CNC Routing Clear Cast Acrylic (Plexiglass)

Why cast acrylic routes cleanly

Acrylic is made as cast or extruded sheet. Cast acrylic is harder and less gummy under a cutter, so routed edges come out clean rather than melted, and it engraves and polishes well — which is why the catalog stocks clear cast. Ask the shop about colors and frosted or diffusing grades before you design around them.

Cast sheet has a trade-off: its thickness varies more across a sheet, and from sheet to sheet, than extruded sheet does. Measure the sheet a part has to fit, give slots, channels and frames clearance, and expect a pocket’s floor to sit at its set depth below a face that isn’t quite even.

Edges and finish

A routed acrylic edge is smooth but frosted, with light tool marks. That’s fine for parts that sit in a frame, a channel or behind a bezel, but a glass-clear show edge takes a separate polishing step. Polishing isn’t part of an instant routing quote, so ask the shop before you order whether it can be done.

Acrylic sheet usually comes with protective paper or film on both faces. Where it’s supplied, leave it on through handling and peel it at install — but don’t park a masked panel in the Las Vegas sun, where heat can bake the film onto the face.

Designing acrylic parts

Acrylic is stiff but notch-sensitive: sharp inside corners and holes close to an edge are where cracks start. Give inside corners a generous radius, keep holes back from edges, and use slotted holes with washers for mounting so panels can move with heat. Lines engraved on the back face read through to the front, which is how edge-lit signs carry their artwork. The CNC routing page has the router’s full design rules, and the material comparison weighs acrylic against HDPE, MDF and plywood.

Edge-lit signs trap light inside the sheet: LEDs shine into one edge, and the engraved lines scatter it out toward the viewer. When the artwork is engraved on the back, mirror it in your file so it reads correctly from the front, and pick the back when the quote asks you to confirm the machined face. Keep the lit edge straight so it sits flush against the LED strip.

Standoffs and screws need round holes kept well back from the edges. Draw each hole at the hardware’s size plus room for the sheet to move with heat, keep it a couple of sheet thicknesses from any edge, and let the drill bank make it — round holes down to 3 mm (0.118″) are drilled. Even the 1/8″ bit leaves a 1/16″ radius in each inside corner; draw a larger one wherever a corner will carry stress.

Lit signs and Las Vegas heat

For backlit faces, a white diffusing grade spreads LED light evenly where clear sheet would show hot spots; ask about it when you order. Cast acrylic stands up well to sunlight, but it expands with heat, so leave room around panels mounted outdoors or close to warm light boxes. For a printed face that isn’t backlit, Dibond (ACM) panels are the usual substrate.

Acrylic grows with temperature several times as much as aluminum or steel, and a sign face in a Las Vegas summer swings a long way between a sunlit afternoon and the night. Mount outdoor panels in channels or on slotted holes with room at the edges, don’t glue them tight to metal, and avoid a dark backer right behind clear acrylic in full sun, where heat builds up between the two.

Common acrylic parts and thickness

Thin sheet suits framed sign faces, inserts, sneeze-guard windows and diffusers; display risers, shelves and freestanding signs need heavier sheet to stay flat; an edge-lit panel needs an edge thick enough for its LED strip. Clear acrylic is heavier than plywood of the same size and creeps under a constant load, so support long shelves at the ends and in the middle.

A freestanding guard or sign can stand in slotted feet cut from the same sheet, a tab-and-slot base that comes apart for storage — the tab-and-slot design guide covers the fit, and acrylic wants the generous end of it. Acrylic is billed by the whole sheet, like every routed material, and the example prices show how one sheet’s cost spreads over the parts cut from it.

What an acrylic order includes

Acrylic parts ship as cut, with frosted routed edges and whatever masking the sheet came with. Edge polishing, bending, solvent-cement bonding, printing and installation come after the parts leave the shop — ask the shop before you order if a job depends on any of them. For a display case or lit sign built start to finish, send a custom fabrication inquiry; the retail fixtures and displays guide covers acrylic in store fixtures.