Shop Solutions: Overhead Robot Feeds Multiple EDMs, CMM
An overhead robotic system that loads and unloads six wire EDM machines and a CMM machine has enabled a major manufacturer of plastic molds and molded products to increase its level of automation and increase productivity.
Moldmakers Inc. (Germantown, WI) is a member of MGS Mfg. Group, a full-service organization that services the plastic injection and blow molding industries throughout the US and globally.
Founded in 1982, Moldmakers Inc. provides high-end engineering services and expedited mold-build capabilities, both to MGS Mfg. Group's custom molding operations and to outside customers. The company provides ready-to-assemble mold components accompanied by three-dimensional output that is verified automatically—much like a printer connected to a computer would print an engineering drawing.
Moldmakers' John Berg explains: "The goal of our engineers and programmers is to feed 3-D, quality-controlled data directly into the manufacturing pipeline by creating a system that could machine steel or graphite, and subsequently measure and verify the accuracy and repeatability of the machining operations."
Originally, the firm used several three-axis robots, each serving two EDM machines arranged in a circular layout to match the robot's reach pattern. "We integrated two wire EDM machines, the robot, and a storage/staging area. A web-based vision system was added to allow off-site monitoring," Berg says.
To improve flexibility and efficiency, and optimize use of manufacturing floor space, company management decided to change to a linear layout for the six EDMs and a CMM. Moldmakers selected a Fanuc Robotics M-710iB/45T overhead rail-mounted robot from Fanuc Robotics America Inc. (Rochester Hills, MI). The robot is a six-axis, electric servodriven, articulated gantry robot designed for material handling and machine tending.
To design and integrate the system, Moldmakers partnered with Promatech LLC, (New Berlin, WI). A major problem to be overcome was that the wire EDM machines did not communicate the same way because they were not all made by the same manufacturer. As a result, Promatech engineers needed to develop a communications method that could be used with the Fanuc and Mitsubishi EDM machines, as well as with a Zeiss CMM.
The entire process of developing the system, from the first quote until the system was up and running, took just over a year. Glenn Szpot, automation/quality control at Moldmakers says: "We're able to run it around the clock now, and it's definitely living up to the expectations we had."
The rail on which the robot travels is about 83' (21.5-m) long, not including guarding and other details. The layout is arranged with four wire EDM machines and the CMM on one side of the rail, and two wire EDM machines plus pallet storage on the other side. While the system currently serves these seven machines, it can handle up to 10 stations, allowing expansion within the same space by adding EDM machines or auxiliary equipment.
Sean Wells, an automation engineer at Promatech, says the company would have had to set up three separate cells with three-axis robots, each serving a maximum of three EDM machines, to achieve similar results. "The gantry design we used cost about two-thirds as much, and the individual cells would not have interconnected with each other. They also would have required an operator to go from one cell to the next, which would have been less efficient." In addition, he says it would have been difficult to integrate the CMM machine into the process.
Promatech developed and programmed the human-machine interface (HMI) that controls the operator interaction. It implements the instructions to the robot, and also manages the status of which cell locations are occupied and which are available for storage.
"There are a number of storage/staging locations specifically set aside for an operator to input or remove parts, Wells explains. "Once they introduce a part, everything is automatic until you bring the finished part back out of the system. The system handles it all the way from the storage shelves through the machine, the CMM, and finally to the outbound shelf."
The HMI is PC-based. It uses Interact X from the CTC Division of Parker Automation Technologies (Milford, OH), enabling the different machines and the robot to communicate. Wells explains, "Because the machines operate in different languages, we put a Mitsubishi PLC into some machines. This allows the machine to talk to the PLC, which, in turn, communicates with the PC via an Ethernet connection. The PC can be in a separate office or even off the premises."
This approach allows Moldmakers to operate the system continuously, even when an operator is not present. Wells says, "They can check error logs or change the status of any operation from almost anywhere." Because the cells are equipped with Web cams, they also can see what is happening in real time.
