Switching from conventional power tools to a computerized numerical control (CNC) router helped reduce the time to produce automated wet process machines from 1900 to 1000 hours. Poly Design was able to reduce its price for a three-position automatic transfer machine that cleans cassette boats filled with CD-ROMs or semiconductor wafers by 25% to $275,000 while increasing its profit margin. For example, in the past it took five days to cut the parts for the eight cassette boats used this machine and two days for assembly. The CNC router automatically cuts the parts in only four hours and its accuracy is so much higher than power tools that assembly time is reduced from two days to one day. The time savings for producing one machine (1900-1000=900 hrs.) more than pays for the router at any reasonable hourly labor rate.

Poly Design produces a wide range of clean room equipment including wet process stations, equipment for process stations, stainless steel fixtures, and quartz cleaning stations, desiccators and storage cabinets, chemical transporting carts and benches and work tables. Each unit produced by the firm is designed to solve a specific application problem and no two units are exactly alike. While some applications require the design of an entirely new assembly, most need only a minor modification to one of the company’s broad line of existing products.

Automated transfer machines

One of the firm’s more popular products is automated transfer stations designed for cleaning cassette boats. These machines replace a slow and difficult manual process in which components are loaded into boats and then dipped into a series of several tanks filled with cleaning fluids. The boats, which weigh about 16-pounds when fully loaded, must be held submerged in three different tanks and shaken for about 10 minutes in each order to thoroughly clean one load. One operator is able to process about 200 parts every hour using this approach and the job has a potential risk of repetitive stress injury.

Poly Design has automated this cleaning process with a transfer machine that provides superior cleaning and a cycle time of only 4 minutes. This machine processes 1500 units per hour and the danger of injury is eliminated by the fact that rather than continuously dipping and shaking the boats, the operator only needs to load a boat onto the machine every 4 minutes. The machine also includes a wet loading area that holds four runs at a time, a filtered and re-circulating heated acid bath, two quick dump rinsers, a stainless steel ultrasonic cleaning tank and a wet unload area that also holds four runs.

Acid bottle cart produced by Poly Design
Plastic machining
Each station is 4.5 feet wide, 12 feet long and 7 feet high. The majority of the machine, including the cabinets for each station, the shell tanks and the baskets, is machined from polypropylene, although the boats are made of polyvinylidene fluoride (PVDF). These types of plastics are used because they are corrosion-resistant and do not emit particles that might contaminate electronic components. In the past, the panels and other components used to build the cabinets and tanks were machined using table saws, routers and hand saws. This was a time-consuming manual process. It took one person about 40 hours to cut out and prepare the parts for the eight baskets used for one machine, for example. Cutting out all of the components needed for one machine took about 900 hours.

The polypropylene components are assembled using a Laramie welding gun that directs heated air onto the joint. First, the joints are tacked together with the welding gun, and then triangular polypropylene welding rod is melted into the joint to create the final weld. The relatively poor accuracy of the power tools used in the past meant that a considerable amount of touchup work and hand fitting was required during the assembly process. As a result, it took three to five people about 900 hours or a total of about 3600 hours to assemble and test the machine.

Innovative router

In an effort to reduce the amount of labor required to produce these machines, Poly Design managers evaluated a number of different CNC machine tools. First, they considered conventional machining centers but they discovered that the cost of a machine large enough to handle the 4 foot by 8 foot sheets used to produce the components would have been around $200,000. Next, the company looked at a new breed of gantry routers that interface with CAD systems, have a large cutting area, and a relative low price. These machines are not capable of handling heavy cuts in ferrous metals, however, they can handle heavy cuts in plastic and wood and light cuts in metal which made them ideally suited for Poly Design’s workload.

Poly Design managers looked at several machines of this type and ended up purchasing the Techno Series III from Techno, Inc., New Hyde Park, New York. The selected this machine because it offers an unusually good mix of accuracy, size and price. The machine's 0.0002 inch resolution and repeatability and 0.003 inch/foot absolute accuracy ensure that plastic components are faithful representations of the designs created on the computer. The machine’s working area of 59 inches by 102 inches with a Z-axis height of 8 inches is large enough to handle everything that Poly Design makes. The price is less than $42,000 and includes CNC software used to program the machine.

