I treat aluminium composite material (ACM, also sold as ACP, and known on most shop floors simply as dibond) as a specified assembly, not a generic white sheet. It makes flat sign faces and crisp folded fascias efficiently, but the wrong core, skin or fixing detail turns an attractive panel into an expensive remake. "Dibond or equivalent" on an order is not enough information to release a job.
Read the sandwich before the brand
ACM is two aluminium skins bonded to a core. The separated skins give the panel its bending stiffness without making it solid metal, which is why a 3 mm panel behaves nothing like a 3 mm aluminium sheet. The brands you hear on the floor are product families, not interchangeable specifications.
Standard signage panels come in 2, 3, 4 and 6 mm with thin skins of around 0.3 mm; a 3 mm panel weighs under 4 kg per square metre. Architectural and fire-rated grades use thicker skins of about 0.5 mm and a heavier mineral core, so a 4 mm panel can weigh twice as much. Total thickness on its own tells you almost nothing about whether two panels are equivalent.
| Core family | Where you meet it | What it means for the spec |
|---|---|---|
| Polyethylene (PE) | Standard signage panels | Combustible core; the metal faces do not make it suitable for a facade |
| Fire-retardant mineral-filled (FR) | Mid-range cladding and fascias | Better reaction to fire, typically class B; still not A2 and not a blanket approval |
| Mineral-rich A2 grade | External walls, rainscreen, high-risk buildings | Classified A2-s1,d0; the exact product classification and installation conditions still have to be confirmed |
Even "mineral core" does not identify a single grade: some manufacturers also offer an A1 version. Always ask for the classification of the specific product, not the family.
For signage I distinguish flat wayfinding panels, cut-out letters and letter backs from folded fascia trays, pylon skins and architectural cladding. ACM is opaque; an illuminated letter needs a separate light-transmitting face or a cut-through detail. A pylon skin is not a substitute for its engineered frame. Wind loads, supports and maintenance access belong in the design, not in a conversation on site.
Cut cleanly and prove the fold
ACM saws and routes well, provided the tooling is sharp, the sheet is supported, swarf is extracted and the first cut is inspected before the batch. Do not transfer a solid-aluminium machining recipe blindly to a bonded panel: the core clogs and the face skin tears if the feed is wrong.
Routing and folding, often called V-grooving or rout-and-return, removes the rear skin and most of the core along the fold line while preserving the visible skin. The remaining sliver of material becomes the bend zone. This is not an ordinary sheet-metal bend allowance, and the correct groove depth depends on the product, the thickness and the coating.
My release sequence for a folded tray is always the same:
- Identify the grade, the coating direction and the actual sheet thickness.
- Set the groove geometry and the residual core for that product, not a remembered universal depth.
- Rout a coupon, fold it in a supported jig, and inspect the face and the finished dimension.
- Notch the corners, form the tray and reinforce or connect its returns as detailed.
Too deep weakens or cuts the face skin; too shallow gives a reluctant fold and the wrong geometry. Folding a bend twice risks cracking. Roll-curved panels are a different process again, and not every grade can be press-brake bent: some fire-rated cores cannot. A substituted core is therefore a process change, not just a purchasing change.
Join the skins and leave room to move
Rivets, screws, backing angles and approved adhesive systems all have a place. Adhesive attachments go on the aluminium faces, never on the exposed core edge. Clean and prepare the actual coating, test compatibility, allow the specified cure, and design the joint for the load and the movement. Double-sided tape is not automatically a structural fixing.
Aluminium composite moves with temperature: roughly 2.4 mm per metre for a 100 °C change is a fair working figure, so a 3 m panel seeing a 50 °C swing between a winter night and a sunny afternoon moves about 3.6 mm. That is a calculation, not a universal joint width: the support movement, the installation temperature and the chosen fixing system still matter.
Use fixed and sliding points rather than clamping every hole rigidly. Overtightening compresses the core; contact between incompatible metals promotes corrosion. On the shop floor I also check the coating-direction arrows, swarf trapped under the face, and protective film caught beneath permanent fixings.
Factory colour, direct print, vinyl and compatible paint are different finish systems. Approve adhesion, colour and cleaning on a sample; do not assume the reverse coating matches the front. Keep access panels replaceable. A beautiful finish glued across a service joint is poor detailing.
Fire classification is not permission to install
Reaction-to-fire classes describe how a material behaves in a fire test, not how long a wall resists fire. The letters after the class describe smoke production and flaming droplets. "FR", an old "Class 0" claim or a brand name does not replace the classification report for the specific product, and the report has to cover the complete build-up: graphics, adhesive, insulation, cavities and cavity barriers.
In practice, for Ireland and the UK: a PE-core panel is not an option on an external wall or on anything attached to it, regardless of building height. The rules that followed the cladding fires target exactly this material. "Below 18 metres" is not a general permission to use PE, and the requirements differ between England, Scotland, Wales, Northern Ireland and Ireland, so the answer for a job in Dublin is not the answer for a job in Belfast.
For a fascia, establish first whether it forms part of the external wall; only then choose the stock. For a freestanding pylon, do not automatically import the wall rule, but do not assume there are no fire obligations either. Boundary distance, building use and the height of the top floor all change the answer. Have the project's fire designer confirm the applicability and the complete wall system. An article is not a project-specific fire approval, and neither is a datasheet.
Price the finished job and the waste route
I compare delivered sheets, usable yield, routing and folding time, subframes, fixings, finishing and installation, never an isolated price per square metre. Setup time, yield and remakes are the three numbers worth tracking per job; they explain most of the difference between a profitable fascia and a loss.
Availability has a cost too. Special colours and fire-rated grades often come with minimum order quantities of well over a hundred square metres and lead times of a month or more, which is fine for a rollout and a disaster for a single shopfront. Check local stock before designing around a special finish.
On sustainability, the recycled-aluminium claims on the box are usually mass-balance figures for the skins, not for the whole panel, and they say nothing about local collection. Ask for an environmental product declaration, design separable fixings, and find a recycler that accepts the actual composite together with its graphics. "Recyclable" without a destination is an incomplete waste plan.
What I put on the order
My production support checklist for ACM is short:
- Exact manufacturer, grade, core, skin thickness and total thickness; no unapproved substitution.
- Finish, batch and orientation; an approved printed or painted sample.
- Fire classification report and its scope, checked against the project's jurisdiction and build-up.
- Panel sizes, loads, supports, fixing and movement details, plus access requirements.
- A proven groove-and-fold sample, delivery terms and an agreed offcut and end-of-life route.
Specify the panel and its use together. The colour swatch can come after that.
