leave the booth to keep its packing date. The booth runs two shifts. Heizer et al. (2020) describe two standard priority rules for a single work center: shortest processing time (SPT), which minimizes average flow time, and earliest due date (EDD), which minimizes the maximum lateness. Both are applied below to the identical job set.

SPT runs J5, J2, J4, J6, J1, J3. Its completion times sum to 78 hours, an average flow time of 13.0 hours, and the average number of jobs in the system over the 28-hour span is 78 divided by 28, or 2.79. One job is late: J6, the Topeka order, leaves the booth two hours after its due time. EDD runs J2, J6, J4, J1, J5, J3. Its completion times sum to 89 hours, an average flow time of 14.83 hours and 3.18 jobs in the system, but no job is late and the latest finishes two hours early.

The measures answer different questions, so they are reported separately rather than combined. SPT is better on flow and inventory in process; EDD is better on the promise. For a plant whose first competitive priority is reliable delivery, EDD is the rule. One refinement was tested and rejected. Running the Lincoln white job straight after the Topeka white job would save one purge, about 0.4 hours, but it would push the Wichita job's finish to hour 17.6, 3.6 hours late. The saved purge is not worth a late order, so the EDD sequence stands as computed.

Tracing a Port Hold Through the Chain

The disruption starts two tiers above the plant. A container of hinges bound for Prairie Hardware Supply is held 12 working days at the port. Prairie's stock was meant to be refilled by that container, and it has 2,600 hinges on hand when Tallgrass places its regular order of 10,000 at the reorder point of 3,661. Prairie ships the 2,600 on the normal eighth day and the balance of 7,400 on day 17, three days after the delayed container reaches it.

At 416 hinges a working day, Tallgrass's 3,661 falls to 333, its safety stock, on day 8. The partial shipment lifts stock to 2,933, which lasts about 7.05 days, so the hinge bins empty early on day 15. Packing stops from then until the balance arrives on day 17, about two working days, or roughly 830 hinges and 415 cabinet boxes that cannot ship. Most orders have slack left when they reach packing, but in the 2025 composite records about one order in four reached packing with less than two days of slack, usually because it had waited longest at the booth. Of the roughly 21 kitchen orders that would have packed in those two days, about five would miss their promised delivery date. The booth schedule cannot recover them, since the booth sits upstream of the stoppage. The delay is also an example of what Lee et al. (1997) warned about: Prairie saw its own customer's orders but Tallgrass saw nothing of Prairie's inbound supply, so the warning came from an empty bin rather than from the port.

What Mitigation Would Cost

Tang (2006) groups supply risk measures into those that add buffers and those that add information or flexibility, and each has a price. Three options are costed here at the discounted hinge price of $3.05 and the 24 percent holding rate, a holding cost of $0.732 per hinge per year.

Raising safety stock to cover a full 12-day hold would add 4,992 hinges, costing about $3,654 a year to hold. Moving 20 percent of volume, 20,800 hinges, to the Twin Cities distributor at 20 cents more per hinge would cost about $4,160 a year, and it would split the risk rather than store against it. Air freight arranged after a hold is reported would cost roughly $6,500 each time it is used, and it only works if someone learns of the hold in time.

The recommendation combines the cheaper parts. Tallgrass should take the second source, which also brings weekly container visibility, and add 2,500 hinges of safety stock, about six days of use, for roughly $1,830 a year. The total of about $5,990 a year is less than the cost of five late kitchens in dealer goodwill at a firm whose main order winner is reliability, and it leaves air freight as a fallback rather than the plan. The file closes where it began: the nine days of slack belong to the booth, and the hinge link must not be allowed to spend them.

References

Chopra, S., & Meindl, P. (2016). Supply chain management: Strategy, planning, and operation (6th ed.). Pearson.

Dickson, G. W. (1966). An analysis of vendor selection systems and decisions. Journal of Purchasing, 2(1), 5-17. https://doi.org/10.1111/j.1745-493X.1966.tb00818.x

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

Lee, H. L., Padmanabhan, V., & Whang, S. (1997). Information distortion in a supply chain: The bullwhip effect. Management Science, 43(4), 546-558. https://doi.org/10.1287/mnsc.43.4.546

Tang, C. S. (2006). Perspectives in supply chain risk management. International Journal of Production Economics, 103(2), 451-488. https://doi.org/10.1016/j.ijpe.2005.12.006