Computerized machining

Now, the firm’s engineers begin the design process by using the FastCAD or AutoCAD Lite software to sketch out their design on the computer. By manipulating their model on the screen, panning, zooming and rotating, they are able to validate all critical dimensional relationships before they even begin to cut plastic. To provide a final validation step, they put a marker in the machine spindle and used it to trace the outline of the program on poster board. Once the components for a machine are designed, they are nested together onto a 4 foot by 8 foot pattern to minimize waste. This optimization of the nesting process has saved a considerable amount of material relative to hand nesting.

The Techno router cuts out the parts considerably faster than the previous manual process. It takes only 4 hours, for example, to cut out the parts for all 8 baskets for one transfer machine. All of the components needed for a machine can be produced in only 100 hours of cutting, a reduction of about 89% compared to power tools. Further savings have been achieved because the machine does not even require the continuous presence of an operator. The operator typically performs some other operation nearby. When the machine completes all the components nested on one sheet, the operator loads a new program and a new sheet and restarts the router.

Greater accuracy

The Techno machine's accuracy 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 permit play-free motion that makes it possible to produce accurate circles and inlays. 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.

Faster assembly

The much higher level of accuracy achieved by the router saves a considerable period of time during the assembly process. Everything fits together perfectly, so the need for manual finishing and fitting has been eliminated. As a result, two people can assembly and test a machine in only 700 hours. The total assembly time is only 1400 hours, a 61% reduction. Besides these time savings, the quality of the finished machine has been improved. Customers notice that everything fits together better and opens and closes more smoothly. Servicing the machines built with the router has also become much simpler since the components are now all interchangeable.

As a result, Poly Design has been able to reduce the cost of their wet process machines by 25% while actually increasing the firm’s profit margin. While the firm originally targeted these machines at producers of CD-ROMs, their high quality and low price has made it possible for the firm to enter the market for cleaning semiconductor wafers. The Techno machine has provided outstanding service, requiring nothing other than minimal preventive maintenance in six months of near continuous operation. The dramatic improvements in cutting and assembly provided by this machine contrasted with its low price means that it easily pays for itself every month.

A more efficient airfoil design combined with computerized manufacturing technology is helping professional windsurfer racers improve their performance. The author is a former aerospace engineer who applies optimized aerodynamic profiles to the fins of windsurfing boards which are critical to their racing performance. Accurate machining is critical to the success of this approach and it was achieved by using an inexpensive CNC gantry machine that produces the fins to a much higher level of precision than conventional manual methods.

High performance windsurfing boards, which are generally 7'8" to 9'4" long, operate normally in a planing condition with only the rear one-fourth to one-third of the board touching the water. This makes it impossible to use a centerboard like that used in a sailboat to counteract the side force of the sail. The only device providing counterforce is a small fixed fin at the rear of the board. The side force provided by the fin stabilizes the board and balances most of the side force generated by the sail under normal operating conditions. By allowing the use of larger sails in higher winds, the amount of balancing side force generated by the fin controls indirectly the level of attainable forward speed of the sail board. In many cases, the performance of this fin is the most significant factor in determining the overall performance of the board.

The fin operates in much the same manner as an airplane wing. However, unlike the wing of a conventional airplane, the fin must work in both directions. In this respect, it is similar to the function of wings used in certain fighter and aerobatic airplanes that are designed to fly equally well upside down. While racing windsurfing fins have traditionally been designed by trial and error, it occurred to the author, who worked for 14 years as an aeronautical engineer, that optimized airfoil designs which have been developed for aircraft could be transferred to sailboard fins with little or no modification. Many of these designs were developed by the National Advisory Committee for Aeronautics (NACA), the predecessor of the National Aeronautics and Space Administration in the first half of this decade.

The problem in implementing this idea was how to produce these airfoil designs to the required high level of accuracy. Fins for mass produced windsurfing boards are produced from injection molded plastic. These fins are not used for high-performance boards because the injection molded fins change their shape slightly as they cool. These small changes can drastically reduce the performance of the board.

Fins for high performance boards are traditionally produced by far more expensive manual methods. An experienced craftsman begins by building a series of templates that describe the contours of the fin. The craftsman then uses these templates as guides in producing the final form with a hand grinder. It typically takes about a day to make a high performance fin. The accuracy of this approach leaves much to be desired so it is necessary to test the fins in the water to determine whether or not they are effective. A top name competitor will typically accept 2 out of 10 fins produced by these methods.

