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Putting a new face to machine value.

With extended use, all machines tools eventually get old and wear out. The old machine finally reaches a point where it becomes sloppy, holding tight tolerances becomes difficult, and repeatability wanes. For years, regaining machine integrity was sufficient motivation to contemplate rebuilding or replacing existing machines. However, in recent years, advances in CNC controls offer even more inducement. Now, a machine shop can not only make its old machine like new, but can make it better-than-new through the addition of modern CNC controls.

When you consider the fact that most machine tools can be rebuilt to like-new condition for about 30% to 50% of the cost of a similar new piece of equipment, it's not difficult to understand why retrofitting has become a multimillion dollar business in the United States. According to Market Intelligence Research Corp, the total CNC market in 1992 is expected to reach $692.2 million. By some industry estimates, as much as 20% of those controls will be going into retrofit applications. By retrofitting an existing machine, users benefit in many ways:

* The retrofitted machine will be as accurate and as tight as it was originally. In fact, it may be more accurate because after many years the original machine castings are fully stress relieved and more dimensionally stable.

* With new CNC controls, the machine will be more versatile and more easily programmed than it was originally. Frequently, timesaving diagnostic capabilities are built into the new control.

* A rebuilt machine can use its original foundation, thus avoiding excavation and other costs associated with installing, tooling, and fixturing a new machine.

Sound iron, geriatric controls

Two years ago, R Scott Smart's desk was piled high with work that left him little time to market his company, Canton, OH-based Superior Machine Co. The problem the company faced was what to do with its 15-year-old, four-axis, 12-station, Warner & Swasey (W&S) turret lathe that refused to hold tolerances for the special forging dies and tooling it produced for automotive and aerospace customers.

In addition to the dies, Superior's 10- to 12-man precision machine shop also handled small-lot computerized numerical control (CNC) turning. "We had three relatively new Wasino LG 81 CNC lathes that easily handled our high-precision turning needs," recalls Mr Smart. "What we needed, however, was to upgrade or replace the W&S for bigger pieces and work requiring more flexibility."

Superior used the W&S for tooling and forging-gage tooling. According to Mr Smart, the machine's turret was relatively flexible but not as fast as a gang-tooling type lathe. With its 10" chuck, the W&S swings 7.5"-dia work and, with the tailstock, can handle workpieces 14" to 16" in length.

Once a top-notch performer and still mechanically sound, the tape-driven W&S took what Mr Smart called: "an inordinate amount of programming time. Plus its servos and main spindle regularly acted up. One week, with a lot of TLC, it might run satisfactorily for three or four days. Then we would be lucky to get a full day's work out of it."

To replace the lathe, Mr Smart was looking at $150,000 or more. So goaded by the large and growing increments of time he spent keeping the W&S running, Mr Smart began thinking about updating it. He contacted Mike Pearman (a retrofitter with NC Repair Service in Lehi, UT) who inspected the machine and recommended several modifications.

"The ways and ballscrews were fine," said Mr Smart. "If they had a little taper, we could compensate for that. But it was just that the hard-wired parts of the machine were wearing out, so it wasn't anything that could be compensated for by programming.

The original General Electric 25hp DC spindle drive and motor were replaced by a 20-hp intelligent AC motor that, "resulted in much more precise and consistently maintained rotation (within approximately 1%), smoother finishes, and longer tool life," explained Mr Smart.

Finally, the tape-driven control system was replaced by a Mitsubishi M320L CNC control. In total, the complete upgrade and retrofit came to about one-third the cost of a new machine. "I knew the lathe itself was still a good machine, and we knew from our experience with other CNC lathes that we could rely on the new solid-state controls to give us the accuracy we were lacking," said Mr Smart.

Specifically, the M320L can control up to three axes simultaneously and employs an all-digital, intelligent AC servo for improved machining performance. Additional features include dual-spindle capabilities, C-axis control for milling, threading graphics, RS-232, vector fine interpolations, and dual-system operation beyond traditional lathe applications.

"Incorporating the new control with the lathe enables the machine operator to perform the job he was hired to do, and allows me to devote my time to increasing sales," explained Mr Smart. "We used to have to program line-by-line. With the MC320L's canned cycles, maybe six or seven lines will take the place of 30 lines and greatly minimize errors. Now all that's necessary is to be sure the setup is right, plug the G-code into the proper cycle, indicate the pitch, quantity of material to remove per pass, and how deep to cut the threads. The computer takes care of the rest."

