At Onsrud, "Fixed Bridge" means cast iron. It also means the spindle travels the stationary bridge along the width of the tables while the tables pass underneath the bridge along their short dimension. This design (like our moving gantry design) only uses half of the floor space that a typical "Tubular Fixed Gantry" design would use. Its design is extremely efficient, shuttling the twin tables for continuous production and 100% cutting time. With this design, the CNC's table can be loaded and off-loaded without interrupting the cutting and production that is occurring on the other table. Its heavier and thicker cast iron frame tends to naturally absorb or dampen any cutting vibrations.

Simply put, cast iron just has a better ability to absorb and dampen cutting vibrations, while steel will tend to amplify and transmit these oscillations to the rest of the frame. When you are cutting man-made materials most of the time, a heavy, tubular steel frame like our Panel Pro Series is acceptable. But, if you intend to cut primarily solid wood or non-ferrous metals, which creates significantly more vibrations, then you will definitely want the additional dampening ability of a cast iron frame, such as the Onsrud "Super Duty" Series. You'll quickly find that the cast iron frame design will not only contribute to the overall weight, mass, and rigidity of the machine, but will also promote faster feed rates, better finishes, longer tool life and less maintenance. A cast iron frame design will usually cut much deeper per pass and machine much faster while maintaining a better finish. It will simply out-produce all other designs and make more money for you in the process. Take a look at the most expensive and productive model offered by any "high-end" CNC router manufacturer. It will almost always use the same cast iron, Twin Table, Fixed Frame design as the C.R. Onsrud "Super-Duty" series routers.