When the author originally developed the idea of building fins according to optimized aerodynamic profiles, he assumed that it would be necessary to build them using conventional manual techniques. While, as explained before, these methods are quite expensive, an even greater problem in this case is their lack of precision. Precision is much more important on fluid dynamic profiles because they are more sensitive to minor dimensional inaccuracies which can cause the flow to separate from the fin, suddenly reducing the side force and, in extreme cases, causing the board to suddenly shoot sideways ("spinout").

It was no secret that much greater accuracy could be achieved with CNC machining but this alternative was not given serious consideration because it was assumed that the machinery and software required to implement this technology would cost at least $100,000. Unfortunately, the market for fins for high performance sailboards is not large enough to justify this expenditure. Bernie Brandstetter, a former Worldcup racer and the first manufacturer of CNC-milled sailboard fins on Maui, introduced the author to the Techno-Isel machine.

Tectonics, Maui purchased a 3-axis CNC machine from Techno, Inc., New Hyde Park, New York, with the MAC100 controller for only about $18,000. This system has an accuracy of +0.1 mm (+0.004) in 300 mm and a repeatability of +0.01 mm (+0.0004). Techno machines have anti-backlash ball screws for play-free motion that make it possible to produce circles that are accurate to the 0.0005 inch 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. The ability to achieve this accuracy at a low cost made economical fin machining possible.

An aerodynamic reference book provides coordinates of the profile. These coordinates are then entered into the Mastercam™ CNC programming software package developed by CNC Software, Inc., Tolland, Connecticut, and provided with the Techno machine. The result is a plan view representation of the profile. The next step is scaling the profile to create 30 to 40 ribs that give the fin's planform its third dimension. The reference book provides the unit length of the profile used. The author wrote a BASIC program that generates an array of points for each of the ribs scaled to the cross sections of the fin's planform. The program produces its output in CadKey's™ CADLINK format which can be read by Mastercam. Mastercam reads these points as a series of splines. A surface is then applied to these splines using Mastercam's lofted surface feature. Another feature of the program, called synch, makes it possible to space the chain intervals closely at 0.2 mm for the first 10% of the profile where accuracy is the most important. Chaining intervals are spaced at 0.6 mm for the remainder of the curved portion of the profile and at 2.4 mm for the flat portion in order to save time generating the tool path and reduce the file size.

The milling machine makes it possible to produce fins to precise aerodynamic profiles at a cost that is less than the cost of hand-producing high performance fins. It takes about 4 hours to produce each fin. Feed rates are limited because the G-10 plastic material used, the same type of material used to produce printed circuit boards, is so tough. The material is supplied in half inch panels consisting of about 25 layers of fiberglass embedded under pressure in a plastic shell. A carbide bullnose endmill is used to cut this material. This tool is 3/8 inch in diameter, has 4 flutes, a 1/8 inch flat section around the centerline and 1/8 inch radius on each corner. It makes a smoother surface than the more common ball nose end mill.

The (NACA) 63A010 profile is one that has been found to provide excellent performance under a wide range of racing conditions. The maximum thickness of this profile is 35o back from the nose. Some modifications are required for aerospace profiles because they are designed for considerably higher speed operation than windsurfing fins. Tectonics, Maui uses a computational fluid dynamics program that lets them simulate the operation of the profiles at the 30 to 40 mph speeds common to sailboard racing. The gantry machine provides sufficient accuracy to make systematic dimensional changes that allow performance to be optimized. The most critical consideration is the prevention of the onset of turbulence, which causes a phenomenon similar to stalling in an airplane. The fin than loses its side force and the sailboard begins rapidly moving sideways. The accuracy of a computer milled fin makes it possible to reduce the wetted area of the fin by 10%, reducing friction drag and increasing the attainable speed of the board.

Many races have been won with fins produced by computing milling. Anders Bringdahl is only one of the well-known racers that have used the fins to beat their best previous times. Other fin producers have tried to copy these profiles using manual manufacturing methods and/or copy milling machines but found that performance is substantially reduced by machining inaccuracies. The aerodynamic profiles have also been used to produce molds, so far with mixed results due to uncontrollable shape changes (see earlier in this article), used to produce mass-market sailboard fins. All in all, computer milling technology is having a major impact on windsurfing by providing a better performing fin at a reasonable cost for the performance achieved..

