Can Case Internal Divider cells simply round to 100 mm?

Yes, if the cavity divides evenly; four cells at 100 mm leave 6.7 mm walls that sink in moulding.

How thick should the blocks in a Case Internal Divider be?

15 mm under 1 kg, 25 mm at 2 to 3 kg, and 20 mm with panels once cells pass 3 kg.

Die cutting or hot pressing for a small batch?

Below 300 pieces, die cutting: an 1800 yuan tool is 18 yuan a part at 100 pieces and 3.6 at 500.

Why lay out cells from the centre outwards?

Error accumulates: centred layout pushes the maximum into the end clearance.

Using blocks and panels together, does cost go up?

One yuan up per part, often down per case, since EVA falls to 20 mm and saves 5 yuan.

What gets missed most often in a quote?

Tooling amortisation and scrap: 8 to 12 percent of unit cost at 500 pieces, 30 percent at 100.

11 Yuan More per Cell: Case Internal Divider Specs

Quick answer: Case Internal Divider specs are derived backwards from cell load. A 2.5 kg cell sets 96 mm cell width, which sets 20 mm EVA blocks, which sets slot width and the tolerance chain. Going from 20 to 25 mm blocks adds 11 yuan per part; one rework of 25 minutes at 32 yuan an hour costs far more.

Load First: Where Case Internal Divider Specs Start
Cell Width, Foam Thickness, Structure
Three Ways, Side by Side on Cost
Tolerances and Rework: When Cheap Turns Expensive
FAQ

1. Load First: Where Case Internal Divider Specs Start

Take a cavity of 420 by 320 by 150 mm holding 12 items of 1.8 to 2.5 kg, drop tested at 1.2 m on six faces. A Case Internal Divider cannot start with how many cells look right. Start with the longest item, 310 by 80 mm, one per cell along the 420 mm direction, then the load of 2.5 kg per cell.

The sequence is fixed: load sets cell width, width sets thickness, thickness sets slot width, shrinkage sets the tolerance chain.

Load per cell	Cell width	Block thickness	Support	Cost per part
Under 1 kg	110 mm	15 mm EVA	Bonded four sides	26 yuan
1 to 2 kg	100 mm	20 mm EVA	Three sides plus floor pad	31 yuan
2 to 3 kg	96 mm	25 mm EVA	Three sides, pad, top press	42 yuan
Above 3 kg	80 mm	25 mm EVA plus 5 mm PP	Fully enclosed	57 yuan

2. Cell Width, Foam Thickness, Structure

Four cells in 420 mm give 96 mm each, leaving 36 mm for three 5 mm walls and 10 mm at each end. Five cells drop to 76 mm, too narrow for an 80 mm item; three cells reach 130 mm, where a 2.5 kg load bulges the block by more than 2 mm.

Case Internal Divider: black hard-shell case on a white table, two yellow latches near the camera, arc handle recess, thin ribs on the lid

Block thickness follows cell width. EVA at 65 kg/m³ and Shore C 38, 20 mm thick over a 96 mm cell, sinks 1.2 mm under 2.5 kg and deflects 4 mm at the drop peak, still elastic. At 15 mm it sinks 2.6 mm and peaks at 7 mm, crushing cells shut. The gain of 25 mm appears after the drop: residual set falls from 1.8 to 0.6 mm.

Structure splits at 3 kg, where EVA only cushions and a 5 mm PP panel takes lateral location in blind slots, cut at panel thickness plus 0.6 mm. Split that way, EVA drops from 25 to 20 mm and the assembly gets 3 yuan cheaper.

Processing belongs in the spec: die cutting holds plus or minus 0.8 mm on the edge and 0.5 mm on squareness. Corners and reliefs need CNC routing at 0.3 mm, where a 6 mm cutter limits inside corners to R3. Hot pressed EVA trays run at 155 °C and 2 percent shrink, so tools are cut oversize.

3. Three Ways, Side by Side on Cost

Cost item	Die-cut EVA	Hot pressed tray	PP plus EVA
Material	31 yuan	42 yuan	26 yuan
Labour	9 yuan	6 yuan	11 yuan
Tooling amortisation	0 yuan	3.6 yuan	1.8 yuan
Cost per part	41 yuan	52 yuan	40 yuan

Amortisation assumes 500 pieces: 1800 yuan for the press tool, 900 for the injection tool. At 100 pieces those become 18 and 9 yuan, the pressed part jumps to 66 yuan, and die cutting wins.

Scrap is a rework figure: the 8 percent on PP panels is mostly slot whitening, and one scrapped panel drags a 25 minute rework.

4. Tolerances and Rework: When Cheap Turns Expensive

An unbalanced tolerance chain makes cheap expensive, on the line rather than on the quote.

Case Internal Divider: blue hard-shell case on a white table, two red latches at the front corners, recessed handle and ribbed lid

Across 420 mm, 0.5 percent shrinkage takes 2.1 mm out of the length. Three walls held to plus or minus 0.15 mm and cells to 0.3 mm put 1.2 mm of position error at the far cell, which will not seat against a side wall. Laying cells out from the centre is a tolerance requirement.

Position error past 1.2 mm adds 3 minutes of hunting per case.
Blocks off by more than 0.3 mm will not press flat in one cell.
Edges out of square by 0.5 mm open a seam and the adhesive lifts.
A tray cut without the 2 percent allowance eats the end clearance.
A slot at 0.3 instead of 0.6 mm needs a mallet and whitens.

The rework arithmetic: 8 minutes to open, 6 to strip, 9 to fit, 2 to recheck, so 25 minutes at 32 yuan an hour is 13 yuan, plus a 41 yuan scrapped part, plus 60 yuan per case in freight once shipped. Spending 11 yuan more per cell breaks even after one avoided rework.

Conclusion

Case Internal Divider specs are a chain that starts at load: weight per cell sets cell width, width sets block thickness, thickness sets slot width, and shrinkage sets the tolerance chain. Every link can be cheapened, and every saving returns doubled at rework, so the 11 yuan per cell normally pays for itself after one avoided rework.

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.

11 Yuan More per Cell: Case Internal Divider Specs

Table of contents

1. Load First: Where Case Internal Divider Specs Start

2. Cell Width, Foam Thickness, Structure

3. Three Ways, Side by Side on Cost

4. Tolerances and Rework: When Cheap Turns Expensive

Conclusion

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