Once a Moldmakers' programmer downloads a program to a machine, that machine asks the robot for whatever part it needs for the operation. Operators can load parts into the system at a limited number of locations, from which the robot picks them up and moves them to a machine or storage.
"The operator goes to a screen and tells the robot what piece is being loaded into a cell. The robot then stores it and remembers its location." If the CMM, for example, calls for a certain pallet, the robot brings it to the machine and the machine doors close. The operator then runs the necessary procedure, and the CMM computer calls for the pallet to be removed and another one delivered." Data are memory-resident in the system, so a power loss will not cause a loss of the storage location data.
Promatech engineers designed the system with a passageway or tunnel underneath the rail at the center of its length to eliminate the need for operators to walk all the way around when they need to reach the other side. Wells points out that the tunnel also was designed to withstand impact from the robot in case of any program malfunction.
Safety is provided by light curtains and safety keys from Sick (Minneapolis). Wells notes, "We have a safety door at each machine location that is equipped with safety sensors that allow the door to move down so the robot can go over the side of the machine. The operator is in front, and if the operator goes through the light curtain, the robot will pause. As long as the door is closed, the operator can do whatever is necessary, but when the door opens, the light curtain becomes active to prevent anyone from reaching into the machine."
This approach makes it unnecessary to completely block the machines with a light curtain, which would prevent interaction and shut down the entire system instead of the individual machine.
In addition, the light curtain helps provide added flexibility for the system. "They can take a machine out of the system and operate it manually, to run a prototype, for example. Each wire EDM unit is part of the system, but it also can operate independently, because the light curtain guards each machine rather than the whole side of the system," says Wells.
Berg says that one major benefit of the new system is its ability to work around the clock and provide ongoing, comprehensive reports of its activity. "When the programmers and toolmakers open their e-mails in the morning, they receive automatically generated reports. They can go through them quickly, and inspect the data to verify that the materials moved through the system and were measured to ensure the accuracy of the machining operations to meet customer requirements.
Process Drives A Manufacturing Success
At a time when many manufacturers are reconfiguring existing systems and facilities to meet new challenges, Nasser and Iraj Barabi have taken a different tack.
Starting from scratch, they developed a business plan for an engineering/manufacturing concept based on flexibility, fast turnaround, and capacity for growth. The result is a business that has skyrocketed from $560,000 in sales in 2003 to approximately $15 million in 2006, results that have placed Essai at the top of Silicon Valley's Fast 50 list.
After assisting in transitioning their former high-tech company they had sold, the brothers found themselves eager to develop a new venture. Seeking a niche market offering high potential, they discovered opportunity in the engineering and manufacture of testing products for companies that produce semi-conductor chips. Specifically, the parts are used to connect the chips to the testing system and to manage the chip throughout the process.
According to Nasser Barabi, "The market we chose to serve is extremely exacting in terms of engineering, production, and delivery. The largest parts we create measure 6 x 2" (152.4–50.8 mm). Most are in the 4" (101.6-mm) range, although some are less than 1" (25.4-mm) in size. Thicknesses range from 0.04 to 2" (1–50.8 mm). Materials include high-end plastics, copper, or steel, and machining must be accomplished on four to five sides depending on the individual configuration.
"Typically, 20 to 30 operations are performed including milling, drilling, and tapping. Tolerances run as tight as 0.0001" [0.003 mm], and a number of the operations require five-axis capability. In all cases, geometries are extremely fine. On average, we use about 20 different tools for each individual part, and cycle times can run from 15 min to 3 hr. Volume is relatively low, and ranges from two parts per order to several dozen."
To address the needs of the market, the Barabi brothers worked with an IT consultant to create a process-oriented business architecture that would optimize workflow at all levels by eliminating repetition, providing comprehensive real-time information to employees, and giving workers the ability to find and implement shortcuts and improve methodology.