About the author: Gerhard Opel is a retired airline captain and a former bush pilot, having flown in the Alaskan and Canadian arctic. He spent 14 years as an aeronautical engineer working on various U.S. and European transport and fighter aircraft. He holds a Graduate M.E. degree from the T.U., Vienna, Austria and a M.S.C. (ME) degree from the Massachusetts Institute of Technology. He is also an enthusiastic board sailor learning a lot from testing his own fin designs. He can be reached at 808-572-2294

A manufacturer of personal care products is saving money and reducing time to market by switching to a low-cost computerized numerical control (CNC) router that makes it possible to produce point of purchase displays internally. When contract manufacturers produced Kiss Products’ displays, there were delays in getting new designs to retailers and the cost of producing the displays was continually rising. Kiss made the decision to make their own displays and the company searched for an inexpensive and easy to use new router that provides the ability to produce plastic and wood components to high levels of accuracy. "With the router we can now design and begin to produce new display designs in a single day," said Mike Llewellyn, Shop Supervisor for Kiss Products. "The router has features normally found in more expensive machines like ball screws and servo motors that make it possible to produce a very professional looking product. We could afford a more expensive machine but we don't believe in throwing our money around. We are saving money and we can now turn on a dime to meet the changing requirements of the retail market." Ball screws have a number of advantages over racks. They don’t have the play or the requirement for adjustments that racks do, they also do not wear as easily as racks do and they are far less likely to get debris in the mechanism than racks to cause skipping and errant motion. Servomotors, unlike stepper motors do not "lose position" and cannot skip steps. Servos are also far better for 3D applications because they can change speed on the fly without losing power as steppers do.

Kiss is the world's largest manufacturer and distributor of professional quality nail products. The company originated in the lucrative beauty supply market. As the popularity of the products soared, distribution was quickly expanded to the mass-market arena. Capitalizing on this success, Kiss became the first company to bring professional nail care directly to the consumer, creating easy-to-use, all-in-one kits that make it possible to achieve salon results at home. Today, the Kiss line of professional products has expanded to include nail care, nail color, nail jewelry, nail art, and pedicure products. More recently, Kiss launched its second brand, called Broadway to allow women to achieve salon-like manicures at home, quickly and easily. Each of these ingenious products originated from Kiss's innovative thinking and vast salon experience. Kiss Products Inc. is located in New York just 20 miles outside of New York City on the exclusive north shore of Long Island.

Displays were outsourced in the past

The company’s products are manufactured in Kiss Products’ factory, then shipped to its Long Island facility where they are packaged. The company ships them to retailers with displays made of acrylic sheets that hold the individual products. The displays range from approximately 9 inches high, 8 inches wide and 8 inches deep to as much as 24 inches high by 12 inches wide and 8 inches deep and have either two or three tiers of shelves. The product is placed loose in the shelves and shelves are tilted backwards slightly so they don’t fall out. The shelves are held to the walls with acrylic solvents. The company frequently develops new styles of displays in order to accommodate a new product or promotion. In the past, some of these displays were built by subcontractors. One problem with this approach was that a considerable amount of back and forth was required in order explain the company’s concept for the display; get the initial prototypes right and then go into production. Another problem was that the cost of producing the displays was continually increasing.

Kiss’s local operation, called JC Solutions, had considered for some time the possibility of producing the displays internally but was unable to find a manufacturing method that met the company’s cost and quality requirements. "We first bought a table saw and a band saw but we didn’t like the results we were seeing," Llewellyn said. "The cut edges are displayed when the displays are assembled and the ones we were making were much too rough. We also had a lot of difficulty holding the tight tolerances that are needed to make a professional-looking display. The quality and appearance of the finished product depended on the ability and attention of the saw operator so the shelves produced by this method often just weren’t right. We were looking for CNC routers but the ones that we had seen were either expensive and complicated machines that cost $30,000 or so which was more than we could justify for this application. On the other hand, we also saw a lot of inexpensive routers but it was hard to believe that the light weight frames, the looseness of their rack and pinion drives and loss of position associated with steppers would produce the quality and accuracy we were looking for."

