What is the smallest quantity for a Small-Batch Custom Case order?

Answer: With a stock mould and a new insert, 100 units is usual and 50 is accepted, at 29 CNY of die per set; soft tooling reaches 20 units at over 150 CNY.

Does a hundred-unit colour change need 25 kg of masterbatch?

Answer: Suppliers sell by the bag: a hundred cases use 0.86 kg, and the other 24 kg can be held against repeats.

Can a soft tool hold the wall thickness?

Answer: Plan for ±0.5 mm, since a soft cavity flexes under pressure; at 0.3 mm, move to aluminium.

How much dearer is 100 units than 2,000?

Answer: 35% to 60% on one route. On inserts, 100 units cost 67.5 CNY against 54 CNY, the gap being the die and 4.5 fixed hours.

Which route wastes least if volume grows?

Answer: Start on inserts, then cut steel when volume arrives. Most insert dies transfer to a steel-tool body, and leftover masterbatch carries over.

Small-Batch Custom Cases: Three Routes at 100 Units

Quick answer: A Small-Batch Custom Case run of 100 units only works when the one-off spend moves to the cheapest stage, namely an insert die at 1,450 CNY, a colour change at 1,000 CNY, or soft tooling from 3,000 CNY.

Where a Small-Batch Custom Case Order Stalls at 100 Units
Route One: Stock Mould, New Insert
Route Two: Stock Mould, Custom Colour
Route Three: Soft and Aluminium Tooling
Choosing a Route and Sampling Plan
FAQ

1. Where a Small-Batch Custom Case Order Stalls at 100 Units

At 420 g per unit, a hundred bodies weigh 42 kg. A 250-tonne press runs one cavity at 55 seconds a cycle, which makes 1 hour 32 minutes of moulding. Only resin, masterbatch, foam and cartons shrink with volume. Mould change, heating, setting and first-article approval still take 4.5 hours. That is 9.5 CNY a unit at 100 pieces. At 2,000 it is 0.47 CNY.

Fixed cost has to happen somewhere cheaper: a steel tool at 110,000 CNY adds 1,100 CNY a case, while an insert, a colour or a short-life soft tool costs 1,000–5,000 CNY.

Route	One-off (CNY)	Unit before tooling	Unit at 100	Days
Insert only	1,450	53	67.5	7–10
Colour only	1,000	52	62	12–15
Soft tooling	3,000–5,000	56	86–106	18–22
Aluminium tool	12,000–18,000	56	176–236	20–28
Steel tool	110,000	49	1,149	35–45

The aluminium row gets misread: the tool is cheap, spreading it over a hundred pieces is not. its window is 500–3,000 units at 4–36 CNY.

2. Route One: Stock Mould, New Insert

Replacing only the insert is the fastest Small-Batch Custom Case route. The body comes from one of six stock sizes, so a die at 1,450 CNY and 3 days of cutting ships in 7 to 10 days.

Small-Batch Custom Case interior: an open white case on a steel bench, egg-crate foam trays holding wrapped parts, shelving behind

Across 100 sets the die adds 14.5 CNY each, more than the foam. The insert is 38-density EVA at 12 mm, about 9 CNY a set, so set 101 costs 9 CNY plus 4 CNY of labour.

Lid ribs stand 6 mm proud, so pockets need 8 mm of clearance or the foam takes a mark when the case shuts. Radii under R3 need CNC cutting, adding 12 minutes a set.

3. Route Two: Stock Mould, Custom Colour

Colour runs into pack size on any Small-Batch Custom Case order. Masterbatch sells in 25 kg bags and at 2% let-down covers 1.25 tonnes of resin, enough for 2,900 cases; a hundred units use 0.86 kg.

Purging a dark shade to a light one needs three passes of 6 minutes plus hopper and screw cleaning, burning 5–8 kg, or 12–19 cases at 420 g, billed into the first batch at about 2 CNY per unit.

Colour control sits at ΔE 1.0 with a 2.0 ceiling. At 40 CNY a kilo a bag costs 1,000 CNY, and suppliers load 30% into the first order, or 3–4 CNY a case; colour adds 5 days over inserts.

4. Route Three: Soft and Aluminium Tooling

When the outline must change, tooling is new. Silicone soft tools cost 3,000–5,000 CNY and last 50–200 shots, enough for 100–200 units, holding walls to ±0.5 mm.

Small-Batch Custom Case in storage: a closed white case with two butterfly latches and scuffed corners on galvanised racking

Aluminium 6061 takes 12–15 days to machine, costs 12,000–18,000 CNY and lasts 3,000–10,000 shots. It wears soft, so cavity edges round over; past 8,000 shots, watch the flash.

Steel at 110,000 CNY and 500,000 shots adds 1,100 CNY a case and only pays above 3,000 units a year. A Small-Batch Custom Case run under 300 units goes soft, 300 to 3,000 goes aluminium.

5. Choosing a Route and Sampling Plan

Under 500 units a year, fixed outline: insert only.
A fixed brand colour, repeats above 2,000: colour change.
Outline must change, under 300 units: soft tooling, ±0.5 mm.
Outline must change, 300 to 3,000: aluminium, flash checks after 8,000 shots.
Above 3,000 units: steel.
Samples only: 20 pieces off a soft tool, 150–250 CNY each.

For a lot of 100, level II at AQL 2.5 means 20 samples, accept 1, reject 2; latch retention and seal integrity sit at AQL 1.0, also 20 samples, accept zero.

Item	Standard	Samples	Accept / reject
Appearance, colour	AQL 2.5	20	1 / 2
Dimensions, wall	AQL 2.5	20	1 / 2
Latch retention	AQL 1.0	20	0 / 1
Air tightness	100%	100	0 / 1

Full inspection is dearer, not safer: 100 pieces at 2.5 minutes each is 7.5 person-hours, near 300 CNY, or 3 CNY a case against 1.2 CNY for air tests.

Conclusion

One-off spend divided by batch size is the whole arithmetic, and a Small-Batch Custom Case decision only changes the denominator: a 1,450 CNY die, a 1,000 CNY bag of masterbatch, or soft tooling from 3,000 CNY. Fund what can be reused at small volume; reach steel sooner at scale.

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.