Designer Woodworking

Woodworkers Can Expand Business by
Using a CNC Router

By Ed Krieger - President, Designer Woodworking
Manhattan, Kansas

















Designer Woodworking, a custom woodworking business near Ft. Riley, Kansas, now takes on jobs it wouldn't have wanted in the past. Tricky one-of-a-kind restoration projects and intricate architectural milling work that used to take too much time to be profitable have become a source of growth and profit. By completing difficult jobs like these in hours rather than days, the company makes a profit on them yet keep its fees in the range the customers can afford.

Designer Woodworking is one of the latest woodworking businesses to benefit from automation, although not in the large-scale, mass-production sense of the term. The company still does mostly one-of-a-kind jobs, but by doing them on a computer-controlled router, its level of efficiency matches that of mass-production operations. This efficiency has opened a wealth of new business opportunities as a result.

In business for 10 years, Designer Woodworking specializes in restoration, of both antiques and also modern furniture that has been damaged during moving or by excessive use. In addition to restoration work, which makes up about 75% of its business, Designer Woodworking also does woodwork for local architectural projects. Examples include stair rails, custom redwood screen doors to match decks, unique moldings, and so on. For both types of projects, the company formerly lost some jobs and didn't bid on others in situations where too much time was involved to make their work cost-effective.

















Typically, the problem was curved pieces. Prior to acquiring the CNC router, things like curved moldings in restorations and stair rails with sweeping curves were very time-consuming. Designer Woodworking personnel worked from templates and in some cases, just getting the template right took many tries. Following the templates, they cut the pieces by hand, but since hand cutting was imprecise it was usually followed by a great deal of sanding.

In January, 1995, Designer Woodworking purchased a CNC three-axis gantry router from Techno, New Hyde Park, New York. The router cuts according to instructions from a CNC programming package called Mastercam® from CNC Software, Tolland, Connecticut. Once a program is generated, producing a part, even one with curves or ellipses, it is simply a matter of loading a piece of wood and pushing a few buttons to start the router.

A recent project involving a custom walnut door offers a good comparison of the CNC router versus Designer Woodworking's previous hand practices. The door was a narrow solid door designed to be placed between a shower and a hot tub room. The designer wanted the door to contain an ellipse-shaped inset starting at about two feet from the floor and going up to about six inches from the top of the door. The door itself was 1.5 inches thick; the inset panel was 3/4 inch thick.

Without a computerized method of cutting out the ellipse shape, Designer Woodworking would have attached a pattern to the door to guide the cutter. With the cutter's ball bearing riding against the pattern, the operator would have cut out the shape. The greatest difficulty was making the pattern perfectly. Typically, a number of tries would have been needed to get it right. In all, just making the pattern would have taken at least one day.

With the CNC router, creating the shape of the ellipse in the computer, then instructing the system to program the instructions

for cutting took between 15 and 20 minutes. Another 15 minutes were needed to set up the door on the table, so that within an hour Designer Woodworking was accurately cutting the ellipse. Because the computerized router eliminated at least seven hours on this project, Designer Woodworking's price of $800 was acceptable to the customer. Working by hand, the company would have charged between $1200 and $1300 and probably wouldn't have gotten the job

The efficiency made possible by the router has allowed Designer Woodworking to take on all kinds of jobs that previously weren't profitable. For example, the company is often asked to repair Schrunk wall units that local soldiers bring back from Germany. These units have crown moldings that often get broken in transport. The sweeping curves in the moldings made this a difficult job in the past, but they are now easy to reproduce. Similarly, Designer Woodworking sees a lot of broken rockers on rocking chairs. These, too, had been difficult items to make profitably by hand due to their long curves. But it takes only a few minutes to program rockers on the computer. The actual cutting takes only minutes, as well, so that Designer Woodworking can handle a few dozen rocking chair repairs each week.

Although the efficiency made possible by the router has been key to winning new business, Designer Woodworking also finds that the greater accuracy they can now deliver also helps win work. In the past, the company didn't bid on projects like a 30-slot mail insert for a roll-top desk because dividing the area into 30 slots of identical size would have been nearly impossible by hand.

Using Mastercam® for this project, the operator simply created a line of the desired width, 1.5 inches, duplicated it 30 times, and then used the resulting geometry as the basis for the toolpath. This took about 15 minutes. Grooves for the dividers in both the top and bottom halves of the insert met perfectly and each slot was exactly 1.5 inches wide. Cutting took between 30 to 45 minutes compared to three hours by hand, but results would not have been nearly as accurate. The entire job took about eight hours, which included finishing and installation in the desk. This was about half the time this project would require if done manually.

The Techno router has a positioning accuracy of +.1 mm (+0.004) in 300 mm and a repeatability of +0.01 mm. Since this is far greater than hand cutting, manual finishing operations are minimal. This also cuts down on the time Designer Woodworking must allot for its projects.

The accuracy of the router is the result of several features inherent to the table, such as the use of ball screws and servomotors. For example, anti-backlash ball screws in Techno routers permit play-free motion that makes it possible to produce circles accurate to the 0.0005 inch machine resolution. These ball screws also make it possible to produce wooden parts as accurate as the machine resolution. The ball screws have excellent power transmission due to the rolling ball contact between the nut and screws. This type of contact also ensures low friction, low wear and long life.

Designer Woodworking opted to have its router equipped with a servomotor rather than stepper motor because a servomotor gives smoother cuts on long curves. Normally, when a router hesitates, it either cuts too deeply or burns the wood. When working on a long curve like the ellipse in the walnut door, it is important for Designer Woodworking to have a continuous motion to prevent this. A servomotor is better than a stepper motor in providing continuous motion because it works on the principle of constant feedback. The program tells the router to follow a specific path by giving it a series of voltages. It drives to the locations by getting constant feedback along the way. In contrast, a stepper motor takes a large number of little steps.

Stepper motors have significantly less power than servo- motors to change direction and follow curves. Stepper motors are less expensive than servomotors and are fine for straight line motions and simple circular arcs. But, in general, servos are up to three times faster and more reliable when performing arbitrary curves like splines or 3D carvings.

Designer Woodworking enhanced the functionality of its Techno router even further by adding a Carter flip-pod vacuum piece-part holding system to the table. Designer Woodworking's table has 87 pods, into which any pattern can be utilized to align and hold pieces for cutting. The pod pattern is cut (on the Techno router itself) out of UHMW plastic, assuring accurate alignment of the x-, y- and z-axis. The pods serve dual purposes; they act as vacuum pods to hold work and they can also be used as fixed stops for locating edges of parts. If the pod is not needed for either function, it can be flipped so that its top sits flush with the table and is out of the way, allowing the operator to rout around edges or through boards while the piece is held on the table.

The accuracy provided by the router / vacuum table combination came in handy when cutting the ellipse out of the walnut door. The door was so long that it exceeded the length of the machine but Designer Woodworking was able to cut half, flip the door over, and cut the other half. Both sides matched perfectly. Another advantage of the Carter system is that it makes it possible to set up very quickly. It isn't necessary to make jigs or spoil boards to hold parts. This helps Designer Woodworking price jobs like rocker repairs competitively.