Why is the minimum colour run 300 pieces for a custom color plastic case?

Answer: It comes from the pack: a 25 kg bag at 2% colours 1.25 tonnes, about 300 shells at 1.8 kg, plus 40 minutes of purging.

Is a Pantone code enough to start production?

Answer: No. The code sets the target only; the recipe is re-tuned for resin, opacity and texture.

Is Delta E 1.5 an industry standard?

Answer: A common acceptance limit, not a mandatory one. Write 0.8 in-batch and 1.5 between into the contract and it binds.

Can one batch vary inside itself?

Answer: Yes. Cavity spread, dosing fluctuation and residence time all create in-batch drift, which is why that limit is tighter.

How long should retained samples be kept?

Answer: 24 months, re-read every 12, stored dark. A dispute is settled by the sample, not by memory.

Does outdoor use need a weather-grade upgrade?

Answer: Usually. Without UV additive, 1000 hours of xenon arc pushes Delta E past 3; 0.5% HALS brings it under 2.

Custom color plastic case: why one colour code varies by batch

Quick answer: A shade that shifts between batches is rarely a wrong code. It is masterbatch dosing, melt and mould temperature never locked. A custom color plastic case needs the code translated into a dosing ratio, a Delta E limit and a retained sample.

Custom color plastic case: where the colour drift enters
From masterbatch ratio to Pantone 4195C
Delta E 1.5 is measured, not judged by eye
Sealed samples, retained samples and batch control
1000 hours outdoors: UV colour fastness
FAQ

1. Custom color plastic case: where the colour drift enters

A customer once put three months of dark grey shells on a table and pointed at the middle batch: it read faintly red. All three ran the same Pantone 4195C from one supplier. Colour is the only property of a custom color plastic case guaranteed by a recipe, not a dimension.

Drift is never one thing: base tint, dispersion, drying, residence time and mould temperature each move a little.

Stage	Symptom	Control point
Masterbatch dosing	banding within a batch	loss-in-weight, ±0.05%, every 30 min
Resin base tint	half-step shift on resupply	200 g sample, plaqued first
Drying	milky haze on pale parts	80 °C, 2 hours, dew point −20 °C
Melt and residence	local yellowing on dark parts	225–235 °C, under 4 minutes
Mould temperature	cavities differing in shade	60 ±3 °C, spread under 2 °C

Dosing is hardest to hold: a 0.1 point slip at 2% hides in black and streaks in ivory.

2. From masterbatch ratio to Pantone 4195C

A custom color plastic case code cannot be tabled into a recipe; resin, opacity and texture sit in between. The same 4195C on gloss ABS and textured PP differs by 0.4 points.

Custom color plastic case: beige cases on a factory roller conveyor, the nearest standing on edge, cartons stacked behind and a light tube above

Colour class	Ratio	Minimum run	Proofing
Pale and ivory	0.8–1.2% plus 0.3% titanium dioxide	300 pcs	5 days
Mid grey and olive	1.5–2.2%	300 pcs	5 days
Dark grey and black	2.5–3.5%	300 pcs	6 days
Fluorescent and metallic	above 3.5% plus pearl	500 pcs	8 days

The 300-piece minimum falls out of the pack size: one 25 kg bag at 2% colours 1.25 tonnes, close to 300 shells at 1.8 kg. Below that the bag is bought whole; a colour change adds 40 minutes of purging and 8 kg of scrap.

Pale and dark fail in opposite ways: pale shades rely on titanium dioxide, and one extra point turns them dull; dark shades rely on concentration, and thin walls go translucent. On one shell, a 3 mm wall and a 4.5 mm wall read half a step apart.

3. Delta E 1.5 is measured, not judged by eye

Visual comparison only screens. Judging needs a spectrophotometer at D65, 10 degree observer, 45/0 geometry, three readings averaged.

Delta E splits into Delta L for light and dark, Delta a for red and green, Delta b for yellow and blue. Delta L is what the eye catches: on dark grey, 0.6 reads as a paler batch, while 0.6 in Delta b is blamed on lighting.

Set limits by position: under 0.8 within a batch, 0.8 to 1.5 between batches and against the sealed sample, above 1.5 a rework. Buy a custom color plastic case without those numbers and the argument goes to whoever speaks loudest.

4. Sealed samples, retained samples and batch control

When the first 300 pieces of a custom color plastic case come off the line, five are pulled as sealed samples: three stay at the plant, one goes to the customer, one enters the retention cabinet with the colour code, masterbatch lot and temperature ranges on the label.

Custom color plastic case: a grey case open on a van floor, black foam in the lid, empty grid foam below, blue crates stacked right

Retention is not paperwork. The cabinet stays dark at 23 ±5 °C, samples are re-read each 12 months, and any code in production beyond 24 months triggers a supplier check.

Batch control runs on three rules: buy the masterbatch for a whole order at once, re-plaque after any lot change, and hold the line when a five-piece trial reads above 1.5. The second bag can carry the same grade name one dispersion class lower; dark parts then cloud at Delta E 1.2, passing on the instrument and failing in the hand.

5. 1000 hours outdoors: UV colour fastness

Outdoor use adds a test unrelated to matching a code. Xenon arc exposure runs to four fixed conditions:

Irradiance 0.51 W/m² at 340 nm, black panel 65 °C
50% humidity, 18 minutes spray and 102 minutes dry per cycle
1000 hours accumulated, roughly two years of sun
Pass at grey scale 4 or better, Delta E no higher than 3

Olive and mid grey stay under 1.5 at 500 hours; by 1000, a compound without UV additive jumps past 3 and fades visibly. Adding 0.5% hindered amine light stabiliser with a weather-grade masterbatch pulls 1000-hour Delta E back under 2.

Conclusion

Colour is settled by paper, not by eye: a code turned into a dosing ratio and a minimum run, Delta E into 0.8 in-batch and 1.5 between, retained samples into 24 months of traceability. A custom color plastic case carrying all three argues about numbers, not perception; outdoors, add 1000 hours of UV.

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.