ACM (aluminum composite material)
ACM, aluminum composite material, is a sheet made of two thin aluminum skins bonded to a plastic or mineral-filled core. Sign shops use it for flat panels, letter backs and routed letters; Dibond is one well-known brand.
What it is made of
An ACM sheet is a sandwich: a painted aluminum skin on each side, often about 0.3 mm (0.012 in) thick, and a core between them. The core is usually polyethylene in standard sheets; fire-rated grades use a mineral-filled core where building codes ask for it. The result is flat, stiff and light compared with solid aluminum of the same stiffness.
| Common spec | Typical value |
|---|---|
| Sheet size | 48 × 96 in, also 48 × 120 in and 60 × 120 in |
| Thickness | 3 mm is the most common for signs; 4 mm and 6 mm for bigger panels |
| Finish | Painted both sides, white most often, plus many colors and brushed looks |
These are typical values; check your supplier's sheet for the exact skin, core and sizes.
How sign shops use it
- Flat signs and panels, printed directly or covered with vinyl.
- Letter backs for channel letters, and routed panels with push-through letters.
- Flat cut letters and logos for walls and fascias.
- Folded shapes: a V-groove routed through the back skin and core lets the sheet bend cleanly along a line.
Cutting ACM
ACM is cut on a CNC router, a panel saw or by scoring. On a router, single-flute (O-flute) bits made for aluminum or plastics are typical, often 1/8 in or 1/4 in. It is not usually cut on a CO2 laser, because the aluminum skins reflect the beam and the plastic core melts. Because sheets are fairly expensive, nesting letters and backs tightly, and keeping the leftover pieces, makes a real difference on bigger jobs.
How NestSigns handles it
NestSigns nests ACM letters and backs by their real outlines onto full sheets and leftovers, keeps a separate stock list and price for each ACM color and thickness, and sets the part spacing from your router bit. See ACM nesting for the details.
Related: ACM nesting · Letter backs · Kerf · Channel letters · All glossary terms
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