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Carpentry and CNC Milling
CNC Routers Help Carpenters Win New Business,
With the Techno 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 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 CAD/CAM 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.
Culin & CollelaCulin & Collela, Mamaroneck, New York, produced miles of curved moldings and other custom millwork using a Techno CNC wood router in 4000 hours, approximately half the time it would have taken using traditional methods. The router also improved the accuracy of the work by a factor of ten, helping Culin & Collela deliver curved moldings, cabinets, and bookshelves that drew praise from the architect on the project. Creating large curved wood pieces by hand would have meant making a trammel and physically swinging an arc to figure out the radii of curves. Instead, Culin & Collela created shop drawings in its CAD system, then transferred the CAD data to the router's CAM system to create toolpaths for the router. The Techno router then generated the highly accurate fiberboard templates, knife grinding templates, and cauls needed for the project. A caul is a template used for bending that clamps wood into a curved shape.
Culin & Collela occupies a 12,000 square foot building in Mamaroneck, New York. The company was formed when its president and vice-president, who each had a custom furniture business, met, married and later merged the two businesses. The company employs 23 people and has recently been doing work at the Conyers Farm development outside Greenwich, Connecticut. This is an exclusive enclave of multimillion dollar homes on lots of at least 10 acres.
One of Culin & Collela's recent jobs was the woodwork for a 25,000 square foot house with a curved front wall. Culin & Collela produced the entire interior molding package, which included miles of curved cornice molding, baseboard, and chair rail, as well as wainscot paneling for the curved front wall. Every piece of the molding in the house had a custom profile designed by the architect. In all, the house had at least 150 different molding profiles. Culin & Collela also created the entire kitchen package for the house. This consisted of natural cherry cabinets with curved doors, as well as the wainscot paneling in the breakfast room. Other work for this house included a curved bookcase for the library, a chestnut wainscot wall and chestnut tongue-and-groove ceiling in the family room, and a spiral staircase with wainscot paneling that went up three stories to the children's living area.
Creating curved woodwork using traditional methods presents several challenges. Typically, a template is cut from a piece of fiberboard, either by hand or with a router, and then parts are trimmed flush to the template. The template must accurately depict the radius of the curve. Drawing the radius requires the use of a trammel or beam compass, and building one of these is a big undertaking for larger wood pieces. If a particular piece of wood needs to have a 50-foot radius, for example, someone has to take a 50-foot length of wood and put a point at one end and pencil at other end, then physically swing the arc to get the proper curve.
Curved kitchen cabinets present additional challenges. Not only must the doors be curved, but the box of the cabinet, face frame, styles, and rails must also be curved, and they all require different radii to fit together perfectly. For example, assuming the curve of the cabinet is concave, interior parts such as the box must have one radius while parts farther out such as the door must have a larger radius. The kitchen cabinet doors for the Conyers Farm house had a 45-foot radius. With this large radius it wasn't obvious that the doors were actually curved. If they had not been curved, the installed cabinets would have had a faceted appearance. To draw the different radii for these cabinets by hand would have required using the 45-foot compass and then adjusting the resulting radius for each cabinet part.
Culin & Collela executives realized that CAD/CAM technology could alleviate some of this work, but when they looked at computer-controlled woodworking machines, they saw prices in the neighborhood of $60,000. That was impossible to justify at the company's current workload. Then the company heard about the Techno CNC wood router, which costs less than $16,000 and is designed for production routing and drilling on a wide variety of materials including wood, plastic, MDF, solid surfacing materials and nonferrous metals.
By using this router, Culin & Collela has greatly simplified the process of producing complex curved millwork. The router works in conjunction with the company's AutoCAD design software (Autodesk, San Rafael, California). They export AutoCAD files, which contain accurate curve radii for all parts, to CAD/CAM, generate CNC programs, and produce templates and finished parts on the router. Production time has been reduced by an average of 50% on the items produced by the router. And, quality has been substantially improved because the computer-generated programs provide far more accuracy than the company was ever able to achieve with manual methods.
The process Culin & Collela followed started with the creation of shop drawings in the AutoCAD system and submitting them for the architect's approval. Once that was done, a full-time employee worked with the production manager to determine what templates and cauls were required for what operation. That employee then took the appropriate drawings from the CAD system and transferred them to CAD/CAM to generate all the toolpaths required to create those templates and cauls. The CAD/CAM work took about 200 hours for this house.
They used the router to make two types of templates: fiberboard templates for use with the shaper and knife grinding templates. Knife grinding templates are used to create the knives that go into the molder head and cut the profile of the molding. Molding knives are only as good as the template, so the CNC router was important in this project to get a high degree of precision. After templates were created, they were taken to the molder or the shaper to cut the actual part. The molder was a Weinig Profimat four-headed molder with automatic head positioning. The shaper was an SAC 10 hp tilting arbor shaper capable of profiling edges of curved pieces and trimming on a curve. The cauls used in this project held strips of solid cherry molding in a curved shape while the glue that held them together dried. The router was used to cut all the ribs and parts for cauls so they had the exact radius needed.
CNC enabled them to produce knife grinding templates in one-third the time needed by hand, or about 20 minutes/knife template vs. one hour by hand. In all, producing the curved millwork for this house took approximately 4000 hours, which Culin & Collela estimates would have been closer to 8000 hours without the Techno CNC router. In addition to the time it saved, the accuracy of the router won Culin & Collela high praise from the architect for the quality of their work.
The CNC router concept is clearly an idea whose time has come in the carpentry business. It makes it possible to improve the quality of many products by allowing complex geometries to be produced to a high level of accuracy. At the same time, costs are reduced because of the elimination of time-consuming hand work. Best of all, the Techno routers are available at a fraction of the cost of traditional CNC machining equipment.