Mr Smart adds: "With the new controller, we have a much better machine now than when it was new. It's much easier to program and can hold tolerances to 0.000 1". For all practical purposes, we have a new machine."

A moving retrofit

The Electronic Systems Division (ESD) of Cincinnati Milacron just completed a major retrofit project for the Lockheed Aeronautical Systems Co in Burbank, CA. Lockheed contracted the Milacron division to retrofit multiple Kearney and Trecker profilers with new Milacron-built ACRAMATIC 950 Computer Numerical Controls (CNC) as well as new electric drive systems. Upon completion, Milacron was also responsible for relocating the machines from Burbank to Lockheed's plant in Marietta, GA. Lockheed prefers to have one company provide single-source responsibility in managing such projects whenever it is practical to do so. This is especially true for a project of this magnitude that involved multiple large profilers, the production value of which can scarcely be overstated.

The profiling machines had been well maintained and were in good mechanical condition when the work began. However, Lockheed wanted to extend the useful life of the machines while concurrently enhancing their capabilities and improving uptime through increased reliability. Lockheed found the cost-benefit ratio provided by retrofitting was substantially better than it would be for buying new machinery.

The control was a major purchase consideration in itself. The ACRAMATIC 950 CNC, manufactured in Lebanon, OH, by Cincinnati Milacron's ESD, met Lockheed's specifications "handily" according to Milacron. The 950 incorporates state-of-the-art technology to provide older machine tools such as the Kearney and Trecker profilers with what are essentially new machine capabilities. The control is equipped with a 20-Mb hard disk for nonvolatile storage of executive software and user information, a 3.5" floppy disk drive for part program input, and a 14" color CRT with touch-screen and pop-up windowing capabilities for ease of operation.

The two-year project, which was completed in Nov 1991, will provide Lockheed with many benefits:

* Reduced troubleshooting time resulting from the control's comprehensive maintenance and diagnostic tools.

* Improved part quality due, in part, to the control system's bi-directional axis-error compensation capability. Other control features such as axis-limit acceleration and deceleration and torque-controlled machining are expected to yield similar improvements in cycle times.

* Better machine utilization resulting from implementation of the RS-494 protocol (also termed Binary Cutter Location, or BCL), which provides part program transportability among similar but different machines.

* Increased functionality from the control's true real-time multitasking operating system that enables the control to perform several operations simultaneously. For example, the 950 can control machine operation while an operator edits tool data, without any degradation in part quality or operating efficiency.

* Increased spindle availability due to the control's redundant processors. If a processor fails, a backup processor takes over the task while simultaneously alerting the operator of the failure through the control's diagnostic system.

Milacron agrees that retrofitting or rebuilding old machines is not always an appropriate course of action. The mechanical integrity of the machine must be factored into the decision. However, due to the savings that retrofitting or rebuilding can offer, it is almost always worthy of consideration.

Planned upgradeability

There are many factors to be considered when contemplating the replacement or enhancement of existing machine tools. No factor is more important than the benefits a modern machine control can bring to an existing machine: faster microprocessors, more memory, more versatile program storage, and simplified programming, to name just a few. Often, just the improved performance a modern control offers an existing machine is sufficient inducement to upgrade.

Many of us marvel at the control advancements that have been made over the last ten years, but what about the next ten years? Will the leading-edge control that is purchased today again be obsolete? Upgrading an existing machine with a modern control is an expensive proposition. Is there any way to avoid that cost again in the future?

Companies that wish to stay on the leading edge of control technology while minimizing future upgrade costs may want to take a look at PC-based controls such as Anilam's Series 1400. At the heart of the control is a widely available, relatively inexpensive, IBM-compatible 386SX PC clone.

Together with a user interface and motion control card, the Series 1400 offers users 32-bit PC hardware, conversational G-codes, integrated CAM programming, enhanced mold and die capability, color graphics, and advanced programming. Perhaps more important, however, use of existing PC technology reduces the cost of the control and provides an open architecture system that facilitates the use of network (i.e. MAP, LAN, etc) and other accessory cards. In the future, if a company finds it needs more computing power, it can upgrade the control system by going to a faster 386, 486, or 586based computer. The user is not tied to a dedicated controller. Instead, users can purchase the PC that best suits their needs.
COPYRIGHT 1992 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1992 Gale, Cengage Learning. All rights reserved.

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Title Annotation:retrofitting old machines
Publication:Tooling & Production
Article Type:Product Announcement
Date:Mar 1, 1992
Words:1680
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