How many rush orders can a plant take each month?

A: At the 12% ceiling, 1,680 units, or 3 insertions of 500. From the fourth, use an equal swap or price it into the quotation.

Can a colour change skip a full changeover?

A: On the same mould and grade, yes: purging still costs 25 min, but mould change falls from 2.5 h to 40 min and regrind from 180 kg to 45 kg.

What if the customer refuses a split delivery?

A: Then a split run is out, since it needs one signed sheet for two shipments. Fall back to an equal swap; the slip drops from 5 days to 2.

Should a rush fee be a separate line?

A: In the 500-unit case the 3,600 yuan spread exceeds a tenth of unit cost, and a separate line is easier to defend than a padded price.

Rush Order Scheduling

Q: Who carries the delay?

A: The contract governs. The usual practice is to record the displaced job's new date on the confirmation and have both sides sign.

Quick answer: A rush order buys days with changeovers, not with extra capacity: 2.5 h and 180 kg of regrind each time, so price the swap before you accept the date.

Price the swap before you promise a date
Three ways to make room
Four gates that keep impossible rush orders out
The arithmetic for 500 units
Holding the 12% ceiling
FAQ

1. Price the swap before you promise a date

Five hundred units on top of a 14,000-unit month is 3.6% more volume, harmless on a load chart. The real move is the mould position: one changeover costs 2.5 h and 180 kg of regrind, and the three methods need one, two and three.

Capacity inside a month is fixed, so any order admitted pushes another out. The question is whose job slides, by how many days, and who pays.

There is no zero-cost method, only a choice about which side absorbs the cost.

Planners ask if a press is free and stop there. Trimming, hardware and foam cutting sit behind moulding, so a saturated finishing line jams a fast insertion.

Insertion method	Changeovers	Original order slip	500-unit completion	Cost shape
No insertion (baseline)	0	0 days	Day 12	Ships on plan, no extra downtime
Tail loading	1	0 days	Day 9	Uses 2 spare shifts at the plan end
Equal swap	2	2 days	Day 6	Moves 1 live job, changeover each way
Split run	3	5 days	Day 4	Two presses, plus a reset changeover

Inside the 2.5 h, mould removal takes 40 min, purging 25 min, mounting and alignment 55 min, and first-article approval 30 min. The press runs but sells nothing for close to 2 h.

At a 25% regrind credit, 180 kg of runner becomes 135 kg of real loss.

2. Three ways to make room

Tail loading drops the 500 units into the next free window and leaves live jobs alone. The coming 72 h must hold 2 spare shifts, 16 h in total; if rework eats them, the insertion becomes a late order overnight.

Rush order queue at a wooden table with black cases awaiting check, an olive-green case and shrink-wrapped pallets behind

An equal swap is steadier. Lift one live job of 200 units or more, run the rush batch in the freed position, pay one changeover out and one back, and the displaced job slips 2 days. Its owner signs.

A split run is fastest and dearest. The 500 units break into 300 and 200, each press takes a 36 h window, and resetting the second machine adds a third changeover. The original slips 5 days.

The three differ less in machine time than in who carries the delay.

Pick by three facts: does the original customer accept a 2 to 5 day push, does the rush part share a mould with running work, and how many changeovers the month has left.

3. Four gates that keep impossible rush orders out

A gate gives refusal a basis. Written as numbers, four thresholds let a planner decide without instinct.

Gate	Threshold	Action when it fails
Mould shot balance	15% or more left	Another press, or tail loading only
Resin cover	3 days or more	Draw the same grade, else decline
Finishing load	85% or less	Split the batch or push one shift
Customer consent to split	1 signed sheet	Switch to an equal swap

The 15% shot balance measures distance to the next service. On a 25,000-shot interval, inserting below 3,750 shots left squeezes the maintenance window out, and the tool runs damaged to the next interval.

Three days of resin is the floor. Five hundred units at 2.3 kg each need 1,150 kg of pellets, 1,242 kg after an 8% setting loss; short of that grade, a rush purchase takes 2 days.

The 85% finishing load is a soft line. Cross it and the parts wait a full shift at the trim bench.

If any gate fails, change the method rather than the promise.

4. The arithmetic for 500 units

Two cavities at a 41 s cycle give 175 units an hour, 161 after an 8% setting allowance, so one press yields about 3,200 units in a 20 h day.

Rush order planning starts at the material silo: injection machines inside yellow frames, tan resin sacks stacked on a pallet nearby

Tail loading: 2.5 h of downtime strips 402 units of machine time, 180 kg of regrind is worth 1,656 yuan at 9.2 yuan a kilo, and expedited freight adds 2,400 yuan for two pallets. Near 4,100 yuan, day 9.

Equal swap: 5 h and 805 units of machine time, 360 kg of regrind at 3,312 yuan, plus one air freight differential at 2,800. About 6,100 yuan for day 6.

Split run: 7.5 h and 1,208 units of machine time, 540 kg of regrind at 4,968 yuan, and overtime of 16 h across 4 operators at 42 yuan an hour adding 2,688. About 7,700 yuan for day 4.

The 3,600 yuan spread buys 5 days. At 6,000 yuan a day of customer stoppage, the split run is cheap.

5. Holding the 12% ceiling

Rush volume stays under 12% of monthly output. On 14,000 units that is 1,680 units, or 3 insertions of 500; the fourth goes to a swap.

Insertions per month	Share of output	Cost booked	Recommended route
1	3.6%	About 4,100 yuan	Tail loading, keep the window
2	7.1%	About 8,200 yuan	Tail loading plus a swap
3	10.7%	About 12,300 yuan	Mixed, hold 1 window in reserve
4	14.3%	Past the ceiling	Defer, or add a press

Approval runs on 2 levels: planning clears the gates and the costing, production clears changeovers and the service point. Both answer within 4 h; silence is refusal.

Conclusion

Three methods, one bill: tail loading keeps the date for about 4,100 yuan, an equal swap moves it 2 days for 6,100, and a split run trades 5 days for 7,700. Write the shot balance, resin cover and finishing load into the gate, cap the month at 12%, and rush order scheduling becomes a sum with an answer.

This article covers case-side specifications only and does not address any handling, loading or use of the contents.