Folding an aluminum composite panel after V-groove routing in the shop

Bending the ACP panel: routing, sharp folds, returns.

Façade returns, box corners, sign edges: wherever a clean angle replaces a joint, the composite panel folds. The process takes two moves — the V-groove, then the fold. This guide covers both, plus gentle curves and the classic mistakes.

Request a sample → See cutting & machining

The principle

Route first, fold second.
Two moves.

A 4 mm panel doesn't fold like a sheet: it folds because a band of core is removed in exactly the right place.

The V-groove

A V-shaped router bit removes the PE core and part of the inner skin along a narrow, even band. The outer skin stays in place: it becomes the hinge of the fold.

The fold

By hand for a panel light enough to handle, on a press brake for long lengths: the panel folds crisply along the groove, at 90° or any angle needed.

The result

A sharp angle, no joint, with the decorative face continuous on the outside. It's been the standard for sign boxes and façade returns for decades.

On the job

The folds a project
actually asks for.

Four fold families cover nearly all real-world needs.

↳ 90°

The sharp right-angle fold

The classic: façade returns, box sides, angle trims. One groove, one fold, and the corner is done — no accessory, no corner joint.

↳ OBTUSE

Angles other than 90°

The groove angle and depth set the final angle: obtuse and acute folds use the same process, adjusting the bit pass.

↳ RADIUS

Gentle curves

A wide radius is done cold, by progressive bending. For tight radii: sequential, closely spaced grooves — the standard method for curved façades.

↳ RETURN

The shop-made return

In cassette systems, returns are folded in the shop and the piece arrives on site ready to hang. The fold happens once, well, at the bench.

In the shop

The three classic
bending mistakes.

Every sign shop knows them — and all three are avoided with a test run on an offcut.

Groove too deep

If the bit touches the decorative skin, the fold marks or cracks. Route from the inner side, stop before the outer skin, and check on an offcut.

Groove too shallow

If too much core remains, the fold is soft and the inner radius thick. The core must come out across the full width of the V — it's what resists the fold.

Folding in the cold on site

Quality folds happen in the shop, panel at room temperature and flat. Improvised site folds, backlit and on the knee, rarely end up square.

Shop decision

Fold it yourself,
or have it folded?

Not every shop has a router — and not every project needs one. Three situations settle the question.

Few folds, occasional piece: a sample, an offcut and a simple routing pass are enough — the ACP fold forgives if the groove is set with care. Many installers fold their returns by hand with a straight rail.

Regular production of boxes and returns: the router and press investment pays for itself quickly. That's the sign-shop profile — folding at the bench and shipping ready-to-install pieces.

Full façade in a cassette system: returns are folded in series, often before the panels are even ordered. Here, coordinating the project layout with the folding plan matters more than the tool — that's where a direct supplier who talks format and layout makes the difference.

FAQ

ACP bending:
your questions.

How do you bend an aluminum composite panel?

In two steps: first a V-groove route that removes the PE core and part of the inner skin along a narrow band, then folding by hand or press along the groove. The fold happens on the routed side, leaving the decorative face intact on the outside.

How deep should the groove be for a 90° fold?

The groove must remove the core without cutting into the decorative skin: route the inner face until the outer skin remains as the hinge. The exact depth depends on the tool and the result — test on an offcut before the final piece.

Can you give curves to an ACP panel?

Yes, within the panel's elasticity: a gentle radius is done cold by progressive bending, and the sandwich construction springs back if the radius is too tight. For tight radii, sequential routing (closely spaced multiple grooves) remains the industry-standard method.

Is the fold as strong as the rest of the panel?

The fold is the panel's most stressed zone: that's a design consideration, not a defect. Done right — clean groove, sharp fold, fixing that follows the project's specified system — it lasts the life of the panel. It's also why cassette systems fold their returns in the shop.

Check the fold on a real offcut.

Order a sample to dial in your router and validate the fold in the real conditions of your shop.

Request a sample Cutting & machining Installation guide

ACM cladding ACP for signage Formats 4×8 / 5×10