Which milestone in case lead time slips most often?

Answer: Machine queueing and assembly inspection. Their thresholds are 1 day and 2 days, and neither sits fully inside the supplier workshop, so both need separate tracking.

Is a three-day buffer enough?

Answer: It depends on the thresholds. Six milestones allow 1 day and two allow 2, so a worst case consumes 10 days, far beyond the buffer, which is why thresholds trigger escalation rather than draw it.

Should the two-day variance warning go into the contract?

Answer: Better as a milestone agreement than a penalty: one daily report, escalation at two days, buffer shared by both sides, with terms per contract.

Can the 30% overtime gain be run permanently?

Answer: No. It is a ceiling for the 7-day moulding segment at two extra hours a day, and two weeks of it lifts defect rate and mould wear, moving cost from schedule to quality.

When is air freight at 8 CNY per kg worth paying?

Answer: When the gap is two days or less and a stopped line downstream costs more than 36.8 CNY per case. Past three days, rescheduling beats re-routing.

Case Lead Time: Eight Milestones

Quick answer: Case lead time is run milestone by milestone, eight checkpoints each carrying one deliverable, a variance threshold and a named owner.

Why Case Lead Time Starts With Eight Milestones
First Four: Confirmation to Moulding
Last Four: Secondary Work to Shipment
Where the Three-Day Buffer Sits
Five Delay Causes and What Each Costs to Recover
FAQ

1. Why Case Lead Time Starts With Eight Milestones

Thirty-two days is not one continuous run but eight segments joined end to end: confirmation 3 days, material arrival 5, queueing 3, moulding 7, secondary work 4, inspection 5, packing 3, shipment 2. Only seven of those days touch an injection machine; the other twenty-five are spent waiting on material, on a slot, on inspection capacity.

Each milestone carries something signable rather than a verbal assurance: a confirmed schedule, a goods receipt, a slot sheet, a first-shot sample, a handover sheet, an inspection report, a packing list, a bill of lading. Case lead time is really the question of whether those eight documents arrived when promised.

A milestone without a deliverable turns every delay into an argument about memory.

Milestone	Cycle	Deliverable	Threshold
Order confirmation	3 days	Signed schedule	1 day
Material arrival	5 days	Receipt, grade batch	2 days
Machine queue	3 days	Slot sheet	1 day
Moulding	7 days	First-shot sample	1 day
Secondary work	4 days	Handover sheet	1 day
Inspection	5 days	Report, release	2 days
Packing	3 days	Packing list	1 day
Shipment	2 days	Booking, bill of lading	1 day

2. First Four: Confirmation to Moulding

Order confirmation takes 3 days and ends with a signed schedule holding two dates: when material lands and when the machine is reserved. The threshold is 1 day, and a slip means asking whether material or a slot is missing.

Case Lead Time photo of a black closed case at forty-five degrees, two red latches shut, even lid seam, white backdrop

Material arrival takes 5 days, and the risk sits in grade and batch rather than quantity. A changed PP grade sends melt flow and shrinkage back for confirmation, so the threshold is 2 days and an alternative batch should already be moving by day three.

Queueing is the only segment that compresses on purpose, and the price is a machine change. Moulding runs 7 days at 600 cases a day, 4,200 cases in all; one day lost is 600 cases that come back through overtime or are borrowed from secondary work.

3. Last Four: Secondary Work to Shipment

Secondary work takes 4 days, with drilling, screen printing and labelling in series, so a rework at the first station holds the other three. The threshold is 1 day, because nothing here hides behind a machine.

Assembly and inspection take 5 days and follow ISO 2859-1 sampling. Inspection scheduling slips more often than inspection itself, so the threshold is 2 days, beyond which an extra shift goes on.

Packing and shipment are the two segments everyone underestimates. At 4.6 kg gross and 12 cases per pallet layer, one day lost in packing pushes the booking by a day. Shipment carries a 1-day threshold, and past 2 days the answer is usually a different port rather than a longer wait.

The last four run in series with no parallel slack, which is why one day late there becomes a day late on the order.

4. Where the Three-Day Buffer Sits

The 3-day buffer sits at the end of the critical chain and never gets distributed across the eight milestones. Spread out, eight small buffers leave nobody able to say how much remains; held at the end, any of the first seven segments can draw on it, and the escalation arrives with the arithmetic intact.

Case Lead Time image of a black case open upright, four round clip seats on the lid, empty shell, white background

Ownership is written into the milestone table: procurement controls 2 days, the supplier 1, and every draw is logged. Without a log the three days vanish inside a week.

A variance warning at 2 days is an escalation line, not a delay line. Once a milestone falls two days behind, the routine is fixed: one daily report, a buffer check by procurement and planning, a recovery plan from the supplier by evening. The call happens the same day, and the report records days lost, buffer consumed and signatures.

Achievement is measured at 95% or better on milestones rather than orders. Two hundred orders at eight milestones is 1,600 milestones, so 95% allows 80 breaches, and every breach needs a cause attached.

5. Five Delay Causes and What Each Costs to Recover

Delay causes fall into five groups, and attributing a delay to the wrong group produces the wrong recovery. Bad material batches, mould failure, a machine pulled for another order, secondary rework, and documents or booking cover nearly every case, with recovery costs running from nothing to 8 CNY per kg. Attribution is recorded per order rather than per supplier, because a pulled machine and a rework are different costs.

Overtime adds 30% output and is the one universal lever: two extra hours a day across the 7-day moulding segment returns 1,260 cases, paid for in overtime and a higher defect rate, so it suits gaps of 3 days or less.

Air freight costs 8 CNY per kg more than sea. At 4.6 kg per case that is 36.8 CNY, or 36,800 CNY across 1,000 cases, which makes it a tool for gaps of 2 days and nothing longer; past 3 days, rescheduling beats re-routing.

Cause	Frequency	Recovery	Cost
Bad batch	12%	Swap batch	0.4 CNY per case, 2 days
Mould failure	8%	Repair, backup machine	2 machine days
Machine pulled	20%	Change machine, overtime	900 CNY per day
Secondary rework	15%	Add a shift	1.5x hours
Documents	10%	Change port or fly	8 CNY per kg

Conclusion

Case lead time is a variance problem, not a calendar. Thirty-two days split into eight milestones, each with one deliverable, one threshold and one owner, puts the buffer where it can be counted: three days at the end of the critical chain, escalation at two, achievement measured on milestones. Recovery has a price list, 30% overtime or 8 CNY per kg by air, both finite tools.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.