"We want the business to be as agile as possible," says Iraj Barabi. "We have to be flexible to meet the demands of our customers. We don't want our employees spending time doing things that aren't needed, such as repeated tasks. The managers need to know what is happening in the business as it is happening. The right business system helps to automate processes and get the company operating as effectively and efficiently as possible."
The manufacturing operation at Essai posed unique challenges. According to Nasser Barabi, "We wanted a fully automated system capable of three-shift production. The exacting nature of the work made precision a primary consideration. Obviously, reliability was key, and we wanted to be able to mix short-part runs with more extended ones." Anticipated machine life was also a consideration, as it was impossible to cost-justify production units based on any single part or customer.
"In reality, what we are defining is a fully automated system capable of constant change. For instance, last year we integrated 1800 new designs into the manufacturing process, and this year expect to include over 2500. Also, we are continually re-engineering existing parts and changing quantities," Nasser Barabi says.
To meet these exacting demands, the company chose production cells consisting of two Hermle C 30 U five-axis machining centers from Hermle Machine Co. (Franklin, WI) served by an Erowa ERS parts handling system from Erowa Technology Inc. (Arlington Heights, IL) capable of storing up to 180 parts. Equipped with full five-axis capability, the C 30 machining centers not only handle complex parts but simplify fixturing and workholding.
The machines are equipped with 280-mm NC swiveling rotary tables. An optional tool magazine extends capacity to 189 pockets that serve an 18,000-rpm HSK-A63 spindle. The tooling system is enhanced with a Blum laser system from Blum Laser Measuring Technology (Erlanger, KY) for length and radius compensation, as well as broken tool detection. A Renishaw touch probe from Renishaw Inc. (Hoffman Estates, IL) can be used for part ID or post-machining inspection.
Other options include an external MQL (Minimum Quantity Lubrication) oil-mist cutting assist and Event Messenger software.
Interface with the Erowa clamping system is via a pneumatic extension. The robot and control software is via ethernet.
The Erowa ERS utilizes a pallet system capable of handling pallets either 72 mm or 115-mm in diam. Pallets feature RFID scan capability to define the proper program and determine whether the correct tooling is in place prior to beginning operations.
Due to the large diversity of part types and sizes, a mechanical fixturing system was determined to be the most efficient. Parts are typically clamped on the pallets and automatically introduced to the machine for primary operations, then repositioned and bolted for secondary machining. The system has been successful with results of less than 0.000080" (0.002 mm) in variation.
The production process follows a smooth pattern. Once a part has been designed by engineering, solid modeling software is used in conjunction with an integrated CAM system to derive a program. Thanks to the operating system, programs can be optimized or changed as needed.
Since the first installation in 2003, Essai has added two more cells similarly equipped with Hermle machining centers and Erowa parts handling systems. "By standardizing, we built partnering relationships with our equipment vendors and, at the same time, simplify training, maintenance, and tooling, and software requirements," says Nasser Barabi. "Also, as we continue to grow, we can more easily plan expansion in the manufacturing area."
"By sharing information with our employees, they are not only able to operate more effectively but realize the contribution that they are individually making to the business. We have managed to assemble an exceptional team, and the results speak for themselves," Iraj Barabi says.
The company's name "Essai" (pronounced "Essay") is a French word meaning "To test, endeavor, or attempt or try new things."
"That," states Nasser Barabi, "is essentially what we do."
Precision Cleaning With A Flare
Environmental issues plague most job shops in this modern era of EPA rules and regulations. Principal among them is the cost both in time and capital of handling hazardous waste that may be generated in the parts-cleaning process.
Cleanliness of components used in the signal flares it manufactures for government projects and military use is critical for Security Signals Inc. Lives often depend on how well the company's flares work in a crisis situation.
Founded in 1948, Security Signals Inc. manufactures fuel pellets for the rockets at its Oakland, TN, facility. Pyrotechnics are loaded as parts are assembled. Tail fins are added to a stainless tube of the assembly, and a charge is loaded in the delay housing. These components are inserted into the base assembly, and the hand-held signal is ready to use.
