CNC ArticlesPhone: 516-328-3970www.technocnc.com127A scaled model of the Technodome project.A Techno router can help create models in various plastics, woods and composites.CNC equipment. The first was heavy and expensive machining centers primarily designed for metalworking. They would deliver the accuracy he needed, but the smallest machining centers start at $30,000 and machines in this price range have working areas that are too small for all but a fraction of McCann’s work. A machining center with a table large enough to handle nearly all his work would cost in the $100,000 price range, considerably more than he wanted to spend. McCann ruled out most routers, on the other hand, because they could not provide the accuracy he needs. Then McCann heard about the Techno CNC router, which provides the best of both worlds. For the price of $45,000, PMAMI got a 49-inch by 40-inch working area and z-axis travel distance of 6.5 inches – large enough to produce most architectural model parts.Another reason McCann chose the Techno machine was that even though it was one of the more affordable CNC machines, it had a number of high-end features that would allow it to produce parts with the level of the accuracy PMAMI’s work required. For example, each Techno router is constructed from extruded aluminum profiles. It has four ground and hardened steel shafts and eight recirculating bearings in each axis. This shaft-and-bearing system produces very smooth, play-free motion and an extremely rigid system that produces high-quality cuts. The machine also uses antibacklash ball screws. These screws have excellent power transmission due to the rolling-ball contract between the nut and screws. This type of contact ensures low friction, low wear, and long life. The ball screws also make it possible to produce parts to the machine resolution of 0.0005 inch.The first step in cutting the roof molds for the Technodome model was to import the architect’s AutoCAD 2000 file into the CNC programming software that comes with the Techno system. Originally designed for machine and cutting all the roof molds took two weeks. Accuracy and Other Benefi tsIn addition to saving three weeks on the construction of the roof, the use of the CNC machine gave PMAMI a level of accuracy that would have been impossible to achieve by hand. That was important in this project, which was built as 13 separate sections because of its size. When it was time to put all of the sections together, the roof pieces matched perfectly, saving the fi rm the rework that would have been needed otherwise. The customer was very pleased with the model, which also included a detailed interior complete with lights. McCann has found that many projects benefit from the combination of laser cutting and CNC machining. “The laser is perfect for cutting 2D pieces, while the Techno handles the 3D pieces without the mess of cutting and sanding,” McCann explains. “As we use the CNC machine more, we’re fi nding that it really eliminates the aggravation we used to have with some of the more complicated 3D parts. We just do the programming, turn on the machine, and let it run.” Having the CNC machine has also opened up new business possibilities for PMAMI, including signs and prototypes. “It makes us a lot more versatile and sets us ahead of pretty much everyone in the area,” McCann adds. On the Technodome project, the use of the Techno CNC machine generated a savings of at least three weeks in the production of the roof molds. In addition to the difference between the cutting time on the machine versus carving by hand, additional time was probably saved by the accuracy of the finished pieces. The fact that all the roof pieces fit perfectly when the model was assembled eliminated the need for rework. For complicated 3D shapes such as the roof of the Technodome, PMAMIfinds the Techno CNC machine to be the perfect tool.metalworking, it is also well-suited for wood and foam because of its ability to generate the most complex contours with little programming effort. In the programming software, McCann separated the roof from the rest of the architect’s model. Since it was a 3D wireframe model, he needed to add surfaces to the outline of the roof because the toolpaths would be derived from the surfaces. Next, he divided the roof into different mold shapes that could be used to form the acrylic pieces. Most molds produced multiple acrylic pieces. Once this preliminary programming work was done, McCann gave the command to software to create the toolpaths for each of the molds. After supplying some additional information such as feed rates and cutting speeds, the system was ready to go. For each mold, a piece of Renshape, MDF, or a plaster block was placed in the Techno machine. An operator hit the “start” button and the 3D mold was carved automatically. The actual cutting took only about one hour for most of the molds. The entire process of programming the CNC
