Human Touch

Don’t bother waiting for the machine shop of the future to arrive. It’s already here.

You may not have recognized it, though, especially if you were expecting to see rows of robotic machines taking orders from a handful of operators punching buttons on a remote control panel.

Sure, the modern shop is full of automated wonders, but they aren’t the super-intelligent machines envisioned by futurists. A state-of-the-art machining center can follow the steps of a part program with precision, but it can’t be left on its own to make decisions and counter unforeseen problems that arise. It still takes a machinist skilled in both programming and machine tool operation to produce a steady flow of acceptable parts.

True, some shops have been able to reduce the number of craftsmen needed on the shop floor, but nearly all of these are production shops with long part runs. Programmers at these shops work at PCs or workstations in an office-like environment away from the machines. Their computers are equipped with CAM software that reads workpiece dimensions, surfaces and contours directly off of electronic part files produced by CAD systems and then uses the data to calculate tool paths. On the shop floor, operators, who may be less skilled than traditional machinists, download fresh programs, load and unload parts, and monitor the work of the machine tools.

Production shops with a lot of resources at their disposal parcel out responsibilities to a number of specialists, according to Mike Lynch, president of CNC training and consulting firm CNC Concepts Inc., Cary, Ill. Any number of people might be involved in machining a part at a production shop: designers, process engineers, programmers, setup personnel and operators. By distributing tasks and responsibilities, a production shop makes the best use of its equipment and its employees’ individual talents.

This division of labor provides numerous benefits. Because several functions, such as programming, can be performed simultaneously, preparations for one job can be completed while a different job is running on the machine. By the time the current part run is finished, the next program is ready to be downloaded to the machine.

Adding the programmers and programming equipment necessary to operate this way certainly represents a significant investment. But according to Ian Yellowley, a professor of mechanical engineering at the University of British Columbia in Vancouver, production shops can easily justify such outlays.

Consider as an example a shop that runs a number of machines that each have a burden rate of $50 an hour or more. If the addition of a programmer improves productivity by 10 or 15 percent, the shop could significantly increase its revenue. Letting machines sit idle while they are being programmed for the next part is a terrible waste of money, said Yellowley.

He believes that a production shop can’t afford to have people program machines. It would mean “using a half-million dollar machine as an editing terminal,” he said.

Short-Run Programming
In shops that run just a few parts per job, however, it doesn’t make sense to divide the labor among different employees. Even though firms that specialize in short runs—such as job shops, tooling producers and prototype houses—may be equipped with machines that are every bit as modern as a production shop’s, most assign all the tasks to program, set up and run a job to just one person.

At these shops, parts are programmed at the machine by machinists using the CNC’s console and the development tools built into the controller’s software. Lynch estimated that 60 percent of the shops with CNC machines create their part programs this way.

He said this approach makes sense for short-run shops because of the nature of the work. There simply isn’t enough time, money or staff to program offline.

Furthermore, programming offline doesn’t work in a short-run shop, said Lynch. With machines producing only a handful of parts at a time, a programmer couldn’t keep pace with machine operators. A machine that has just completed one job would sit idle while waiting for the next job to be programmed.

One oft-cited advantage of programming offline is that it allows programmers to concentrate on a program’s details in relatively comfortable surroundings. While the noise and dirt of a typical shop floor might not be the ideal programming environment, modern technology has stepped in to make the task simpler and less painful than it once was.

Conversational systems reduce programming to answering a series of questions and filling in blanks that appear on-screen. Canned cycles that are preloaded into the control’s memory before it leaves the CNC manufacturer’s factory use this data to customize common operations. For instance, the machine may have a canned cycle for thread milling, a procedure that involves programming tool movements in three axes. Using a canned cycle, all the machinist has to enter are the hole and thread dimensions. The controller then calculates the tool movements and writes the code.

In Lynch’s opinion, a shop with conversational controls gets the best of both worlds. The conversational interface simplifies programming while allowing the machinist to perform all the necessary tasks right at the machine. In some respects, Lynch said, these systems offer benefits that offline CAM programming can’t match. By calculating tool positions and cutting conditions, conversational controls minimize setup work and reduce the amount of programmer intervention that is necessary to get a job up and running.

“These are things that would still have to be considered after a program had been prepared on a typical CAM system,” said Lynch.

Other innovations allow machinists to program at the machine while taking advantage of the convenience of offline programming. CAM systems have begun to move to the shop floor, permitting machinists to work with electronic part files at their machines. Additionally, multitasking controllers let programmers write the program for a job while the machine is running another program. Also entering the market are software packages that help the machinist calculate an operation’s optimal speed and feed rates.

While many agree that programming at the machine is the best way for short-run shops to reap the benefits of automated metalcutting, at least one shop owner has found it an awkward way to combine the tasks of programming and operating a machine tool.

John Kosiarski, president and co-owner of Pro-Mac Machine Inc., Bradenton, Fla., had an online CAM system installed on the machine in his three-man shop. It was supposed to let him work on more than one job at a time. But, he said, he wasn’t impressed with the results. “They say you can do multitasking—run the machine while you write programs—but it’s hard to concentrate on both things and be effective at it,” Kosiarski said.

Craftsmen Still Needed
While CNCs and CAD systems have brought the industry closer to that future world where intricate parts can be programmed and machined at the touch of a button, technology hasn’t sent the machinist the way of the dinosaur and the 5-cent candy bar just yet. If anything, automation in small to medium-size shops has increased the need for personnel with a broad set of skills.

An employer with CNC equipment must find machinists who are both craftsmen and technicians, capable of operating in the abstract, symbolic world of part programming and in the visceral, tangible world of machining.