The user pulls the top off the flare, attaches it to the bottom, holds the barrel, and bangs it against a surface or the palm of the hand. The flare screams to an altitude of about 600' (183 m) before the payload ignites. Flares are manufactured in white and green versions, as well as a red smoke flare that floats slowly to earth attached to a small parachute.
Not long ago, Security Signals celebrated its two-millionth flare assembly. To meet the government's demand for these products, 1500 parts are produced every day for these assemblies. Currently the company's job shop is located at the Cordova campus just east of Memphis, while the assembly and testing facility is located in Oakland, TN. The job shop's workload is roughly 80% government contracts, with all manner of commercial products making up the remaining 20%, including: after-market automotive parts; air conditioning; plumbing; and other industrial applications.
Larry Pyron, machine shop manager, started his career at Security Signals in 1968 as a toolmaker. He has seen a lot of changes in his time, and is responsible for the most recent one, the addition of a Dürr Ecoclean hydrocarbon cleaning system from Edge Technologies (St. Louis) for cleaning precision components.
"We've been through water cleaning, different solvents, different makes and kinds. We found that vapor degreasing is the best way for us to clean our parts. When I learned that this [Dürr Ecoclean] had a vapor system built-in, and was also very environmentally friendly, I made a call to Edge Technologies," Pyron says.
Rick Bauer of Edge Technologies suggested a series of tests on Security Signals' toughest applications. "Rick [Bauer] was a great help. We tested a smaller part in the Durr model 85C, and a larger part in the 81C. Both worked very well," Pyron says. "After the tests, we settled on the 80C, the mid-sized unit; it worked for our needs. Also, it was available for a quick delivery because it was at the IMTS show."
The most difficult cleanliness specs involve parts that are loaded in a signal flare. The assembly includes a stainless tube with an exhaust plate on one end and a delay housing on the other. The assembly is held together with a special shaft that is integral to the ignition of the payload.
The shaft includes a blind hole about 0.9" (22.8-mm) deep, with a cross hole 0.7" (17.8-mm) deep. In the past, oil would get trapped in the bottom 0.2" (5 mm) of the blind hole, damaging the powder and rendering the charge inoperative.
"The parts have to be perfectly clean. Dürr's vacuum system, which is used in each step of the cleaning process, makes it almost impossible for contaminates to adhere to any surface of the parts, including these types of holes," Pyron explains.
Government contracts are not the only cleaning issues Larry has to tackle. Commercial accounts have increasingly tightened controls on cleaning specifications. "They want perfectly clean parts every time. The contract cleaning specs usually read; 'must be free of all oil, chips and contaminates,' so we need a reliable cleaning system for those applications. The government gives us a Mil [Military] Standard on their specifications." Pyron adds, "The Dürr machine takes care of all these issues for us."
No special automated load/unload is required. Pyron explains: "We have a brass valve part that is a disk that has a protrusion on one side, and a hole on the other. I was taking great care to stack them so nesting didn't occur. One day I just dumped them in to see what would happen. When I got them out and started checking the ones nested together, there was no oil or chips. The surfaces that were nesting were perfectly clean."
The job-shop staff transports full part-bins directly from the shop's lathes to the Dürr before the oil dries, reducing the time required for the wash cycles. Technicians use a hand cart with an air-operated lift to bring bins, some weighing up to 50 lb (22.6 kg), up to conveyor height for an easy transfer of the parts into the stainless baskets that are then inserted into the wash chamber.
All parts made in the job shop, government or commercial, steel, brass, or aluminum take their turn in the Dürr. Each part type has a different program that controls wash time, agitation type, vapor degreasing, and the drying cycle. The operator selects the appropriate program for the part, starts the process, and the Dürr takes over, allowing him to return to another task until the clean parts are ready to be extracted from the chamber.
