How much clearance does a Custom Case with Foam Insert cavity need?

Answer: Two millimetres per side, covering moulding and cutting tolerance. More and the insert slides; less and it buckles.

Can the three foam layers be combined into one?

Answer: Yes, at the cost of flexibility. A combined block fixes slot depth, so a new product needs a new insert.

What kerf should the die drawing use?

Answer: 1.5 mm with R3 corners. Without it the slot cuts small and the part goes in tight.

Are two trial rounds necessary?

Answer: They are the cheap route. EVA corrects the outline, production foam proves compression; cutting steel first risks scrapping it.

Which document goes missing most often on a reorder?

Answer: The die drawing revision. Without it the factory cuts from whichever copy is nearest, and a small shift rejects the batch.

Custom Case with Foam Insert Specs: Cavity, Layers, Drawings

Quick answer: A Custom Case with Foam Insert is specified backwards: lock the smallest clear cavity dimension, split the foam into three layers by part height, then prove the layout on a 1:1 die drawing over two trial fits.

A Custom Case with Foam Insert Starts at the Cavity
Fit Clearance Between Insert and Cavity
Splitting the Foam into Three Layers
Die Drawings and Trial Fits
The Drawing Pack You Should Receive
FAQ

1. A Custom Case with Foam Insert Starts at the Cavity

Datasheets for a Custom Case with Foam Insert usually open with outer dimensions, the easiest order to write and the easiest to get wrong. The shell follows the mould; the cavity holds the equipment, and only once it is fixed can foam thickness be calculated.

Three figures belong there: mouth clearance, floor clearance and smallest clear dimension. Draft pulls three to four millimetres per side between mouth and floor on a 520 by 380 by 190 mm cavity, so long items jam halfway down. The lid recess needs its own figure, or the lid liner eats twenty-odd millimetres.

Cavity item	What to write	Why it matters
Clear size	L, W, D plus smallest clear dimension	Draft narrows the floor
Lid recess	Say if counted in total depth	Sets usable lid foam
Corner radius	Give the R value	Foam corners follow it

2. Fit Clearance Between Insert and Cavity

The gap between insert and cavity is often written as matched to cavity, which says nothing. It absorbs moulding and cutting tolerance, which stack to plus or minus 1.5 mm, so 2 mm per side is the safe band.

Custom Case with Foam Insert: a dark grey case closed at a three-quarter angle, two draw latches, a folding handle and a round pressure valve

Foam compression is a separate sum. A Custom Case with Foam Insert holds parts at 15 to 25 percent compression; under 15 they rattle, over 25 the slot mouth collapses after repeated use. Past 40 percent of pad thickness the foam densifies and shock passes straight to the shell.

3. Splitting the Foam into Three Layers

Three layers is the common build: base for load, middle for location, lid for hold-down. Base is PE at 45 kg/m³ and 30 mm; middle is EVA at 30 kg/m³ and 20 mm, slotted 3 mm shallower than the part; lid is 25 mm convoluted PU. That totals 75 mm, leaving 115 mm of a 190 mm cavity.

Make the middle a removable block and a Custom Case with Foam Insert takes a second product while base and lid stay. Leave 1 mm of pull clearance plus a half-round notch for fingers, and never glue the layers solid.

4. Die Drawings and Trial Fits

The die drawing must be 1:1 and show outline, slot depth and kerf. Kerf runs 1.5 mm with R3 corners, or the slot cuts burred. Knobs and ports need relief cuts 2 mm larger, or the part bottoms out while the depth looks generous on paper.

Custom Case with Foam Insert: two dark grey case halves, flat foam in the left lid, a die-cut insert in the right base

Two trial rounds follow: EVA first, then production foam, five units each, rehearsing load, open, invert and reload. First-article approval then takes 48 hours and files the measurements later batches are judged against.

Trial round	Material	Units	What it proves
First	EVA trial cut	5	Outline and handling feel
Second	Production foam	5	Compression and lid force

5. The Drawing Pack You Should Receive

A case often ships with one insert outline, and by the second order nobody knows the slot depth. Six documents prevent that.

Document	Content	Used for
Cavity drawing	Clear size, radii, bosses	Tooling and inspection
Layer drawing	Three thicknesses, densities	Material planning
Die drawing	1:1 outline and kerf	Cutting and rework
Assembly drawing	Layer order, location	Line assembly
First-article report	Measured sizes, photos	Batch comparison
Material certificate	Density, flame rating	Audit and export

Version control belongs in the same pack: change the insert drawing and the die, assembly and first-article documents of a Custom Case with Foam Insert step up together, with drawing number and revision marked on every carton.

Conclusion

The order is cavity, clearance, layers, die, documents: the first two decide whether the part fits, the last three whether the build repeats. Put all five on paper with a revision trail, and a Custom Case with Foam Insert can be reordered without starting over.

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.