Key takeaways
- A sandwich panel is two steel skins bonded to an insulating core — the core decides fire class and insulation value, the skins carry the load.
- Continuous lines foam the core in place and suit high-volume PU and PIR production; discontinuous lines suit EPS and rock wool where the core is laid in by hand.
- PU and PIR give the best insulation per millimetre but are combustible; rock wool is the only non-combustible core.
- A continuous PU line occupies 40–60 m, so site planning matters as much as machine specification.
What the line actually does
A sandwich panel production line takes two coils of pre-painted or galvanised steel, profiles each into a face sheet, and bonds them to an insulating core between them. The result is a rigid panel that insulates and carries load at the same time — which is why it dominates cold stores, clean rooms, food factories and increasingly fire-rated facades.
The two skins do the structural work. The core does the insulation, and on a fire-rated building it also does the fire separation. That division is why the core choice is a compliance decision, while the skin thickness is a structural one.
Continuous versus discontinuous
A continuous line runs the core in one uninterrupted process. For PU and PIR, liquid chemicals are metered onto the lower skin and foam in place as the panel passes through a heated double-belt press, which sets the thickness and cures the foam. Line speed is 3–8 m/min and panel quality is very consistent, but the capital cost is high and the line occupies 40–60 m.
A discontinuous line builds panels in batches. Rock wool or EPS slabs are laid onto the lower skin, adhesive is applied, and the assembly is pressed and cured. Line speed is lower and more labour is involved, but capital cost is much lower and the format suits lower volumes and thicker panels.
The practical choice: if you are producing one core type at volume for a stable market, a continuous line pays back. If you produce a mix of cores and thicknesses, or serve a regional market, a discontinuous line is usually the better business decision.
Choosing the core
Core choice is usually driven by building regulation, not by preference. PU and EPS are combustible and reach B2 or E class, so they cannot be used where a fire rating is required. PIR reaches B1 or Euroclass C, which satisfies many codes for occupied buildings. Rock wool reaches A1 or A2 — non-combustible — and is the only core that satisfies fire-rated facades, escape routes and food factories.
Insulation performance runs the other way. PU and PIR are the best insulators per millimetre, EPS is mid-range and rock wool the weakest. So there is a genuine trade-off between fire performance and thickness, and it is worth calculating both before choosing.
| Core | Fire class | Thermal conductivity | Relative cost | Choose when |
|---|---|---|---|---|
| PU | B2 / E — combustible | 0.022–0.026 W/mK (best) | Lowest | Cold stores and industrial buildings with no fire rating |
| PIR | B1 / Euroclass C | 0.023–0.027 W/mK | Low–medium | Codes require a fire class above B2 but you want PU-level insulation |
| EPS | B2 / E — combustible | 0.033–0.038 W/mK | Low | Cheapest option for non-rated, lightly loaded partitions |
| Rock wool | A1 / A2 — non-combustible | 0.040–0.045 W/mK | Highest | Fire-rated facades, food factories, escape routes, plant rooms |
What else is on the line
Beyond the press and the foam unit, a complete line includes double decoilers for the two skins, profile forming machines for each face, a metering and injection unit for PU or an adhesive applicator for rock wool, a cross-cut saw with dust extraction, and a stacker or vacuum lifter.
Two details are worth attention at specification stage. First, roof panels need an additional profile set for the overlaps and a higher-density core for point loading — so if you intend to sell roofs as well as walls, say so up front. Second, the saw must have effective dust extraction, because rock wool and PU dust are both unpleasant and the cut edge is the visible face of the finished panel.