One of the biggest issues that drove Pyron to look for an alternative to his existing cleaning method was the waste. His previous system was a trichlor (trichloroethane) open-tank system. An environmental disposal company had to be called to come in, register it, label it, and ship it off to a handling plant. These steps were timeconsuming, and were not cheap.
"It [the Dürr] did solve the problem with the environmental issues, the EPA, and all that." Pyron remarks. "I've seen turbo washers, water washers that have all the spraying and turbo action, and they claim that they can get all these contaminates out, but they've never done it." Pyron used water systems with soap, and used spray water with soap, but eventually moved to a trichlor system. "They [the manufacturers] are making those systems that are totally enclosed. It did the job, but as the EPA started clamping down on the solvents, you still have to deal with the waste," he adds.
Security Signals previously bought trichlor by the pound. A 55-gal (208-L) drum was 600+ lb (272 kg) with a price of approximately $1.10/lb (0.45 kg). During warm weather it was harder to keep trichlor in the machine because of the heat, and the job shop was using about 50% more in summer. Parts that were lowered into the solution too fast would cause a flushing effect, allowing the vapors to escape, exacerbating the problem. On average Pyron's team would use a 55-gal (208-L) drum every six weeks. "It's March, and I've only used about 15 gal (56.7 L) of Isopar in the Durr since October," Pyron says.
The cutting oil reclaimed from the Dürr may be used again in Pyron's lathes, "We have 1½ 55 gal (208-L) drums of re-claimed oil, which we will test for lubricity and cutting agents before re-introducing into the lathes. If it still has its cutting properties, we'll use it."
Pyron is sure that the EPA will be contacting him soon, "They'll [the EPA] want to know what happened. They may think I'm illegally dumping the stuff. I'm expecting a letter from them asking, 'Where's all your hazardous waste?' I'll be able to tell them, 'It's gone. There is no more.'"
Precision Production Match For Auto Parts
US manufacturers of tight-tolerance precision components operate within a highly competitive market. Investing in new technology can provide the edge needed if it matches the precision and production volumes typically required for components such as auto fuel injectors.
Camcraft (Hanover Park, IL), a manufacturer of precision-engineered components for the automotive industry, selected a Multistar CX-24 rotary transfer machine from Mikron Corp. Monroe (Monroe, CT) to machine a complex part for one of its automotive customers.
About 85% of Camcraft's business comes from the automotive, truck, and off-road vehicle markets. A specialist in hydraulics and flow components, Camcraft had experienced growth, starting in 2000, when it forged a niche in highly engineered components and assemblies, especially difficult turned parts for the automotive industry. As a result, most of the parts it supplies vehicle manufacturers are for flow applications, especially fuel system components.
Because many of the company's automotive customers rely on rapidly changing technologies, Camcraft often is required to find equipment to handle special component needs. The company frequently purchases new machines to meet a specific bid. In one case, a North American automotive company planned to launch a 2007 vehicle that featured a new fuel-injector application. Camcraft was among a list of suppliers called to bid on a proposal by a global supplier, which happened to be a customer.
The fuel-injector application demanded a high level of accuracy because of its role in engine performance and emission standards. The components in the bid required large volumes, complex machining, and extremely tight tolerances. Camcraft had four years experience with the manufacture of a variety of fuel-injector components, but winning the contract would require devising a manufacturing and quality control process to meet the customer's quality requirements.
The part, in fact, had machining requirements that were unique to a limited number of rotary transfer systems. The part required drilling, milling, reaming, and chamfering. Although Camcraft's plant held equipment suitable to produce the part, the existing machine's volume capacity was too low to support the supplier's bid requirement of 2.7 million parts per year. Camcraft recognized that it could outbid its competitors only if it purchased a new machine that produced high-quality and very-tight-tolerance parts at a lower cost.
