Why does the price of an OEM plastic case change between enquiries?

Answer: Resin tracks the polymer market and moulding tracks press loading, moving a unit price by 8 percent.

Can tooling cost be folded into the unit price entirely?

Answer: Yes, but name the spread volume and the shortfall rule.

Is a 500-piece order realistic?

Answer: Yes. The 340 CNY colour change lands it 18 percent above the 3,000-piece tier.

Does the 45-day lead time include tooling?

Answer: No. New tooling adds 25 to 35 days, plus 8 for dies and screens run in series.

Can wall thickness change after the sample is signed?

Answer: It can, at the cost of a tool change: beyond 0.5 mm means a new core, 10 to 15 days.

OEM Plastic Case Procurement: Quotes, MOQ and Lead Time

Quick answer: An OEM plastic case quote has five blocks: resin, moulding time, tooling amortisation, secondary work and packing. Tooling ownership decides whether the last sits in the unit price, and that one clause holds total cost better than haggling.

What Makes Up the Quote for an OEM plastic case
Mould Ownership and How Amortisation Is Priced
Setting a Minimum Order Quantity That Works
Building the Lead Time From Its Segments
Sign-Off Gates and Payment Milestones
FAQ

1. What Makes Up the Quote for an OEM plastic case

An OEM plastic case quote is a sum of five blocks. Resin is shot weight times price: PP homopolymer at 9.6 CNY a kilogram, 2 percent masterbatch, 3 percent scrap, so a 1.35 kg shell carries 13.4 CNY. Moulding is 165 CNY an hour over a 62-second cycle, 2.84 CNY a part.

Quote block	Basis	Share	Document to check
Resin	Shot weight × price, 3% scrap	28–36%	Resin invoice
Moulding	Press rate ÷ shots per hour	18–24%	Cycle card
Tooling	Cost ÷ spread volume	0–12%	Ownership clause
Secondary work	Station hours × rate	8–15%	Route card
Packing	Carton, insert, pallet	4–7%	Packing spec

Secondary work is where quotes drift: print at 0.9 CNY a face, a foam insert at 380 CNY for an A3 die. Two suppliers quoting one mould came out 11 percent apart: 62 seconds trimmed to 55 removes 0.32 CNY.

2. Mould Ownership and How Amortisation Is Priced

Ownership decides whether amortisation appears at all. A buyer-owned tool stays out of the unit price; a fully amortised one adds 0.29 CNY a case across 30,000 pieces; a 60/40 split halves that for 18,000.

A single-cavity shell mould for a 600 × 400 × 220 mm case in P20 steel, 1.9 tonnes, quotes at 86,000 CNY, plus 42,000 for a two-cavity lid. Hardened S136 runs 800,000 shots at 35 percent more tooling cost, pulling amortisation from 0.29 to 0.18 CNY.

OEM plastic case: black case open on grey, foam cut-outs holding an audio mixer, microphone and speaker, square pad in the lid

Trial moulding is the dividing line: T1 yields 300 parts and a 12-dimension report at CPK ≥1.33, T2 re-runs 200. Two corrections free, then 120 CNY an hour.

3. Setting a Minimum Order Quantity That Works

MOQ is the largest of three limits: a colour change at 2 hours of purging and 8 kg of scrap; resin at 500 kg a grade; packing at 50 per carton.

Order size	What sets the floor	Production	Unit price
500 pcs	Colour change breaks even	12 days	+18%
1,000 pcs	Standard minimum batch	12 days	+6%
3,000 pcs	Tooling amortised	15 days	Base
10,000 pcs	Two-cavity mould viable	20 days	−9%

At 500 pieces the colour change carries 340 CNY, or 0.68 CNY a case. A permanent colour becomes a running colour and the charge goes from batch two.

Two colours from one mould at 3,000 pieces beat two orders of 1,500 by 7 percent. An OEM plastic case MOQ trades in purges.

4. Building the Lead Time From Its Segments

Lead time mixes serial and parallel steps. Drawing freeze to first shot takes 25 to 35 days, T1 three, sample approval five, production 12 to 20, booking seven. A repeat order ships in 45 days; new tooling lands at 60; foam dies and screens push it to 75.

Buffer per segment: five days on tooling, three above 650 tonnes, four on freight.

OEM plastic case: close view of a white corner, white foam with fine cells and several round cut-outs, seal groove along the rim

The foam die and the screen, five and three days, can be cut while the tool is machined. Inside the 30-day window they take an OEM plastic case order from 75 days to 63.

5. Sign-Off Gates and Payment Milestones

Write numbers, not adjectives: ΔE ≤1.5, a 0.3 mm gap, 60–90 N of latch force. Drop from 1.2 m onto six faces; no crack and no latch release is a pass.

Above 2 percent defects the supplier reworks or replaces, above 5 percent the buyer may reject the batch.

Gate	Deliverable	Pass value	Payment
Drawing freeze	2D drawing, 3D file	Tolerance sheet signed	30%
T1 trial	300 parts, dimension report	CPK ≥1.33 on 12 dimensions	30%
Signed sample	Colour chip, sample	ΔE ≤1.5, gap ≤0.3 mm	20%
Pre-shipment	AQL 1.0 record	Latch force 60–90 N	20%

Conclusion

The work on an OEM plastic case happens outside the quote sheet: splitting five blocks, fixing ownership in the contract, turning MOQ into colour changes, buffering each segment. What separates two bids is that ownership clause, not the OEM plastic case price.

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.