Display Connection

Simplicity of CAD/CAM Software, CNC Router Is
a Profitable Surprise

By Dave Salverson - Production Manager
Display Connection, West Chicago, Illinois






















Switching from a pin router to a CNC router has cut the time required to produce point-of-purchase displays by up to 80% while substantially improving their appearance. The major drawbacks of the pin router are the lengthy period of time required to build the pattern and the difficulty of following the pattern when cutting the display, which leads to inaccuracies. The CNC router makes it possible to define the geometry of the display on the computer in a fraction of the time required to build a pattern. Once the geometry is defined, it can be produced with perfect accuracy without relying on the operator. The use of CAD/CAM software and the CNC router originally appeared daunting to a small shop with no automation experience, but the simplicity and ease of use of this technology was a pleasant surprise. It is now possible for Display Connection to easily beat the prices, quality and delivery time of competitors who still mainly produce displays by hand.

Display Connection produces wood, plastic and laminate point-of-purchase displays, prototypes and models. In the past, the company produced these products with a pin router. Layouts for these parts were produced in actual size on a piece of paper on the pattern material itself. Either a bandsaw or jigsaw was then used to cut the pattern along the layout line. The pattern was then fastened to the actual material so that it could serve as a guide for the router.

One problem with this approach was the amount of time required to produce the pattern. Another was that any inaccuracy in the pattern or in the way that the operator followed the pattern was immediately transmitted to the finished part. The pencil line itself produced a built-in error that limited the level of precision that could be achieved. If the customer wanted to make a change in the part, it usually meant that the pattern had to be rebuilt from scratch. The pin router was also poorly suited to certain types of displays such as a design with a large number of cut-out shapes. Each shape required that a hole be drilled and the router bit dropped into the hole to finish out the shape, a difficult job for all but the most experienced workers.

Display Connection executives realized that CAD/CAM technology could alleviate some of these problems, 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 Series III PC-driven CNC wood router (Techno, Inc., New Hyde Park, New York) 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.

Working area for the router is 56" x 96" and Z-axis height options range from 4" to 19". Table technical specifications include a rapid travel rate of 200" per minute, a Z-axis cutting force of 200 lbs. maximum, 0.0005" resolution and repeatability and 0.003 inches/ft. absolute accuracy. The system includes the Mastercam® CNC programming system (CNC Software Inc., Tolland, Connecticut) which, although originally designed for metalworking, is ideally suited for point of purchase displays because of its ability to generate the most complex contours with little programming effort. The program features true 3D geometry construction plus IGES, DXF and CADL converters so that geometry can be uploaded from nearly any CAD system.

Now, the company uses the CNC programming software to define the geometry for the display. This takes far less time than is required to produce an equivalent pattern. Better yet, the computer program draws perfect lines and circles and allows geometry to be copied, moved, rotated, and so on with perfect accuracy. Once the geometry is defined, it can be precisely cut with the operator only needed at the beginning to load the router. If the customer makes changes, they can be easily incorporated into the program. The changes can usually be made in minutes on the screen and a new display cut directly without having to spend hours creating a new pattern.

A 25" wide x 18" high display has 4 rows of 10 triangular holes that are later filled with golf clubs. Producing this type of display with a pin router was difficult because it took a long time to set up a drilling jig and the operator had to follow the pattern very carefully to avoid jumping the pin. It took about 2 hours to build the pattern and 15 minutes to drill and route each hole. With the pin router, it takes only 10 minutes to produce the pattern using CNC programming software. One of the reasons this goes so fast is that the operator only has to draw one triangle, copy it nine times to create one row, then copy the row three times. Each hole can then be produced in 5 minutes by a relatively inexperienced operator.

Another typical display produced by the company requires a large script letter. The problem in producing this letter with a pin router is that it has several thin spots where, if the operator isn't very careful, the pattern will start to vibrate and produce a rough cut or even knock the pin off track and destroy the material. It took several hours to produce the pattern and 15 minutes to drill and route each hole with the pin router. It takes only 10 minutes to produce the pattern using the CNC router and CAD/CAM software.

Display Connection recently produced 18,000 plastic meal holder displays for a fast food company with the CNC router. The company never would have received the job without the new router because cost and delivery time would have been too great. The CNC router made it possible to program the geometry in about one hour and then cut each piece in about 2 minutes with a bull nose end mill. A bull nose end mill is like a conventional square end mill except that it has radiused corners.

The Techno router has a positioning accuracy of +0.1 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 Display Connection 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" 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 screw. This rolling contact also ensures longer life and greater rigidity during the life of the system because of the reduced wear as compared to ACME screws and nuts, which have a sliding friction contact.

In two years of operation, the company has never had any problems with the router. This is partly due to the strength and rigidity of the table. The Techno router is constructed from extruded aluminum profiles that can support all the materials that Display Connection uses and provides easy clamping capability. The router also 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.



















When Display Connection recently purchased a second and third Techno CNC router, it opted to have them equipped with a servomotor rather than stepper motor because it provides smoother curved cuts. 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. 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.

All in all, Display Connection has improved productivity by 200% to 1000% in producing a wide range of point of purchase displays and prototypes. Quality of the company's products has increased by a similar factor. Productivity gains of this magnitude have made it possible for the company to increase profit margins even while lowering its prices to its customers by as much as 50%. The relatively small investment in the CNC router and CAD/CAM software has provided a dramatic return on investment. The result is a dramatic improvement in the company's competitive position – it can do the job better, faster and for less money.