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Quick-change chuck anchors JIT cell.

In the early 1980s, Falk Corp, a subsidiary of Sunstrand Corp, launched a program to reduce in-process and warehouse inventories in its speed reducer and drive coupling manufacturing plants. This meant handling smaller component lot sizes and order frequency that varied according to fluctuations in market demand.

One of the changes made by Falk engineers to implement the just-in-time manufacturing philosophy was the formation of manufacturing cells configured to produce families of parts differing in size but having similar machining requirements. Within cells, the engineers focused on minimizing downtime from increasingly frequent changeovers. This led to the purchase of a KNCS chuck from SMW Systems Inc, Santa Fe Springs, CA. The quick-change chuck allows either jaw repositioning or changing from hard to soft jaws in one minute. It also eliminates the need to rebore soft jaws for repeat runs of a workpiece, and has a range of hard jaw adjustments that significantly reduce the number of jaw sets needed to cover the full clamping range of the chuck.

"Used in conjunction with a quick-change tooling system on the lathe, we were able to cut changeover downtime 25% overall," says Dan Sterk, manufacturing engineer at Falk's Milwaukee, WI, plant. Falk has since purchased a total of 13 more of the chucks, he adds.

Typical of these applications is a flexible work cell that produces a family of speed reducer gears in lot sizes from one to 500. A twin-spindle Mazak Multiplex 430 CNC lathe performs all turning operations in the cell. After rough and finish turning in the Mazak, the gear teeth are hobbed, deburred, and shaved on other machines in the cell. The entire cell is attended by one operator, who also performs changeover duties.

A new order comes to the cell in the form of blank slugs and a routing sheet. The cell operator enters part number data into a personal computer workstation, which automatically displays all necessary information for changeover to produce the new part. This includes jaw numbers when jaw changeover is required, as well as the notch number, which is scribed on the face of the chuck, to which the operator must reposition the existing jaws or position the new jaws to clamp the new workpiece.

Also included in the display are the tool numbers required and command numbers that automatically download the machine control program required. The operator changes tools and jaws if required, and the machine is ready to run the new part. Lathe changeover usually can be accomplished while the other machines in the cell are producing parts from the previous run.

In another application, the KNCS chuck is employed on a single-spindle CNC lathe primarily used to bore drive couplings to custom diameters. In this case, finished coupling halves are taken from stock and rebored to size that fits the order. Most of this work consists of single part runs, each requiring soft-jaw change. Since the soft jaws clamp each coupling on a diameter that only varies according to coupling model and size, the jaws can be reused without reboring.

"Using SMW chucks in conjunction with quick-change tooling and the family-of-parts cell design approach, we've been able to cut our normal order-to-shipment time from 30 days to 15 days. We've cut time on rush orders from 15 days to as little as 2 1/2 hours, and a significant number of orders are completed in 48 hours," says Mr Sterk.

For more information on chucks from SMW Systems Inc, circle 368.

Press automation made simple(r)

What do you do when your application requires the accuracy and reliability of servo control without all the capabilities--and complexities--of a full-blown motion controller? Mecon Industries Ltd, a Scarborough, ON, manufacturer of servo-driven feed systems for large automotive stamping presses, found its answer in a single-axis AC servo position control.

Although they are relatively simple devices, press feeds must be precise and reliable: a misfeed could cause thousands of dollars in damage to stamping dies. Press feeds are also used during setup to position material from the coil within the press. A jog function is used to feed the material for the first part, which is stamped and inspected before automatic press operation begins.

To meet the speed and accuracy requirements of automotive stamping applications, Mecon used relatively expensive machine-tool-type servos to drive its feeds. The cost and complexity of the servodrives put the company at a competitive disadvantage compared to pneumatically operated feeds.

Mecon engineers began investigating alternatives to the relatively expensive and complex servodrive system. The problem, according to design engineer Paul Zwegers, was that the machine tool servo system Mecon was using simply had too many features that were unneeded in this application.

"We're talking about a relatively simple, single-axis, feed-to-length application where speed and feed length are the only important variables," Mr Zwegers explains. "Once the acceleration and deceleration rates are established for an application, we typically don't want the user to change those parameters." On more than one occasion, press operators who attempted to make adjustments ended up with unanticipated results that caused a lot of downtime, he adds.

The search was on for a less expensive, less complex drive that maintained the accuracy and reliability of the servomotor system. Mr Zwegers says he had already evaluated and eliminated ten or more different systems when he came upon HR Series Software Servos from Yaskawa Electric America Inc, Northbrook, IL. The single-axis devices provided the high speeds and precision Mecon needed at a cost roughly 30% less than the previous servodrive system.

Beyond the cost advantage, the Yaskawa servos offer a relatively simple user interface, including 1/4" high numbers for operator-entered data. "With the Yaskawa controller, operators can readily see what length they're going to get from the feed and at what speed they're going to get it," says Mr Zwegers. The previous system's more complex user interface sometimes led to press downtime after unintended operator "adjustments."

The HR servo also offers a standard PLC interface capability, which allows Mecon to simplify control system design and provides servo programming through a laptop computer interface. This is another advantage over the machine tool-type servo system, which required a proprietary programming panel.
COPYRIGHT 1993 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1993 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Manufacturing Solutions; just-in-time
Publication:Tooling & Production
Date:Feb 1, 1993
Words:1029
Previous Article:Doing it all with lasers.
Next Article:Bob Agan's found: TQM - a path to the future.
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