Does 0.4 mm of rim clearance make a Stackable Container loose?

Answer: No. It is per side, so two cases have 0.8 mm between them; below 0.3 mm the lid needs a tool in deep cold.

Is a 3.5 mm wall stronger?

Answer: Slightly. Thirty days of three-high load takes deflection from 1.1 to 0.8 mm while the cycle goes from 78 to 105 s.

Why cross the lid ribs?

Answer: A one-way set leaves a flat band in the other direction. A grid takes the 500 N load from 2.4 mm to 1.3 mm at no height cost.

Can a latch double as a strap point?

Answer: No. A latch resists lift-off, and its 450 N is rated there; a strap pulls sideways and the gasket fails.

Are over-moulded feet always needed?

Answer: No. Plain PP pads suit indoor moves up to three tiers; forklift work is where a TPU foot earns its step.

Stackable Container: Five Structure Details That Hold a Stack

Quick answer: A Stackable Container stacks square only when five details are settled at drawing stage: rim groove and corner posts, wall and rib thickness, lid rib direction, latch and strap points, and base feet.

Where a Stackable Container Gets Its Alignment
Wall Thickness and Rib-to-Wall Ratio
Lid Load and Rib Direction
Latches, Straps and Load Paths
Base Contact and the Feet
FAQ

1. Where a Stackable Container Gets Its Alignment

The ring where lid meets body is the first alignment feature: it centres layer on layer and stiffens the joint. Eight millimetres tall with 0.4 mm clearance per side works; at 0.3 mm the lid seizes when ambient falls from 20 °C to minus 10 °C.

Second are four corner posts, 12 mm across and 5 mm tall, dropping into 90 degree cones 1 mm wider at the mouth, so only the last 2 mm tightens. Third is the corner taper, which sends horizontal load into the corner columns, not mid-wall.

Feature	Tooling demand	Key size
Rim groove	Common mould frame, 0.2 mm coaxiality	8 mm tall, 0.4 mm per side
Corner posts	Lifters, no weld line at the root	12 mm across, 5 mm tall
Base taper	Deeper insert, polished to Ra0.8	90 degrees, 4 mm tall

2. Wall Thickness and Rib-to-Wall Ratio

Thicker is not stronger. At 2.8 mm a Stackable Container keeps margin under a 1 m drop and a three-high stack; at 3.5 mm stiffness rises a tenth, weight a quarter, and the cycle stretches from 78 s to 105 s, since cooling scales with thickness squared.

Stackable Container: a closed grey case, four ribs along the lid, a round valve cap beside the end handle, a latch at the corner

Rib roots at 0.6 of wall, here 1.8 mm, split sink from short shot: at 0.7 the root sinks onto the stacking face, at 0.5 the rib fills halfway. Draft is 1 degree outside and 1.5 inside, because short draft whitens the wall.

From 2.8 mm to 3.2 mm the lid deflects 0.2 mm less after thirty days while the cycle rises twenty percent, so Stackable Container walls stop near 2.8 mm and stiffness comes from ribs.

3. Lid Load and Rib Direction

The lid is the only plate spanning two supports, set at the long ends, so deflection climbs with the cube of a near full-length span; ribs across the short direction cut it to a quarter.

Cross them, or the flat band parallel to the ribs bulges. Ribs 6 mm tall, 1.8 mm thick and 90 mm apart take a 500 N centre load from 4.2 mm to 1.3 mm.

Ribs must stop 3 mm short of the rim, or they deform the lip and an 8 mm groove behaves as 5 mm. A 12 mm dome is stiffer but costs 12 mm of stack height, 48 mm over four tiers.

4. Latches, Straps and Load Paths

A latch on a Stackable Container holds the lid on the rim: 450 N each, two opposite on the long sides, faces aligned within 0.3 mm on one mould frame.

Stackable Container: pale grey cases eight high on orange rack beams, two latches on each front face, pallets and a forklift beyond

It does not restrain layers. When a stack shifts the groove and posts take the load, and strapping across a latch tilts the seat until the gasket fails.

Strap channels 2 mm deep and 25 mm wide keep the band off the rim: at 350 N the wall deforms 0.8 mm with them, 2.1 mm without.

5. Base Contact and the Feet

The base of a Stackable Container does not sit flat. Shrinkage leaves corners down and centre up, so capacity read off the full footprint is overstated threefold, and a plate-tested tier count fails on a warehouse floor.

Base form	Contact share	Wear	Process cost
Four moulded PP pads	about 3.6%	grinds to dust	single shot
Four over-moulded TPU feet	about 3.6%	replaceable	second shot
Full ribbed base	about 72%	traps dust	deeper base
Bolt-on corner blocks	about 2.9%	replaceable singly	parts to stock

An 85A shore TPU foot, 34 mm across and 3 mm tall, compresses 1.5 mm when full; a plain PP pad is cheaper but grinds to dust by the fourth tier. A 2 mm reverse crown lands the centre only under load.

Conclusion

Feet gather load into the corners, corners pass it to the rim, groove and posts hand it upward, lid ribs spread the mid-span moment. Walk that path on paper and the Stackable Container stacks as drawn.

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.