Then Llewellyn heard about Techno’s new low cost LC series CNC routing system. This machine provides a number of critical features that allow it to deliver accuracy to a level that has previously only been available from machines at a much higher cost. Ball screws are provided on all three axes, offering smooth motion, a high level of accuracy and repeatability, and minimal maintenance. A closed loop servo control system provides constant position feedback, higher power, and smooth continuous motion that eliminates the possibility of losing position in the middle of a part. The LC series machine includes a heavy steel ground stress relieved base and an aluminum T-slot table that can be easily converted to a vacuum table by installing the Techno vacuum table accessory kit. The machine comes fully assembled and includes Techno’s Windows-based CNC G-code interface with free lifetime software upgrades. The new machine is available in three sizes, with work envelopes of 30 by 24 inches, 50 by 48 inches and 50 by 96 inches. Each of these models provides a repeatability of 0.001 inches, a resolution of 0.0002 inches and a maximum speed of 250 inches per minutes. A wide range of optional equipment is offered including a laser scanning module, CNC lathe attachment, Porter Cable router, vacuum blower, and fourth axis rotary table. Best of all, the 4-foot by 8-foot model sells for only $13,995, a fraction of the cost of purchasing this capability just a year ago.

New in-house manufacturing workflow

"The Techno LC machine was the only one that had all the technical features needed to produce the quality we were looking for at a price we could afford," Llewellyn said. "Techno worked with us to help us get our process right for producing the displays for the new machine. Leon Moy, in particular, provided a great deal of help in specifying tooling and accessories for the machine and helping us get up and running." To begin with, the company’s designer creates a CAD drawing of a new display. The CAD drawing is then reviewed by the general manager of the company who reviews it and turns it back to the designer. The designer makes any necessary changes to the design, then he graphically nests the individual pieces required to make the display onto a 4 foot by 8 foot acrylic sheet and saves the resulting drawing onto a CD. Mitchell Cruz, the CNC operator, generates toolpaths, makes adjustments to compensate for the thickness of the sheet and creates a CNC program for producing the parts. He loads a new sheet onto the router, secures it with vacuum clamp to the table, uploads the program into the machine control and with the click of the mouse starts the machine. The machine then establishes the zero point for the Z-Axis, and then runs by itself for 30 to 120 minutes, producing enough parts for as many displays as is possible to nest onto an acrylic sheet. The operator, in the mean time, is able to walk away and perform other tasks while the machine is running. For example, he might spend the time flaming parts that were produced previously or breaking-up the acrylic left over from the machining operation which the company sells for scrap.

When the machining operation is finished, the operator then removes the pieces and then applies a torch to flame the cut edges to produce a glossy finish. Then he delivers to the pieces to the assembly department where operators put them together by applying acrylic solvent with a syringe. "The higher accuracy of the new machines means that every piece comes out perfectly," Llewellyn said. "The accuracy of cutting enabled us to develop a tab and slot construction in some of our displays which overcame some of the difficulties that assemblers were having in alignment of walls and partitions and provided better positioning in line bending. The new machine is also much faster than the power tools that we have tried in the past. The fact that it works without operator attention is another important advantage. Getting all these capabilities for such a low price means that we can now move the entire display manufacturing process in-house with all the advantages that that entails. The time required to respond to market trends by creating new displays has been cut to a fraction of what was required in the past. In fact, on several occasions we have come up with an idea for a new display in the morning and had several built and assembled by the end of the day. Building our own displays also makes it much easier to respond to special requests from customers. And, of course, the money that we save in contract manufacturing costs goes a long way to helping us stay competitive in this low-margin business."

Two CNC routers that cost a total of $40,000 annually generate $750,000 worth of plastic display products at Artistic Plastics. The PC-controlled routers produce as many parts as five people working with hand routers. The use of these machines has lowered the labor cost of router operations, enabling Artistic Plastics to charge less for this work and win more of this type of business. The use of the CNC machines also ensures customer satisfaction by producing parts with a better surface finish than is possible to achieve with hand routers.



