What happens if a Small Plastic Case is moulded with a 0.8 mm wall?

Answer: It belongs on a clear window or unloaded lid. A 0.8 mm PP side wall splays 1.2 mm with five empties stacked.

How much clamp force does a sixteen-cavity tool need?

Answer: A 60 by 40 mm box projects 24 cm2 per cavity, 384 cm2 for sixteen, about 134 t at 350 bar. A 380 t press is for runner balance.

How many cycles does a living hinge last?

Answer: A 0.35 mm PP membrane is designed for 20,000, whitening after 10,000. A pin hinge reaches 100,000.

What gasket gets a Small Plastic Case to IP54?

Answer: A 1.5 mm EPDM cord compressed 25 percent in a 1.2 mm groove. Water at a latch means interference is under 0.4 mm.

Small Plastic Case: Where IP54 and a 1.2 mm Wall Come From

Quick answer: A Small Plastic Case is an injection-moulded box within 165 by 120 by 45 mm that one hand can hold: body, lid, living hinge, one to four latches. Walls run 0.8 to 1.6 mm, cavities 2 to 16, and IP54 depends on gasket squeeze.

Size Band and the Palm-Hold Limit
Cavity Count, Tonnage and Cycle Time
Wall Thickness Bands and Sink Marks
Hinge Life and Latch Styles
Where Material Meets the Standards
FAQ

1. Size Band and the Palm-Hold Limit

A Small Plastic Case is bounded by grip, not volume. The band stops at 165 by 120 by 45 mm; above that it becomes a carrying case.

Inside drops one wall per side: a 130 by 90 mm body at 1.2 mm leaves 127.6 by 87.6 mm. Past 45 mm deep a finger cannot reach the bottom.

An adult palm spans about 180 mm, so a body over 120 mm cannot be pinched and must ride flat.

Outside (L x W x H)	Inside	Load ceiling	Cavities
60 x 40 x 18 mm	57.6 x 37.6 x 16 mm	0.4 kg	16
130 x 90 x 35 mm	127.6 x 87.6 x 33 mm	1.8 kg	4
165 x 120 x 45 mm	162.6 x 117.6 x 43 mm	2.6 kg	2

2. Cavity Count, Tonnage and Cycle Time

Tool cost climbs almost linearly with cavity count while the per-part share flattens after eight, because cycle time and tonnage step up together.

Small Plastic Case: white body open on a steel bench, black lid gasket, dark inserts and kraft envelopes inside, grey egg-crate foam, ribbed walls

Two cavities: 32,000 CNY tool, 90 t press, 18 s cycle.
Four cavities: 46,000 CNY tool, 180 t press, 20 s cycle, 9.2 CNY per part at 5,000.
Eight cavities: 78,000 CNY tool, 250 t press, 22 s cycle, pays above 20,000.

Clamp force is projected area times pressure: 117 cm2 per box, 468 cm2 for four cavities, 164 t at 350 bar, so a 180 t press leaves ten percent.

Cooling owns the cycle. A 1.2 mm wall cools in about 8 s at 22 C; with 3 s of open and close and 4 s of packing the cycle lands at 18 to 22 s. At 1.6 mm it stretches to 30 s.

3. Wall Thickness Bands and Sink Marks

Wall thickness in a Small Plastic Case is four numbers. Base and sides take 1.2 mm, the lid 1.0 mm, the hinge seat 1.6 mm before thinning into a 0.35 mm membrane, and a clear window 0.8 mm PS.

Wall	Where	Past the limit
0.8 mm	Clear window	Dents under a finger, edges whiten
1.0 mm	Lid	Side bows 0.6 mm under load
1.2 mm	Base and sides	Eight stacked empties splay outward
1.6 mm	Hinge seat, corners	Too stiff, impact goes to the lid

Past a 0.4 mm step, sink marks arrive: PP shrinks 1.5 to 2.0 percent and leaves a 0.1 mm hollow visible after painting. Rib roots run at 0.6 times the wall, corners take R0.5, and below R0.3 every drop cracks there.

4. Hinge Life and Latch Styles

The living hinge divides this class: one moulded part instead of two, with service life resting in a 0.35 mm membrane.

Small Plastic Case: white body half open on a galvanised rack shelf, ribs and corner pads outside, three front latches, two side handles

A 0.35 mm PP hinge survives 20,000 cycles and whitens after 10,000. Two-shot PP over TPE reaches 50,000 for about 40 percent more tool cost, a 0.8 mm stainless pin 100,000 for 0.15 CNY of labour. A kit opened 20 times a day lives on a living hinge; a rental pool opened 60 times needs a pin.

Latches open at 18 N single, 30 N double, 45 N for four, with 0.4 mm interference. Under 0.2 mm the lid works loose, over 0.6 mm it takes the heel of a hand.

PP turns brittle at minus 15 C and the tongue snaps flush, so winter circulation wants a 0.3 mm root radius or ABS.

5. Where Material Meets the Standards

Three standards apply.

IEC 60529: IP5X stops a 1 mm probe via a 1.5 mm EPDM gasket squeezed 25 percent; IPX4 is a 10 minute spray at 0.07 litres per minute.
MIL-STD-810H 516.8 Procedure IV: 26 drops, one per corner, edge and face, from 1.2 m, no crack or latch release.
UL 94: HB burns under 40 mm per minute horizontally; V-0 self-extinguishes within 10 s.
ISO 4892-3: 200 h of UV with a colour shift under 3.

On a Small Plastic Case, material decides which claim holds: PP at 0.90 density and 100 C deflection is the hinge default, PS passes 88 percent of light but holds only to 70 C, ABS doubles the impact strength.

Material	Deflection	Shrinkage	Role on the part
PP	100 C	1.5 to 2.0 %	Body, living hinge
PS	70 C	0.4 to 0.6 %	Clear window
ABS	88 C	0.4 to 0.7 %	Corners, latch tongue

Conclusion

The chain for a Small Plastic Case has four links: size fixes grip, wall thickness fixes stiffness, cavity count fixes cost, hinge and latch fix life. Settle 165 mm, 1.2 mm and 20,000 cycles before arguing about colour; what decides survival is the margin a Small Plastic Case keeps in drop and in opening.

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.