Printer Friendly

Converting your machine tools to CNC.

When Kenwood Machine, Dracut, MA, went into business several years ago, the little company specialized in prototype tooling and other kinds of precision machining. The growth potential for that kind of work seemed limited, though, so James Long, the company's president, decided to expand into production work.

"I knew I'd have to invest in CNC if I wanted to be competitive," says Long. So for one of his milling machines he bought a CNC retrofit--it happened to be from Anilam Electronics Corp, Miami, FL--and six months later he bought another retrofit for a second mill.

Since then, Kenwood Machine's sales volume has increased over 400 percent, Long reports. "I've been able to quote a lot of new work, I've been able to quote a lot of new work, I've hired my own sales rep, and I've brought in full-time and part-time help to meet my new production requirements."

Long points to a recent job as an example of what the CNC retrofits are doing for him. He was running 24 hr a day, machining 1000 extrusions for a computer company.

"I got two times more production from my operators than I could have before the retrofits," he says. "While the machines were cutting chips, the operators were doing secondary operations or making fixtures for the next job."

Stories like this are being repeated all across the country. Some of the instances take place in large companies--aircraft manufacturers, engine builders, and the like--but most are in small machining companies, tool and die shops, and the tool and machining shops of small and mid-sized manufacturers.

Interestingly, the vast majority of those opting for CNC retrofits are first-time buyers. It figures, when you consider the tremendous number of manual machine tools installed. That, plus the facts that numerical control (NC) never really caught on, and that CNC is still relatively new.

What about your facility, though? Have you adopted CNC yet? Perhaps, like many other machine-tool users, you've considered CNC and talked about it, but you're still hanging back. And perhaps that's because you still have questions without satisfactory answers.

In the hope that we can be of some service to you, we talked to nine experts in six supplier companies. According to figures we've seen, you likely are not yet using CNC, so we asked questions that an interested not-yet-user might ask. Following is a brief report on what we found out. Which machines qualify?

Generally speaking, CNC retrofits fall into three categories:

1) Manual machines that are still reasonably sound mechanically.

2) Numerically controlled (NC) machines, where you would replace the controls and perhaps the servomotors and amplifiers.

3) Brand-new machines that were built specifically for CNC but haven't had the controls installed yet. This category includes some machines built in foreign countries.

According to our experts, almost any manual or NC machine tool, regardless of age, qualifies for retrofit with CNC. The greatest potential lies, of course, in small (2 hp to 5 hp) Bridgeport-type milling machines, and in small and mid-size lathes, since so many small mills and lathes are in use.

Some suppliers have put together standardized, low-cost, CNC retrofit kits for the smaller machines. Among these suppliers are Allen-Bradley Systems Div, Highland Heights, OH; Anilam Electronics Corp, Miami, FL; and Bendix Industrial Controls Div, Detroit, MI.

But other types of machine tools can also be CNC retrofitted. Laser cutters, grinders, drills, plasma-arc cutters, machining centers; you name it, and it likely can be upgraded with computer controls.

Larger machines--profiling mills, punch presses, machining centers, and so on--also qualify. Many CNC control suppliers offer packages for large machines, and certain companies specialize in rebuilding and retrofitting of the higher-horsepower equipment. How do you evaluate?

Regardless of their age, most machine tools that are good enough to produce parts today are good enough to be retrofitted with CNC. The question is, though, can you evaluate the machine yourself to determine what would be needed for a successful retrofit? And what about estimated cost, and determining the gains you can reasonably expect?

As a rule, you can't do the evaluation job unaided. A recommended procedure is to find two or three qualified machine-tool rebuilders and retrofitters, call them in, and get their opinions and quotations.

It's preferable that the rebuilders have had experience with your particular type of machine. If a rebuilder had done only small mills and lathes, for instance, you likely wouldn't want him tackling a large-tonnage punch press or a five-axis, three-spindle profiler.

You want the job--including all controls, components, rebuilding, training, run-in, and other elements--to cost appreciably less than the price of a new, equivalent machine equipped with CNC controls.

