Flat or stepped shape, small quantity: cut and fabricate it. No tool, fast samples, cheap changes. Deep cavities, undercuts, ribs, latching pockets, load to carry, or dozens of return trips: mold it.
DBM runs both routes: EPE pearl foam cut and laminated from extruded sheet, and twelve bead foams shaped in a steam-chest mold. The split is geometry, seams and quantity, not a material name.
Both routes end in a closed-cell foam part, often in the same polymer. Cutting reaches whatever a blade, a die or a hot wire reaches; molding reaches whatever the cavity is machined into.
This is not a material table: both columns can be the same polymer. The numbers are ranges each route normally works in, not one part's specification.
| Characteristic | Cut and fabricated | Molded (steam chest) | What it means for your part |
|---|---|---|---|
| Shape freedom | Flat, prismatic and stepped shapes; curves only approximated by stacking layers | Deep cavities, undercuts, ribs, latching pockets and compound curves in one shot | Most selections are already decided on this row. If a sheet reaches the shape, a tool buys nothing; if it does not, no number of bonded layers is more than a workaround. |
| Seams and joints | Every layer boundary is a bonded seam | None: the part is one fused body | A seam is the weak line for load and for appearance, and the way in for moisture and cleaning agents. Under repeated handling that is where parts fail. |
| Load ceiling at 10% strain | EPE pearl foam, 22–88 kPa | Beaded EPE 44.8–241.3 kPa; up to 430 kPa across the bead foams | Above the ceiling the foam works past its plateau on every trip. When load is the problem, changing process moves further than changing density. |
| Density adjustability | Fixed by the sheet you buy: a different density is a different roll | A process setting: the same tool molds several densities | When a drop test comes back and the part has to be firmer or softer, molding changes a parameter while cutting changes a purchase order. |
| Insert integration | Bonded on afterwards | Molded in: inserts, threaded bushes, carbon-fibre rods | This is what decides whether the foam is only a cushion or can be a load-carrying part of the assembly. |
| Tooling investment | None for plain cutting; low for a die | One aluminium cavity per part | The one line cutting always wins, and it often decides the whole case on its own; see when not to tool, further down this page. |
| Cost of a design change | A new cutting programme | Possibly new metal, sometimes a new tool | Before the design is frozen, revisions that land in software are far cheaper than revisions that land in aluminium. |
| Speed to first sample | Fast: nothing to wait for | Slower: the tool is made first | It sets how soon you can put a real part on a drop tester rather than argue about it on a drawing. |
| Batch size it suits | One-off to a few thousand; many part numbers, small quantities | Repeat volume, where the fixed investment is spread thin | The same tool is a disaster in one programme and irrelevant in another. Nothing about the tool changed, only the denominator. |
EPE pearl foam is extruded polyethylene sheet, cut and laminated. Beaded EPE is the same polyethylene, pre-expanded into beads and fused in a mold.
| Property | EPE pearl foam (cut sheet) | Beaded EPE (molded) | What the row tells you |
|---|---|---|---|
| Base polymer | Polyethylene | Polyethylene | Same chemistry on both sides, so heat behaviour, chemical behaviour and the recycling stream are the same too. |
| Long-term service temperature (°C) | 80 | 80 | Owned by the polymer. Molding does not buy a single degree of it. |
| Energy absorption efficiency (%) | 60–70 | 60–70 | Also owned by the polymer: how much of the area under the stress-strain curve is useful cushioning rather than wasted stroke. |
| Compression stress at 10% strain (kPa) | 22–88 | 44.8–241.3 | The load ceiling rises by roughly 2.7 times. Nothing changed except the way the foam was formed. |
| Rebound (%) | 30–35 | 50 | The molded bead structure comes back further, which is exactly what lets a returnable insert hold its shape over many trips. |
Rows the polymer owns are identical; rows the process owns are not. A polyethylene part failing on load or recovery needs a different process.
A cut-and-laminated insert stacks layers with a hole in each, so the pocket comes out stepped rather than shaped. Tapers, ribs and curved backs leave clearance, and clearance rattles. A molded cavity is machined to the part and still holds it after a hundred take-outs.
EPE pearl foam runs 22–88 kPa at 10% strain; above that the foam works past its plateau every trip. EPE rebounds 30–35% against 50% for molded polyethylene, so the cut insert loses thickness where the molded one holds it. Heavier again and the bead range goes to 430 kPa.
Every bond line in a laminated insert is weaker than the foam either side of it in peel and in shear, and it is the way in for moisture and cleaning agents. Under handling the crack runs along the joint. A molded part has no seam.
Multi-component nests run out of degrees of freedom fastest. Each component wants its own pocket at its own depth. Built from layers that is five or six pieces, cumulative tolerance and five or six seams. Molded it is one part.
Then do not. A cut part has no tooling step: the first sample is a cutting programme. A tool is a fixed investment: spread over a few hundred parts it dominates the part cost, spread over repeat volume it disappears.