“If you think you’re going to replace all of those manual Bridgeports with 5-axis machining centers and your productivity is going to go through the roof and you will be able to get rid of all of your qualified machinists, forget it,” said Yellowley.

He added that even when a computer makes many of the machining decisions, the programmer or operator must still know the subtle tricks of the trade to keep productivity high and problems to a minimum. For instance, a CAM system can’t tell a programmer if the tool “sounds right” in the cut or how far a tool can be safely pushed beyond the manufacturer’s recommendations. A machinist with this knowledge must ultimately be responsible for the part program and be ready to override the system when improvements can be made.

Training plays a big part in producing machinists with the skills to out-think a computer. But high-tech computer skills aren’t the most important thing today’s machinist needs to learn. The experts we talked to say you might be able to cut metal if you know how to program a CNC, but you will never learn to operate a machine tool safely and efficiently without getting your hands dirty by practicing the same manual skills machinists have always needed.

“I could take anybody with a halfway decent education and teach programming to them,” said machining instructor Ron Bailey. “But I certainly would want to stand back when they got ready to start.”

Bailey teaches a 32-week course for the Broome Tioga Board of Cooperative Educational Services, Binghamton, N.Y. He takes students from the basics of metalcutting through the intricacies of CNC operation. His charges learn benchwork and layout first, then progress to drill presses. Courses in turning and milling follow.

Each class builds on the knowledge gained during previous classes. In the drilling class, for instance, students make holes in the cubes they squared in the benchwork class. Once they can produce parts on manual machines with no help from Bailey, they move on to CNC machines.

CNC Concepts’ Lynch also believes it’s important to learn basic machining skills, but he said that people with only a fundamental knowledge of machining could be good programmers. With modern CNC and CAM systems, he said, human judgment is less critical to success because the software can automatically make decisions, such as choosing cutting conditions for a particular application. However, a human with enough training and experience to know how to tweak a plain-vanilla part program will probably be able to produce code that can make chips faster with less tool wear.

“I’ll stand by the statement that the more you know about basic machining practice, the better programmer you can be,” Lynch said.

Yellowley agreed that a person must have manual programming experience to be considered a CNC expert. But in his opinion, machinists who have only worked on machines such as manual Bridgeports still need some seasoning before they are ready to take the helm of a machining or turning center.

The difference between machining a part on a Bridgeport and on a 30-hp vertical machining center is quite dramatic, Yellowley said, and a manual-machine operator wouldn’t have the knowledge or confidence to take advantage of the more powerful machining center’s capabilities. “It’s OK to play with Bridgeports—to learn what inches per minute really means and what sort of rpm you use on different sizes of cutters,” he said. “But to actually see real high-end production tooling and to understand something about tolerancing and surface finish, I think you have to be working on the sorts of machines you’re going to end up programming.”

Unlike machining skills, computer skills are not essential for entry-level machinists, according to the experts we interviewed. Having grown up with computers, most kids today are well versed in the basics of keyboard and joystick use, and they should have no trouble picking up the specific commands they’ll need to create part programs. If an employee search ever comes down to a choice between someone with shop experience and a computer guru, the experts say you can’t lose by going with the machinist.

“You can take a person with basic machining skills and teach him how to program a heck of a lot easier than you can take a person with computer skills and teach him basic machining practices,” Lynch said.

Industry pros also agree that in the future it may be possible for shops to operate successfully with employees who only know which buttons to push on a machine tool and when to push them.

But we haven’t reached that point yet. The craft of machining parts, they say, still requires the human touch.

About the Author
Martin Eastman is a former editor of CUTTING TOOL ENGINEERING.

Coded Question
A frequently debated issue in the metalworking industry is just how much programming knowledge an experienced machinist needs. Is it enough for people programming the machine to simply know their way around a CNC’s conversational screens, or must they also be able to manipulate the G code that these systems produce?

Modern CNCs and CAM systems produce G code, but they generally keep this part of the processing hidden. These systems have human/machine interfaces that incorporate friendly screens full of clearly worded commands, questions and forms. The data that the programmer enters is then plugged into the appropriate G code behind the scenes.

In theory, a user working with such a system would never have to see the G code being produced. The translation happens automatically, and the resulting code should be simply a machine-readable interpretation of what the machinist has already entered.

But some argue that machinists still should be able to read and even alter G code in order to optimize the program loaded into their machine.

G-code proficiency is important, according to machining instructor Ron Bailey of the Broome Tioga Board of Cooperative Educational Services. Despite the ease with which a person can produce a usable program via a graphical CAM system, he said, “you can’t correct everything and do everything by just drawing pictures.”

For example, a flaw in the design file could cause the CAM program to cut the part in the wrong place. The tool could also be sent into a corner that is too narrow for its radius, causing it to gouge the sides of the part.

Larry Emricson, president of LMJ Tooling & Mfg., Woodstock, Ill., also believes that machining efficiency rises if the machinist can edit a part program. “I think they need to understand the program and understand what the tools do,” he said.

Emricson said that the safeguards built into CAD programs and CNCs don’t allow a machinist to take full advantage of a machine tool. The margin of safety that software developers have built into their products causes these programming systems to produce codes that are redundant and inefficient. For instance, to avoid pushing the tool too hard, the program might call for extra tool movements rather than a more aggressive depth of cut.

Emricson said that he tweaks software programs to remove the redundancies that prohibit machines from running at peak efficiency. However, not everyone in the industry feels that such tweaking is necessary.

According to University of British Columbia Professor of Mechanical Engineering Ian Yellowley, the code that programming systems produce should be satisfactory for all but the most unusual situations. He added that, typically, code tweaking results in only slight improvements in cycle time or tool life. These improvements might provide some cumulative benefit for long part runs, but the effects would be minimal for one-offs and short part runs.

—M. Eastman