Artistic Plastics is a plastic fabrication company specializing in display materials for the retail industry. The company's products include items such as acrylic sign frames, jewelry holders, and chinaware stands that are used by retailers such as J.C. Penny's to display their wares. Orders range in size from 1,000 to 50,000 pieces, and Artistic Plastics normally ships about $100,000 worth of product each week. This market is very price-sensitive and typically the lowest bidder gets the job. The challenge for Artistic Plastics is to operate as efficiently as possible so that its prices are competitive while still making a profit on the job.



Ninety percent of Artistic Plastics' products consist of square pieces of plastic that are cut with saws. Because it is fast and efficient to cut straight pieces with conventional power tools, there isn't much that automation can do to improve efficiency in this area. But the remaining 15 percent of its parts, the pieces with curves, are not efficiently produced by hand. In the manual production process, operators guide a hand router along a template representing the desired shape. Typically the templates are cut from a piece of fiberboard, either by hand or with a router. The templates must accurately depict the radius of the curve, and making good templates requires patience and a skilled employee. Frequently, templates are ruined and new ones must be made before the job can continue. The other drawback to using templates and hand routers is the fact that the plastic parts must be trimmed flush to the template. This requires the operator to closely follow the template and introduces the potential for human error.


Heavy-duty requirements



In the early 1990s, company management learned about CNC (computer numeric controlled) technology and decided to try this as a way of boosting the productivity of router operations. When they began evaluating CNC routers, one requirement was uppermost in their minds. The system had to be reliable. They knew, from the volume of router work they had, that the machine would need to operate seven to eight hours a day, Monday through Friday, and sometimes continuously over three shifts when the company had a large order to fulfill. A breakdown was unacceptable because it would cause a loss of sales volume and potentially jeopardize customer relations if Artistic Plastics was late with an order. A second requirement for the CNC router was that its price was affordable. This combination of requirements ruled out a number of products on the market at the time. CNC routers that cost several hundred thousand dollars were well made but out of Artistic Plastics' price range. Those that were more affordable appeared to be made with low-end components that didn't seem like they would hold up to a large volume of work.



Then the company found the Techno Series III PC-driven CNC router from Techno, New Hyde Park, New York. This machine sold for the right price, about $18,000 at the time, and featured the heavy-duty construction Artistic Plastics required. Each Techno router is constructed from rigid and optimized extruded aluminum profiles. It has four ground and hardened steel shafts and eight re-circulating 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. It easily supports the plastic sheets that Artistic Plastics uses as well as the vacuum table the company added to quickly change setups. Another feature of the machine that contributes to its durability is the use of anti-backlash ball screws. These screws have excellent power transmission due to the rolling ball contact 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 technical specifications of the Techno machine that Artistic Plastics purchased include a working area of 49 inches by 41 inches and z-axis height of 6". This router was designed for production routing and drilling on a wide variety of materials including wood, plastic, MDF, solid surfacing materials, and nonferrous metals. The price included the Mastercam CNC programming software. Although that program was originally designed for metalworking, it is ideally suited for cutting plastic because of its ability to generate the most complex contours with little programming effort.



High-volume efficiency



Once the CNC router was installed and some pieces were programmed in Mastercam, Artistic Plastics began shifting router jobs to the new machine. It performed so well that it was soon handling 95% of the router work. In fact, within the first few weeks, it had produced enough parts to pay for itself. A key feature of the Techno machine is its ability to cut 3D continuous contours at up to 200 inches per minute, far faster than most machining centers. Compared to a hand router, the Techno machine takes about the same amount of time to cut a single part. The speed advantage of the CNC approach comes when there are multiple parts to produce and several can be put on the table and cut in one operation. This really pays off on high volume jobs, when one operator can turn out as much work as five people working by hand. For example, to produce an order of 50,000 parts by hand, Artistic Plastics would have had five people working for two weeks with each producing about 1,000 parts per day. That same amount of work can be accomplished by one person running the Techno router for the same amount of time.



Because Artistic Plastics' products are visible to the public, customers insist on an excellent appearance, which includes perfectly smooth edges. This is an area where having the CNC router has also been beneficial because it can produce smoother cuts compared to a hand router. The human variability caused by having an operator closely follow a template has been replaced by a machine that never deviates from a computer-controlled path. The machine has a positioning accuracy of ±0.1 mm in 300 mm and a repeatability of 0.01 mm. The CNC router features a rapid travel rate of 200 inches per minute, a z-axis cutting force of 200 pounds maximum, 0.0005 inch resolution and repeatability, and 0.003 inches/foot absolute accuracy.



