Can the cavity of a custom plastic case be enlarged after the mould is cut?

Answer: Only downwards. Inserts take 5 mm out; adding material means a new tool. Fit a real sample before the steel is cut.

What is the minimum order quantity?

Answer: 300 pieces for a colour change on a shared mould, 500 for a new tool, 200 sets with foam. Below that, tooling adds over 30% to unit price.

How much load will a 2.5 mm custom plastic case carry?

Answer: 30 kg static is comfortable, the base is checked at 120 kg stacked five high, drop height 1.5 m. Above 30 kg, move to 3.0 mm.

How is lead time scheduled?

Answer: Three days to first article, 12 days to pilot batch, 20 days to volume; a new tool adds 18 to 25 days.

Can a case pass a 1.8 m drop without bumpers?

Answer: Rarely by thickness alone. Moving from 2.5 mm to 3.0 mm reaches about 1.5 m; 1.8 m needs bumpers or a larger corner radius.

Custom Plastic Case Specifications: Size, Wall Thickness, Load

Quick answer: A custom plastic case is specified cavity first, wall and rib second, load and closure last: clearance around the largest item fixes the cavity, cavity plus wall plus rib fixes the envelope, filled weight fixes the thickness tier.

How Custom Plastic Case Specifications Begin With Cavity Size
Wall Thickness Tiers and Rib Spacing Decide Drop Height
Load Ratings: Static, Stacking and Drop
Latch Count, Hinges and Sealing Specifications
Sampling Parameters and Acceptance Checklist
FAQ

1. How Custom Plastic Case Specifications Begin With Cavity Size

Most forms ask for outside dimensions first, which is backwards. Cavity is the constraint, envelope the output: take the largest item, add 8 mm per side wall, 6 mm between items and 10 mm of headroom.

The shell then follows as cavity plus two walls plus rib height. A 460 × 360 × 185 mm cavity with a 2.5 mm wall and 6 mm rib lands near 500 × 400 × 220 mm, held to ±1.5 mm cavity, ±3 mm envelope and 0.8 mm base flatness.

Outside mm	Cavity mm	Volume L	Empty mass kg	Load kg
400×300×180	360×260×150	14	2.1	12
500×400×220	460×360×185	30	3.4	22
600×450×280	555×405×240	54	4.8	32
760×560×380	705×510×335	120	7.6	55

2. Wall Thickness Tiers and Rib Spacing Decide Drop Height

Wall thickness in a custom plastic case follows drop height and stack count, not feel: 1.8 to 2.0 mm suits loads under 15 kg, 2.5 mm is the general tier, 3.0 mm covers 30 kg and five-high stacking, and 4.0 mm only pays beyond a 700 mm span.

Custom plastic case: orange open case, foam cut for a handset, a round cap and five barrel parts, two front latches, orange handle

Ribs and wall are one parameter set: rib thickness 0.6 of the wall, spacing 90 to 150 mm, root radius R1.5, draft 1 degree. Tall ribs pull sink marks outward, wide spacing lets the panel bulge.

The press must agree: at 0.24 m² projected area, 2.5 mm to 3.0 mm lifts clamping force from 900 t to 1300 t, and forcing thickness on a smaller machine gives flash and short shots in one cycle.

3. Load Ratings: Static, Stacking and Drop

Static load is filled weight, where 32 kg on a 2.5 mm wall is routine; dynamic load is transit impact at twice static; stack load is what the bottom unit carries, so five high means four times that.

Stacking reads 5 layers, 72 hours at 23 °C, deflection under 3 mm, drifting to 4.5 mm at 45 °C. A custom plastic case is dropped from 1.8 m over six faces, three edges and one corner: bumpers come through uncracked, unbumpered walls whiten at 1.2 m.

4. Latch Count, Hinges and Sealing Specifications

Latch count for a custom plastic case is outside length divided by 300: two at 500 mm, three at 760 mm, opening force 120 to 180 N. Lighter catches release in transit, heavier ones get levered with a screwdriver.

Custom plastic case: orange flank close-up, crossed ribs in a grid, moulded handle across the middle, rounded corners, pale backdrop

Hinge pins in 304 stainless hold 96 hours of neutral salt spray, and EPDM gaskets at 55 Shore A compressed 30% need a groove 0.3 mm narrower than the cord. IP54 takes a 4 mm single lip, IP67 a 6 mm double lip plus over-centre feel.

5. Sampling Parameters and Acceptance Checklist

First articles run 50 pieces at 45 °C mould temperature, 230 °C melt, 45 MPa packing and 22 s cooling; one out-of-tolerance cavity, wall or latch force stops the pilot batch.

Item	Value	Method
Cavity dimensions	±1.5 mm	Caliper, three points
Wall thickness	±0.15 mm	Ultrasonic, five-point mean
Latch opening force	120–180 N	Push-pull gauge
Metal salt spray	96 h no red rust	Neutral salt spray
Stacking	5 layers, 72 h, ≤3 mm	Ambient load
Thermal cycling	−20 °C to 60 °C, 24 h	Climatic chamber

Datum choice matters: cavity from the inner base, envelope from the outer base, or ±1.5 mm becomes 3 mm.

Conclusion

Specification is not a size list but four groups holding each other in place: cavity, wall, load and closure. Fix the cavity and its tolerances first, choose thickness and rib spacing from filled weight, then let latch count and gasket geometry deliver the ingress rating. A custom plastic case is hard to specify not because it must be big, but because every size tier has to stay reproducible.

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.