In Travel Case Production, does wall thickness follow the load or the cavity?

Answer: Load first. Load sets rib height and count, span sets the minimum wall, and reversing the order yields a wall that is too thin.

Does a 520 mm cavity always need a 2.2 mm wall?

Answer: That pairs with four 12 mm ribs. Six ribs at 15 mm allow 2.0 mm, but two extra slides cost more than the material saved.

How should rib spacing be laid out?

Answer: Divide the base at about 130 mm, which gives four ribs across 520 mm. Past 150 mm the panel between ribs bulges and splits first.

Is a 380 mm wheel track a maximum or a minimum?

Answer: A minimum. Narrower drops the tipping angle below 15°; wider puts the wheels outside the body line.

Is ±0.4 mm tight enough?

Answer: For a moulded cavity, yes. Tighter needs a sizing fixture at 6 yuan per unit, which only pays off with a precision liner.

How long from sample to volume, and what is the minimum order?

Answer: Tooling 18 days, trial 10 days, production 35 days, so about 63 days for the first batch. Minimum 500 units, colour changes add 3 days.

Four Steps from Load to Wall: Travel Case Production Specs

Quick answer: Specifications for Travel Case Production start from two inputs, a 32 kg load and a 0.9 m drop, not from an outline drawing. Those give a 2.2 mm wall across a 520 mm span; rib height, track and tube follow.

Step one reading wall thickness from load
Step two cavity size and wheel height
Step three handle latch and hinge loads
Step four tolerances validation and drawings
FAQ

1. Step one reading wall thickness from load

Two numbers start the derivation, not a shape. At 32 kg and a 0.9 m drop, an energy estimate puts peak load near 18 times the weight, which is about 1.4 kN at each of four corners. That figure sets rib height as much as wall thickness.

Thickness follows from span. Across 520 mm, polypropylene at 1.4 GPa deflects 1.8 mm with a 2.2 mm wall and four ribs 12 mm tall, inside a 2 mm allowance. At 1.8 mm the span reaches 3.2 mm; below 2.0 mm the melt will not cross a 520 mm flow.

Load case	Span	Wall	Ribs	Deflection
Static at 32 kg	520 mm	2.2 mm	4 at 12 mm	1.8 mm
Corner drop 0.9 m	520 mm	2.2 mm	4 at 12 mm	1.8 mm
Stacked 5 high	520 mm	2.2 mm	4 at 12 mm	2.6 mm

Running the chain backwards costs money: 2.5 mm everywhere adds 0.4 kg and 12% of material per unit.

2. Step two cavity size and wheel height

The cavity is set at 520×360×210 mm, the largest item plus 8 mm per side. Liner and zip tape eat into that margin, and a nominal-litre claim that will not accept the item is worthless.

Travel Case Production: a navy hard case on an airport baggage belt with a black strap, grey tote boxes behind and terminal windows

Wheel height comes from the centre of gravity. Loaded to 32 kg the centre sits about 145 mm off the base, and a 380 mm track holds the tipping angle at 21°. At 320 mm the same load tips at 15° and the case goes over on a narrow step.

Wheel diameter settles at 60 mm, a compromise between climbing and stability.

Dimension the cavity as a net size. Outside dimensions hide 4.4 mm of wall on two sides; a section view removes most of that argument.

3. Step three handle latch and hinge loads

The handle is sized from arm force. Someone pushing a case applies about 80 N sideways, so 22 mm tubes with 1.2 mm wall and 2 mm of clearance survive 5,000 extensions inside tolerance. At 0.9 mm the tube mouth ovalises first.

Latch holding force is set at 150 N, the line that keeps a lid shut when a loaded case rolls over, and the number most often cut to 100 N in Travel Case Production. Hinges take 4 mm stainless pins set 6 mm into each side.

Element	Design load	Specified	Verified by
Handle	80 N sideways	22 mm OD, 1.2 mm wall	Play after 5,000 cycles
Latch	150 N holding	4 mm hook depth	Pull test every unit
Hinge	12 N·m opening	4 mm pin, 6 mm embed	3,000 open-close cycles

Torque the locking screws to 5.5 N·m; past 7 N·m the moulded insert pulls out.

4. Step four tolerances validation and drawings

Tolerances belong to the mould, not to assembly, and this step is skipped most often. Cavity length and width carry ±0.4 mm, base flatness 0.6 mm, and the lid step stays under 0.5 mm; past that the gasket cannot compress and the leak test finds it first.

Travel Case Production: close view of a black case latch on grey, three vertical ribs on the catch, two stiffening ribs across the lid

Shrinkage goes on the drawing. Polypropylene runs at 1.6% with a 65℃ mould and 10 seconds of hold, and all three together decide the dimension across 520 mm. Shrinkage alone puts the first trial shot 0.8 mm out.

A 120-tonne press with three slides covers this cavity: minimum order 500 units at 168 yuan, 35 days lead time, tool ownership attached to the contract.

Conclusion

Specifications in Travel Case Production form a one-way chain: 32 kg and 0.9 m produce 1.4 kN at each corner, a 520 mm span produces a 2.2 mm wall with four ribs, and only then come a 380 mm track, a 22 mm tube and ±0.4 mm of tolerance. Every number is explained by the one before it.

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.

Four Steps from Load to Wall: Travel Case Production Specs

Table of contents

1. Step one reading wall thickness from load

2. Step two cavity size and wheel height

3. Step three handle latch and hinge loads

4. Step four tolerances validation and drawings

Conclusion

Related Reading

Related Products