After using the original Techno router for several years, Artistic Plastics was producing many more routered pieces than it had previously. This was the result of the company's ability to produce higher quality parts for a lower price, and deliver them faster, using the CNC machine. The company then purchased a second Techno machine to keep up with the demand. That CNC router, which cost $22,000, differed from the first in that it was equipped with servo motors rather than stepper motors. The servo motor allows the new router to make even smoother cuts.



Both Techno machines are in use every day, usually for the entire day. Both have proved to be as durable and reliable as Artistic Plastics had hoped. Techno was the first low cost router manufacturer in North American and has an excellent reputation for service and support.



The two Techno routers generate about $15,000 of parts each week or $750,000 annually. Because the CNC machines provide a five-fold increase in productivity over hand routers, this income is available to Artistic Plastics at a much lower labor cost, creating an overall increase in the bottom line. With the efficiency provided by the CNC approach, Artistic Plastics is able to keep its prices as low as the competition's while ensuring that the work is done profitably.

The rigors of pass-fail are not just the pressure-cooker of classroom angst in the world of education. In the business world, the difference between 'Pass Inspection' and ‘Failing to Meet Standards' could amount to thousands of millions of dollars. One commercial pioneer, Electronic Packaging Company (EPC), has developed a new system that considerably reduces the size of the proverbial 'scrap heap.' EPC's particular application involves the repairing of 'failed' printed circuit boards (PCBs); usually because the technician is unable to locate the short. Using their conventional repair stations, an average of 65% of the boards were classified as 'irreparable.'

Now, using a highly accurate CNC Gantry, from Techno-isel, New Hyde Park, NY as the base platform, EPC's new computer-aided PCB repair system has significantly reduced scrapped boards. IBM, for instance, recovered the cost of the repair station in only six months from salvaging scrapped boards. EPC's new station, the Model 5500, projects any 'problem traces' onto the board with an LCD projector, which indicates the most likely areas or faults and it also detects recurring production errors. The Techno CNC Gantry allows the projected images from the LCD to be positioned with accuracy and precision that is essential in today’s densely packed PCBs.

EPC, Dallas, Texas, was founded in 1982 to produce products that aid circuit board manufacturers in the analysis and repair of errors. The company now offers a long list of tools for the electronic products industry including computer-aided repair systems, inner layer inspection tools, loaded board systems, and an audible resistance meter. EPC's customers range from Fortune 100 companies to the smaller, family-owned shops.

Old repair method

PCB manufacturers test finished boards for the soundness of the electrical connections on a device called a bed-of-nails tester. The bed-of-nails is a test fixture that has probes (that resemble nails) arrayed so that each will contact a grid point on the board simultaneously. The fixture is connected to automated test equipment that is programmed to iteratively check each network for opens and shorts. If a board fails, the test system produces a report indicating where the short is located. "The report gives two x-y coordinates," explains Evan Evans, engineering manager at EPC. "For example, it might say that the nail at point X23, Y19 shorted to the nail at point X99, Y87." In the past, repair technicians took the artwork used to create the board and identified the two traces involved in the short. Then they followed them on the actual board to find where the two wires might be touching. That was not difficult when boards consisted of just a single layer and it was possible to see entire traces by turning the board from one side to the other. After locating the problem spot, the technician scratched it with an exacto knife to break the connection. But as circuit boards grew more complex, it became impossible to follow the traces visually. "In today's multi-layer boards, traces go in one hole, then wander all through the inside of the board before coming out the other side," says Evans.

As Evans explains, PCB manufacturers do a lot of testing of inner board layers before they are sandwiched together, so the inner layers are good most of the time. "Eighty five to ninety percent of the shorts are on the outer layers," he says. "There are many more processes on those layers. Along with the etching, there is also soldering to create pads and electrical plating of through holes." But even when a problem is on the outside of the board and it should be possible to repair, if the technician can't follow the traces to find the short, he has to scrap the board. "These boards are designated as having internal shorts and scrapped," Evans adds. "When we asked one board manufacturer to show us all of its scrapped boards with internal shorts, we found that 65 percent of them weren't internal shorts at all. They were just a case of the technician not being able to follow the traces and find the fault."

