Woodworkers Can Expand Business by Using Computerized Router
By Ed Krieger
President
Designer Woodworking
Manhattan, Kansas
Designer Woodworking, a custom wood working 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 wood working 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 efficiently 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
computerized 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 computer-controlled
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, is the
simple matter of loading a piece of wood and pushing a few buttons to
start the machine.
A recent project involving a custom walnut door offers a good comparison
of the computerized 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 computer-controlled 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 required if done
manually.
The Techno machine 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 servo motors. 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 ballscrews also make it possible to produce wooden
parts as accurate as the machine resolution. The ballscrews 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 servo
motor rather than stepper motor because a servo motor 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 servo motor 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
servo motors 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 machine
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 machine 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 machine/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.
For
more information contact: Techno, Inc., 2101 Jericho Turnpike,
New Hyde Park, NY 11040.
Phone: 516-328-3970 Fax: 516-358-2576 E-mail: TECHNO
CNC ROUTER SYSTEMS