Standardizing On Multi-Axis Machines

Located in the Chicago suburb of Broadview, Illinois, Merit Screw Machine Products Co. was established in the late 1920s. At that time, the shop was equipped exclusively with Brown & Sharpe single-spindle screw machines. After surviving the Great Depression, the shop grew and diversified over the years, adding multiple-spindle screw machines to produce a broader range of part sizes in greater quantities. In the late 1980s, Merit installed its first CNC screw machine, thus beginning the most dramatic transformation in the company's entire history.

Today, the firm is reinventing itself again. The shop is selling off its old cam-operated machines, as well as a modest collection of not-so-old CNC machines. Merit is basing its current production on the Deco 2000 new-generation, single-spindle, Swiss-style, CNC, sliding-headstock machine manufactured by Tornos Technologies (Brookfield, Connecticut). According to Merit's president Ronald H. Gustafson, the Deco 2000 produces parts as fast or faster than cam-operated machines, and the parts that it produces are completely machined, requiring no additional operations.

Additionally, Mr. Gustafson has found that the Deco machines can handle 90 to 95 percent of the jobs that his firm quotes. As Merit continues to replace its existing machines with Deco 2000s, Mr. Gustafson expects that nearly all of his firm's quotes will involve the high-precision, complex parts that the multi-axis Deco 2000 is designed to produce. In time, he expects the remaining 5 to 10 percent of his shop's work (involving less complex and lower profit parts) to also be replaced by high-precision work.

"Years ago, having a variety of screw machines allowed us to bid on jobs from companies such as IBM and Westinghouse involving 100 or so different components, knowing that we could make 90 to 95 percent of the parts on our equipment," Mr. Gustafson explains. "But much of that business went away, and our diversity began to hurt us. We had eight machines of one style, 12 of another, 15 of something else, and we needed to find work for all of them.

"Another problem was that our operators and setup people were experts on one type of machine, but not on the next," Mr. Gustafson continues. "We had trouble moving our people from one type machine to another. We became a little nostalgic for the simpler times at our company when we had only one kind of machine and everyone knew how to run it."

"Of course, the parts that we produced on our old Brown & Sharpe machines were a lot less complicated than the parts we're called on to produce today," he quickly adds. "Today's parts usually require milling, cross-drilling, slotting . . . features that dictate secondary operations if the part starts off on a simple two- or three-axis machine. Secondary operations are usually labor-intensive, which means they're expensive. They are also time-consuming. And secondary operations always create the danger that errors will convert parts that already represent a lot of value-added processing into scrap. We wanted a machine that could eliminate the need for secondary operations by producing completely machined parts.

"Also, as a job shop without a product, we wanted a machining capability that would give us an edge over our competition," Mr. Gustafson continues. "We did not want to be just another shop competing on the basis of price alone for jobs that just about anyone could do. We wanted to be able to compete for the more demanding (and more profitable) multi-axis jobs. The Deco enables us to do that."

A Look At The Machine

The Deco 2000 is a single-spindle, sliding-headstock-style, multi-axis, CNC screw machine, available with various bar capacities and ranging in capability from five- to 12-axis machining. According to Tornos Technologies, the machine combines the speed, reliability and productivity of a cam automatic with the flexibility, accuracy and versatility of a CNC machine.

The machine is designed to produce finished parts from bar stock, regardless of their complexity. For example, the machine can use two turning tools at the same time, completing rough and finish cuts in the same operation. One of the machine's cross slides accepts up to four live tools (photo, page 32) for operations such as cross milling and off-center drilling. Polygon milling of flats or contours can be accomplished using the optional C-axis on the main spindle.

At the same time that the bar in the main spindle is machined, operations are performed on the previously parted piece mounted in the counter spindle. For example, the counter spindle can present the part's cut-off end to as many as four live tools or turning tools. In effect, the user gets these operations "free" because they happen at the same time that the part in the main spindle is machined. Consequently, there's no increase in cycle time for the part. Users can minimize part cycle times by balancing operations between the main and counter spindles. As many as 12 axes can be controlled simultaneously on the Deco 2000, and up to four tools can be working at the same time.

A Dedicated System

The Deco 2000 is more than just another new multi-axis machine. It's a complete system that incorporates a dedicated machine control and dedicated software. Each component of the system was developed to eliminate as much idle time as possible, thus minimizing overall cycle time.

The machine's PNC (parallel numerical control)-Deco control reportedly can control 12 axes simultaneously. This control's principal innovations include a central clock (that functions as an electronic camshaft) and virtual electronic cams. During operation, each tool's axis paths are calculated by the programming computer, not the machine control, and this data is stored in tables or virtual cams. Just as a camshaft synchronizes operation of individual cams on a cam-operated machine, the PNC-Deco control's central clock synchronizes the tool movements.

The Deco 2000 is programmed with dedicated TB-Deco software via a remote PC or PC-based workstation. Because TB-Deco runs on Microsoft Windows it's user friendly (minimum requirements are a 486 DX 2/66 with 16 Mb of RAM). The Windows platform also enables programs to be transferred over the Internet and downloaded to machines connected to local area networks such as Ethernet.

The programmer selects the required tool for each operation and enters its geometry. The programmer then writes a corresponding machining program for the tool using G-code. A program model or recommended machining sequence is incorporated in the TB-Deco software. This enables the programmer to get the most from the Deco 2000's several tool systems by following a sequence logic for all machining operations. It also prevents collisions between the lathe components—no small consideration when so many things are happening at the same time.

The TB-Deco software automatically calculates real machining times, taking into account the tool paths, operation sequences and other cutting data entered by the user. It also incorporates canned cycles that speed programming, such as bar stock advance, cut-off, and pick-up by the counter spindle. Additionally, it displays the part's production rate.

