HDU (high-density urethane)

HDU, short for high-density urethane, is a rigid closed-cell foam board made for carved and dimensional signs. It does not rot, swell or split like wood, carves cleanly on a CNC router, and takes primer and paint well, so it is a common choice for raised letters, plaques and carved panels.

Densities and sizes

HDU is sold by density in pounds per cubic foot. About 15 lb is the usual sign grade: firm enough for fine detail and outdoor use. Around 18–20 lb holds sharper detail and edges; lighter grades are cheaper and used for bulk or thick builds. Boards are often 48 × 96 in, in thicknesses from about 1/2 in to 2 in and more, and thicker blocks can be glued up. These are typical figures; brands and stock sizes vary.

How sign shops work with it

Cutting: a CNC router cuts HDU quickly with little force. Profiles are cut with straight or compression bits; carving and V-carved lettering use ball-nose and V-bits. Collect the dust, which is fine and travels.
Holding: the board is light, so small letters can move once cut free. Tabs, an onion skin or a vacuum table keep them in place.
Finishing: HDU has to be sealed. Shops use a primer made for urethane foam, then paint; gold leaf and textured finishes are common on carved signs.
Laser: HDU is not a laser material. Cutting it with a laser gives off harmful fumes.

How NestSigns handles it

For flat cut HDU letters, NestSigns nests the letters by their real outlines onto full boards and leftovers, keeps a stock list per thickness and density, and sets the spacing from your router bit. Carving and 3D toolpaths stay in your CAM software. See HDU sign nesting.

Try it on your own job. Open your artwork, pick a sheet, and see how many sheets you need. 20 free nesting runs, no credit card. After that, $14.99 per month, cancel anytime.
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