Is a bigger case injection molding machine always more stable?

Answer: No. Tonnage follows projected area and cavity pressure. Quoting 200 tonnes above need stretches the cycle; a 530-tonne job on a 780-tonne press costs 0.7 yuan more a unit and buys nothing.

Who pays for the mould, and who owns it?

Answer: It follows the amortisation. Pay the 80,000 yuan outright with a clause that the tool travels with the order and the buyer owns it. Amortise per unit and the supplier holds it, so leaving costs a second tool.

Can a 3,000-unit MOQ drop to 500?

Answer: Yes, on other terms. Shared tooling, a 15-day queue position and natural colour together make 500 workable. Ask for price alone and the answer is a surcharge.

Which quote line grows once volume starts?

Answer: Secondary work. Trimming and printing are left out at trial, then billed at 0.8 yuan a piece, which is 6,400 yuan across 8,000 units.

IP 54 and a 96-Hour Run: Buying a Case Injection Molding Machine

Quick answer: Price gaps on moulded cases rarely come from resin grade. They come from the tonnage, mould ownership and changeover time behind a case injection molding machine. Put those three on the enquiry sheet and a 4.2 yuan spread narrows to 1.1 yuan.

Four quote lines the machine decides
Clamp force and mould ownership: the cost of quoting low
MOQ is arithmetic, not policy
The 25 days of lead time that will not compress
Audit and sample retention: three documents, two signatures
FAQ

1. Four quote lines the machine decides

Two plants quoted the same 420×320×180 mm case with a 3.0 mm wall, and the gap was 4.2 yuan a unit. Neither changed resin: one ran a 630-tonne press at a 52-second cycle, the other a 530-tonne press at 61 seconds.

Nine seconds a unit is 20 hours of press time a year at 8,000 units a month, enough for an urgent run of 2,000.

Quote line	Usual wording	What to pin down	Common trap
Resin	6.8 yuan a unit	Grade, regrind share, 1.9 kg shot	20% regrind billed as virgin
Press time	Folded into unit price	Tonnage, cavities, cycle seconds	Slow cycle recovered later
Mould	80,000 yuan up front	Who owns it, over how many units	Charge continues after payback
Secondary work	0.8 yuan a piece	Trimming, printing, assembly	Quoted late, added at volume

Resin moves least. Press time plus mould amortisation can reach 70% of the price, so a supplier handed only a drawing can cut tonnage, stretch the cycle and recover the margin downstream. Four numbers on one sheet make the ranking obvious and stop a quiet resin swap three months in.

2. Clamp force and mould ownership: the cost of quoting low

Clamp force follows projected area. A 420×320 mm face covers 0.134 m², and 40 MPa cavity pressure needs 5,360 kN, or 536 tonnes. A case injection molding machine quoted at 530 tonnes looks close enough; the missing 6 tonnes appear as a 0.25 mm flash ring opposite the gate.

Case Injection Molding Machine: a black hard case on a seamless white sweep, handle folded flat, vertical parting line and two feet

Flash is not cosmetic. Trimming climbs from 12 seconds to 26 seconds a unit, secondary work costs 0.6 yuan more, and the parting face work-hardens until it sinks.

Ownership slips past buyers more easily than tonnage. One clause lets the 80,000 yuan tool travel with the order; the other leaves it with the supplier, and leaving costs a second tool.

Tonnage	Projected area	Typical inside size	Time per unit	Sensible batch
250 t	0.06 m²	300×220×120 mm	28 s	from 500
530 t	0.13 m²	420×320×180 mm	52 s	from 3,000
780 t	0.20 m²	520×380×230 mm	74 s	from 5,000

Over-quoting costs too. A 780-tonne press on a 300 mm case turns a 38-second job into 54 seconds and adds 0.7 yuan. Fit beats headroom, and that argument belongs in the enquiry.

3. MOQ is arithmetic, not policy

A plant with 2 case injection molding machines spends 4 hours on a changeover and 200 shots flushing colour. Spread over an order, 3,000 units is the break point: below it, changeover eats 12% of scheduled time and the price climbs 18%.

Reaching 500 units is possible on other terms:

Shared tooling: one bolster, swappable inserts, two small cases to a changeover.
Queue position: accept a 15-day wait and take a gap in the schedule.
Colour: natural instead of white saves the 200-shot flush.

MOQ is amortised changeover under another name. Six presses quoting from 1,000 units is slack, not generosity; one press quoting from 300 folds changeover into a line the buyer cannot see.

4. The 25 days of lead time that will not compress

Of a 45-day lead time, 25 go to tooling: 12 for the bolster, 9 for cavity machining, 4 for polish and assembly. The other 20 split into 3 trial rounds at 6 days, 12 days of production, 2 days of packing.

Case Injection Molding Machine: a translucent white hard case, black hinge blocks at the handle roots, dark rear spine and pale square feet

Only overlaps compress. Staging material during the second trial round returns 3 days; running nights takes production from 12 days to 9 for 0.15 yuan a unit.

Stage	Days	Who waits	Room to move
Bolster and cavity	25	Tool room	8% fee, down to 19 days
Trials	6	Case injection molding machine	3 rounds to 2
Production	12	Press schedule	Night shift, down to 9 days

Payment terms move price more than lead time. Thirty percent down with 60-day terms carries about 1.8% financing cost; 100% up front buys another 2%.

5. Audit and sample retention: three documents, two signatures

An audit needs three documents: press specification sheet, material certificates, a full first-article report. The sheet should carry tonnage, screw diameter and 780 g maximum shot; "large machine" is not a specification.

Two signatures matter too. Seal the trial sample, sign off the first production part, keep 3 samples for 12 months.

A 96-hour run tests the stability of the case injection molding machine, not one part's accuracy. Wall thickness between part 1 and part 900 has to stay inside 0.08 mm; drift beyond that points at the screw or the temperature control.

Conclusion

Buying moulded cases means buying scheduling slack: the right tonnage, a mould whose ownership is written down, an MOQ that matches the presses on the floor, all of it decided by the case injection molding machine.

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.