"We usually advise the customer that the rebuild and retrofit should stay below 40 to 60 percent of the cost of an equivalent new machine," says Ted Martin, vice president and general manager of Bendix Industrial Controls Div. "If the estimated cost comes in higher, a new CNC machine may well be the wiser choice."

A specific, hands-on approach to evaluation is recommended by John Shanfelt, president of CNC Sales & Application Inc, North Royalton, OH. This company, located in a southwest suburb of Cleveland, specializes in small mills and lathes, but also retrofits controls for robots, boring mills, and other machines.

"We go over the machine thoroughly, checking for wear, tolerances, response times, and other factors," says Shanfelt. "But we also ask the customer to pick out a typical part that he has been running. We then walk through the process, and compile his total cost for the part. Then we compare that cost with what it would have been with a rebuild and CNC retrofit.

"One of our recent customers was milling a part on a manual machine at a cost of $62 apiece," Shanfelt continues. "Now, after a retrofit, he can mill that same part for an average $2.20 apiece.

"The potential gain depends a lot on the specific parts being produced. You can gain quite a lot on some parts, but not as much on others. An accurate evaluation should include scrutiny of the actual parts and processes involved." What does the package include?

For small milling machines, the CNC rebuild and CNC retrofit packages that you would get from a supplier include control hardware, machine hardware, rebuild services, and sometimes software.

Though some control vendors call their retrofit packages standard, you're still able to choose from a number of options. These give you varying kinds and degrees of automation and versatility.

For example, if you were interested in a relatively simple, inexpensive Allen-Bradley Bandit I package for a small mill, your choices could include:

1) Controls plus motors and drives.

2) a power drawbar, to make tool changing faster and easier.

3) Automatic toolchanger with up to 24 slots.

4) An automatic rpm changer for the spindle.

As you can see, if you bought all these options, you'd be converting a manual mill into a small, CNC machining center. How much does it cost?

Each job must be priced individually. Considering only the controls, today you can buy a CNC package for a small mill at less than $4500. But the job entails more than control hardware.

"The price finally paid depends to a degree on the size of the machine," points out Jay Malina, president of Anilam Electronics Corp. "If it's a typical Bridgeport-type mill, and you're ordering CNC with three-axis control, the final price is typically about $18,000. That includes the controls, new ball screws, installation, and two days of training for the operator and maintenance man."

Naturally rebuilds and retrofits of large, complex machines cost more. Conversion of a standard punch press may come to about $30,000, and converting a big profiler could run into six figures. When you compare these costs, however, with the potential costs of new CNC machines--and then add the productivity gains to be realized--you see some striking advantages to CNC retrofit. How long does it take?

For a punch press, small mill, or lathe, retrofitters usually quote one week, including one or two days of training.

"We did a rush installation for a customer recently in just two days, but that's not typical," says Sam Torrisi, engineering service manager for Automation Intelligence Inc, Orlando, FL. Formerly a part of Westinghouse Electric Corp, the company provides CNC retrofit hardware, software, and services for all types of machine tools, but specializes in larger machines.

"Four to five days to retrofit the CNC to the machine tool is a good average," Torrisi continues. "Normally, it takes 60 to 90 days from the time we receive the order until we install the retrofit package."

If you have a punch press, small mill, or lathe, however, the time from order to startup can be much less. Kits for many of these machines are well-standardized and carried in stock, and local rebuilders can take care of the job quickly. Who will operate it?

If you're typical of not-yet-users of CNC, you may argue, "I may be able to train a few people to run the CNC, but then nobody else will be able to turn out parts"; or "I may lose the skills of my older, more experienced machinists."

To a man, our experts affirm that neither of these concerns is well-founded. "I can take almost anyone off the street and make a good CNC operator out of him," says John Shanfelt. "In fact, the neophyte will end up a better operator, because he won't be preoccupied with how it used to be done.

"If I tell him to run at 8 ipm, for instance, he will run at that speed. Unlike the old hand, he won't slow the machine to 6 ipm because we always did it that way on that part."

As for who can or can't run the machine, Shanfelt points out that it has always been true that only select, trained people can run parts well. "You want someone producing a part to be well trained in making that part, whether on a manual or a CNC," he says, "and in fact control of a process is far easier with CNC."