The other limitation of the past repair systems was that they gave no indication to management of recurring problems. In one example, a company had been building a particular board for three years at 100,000 boards per year. They were unaware that one out of 12 boards was shorted in the same place because there were 20 different repair people and no way to compile their experience to find this sort of trend.

A better approach

The Model 5500 is a significant improvement over the old repair methods because it addresses both limitations—the difficulty of following traces on multilevel boards and the inability to detect recurring problems. When a failed board is brought to this repair station, the operator enters the two x, y coordinates from the test report. The system's fault prediction software examines the CAD data used to manufacture the board and checks all of the pads and traces associated with the two coordinates to determine where the wires come in close proximity. When the fault prediction analysis is complete, the repair station uses a color LCD high-resolution video graphics projector to display repair data (traces, pads, components, and other information) directly onto the circuit board. The colors of the projected image can be changed so that there is maximum contrast between the circuit board and the graphic data.

The system does not just display images, however. "It incorporates intelligence so that it actually walks the operator through the process," explains Evans. "The system highlights the first place to put the test probe, then the second place. It presents the problem areas one after the other so the operator can find the fault." The failure analysis software takes into account whether there might be internal shorts so the repair person does not waste time repairing these external faults only to find that the PCB must be scraped because of a non-repairable fault. A stereo zoom microscope is included as part of the Model 5500 so that location, verification, and repair of very small faults that could not be seen by the naked eye can be performed on the repair station. The repair station also features fault ranking software that collects a history of the faults that are reported and uses this historical data to determine the reparability of subsequent PCBs.

A key feature of the system is the accuracy with which it displays the images of the traces, pads, and so on. Positioning accuracy is critical because of the close proximity of the traces and components on today's PCBs. In designing the Model 5500, EPC had the option of building a gantry system on which to hand the LCD projector and the x, y positioning system. "We had designed many such mechanisms in the past but decided not to reinvent the wheel this time," says Evans. An advertisement in a trade journal convinced them to use a Techno Gantry System III.

This servomotor controlled gantry system delivers 0.0005-inch resolution and repeatability, and 0.003 inches/foot absolute accuracy. It is constructed on steel stress-relieved bases with hardened steel linear ways. Its shaft-and-bearing system produces very smooth, play-free motion and is an extremely rigid system that produces high-accuracy positioning. The gantry's design includes heavy cast aluminum side plates supporting the y axis, giving extra stiffness for accuracy in positioning. Anti-backlash ball screws and nuts are standard. These screws have excellent power transmission due to the rolling ball contact between the nut and screws, and this type of contact ensures low friction, low wear, and long life.

The Techno gantry comes in a wide range of work surface sizes. This allows EPC to offer its repair system in different sizes as well. There are three versions of the Model 5500, built on three different models of the Techno gantry. The EPC 5500 – 027 has an active board area of 21.5 inches by 22.0 inches (54.6 cm by 55.9 cm) and can repair a board of 32.0 inches by 27.0 inches. The EPC 5500 - 054 has an active board area of 40.0 inches by 22.0 inches (101.6 cm by 55.9 cm), allowing a board of 64.0 inches by 27.0 inches (162.6 cm by 68.6 cm) to be repaired. The EPC 5500 - 130 has an active board area of 50.0 inches by 42.0 inches (127 cm by 106.7 cm). It can handle boards of 64.0 inches by 47.0 inches.

The Model 5500 is new but several companies are already using it with excellent success. IBM, as one example, recovered enough failed boards in the first six months of using the Model 5500 to pay for the system. Another example is the company that was producing hundreds of thousands of boards with one out of 12 being defective. This manufacturer used the system's fault ranking software to statistically analyze the historical repair data. This enabled them to find the source of the problem, a smudge in the original artwork that was creating a bridge across two traces. That single find alone went a long way toward paying for the system.

The Model 5500 offers PCB manufacturers a significant improvement over past repair methods. By helping technicians find more fixable faults, it reduces the number of scrapped boards. And by allowing manufacturers to see trends in failed boards, it helps fix production problems before they cause failed boards. A highly accurate gantry system ensures that the Model 5500 has the necessary precision to accommodate today's densely packed PCBs.