"The TB-Deco programming software is very good at taking all the idle time out of cycle times for parts," says Chris Dao, who handles CNC programming at Merit. "It permits the machine to react a lot faster. There is no delay in going from one tool to the next. Instead of taking five seconds to go from one operation to the next, the Deco 2000 does it in 1/2 second.

"If you're using TB-Deco to program, say, a ten-axis machine, you write each axis separately and then put them together," Mr. Dao continues. "The parts can be very complex, but the programming method is clear and easy; you don't make many mistakes. Also, the software has a good simulation function that allows you to view the operations exactly as they will occur on the machine

"The software also flags problems," he continues. "If, for example, two tools are programmed to work in close proximity at the same time, the software provides a warning to the setup person. If the software detects a collision, it will not allow the program to be sent to the machine. There are other safeguards built into the system as well. For example, each program is prepared for a machine with a certain configuration, and the system will not allow the program to be downloaded to a machine with a different configuration."

Merit has been so successful with the Deco 2000 that the shop is standardizing on the machine. The company's first machine, a 12-axis configuration with a 10 mm bar capacity, was purchased in 1997. Since then, the company has purchased seven more 12-axis machines, some in 25 mm and 32 mm capacities. "The Deco 2000 is the only CNC screw machine that can compete with cam automatics on the basis of cycle time," Mr. Gustafson asserts. "But no cam automatic can produce completely machined parts like the Deco 2000.

"We have been steadily replacing our cam-operated machines," he continues. "We have only one more cam-operated machine, and it will be gone this year. We also have several CNC screw machines of another make. Even though these are only four or five years old, we will also replace them in the next 18 months. We found that we could produce parts on the Deco 2000 machines in 15 seconds that took us 30 seconds to produce on the older CNCs. We have frequently been able to cut part cycle times in half with the Deco 2000 machines. It's rare that we can't achieve at least 20 percent time savings.

"We are even finding that parts we formerly produced on our Acme multiple spindle machines can be made as fast and more completely on the Deco 2000s," Mr. Gustafson adds. "As a result, we are reducing the size of our multiple spindle department. Before very long, it will be only one-third of its present size. In the past, the type of part and the production quantities involved determined which machine the job would run on: single-spindle parts would go to single-spindle machines, multiple-spindle parts would go to multiple-spindle machines. Now, the Tornos machines have so much versatility that we can run almost any kind of part and compete very well with the old processes—and in most cases do much better.

"As our work load shifts increasingly to more complex parts that are produced complete on the Deco machines, our need for a secondary-operation department is lessening," he continues. "We have already scaled back our secondary-operations department, and it will probably be halved again over the next several months as the simpler jobs that we have wind down."

Standardizing on the Deco 2000s has also solved Merit's problem of being unable to assign operators to different types of machines. "Our operators like working on the Deco," he affirms. "They find it an easy machine to work on and they're impressed by its capabilities."

Assessing the Gains

The Deco 2000s have had a significant impact on Merit's delivery times. "Lead times of up to 12 weeks were fairly typical 8 or 10 years ago," Mr. Gustafson recalls. "As we put in more Deco 2000s, our delivery times are coming down. Currently, it's about 3 weeks.

"For prototype work, we try to accommodate our customers' needs," he continues. "We try to schedule jobs in such a way that at least one machine will always be open within a short period of time. We've made prototype parts in 2 or 3 days. Even if it takes us 6 to 8 hours to program and set up the part, the parts come off the machine complete and ready to ship.

"We usually have one or two machines doing prototypes in quantities of less than 50," Mr. Gustafson notes. "It has become a very important part of our business, and even if we run 10 or 20 pieces, we try to do all of the cross-drilling, milling . . . anything necessary to drop the part off complete. We don't always make money on prototype runs, but it gives us a big advantage in getting the production order when it's released. Our customers also derive comfort in knowing that their production parts will be made the same way and on the same equipment as the prototypes.

"The Deco 2000s have improved our quality as well," Mr. Gustafson adds. "We don't lose parts in the process of setting up for secondary operations. That's going to help us control our costs quite a bit."

Although Merit runs two 10-hour shifts, the ability of the Deco 2000s to run unattended for long periods of time—each machine is served by a magazine-type bar loader—also has Mr. Gustafson thinking about running an unattended third shift.

"Some jobs are so demanding that we simply would not consider running them unattended," he begins. "However, we're confident that at least 50 percent of the parts we produce could run unattended. We've been experimenting more and more with unattended operation and have progressed to the point where we are installing broken-tool detectors, chip conveyors and other accessories to facilitate operating in that mode."

As a satisfied customer, the firm recently ordered three more 12-axis Deco 2000 machines, including a 16 mm-capacity machine. "When we bought CNC machines from other sources in the past, we usually had problems getting them up and running, or getting them to run efficiently," Mr. Gustafson explains. "By contrast, our Deco 2000s have run right from the beginning, and they have been free of the downtime and maintenance problems that we've had with other machines.

"Tornos Technologies has always been there for us when we needed help. When we have questions, we can call and talk to a knowledgeable representative who knows the machine and usually can provide the answers we need. We've come to regard Tornos as a partner that is genuinely interested in helping us take full advantage of all the capabilities they have designed into their equipment."

Merit Screw Products is convinced that the future of the screw machine industry belongs to firms willing and able to invest in universal CNC machines that are capable of producing a broad range of finished parts within their size capacity. Whether Merit represents the next major trend in this industry remains to be seen, but there's little doubt about Merit's competitive position. Many shops are just now investing in their first CNC machines—a position Merit occupied a decade ago. Meanwhile, Merit is discarding its first-generation CNC machines and investing heavily in newer, faster and more versatile machines.