Quick answer: Case deliveries slip for four measurable reasons — mould changes, resin supply, bought-in hardware and slotting around insert orders or holidays — and each leaves a paper trail, so put the change note, the resin lot, the hardware arrival and the schedule window into the contract.
Table of contents
- Mould Changes Hit Every Cavity
- Resin: Grade Swaps and 5 to 10 Day Gaps
- Bought-In Hardware Eats a Fifth
- Slotting, Holidays and the Delay Clause
- FAQ
1. Mould Changes Hit Every Cavity
Most case deliveries slip on a tool change, not on capacity. Thickening one rib by 0.5 mm means 12 to 20 hours of EDM, 6 hours of polishing and a 4 hour trial; a single-cavity tool is back in 3 days, a four-cavity tool takes 5 to 7. Add a slide and the job stretches to 10 or 12 days.
| Change | Rework | Days lost |
|---|---|---|
| Rib thickened 0.5 mm | EDM, polish, trial | 3–5 |
| Latch pocket moved 2 mm | insert remade, re-aligned | 5–7 |
| Slide stroke changed | angle pin re-matched | 10–12 |
The cost lands on resin already issued: one trial run eats 15 kg of pellets, a four-cavity tool 60 kg per round, so three rounds is 180 kg and 12 hours of press time.
Then a first article: three parts measured in full, 4 hours at the bench. Skip it and a shifted latch pocket surfaces once moulding starts.
The paper trail is the change note and the trial report: the supplier returns cost and days within 24 hours, and anything over 5 days needs written approval first.
2. Resin: Grade Swaps and 5 to 10 Day Gaps
Resin is the second cause, and case deliveries rarely recover from a silent grade swap. Two homopolymer PP grades 2 g/10min apart in melt index differ by 0.3 percent in shrinkage, moving a 600 mm outline by 1.8 mm. A new grade needs two trial rounds, 5 to 10 days.
Drying counts too: above 0.1 percent moisture the surface shows silver streaks, so 3 tonnes of pellets sit 2 hours at 80 °C.
A homopolymer to copolymer swap is the harder one: 2 days of trial at the press and 8 kg of purge before a shell holds dimension.
A discontinued grade is announced 30 days ahead; miss it and the lot is re-sourced, 7 to 15 days to the warehouse and 5 more at the port.
Three habits cut the risk: hold 15 days of resin, require written approval for grade changes, keep 2 kg of each lot.
3. Bought-In Hardware Eats a Fifth
Latches, hinges, wheels and valves are bought in and run longer than moulding: a latch set takes 25 to 30 days, wheels 30 to 35, a valve 20 to 25, so they hold a fifth of the schedule and shells wait.
| Part | Lead time | Share of schedule | Stock to hold |
|---|---|---|---|
| Latch | 25–30 days | 12% | 2,000 sets |
| Wheel | 30–35 days | 5% | 800 sets |
| Pressure valve | 20–25 days | 3% | 1,500 pcs |
Assembly stalls on the same shortage: a shell takes 4 latches, 2 hinges and 2 wheels, so an incomplete kit stops the line.
The usual failure is a mismatch: black nylon latches arrive in natural and repainting adds 7 days; quiet PU wheels arrive as hard PP and go back. A wheel also carries a 500 set minimum, so a 400 unit trial waits for a stock order to fill the line.
Match orders to arrival lots, list hardware as critical, and warn in writing at 5 days late.
4. Slotting, Holidays and the Delay Clause
Insert orders are the hardest to prove. A 650 t press runs 26 days a month; a 3,000 unit rush order turns a 25 day promise into 35, since tool change and purge take 4 hours each.
Holidays can be costed: in the 15 days before Spring Festival attendance falls to 60 percent and output by 40 percent, and yield recovers from 95 to 98 percent over 3 days. Case deliveries crossing a holiday need 20 days of slack.
| Cause | Typical slip | Owner | Clause |
|---|---|---|---|
| Buyer's tool change | 3–12 days | buyer | clock restarts on signed note |
| Resin shortage | 5–10 days | supplier | grade change needs approval |
| Late hardware | 7–15 days | supplier | warning at 5 days late |
| Insert order, holiday | 5–20 days | negotiated | 15 day schedule lock |
Locking the slot is the only measure that holds case deliveries to a date: a 15 day window at order, no insert orders inside it. Small batches need it most, since 500 units carry no leverage.
Partial shipment is the remedy: split 3,000 units into 30, 40 and 30 percent, ship 900 in 20 days, top up weekly. Write damages at 0.3 percent a day capped at 5 percent, and after 7 days pass the air freight to the supplier, capped at 8 percent.
Conclusion
Case deliveries reduce to four figures: the rework days of a tool change, the replacement cycle of a resin grade, the arrival time of hardware, and the output loss around an insert order or a holiday. Agree those as milestones and a slip stops being an argument and becomes a calculation. To protect case deliveries, freeze the design before the slot is booked, hold safety stock against the supplier, and treat 7 days as the line where partial shipment gives way to claims.
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.
Related Reading
- Shipping case problems and fixes
- Reusable containers versus alternatives
- Scoring a case supplier
- Steps in custom case production
Related Products
- 8 Series — Gun Cases; Military Equipment Cases; Camera Equipment Cases; Drone Cases; Watch Cases; Knife Cases; First Aid Cases; Electronics Equipment Cases
- WL8-2812 PP Gun Case — model WL8-2812
- All protective cases and toolboxes: 7 series, 158 models