Marc Bossert, Camcraft's vice president of engineering explains, "We previously worked with a rotary transfer company for a number of years. But that company would not have met this application's requirements for high volume and very close tolerance. Fortunately, I learned about Mikron and its 24-station Multistar CX-24 machine."
Bossert met with Mikron's team several times to learn about their production values and philosophy. Quality was a core criterion for Camcraft's operations. In fact, Camcraft was one of the first companies to receive ISO/TS 16949:2002 certification for maintaining a Quality Management System. Bossert looked into whether the Multistar could meet the customer's quality level and hit its cost target in the process.
Camcraft could have avoided a portion of the capital spent by using individual machining centers. However, this approach would have required numerous machines, additional operators and floor space, all of which would have increased the operation's overall cost. The Multistar's 24 heads could produce various dimensions of the part at high speed and accuracy.
"Although we had machining centers with the same level of accuracy, our production output was no match for a transfer system like the Multistar. I viewed the Multistar on the floor of IMTS 2004 in Chicago and began my due diligence with subsequent visits to Mikron's headquarters. Ultimately, we recognized that this was the best machine on the market to produce the accuracy required for the part," says Bossert.
Engineers from the two companies met several times during the quotation process at their respective Connecticut and Illinois locations. As a team, they participated in an extensive idea exchange to customize the machine for the application. A few months later, Camcraft purchased the rotary transfer machine, and Mikron spent the next seven months assembling and customizing the Multistar to Camcraft's specifications.
Camcraft's experience with fuel-injector applications helped reduce the time needed during this cooperative design phase. Yet, during the development stage, the customer's tolerance requirements increased, requiring modifications to the machine's design and tooling. The Mikron engineering team resolved the issue by adding four CNC units (for face milling the part) on the machine, and, with the use of table indexing and machining units, achieved the tolerance requirements.
Before beginning the installation phase, a Camcraft team flew to Mikron's headquarters in Switzerland for a one-week training session. Because Camcraft purchases numerous machines from Europe, there was no hesitation in making the trans-Atlantic journey. The training session included a hands-on production run. After the first trip, Camcraft's engineers returned with actual parts to show their team back in Illinois. The company made several more trips to ensure the produced pieces would meet customer requirements.
In March 2006, the Multistar was shipped from its Swiss factory and installed in Camcraft's 112,000 ft2 (10,405 m2) plant. The machine and its associated electrical equipment measured 6.6 x 4.5 x 2.9 m. Shipped via airfreight in two pieces, it required minimal assembly, reducing the start-up time considerably. Two weeks were needed to spot the machine, install the electrical connections, and begin parts production. After assembly, Camcraft and Mikron started a minimal production run of 4000 pieces. The initial pre-production approval process met the quoted production rate.
Due to the part's tight tolerance and high output, Camcraft's team, however, continues to monitor the process for any potential hiccups. Currently, Mikron and Camcraft are working together to improve the cycle time by evaluating the production tools and making adjustments to the individual machining process.
Traditionally, the Multistar is developed and assembled using tools designed by Mikron Tool, a division of Mikron Machining Technology. In Camcraft's application, the tools consist of a combination of special Mikron tools as well as standard tooling from Mikron's CrazyDrill line. At final count, the machine is equipped with 30 special and standard tools.
In December, Camcraft started a full production run, operating the Multistar for three shifts, 5 1/2 days per week. The setup allowed just one operator and a quality engineer who monitored and checked 45 features of each produced component. Although there were no physical quality checkpoints for the part, the machine was fitted with nine toolbreak sensors. To this end, if a tool broke during production, the sensor could then identify a problem with the tool, interrupt the production cycle, and alert the operator.
At Mikron's Monroe, CT, facility, the company stocks a supply of spare parts and, if required, could customize uniquely designed parts for Camcraft's machine. In addition, the company's service department added another layer of support with its crew of service technicians, who were trained at Mikron's plant in Europe.
This article was first published in the June 2007 edition of Manufacturing Engineering magazine.