CNC Wood Routers Use Drive for Precision Control
- Friday, 01 December 2006
The woodworking industry is as advanced and under pressure to deliver high-quality goods quickly as any. One of the most versatile tools devised to quicken production with flat panels of wood is the wood router, used to rout (hollow out) an area in the face of a piece of wood, and used for 3D design, cabinets, sign making, molds, and general material cutting. The table-like device, similar to a metal mill, consists of a broad-based wooden hand plane with a narrow gantry-carried cutting implement projecting beyond its base plate. To guide its computer numerical controlled (CNC) ATC wood routers, WartHog CNC (Soddy-Daisy, TN) turned to YET US’s (Manchester, NH) XtraDrive servo drive system, integrating it into the routers’ precision and power controls.
YET envisioned the XtraDrive to address position error issues that precision design companies such as WartHog CNC commonly encounter, and developed a position control method, non-linear control technology, to reduce positioning inconsistencies than can occur during motion and operation. WartHog CNC, whose parent company is LA Enterprises, sells its products on the idea of ease-of-use, and the drive’s simplified structure contributed to the idea of simplicity. The control loop of non-linear control technology is similar to that of a PID loop, and uses non-linear, adaptive feed-forward control algorithms to increase servo motion system precision. With non-linear control technology, position and velocity loops of conventional drives are integrated and divided into four branches, with variable function applied to each branch, which in turn increases gain. The drive’s adaptive control structure compensates for re-tuning by accommodating for changes in the load requirements. The same technology reduces tracking error and settling time in the WartHog routers. WartHog’s routers, including the ATC, also feature particularly strong motors, and needed an appropriate drive. All WartHog CNC wood routers are equipped with YET’s XtraDrive, using the drive as part of the positioning control system, located in the enclosed control panel that sits on the front of the machine.
The drive sends information to and from the router’s motors to determine the position of the cutting mechanism, power needs, and corrects for position error that come from different grades and grains of wood. A wood router is controlled similarly to a metal mill, but with computer-aided manufacturing (CAM) software designed specifically for wood routers that account for a single sheet of material having different densities (wood grains, tree rings, knots, or burls) within it. Drilling (bit-speeds go up to 24,000 rpm) can be done on the X or Y axis, from either side or end of the workpiece, allowing the piece to be carved on all four edges as well as the top surface. The wood router “holds down” panels via suction/vacuum devices, or with pods that lift the panel above the worktable (such would be done in with edge profiling), or for pieces made of solid wood and where a larger degree of production flexibility is needed. It is not uncommon for wood routers designed for cabnet-making to have a number of drill bits that can come down as one or separately. Using a spacing system called the “32 mm System,” the drills are usually spaced 32 mm apart.
Each WartHog CNC wood router is customized to specific dimensions dictated by the customer, who may ask for differently sized spindles, cutting areas, and clearance height. Nevertheless, there are three basic ATC “types,” all of which have a machining speed of 2,000 inches per minute. The standard wood router, the WartHog ATC, has a 5 × 10' cutting area, but comes in a smaller version, the 18 × 18" cutting area “Piglet,” designed for personal use or small signage, and the larger “Hog” model, with a cutting area of 10 × 20' and allover dimensions of 12 × 24'. Specifically made for the housing industry, the “Hog” is designed to manufacture up to 18' stair stringers — the side supports of a staircase whose cantilevers support the individual treads (steps) and must match perfectly to be a successful construction. Using the Hog, a pair of stair stringers can be cut in two and half minutes, whereas a single handcrafted stringer can take half an hour. The larger CNC routers such as the Hog are often used for “nest-based manufacture,” in which multiple components are cut from a single sheet of material.
The WartHog ATC can be programmed with multiple tools, and comes with 10 tools already set as a standard. The ATC is able to “pick up” the various tools with the ability to recognize their intent, allowing users to start and complete a project without having to stop to modify the router. The cabinetry, signage, and woodworking industries have been traditional operators, but WartHogs have advanced outside their original market. With no modification to the drive, WartHog’s routers are being used to cut or etch aluminum, rubber, polyvinyl chloride plastic (PVC), medium-density fiberboard, ice, and foam. Providing it can fit in the collet, any cutting bit can be used; with further customization (such as the addition of lathes or lasers), etching motorcycle paneling, 3D design, cutting industrial-grade felt, and carving out molds have also been accomplished by the ATC.