Returnable packaging changes the arithmetic: the fixed investment is divided by every trip every part makes. The requirement changes too: dimensional stability over cycles, recovery after impact. Ask whether the foam comes back. If it does not, start at cutting.
Which process we open with when this kind of job arrives. A payload, a drop height or a trip count can move any row.
| Application | Start from | Why |
|---|---|---|
| Surface protection, interleaving and wrap | Cut | Thin sheet separates and protects. There is no geometry to mold and nothing to locate. |
| Flat or stepped pads inside a carton | Cut | A blade or a die reaches the entire shape, so a cavity would buy nothing the part uses. |
| Prototype and pre-production transit packing | Cut | Parts in hand before the design is frozen, and each revision is a new programme rather than new metal. |
| Many part numbers, each in small quantity | Cut | Service kits and spares. A fixed investment per part number is what breaks this case, and cutting has none. |
| Multi-component nests and KLT inserts | Molded | Several pockets at several depths, held accurately over dozens of trips. Layers only reach it through seams. |
| Returnable dunnage and trays | Molded | Recovery after impact, dimensional stability over cycles, and no bond line waiting to open. |
| Load-bearing and structural foam parts | Molded | Load is carried, not only absorbed. Molded bead foams reach up to 430 kPa at 10% strain and can take inserts. |
| Parts with molded-in inserts or reinforcement | Molded | Bushes, clips and carbon-fibre rods become part of the foam body instead of being bonded onto it. |
| Insulated boxes and cold-chain shippers | Molded | A one-piece wall with no seam to leak heat, and a lid seal whose shape comes straight out of the cavity. |
| Energy absorbers and impact structures | Molded | The absorbing geometry is the specification: ribs, thickness transitions and crush stroke, none of which a flat sheet reaches. |
These are the cases where a tool is the wrong answer. Better said at the enquiry than after the cavity is cut.
A single sample, a show unit, a first article for a drop test: nothing to spread a tool across, and a cut part answers whether the concept works.
Below the point where the investment disappears into the part, a tool makes every part dearer and buys nothing the geometry needed. The crossover moves with cavity size, cavity count and part count.
Molding earns its keep on geometry a sheet cannot reach. A flat pad, a plain block, a straight-sided liner: cutting reaches those exactly, with no tool.
Once the cavity exists, every design change is a change to metal. If the payload, mounting or drop specification is still moving, cut the early rounds.
Once the process is decided, the material is the next question. These pages each answer one, from the same property dataset.
| Comparison | The decision it settles |
|---|---|
| EPE vs Beaded EPE foam | The same polyethylene, cut from sheet or molded from beads. The closest view of what the process alone is worth. |
| EPP vs EPS foam | Repeated impact and heat against single-trip cost and insulation, once the part is going to be molded. |
| All thirteen foams, ranked | Every material we supply sorted property by property, for when you do not yet know which family you are in. |
Cut foam starts as extruded sheet or roll and is brought to shape by cutting, die-punching, heat-forming and bonding, so the geometry is limited to what a blade or a die can reach and anything deeper has to be built up in bonded layers. Molded foam starts as pre-expanded beads that fill an aluminium cavity and fuse under steam, so cavities, undercuts, ribs and latching pockets come out in one piece with no seam anywhere. Cutting needs no tool; molding needs one.
Molding, and the cleanest evidence holds the polymer still. Cut EPE pearl foam runs 22–88 kPa at 10% strain; the same polyethylene molded from beads runs 44.8–241.3 kPa, roughly 2.7 times the ceiling, and rebounds 50% against 30–35%. Long-term service temperature is 80 °C on both sides and energy absorption efficiency is 60–70% on both, because those belong to the polymer rather than to the process.
Usually not. A tool is a fixed investment recovered across everything it produces, so a small quantity carries almost all of it while repeat volume barely notices it. If the shape is flat, stepped or otherwise reachable with a blade or a die, cut it: no tool, fast samples, and a design change costs a new cutting programme rather than new metal. The case for tooling at low volume is geometry that cutting cannot reach, not cost.
Because a bond line is a plane the foam did not choose. It is weaker than the foam either side of it in peel and in shear, it is the way in for moisture and cleaning agents, and repeated handling concentrates movement there. A molded part has no bond line at all: the beads fuse to one another throughout, so a wall is as strong in the middle as it is where a joint would otherwise have been.
Yes. Density comes from how far the beads are pre-expanded and how the cavity is filled, so the same tool can run several densities of the same material. That matters when a drop test comes back and the part has to be firmer or softer: the change is a process setting rather than new metal. Changing to a different polymer in an existing tool is a separate question, because shrinkage differs between polymers and a cavity cut for one is rarely dimensionally right in another.
Send us the current insert and the part it protects, and say what is going wrong: rattling, collapse after a few trips, failure at a seam, or too many pieces to assemble. We work back from the symptom to the geometry the cavity has to have, then the material, the density and a sample plan. If the part should stay cut, we will say so rather than sell you a tool it does not need.
Send the part, the payload and the number of trips. We come back with a process, a material, a density and a sample plan. 48-hour response.