Most of the operations performed by routers are the same as those performed by milling machines. They both cut stock away from its original form. They both can slot, mill, drill, ream. Both machines can be equipped with as many or as few programmable axes as the other. I’m not sure how the two terms came into being or how the two machine types differ from a technical perspective. But the word on the street is that routers were originally made for lighter stock removal, requiring less horse power, less accuracy, and less capability to perform multiple types of cutting, compared to a milling machine. On the other hand, routers would typically cut faster and handle larger parts (usually “flat stock” like sheet metal, plywood, plate, and various types of plastic sheet).
In the woodworking world, cabinets, molding, furniture and other large ornamental parts helped drive the commercial development of routing machines. Because many of the jobs that needed stock removed started as 4’ x 8’ plywood sheets, their geometry dictated the machines design. The machine needed a large table or platform upon which to place the sheet. Then, edging, grooving, milling, slotting, and conventional routing would be performed from above. Key requirements for the machines utility included lots of clearance to enable placement and repositioning of the sheet and a spindle that could access all points on the sheet with a cutter. Either the table or the spindle or both would need to be movable/programmable. Introducing: the gantry rail design.
But we know that a gantry style machine is not exclusive to high speed, light routing operations. Some of the most complex, expensive machines, are gantry style milling machines and planners. So what is the difference between the routing machine and the milling machine or machining center? The most obvious differences come down to overall rigidity, accuracy, and spindle design. Routers are designed for lighter duty, high speed, less hard stock removal requiring less critical tolerances. Milling machines are designed for heavier hard metal cutting, requiring tighter tolerances.
C. R. Onsrud started building routers for the woodworking industry, first. During WWII Onsrud routers were used to produce metal parts on most aircraft used by the military. Soon the demand for large metal part machining moved Onsrud into the milling and machining center business. Because the gantry concept is as viable for cutting ferrous as non-ferrous metal, and Onsrud had already established the gantry design in thousands of applications, the gantry style machine concept was expanded to accommodate heavy milling applications, by using cast iron, high torque motors, HSK style spindles, tool changers, through-tool coolant systems, etc. Due to the flexibility of the gantry style design much higher productivity was easily achievable through the introduction of multiple spindles mounted to the gantry rail.
What’s the difference between routing and milling machines? Not the machine style. Routing machines and milling machines can look the same. By sticking with their original gantry style machine as they transferred their routing technology to the field of milling, Onsrud leveraged an established design and creates a more productive option for many milling applications.
A high production application on a customized six-spindle machining center is featured in the video.