As for the age and skill of the operator--it depends on the individual, of course, but many older machinists catch on quickly. A case in point is Don Pierce, an over-50 toolmaker with Apex Tool Co, Farmington, CT.

"I have to admit, when I heard about the Crusader (a standard mill retrofit from Anilam), I had some mixed emotions," he says. "I thought I was too old to change.

"This new machine has the type of programming that toolmakers understand, though," he continues. "I was writing all my part programs after only a few days of practice. Also, now I'm doing a lot more sophisticated kinds of work with it, like air foils and mold inserts. Some of those parts would be impossible to do manually." What's in it for you?

Our experts say that if you convert a manual or NC machine tool to CNC, you can expect to realize the following benefits and advantages:

* Higher productivity. "Typically, you can get up to three times more production from a CNC machine than from a manual," says John Tremul, application engineer with Allen-Bradley Systems Div. Other suppliers claim productivity gains ranging up to ten times over manual output. As pointed out previously, it depends on your parts and processes.

* Repeatability. Once you've made a part accurately, you can store and reuse the program for that part. Then every time you run another, it's the same as the previous part and all others in the batch.

* Greater accuracy. With CNC, every dimension cna be set up, checked, and verified on a display. No more eyeballing, and fewer goofs by fatigued machinists.

* Easy storage of all dimensional and toolpath data, and consistent conformity with stored data.

* Predictability of machining times. You know exactly how long it takes to machine a given part, so you can estimate accurately.

* Use of new workers. You can train a new man to run a CNC machine in just days, so you'll worry less about the vanishing skills of older machinists and tool and die makers.

* Versatility. You can perform operations with CNC that were difficult--and in some cases impossible--with manual control.

* Faster, easier programming than is possible with tape-controlled NC.

* Minimal tape handling. The data are stored in CNC memory media, so you needn't be concerned about tapes becoming worn, torn, or degenerated because of grease accumulation.

* Shorter programming times. For instance, Sam Torrisi points out a case in which a job that used to take 1100 program blocks now requires only the equivalent of 60 bloks.

* Reductions in maintenance time. Some of the new CNC controls give you readouts for I/Os, the status of limit switches, the status of servomotors, and so on.

Feedback from the monitoring system tells the operator when something is wrong. This timely information keeps the problem from getting worse, thereby minimizing downtime and maintenance time.

"The latest controls offer true expert-system capability," says Robert Shages of General Electric Apparatus & Engineering Services, Schenectady, NY. "The diagnostic smarts of experienced maintenance men are being built into the software and controls."

* Automatic tool monitoring. In some of the more advanced CNC systems, you can get automatic updates on tool life and offsets. These systems can also recommend when it's time to change tools.

* Dollar savings over equivalent new machines equipped with CNC. If you know you must upgrade, this may be the deciding factor.

* Greater value and more options for resale. Later on, you can sell the machine as is, or without the computer controls. You can also sell the controls separately.

* Transferability. You can remove computer controls from one machine--for instance, one that is worn out mechanically--and mount them on a newer, better machine. Whom can you contact?

If you are still skeptical, get in touch with one or more machine rebuilders and retrofitters, and ask for references. You can then visit several people who have bought retrofits, and get the story straight from your peers.

For information from CNC Sales & Application Inc, circle E80 on the Reader Service Card.

If you'd like free literature, current prices, or other information from the suppliers of computer controls, see the box.

Whatever you do, though, if you're still struggling along with an old manual or NC machine, look into a CNC retrofit. It's too good a deal to ignore.
COPYRIGHT 1984 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1984 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Quinlan, Joseph C.
Publication:Tooling & Production
Date:Jul 1, 1984
Words:2404
Previous Article:Built-in workhanding options.
Next Article:The employee buy-out experience.
Topics:


Related Articles
CNC grinding for the US.
Inside a small-parts lathe.
CNC routers give top-notch performance.
Dial in for high production machining, accuracy.
Tracking machine control technology.
Rotary transfer machining hits the mark.
High speed control slashes machining time.
Can manufacturer just rolls with the changes.
What's new for job shops?

Terms of use | Copyright © 2016 Farlex, Inc. | Feedback | For webmasters