“If I had eight hours to chop down a tree, I’d spend six sharpening my axe.” 

—Abraham Lincoln 

 

The razor-sharp, rapidly spinning blades on a CNC router bit make smooth, easy cuts into some substrates, but make a big, ugly mess out of others. Here’s a list of some of the more compatible substrates:

 

WOOD

Traditional wood—in this case, cedar--is still a great material to use, such as this example being routed on a ShopBot machine. PVC can be used to build all sorts of things with a little help from a CNC router.

Solid wood—Good old-fashioned, beautiful, natural wood is a great routing material. For millennia people have been carving intricate patterns into wood. CNC routers just made it a whole lot quicker and easier. Great hardwoods include: ash, oak, cherry, mahogany, hard maple, etc. Routable softer woods include pine, soft maple, fir, spruce, hemlock, cedar and redwood.

 

MDF—Medium density fiberboard (MDF) is a big player in the sign and exhibit industry.

 

MDF is made by converting wood chips into fibers. Liquid resins are added to create a thick mat that is pressed into boards using heat and pressure. An advantage of MDF for the graphics industry is that the product is uniform throughout, including the edges. MDF edges are smooth and beautiful straight off of the router. One disadvantage of MDF is that paint is generally required to finish it, even if it will be covered with a digital graphic.

 

MDF cutouts can add instant dimension to an exhibit.

Plywood, HDO and MDO—Plywood is one of the earliest signage materials of the last century, and an excellent candidate for routing. Plywood is created with layers of veneers. These layers are alternated with the grain running at right angles, then glued together under pressure in large presses. For outdoor grade plywood, the adhesive used is generally a phenolic resin that is resistant to moisture, bugs, heat and cold. These synthetic resins are also impregnated into smooth top layers to create overlay plywood like HDO and MDO. Plywood’s large size, high strength-to-weight ratio and dimensional stability have made it a staple of the signage and display industry since its inception. Overlay plywood accepts paint and digital prints; however the layered edges need a lot of finishing to look good. Other routable wood-based composites include OSB, LDF, particle board and Masonite.

 

PLASTICS

PVC can be used to build all sorts of things with a little help from a CNC router.

Expanded PVC—Lightweight routable expanded PVC sheet products like Sintra, Komatex, Komacel and Celtec have virtually taken over the middle price point of the indoor display market. Light, tough, stable and very easy to work with, expanded PVC can also be fire resistant and directly printable. Routers cut through it like butter, leaving perfectly finished edges. And they are available in a variety of colors, meaning that no paint is needed for further savings.

 

Acrylics—Plastic acrylic sheet is another product that stands strong in the router marketplace. Beautiful, versatile and durable, these rigid sheets come in a large variety of thicknesses and colors. They make very stylish and unique displays that are easy to fabricate. Special router bits for plastic can polish and finish the edges as well. Some brands include Plexiglas, Acrylite, Lucite and Lexan.

 

Polycarbonates—This is one of the toughest materials on the market. Polycarbonates have excellent impact-, heat-, cold-, stain-, UV- and chemical-resistance. They represent a very long-term, outdoor-durable and flame-resistant solution. Polycarbonates cut easily on a CNC, but the edge finishes are not as clean as acrylics. The nature of the molecular structure of polycarbonate that creates its strength also creates a minor problem that makes the baby smooth edges of acrylics and MDF products more difficult to achieve. 

 

Sign Foam—Sign foams are used quite differently than other materials in this category. Rather than just be used as substrates to carry graphics, they come in thick, easily routed slabs that are ideal for 3-D sculptural signage. In other words, the shapes are the graphics. This wonderful stuff has made a whole new dimensional genre of signage possible. And in comes in a wide variety of qualities, densities and sizes.

 

Other Routable Plastics—There are a number of other plastics that are considered routable and useful to sign makers. They include ABS, polyethylene, PVC, polypropylene, polystyrene, HDPE and PETG.

 

Aluminum is a very durable outdoor material and works great for CNC routed cut lettering.

METAL

Aluminum—Most metals don’t fit into the “easy to CNC” category, with the exception of aluminum and honeycomb aluminum. And for long-term outdoor durability it’s hard to beat this common metal as well. It is completely impervious to any form of weather and 100 percent recyclable- a winning combination. Special CNC bits are available for this material that make cutting smooth and easy, albeit at a somewhat lower speed than many other substrates. 

 

Other Metals—A number of other metals are considered routable, but may not be quite so easy to work as aluminum. These metals include brass, copper, bronze and mild steel.

 

COMPOSITES

A CNC router can be used to facilitate fabrication with composites as well as altering shapes.

Aluminum/Plastic—One of the most common router substrates are the class of composites that employ aluminum and plastic. Utilizing the light weight and moisture resistance of thermoplastics for the core and thin layers of painted or anodized aluminum for the outer surfaces, these relatively new products are perfect for sign production. They often have .012" outer layers with 2mm, 3mm and 4mm core thicknesses. Sizes include 4'x8', 4'x10' and 5'x10' sheets. It is dimensionally stable and weather-proof yet much lighter than solid metal. Composites are a UL-recognized component for electrical signs, have a Class 1 and Class A fire rating and are NCHRP 350 approved for highway and safety signage. 

 

Their layered structure gives them excellent strength and rigidity, meaning that less substructure is required during construction. They are easy to work with using ordinary shop and woodworking tools and come pre-painted for a completely hassle-free experience. CNC routers love these unique products and spin through them with ease. The layered edges may not be quite as beautiful as PVC or MDF, but they are smooth and clean. Some aluminum composite brands include Alupanel, AlumaCorr, Dibond, Graphic-Al and KomaAlu. 

 

So keep your bits sharp, use the right one for the job and try something new today.

 

Click here to view the CNC Routing Materials Resources PDF.