A PUBLICATION OF THE FABRICATORS &MANUFACTURERS ASSOCIATION, INTERNATIONAL®

A PUBLICATION OF THE FABRICATORS &MANUFACTURERS ASSOCIATION, INTERNATIONAL®

A PUBLICATION OF THE FABRICATORS &MANUFACTURERS ASSOCIATION, INTERNATIONAL®

A PUBLICATION OF THE FABRICATORS &MANUFACTURERS ASSOCIATION, INTERNATIONAL®

EXPERTISE TO HELP YOU TRANSFORM METAL INTO GOLD WWW.STAMPINGJOURNAL.COM MAY/JUNE 2014

Improving hinge stampingChanges in QDC Servo press as system

EXPERTISE TO HELP YOU TRANSFORM METAL INTO GOLD WWW.STAMPINGJOURNAL.COM MAY/JUNE 2014

Rigid transfer accelerates throughput

Rigid transfer accelerates throughput

Servo press serves best as a system By Jim Landowski

By Jim Landowski

Servo technology has been used as the drive system of servo-mechanical presses since 2000.

Initially, though, stampers used these presses the same way and for the same applications as mechanical presses—at full velocity and in full rotation mode—and therefore did not really take advantage of servo’s unique characteristics.

For the most part, stampers began to take advantage of servo-mechan-ical presses’ capabilities later, when the use of high-strength materials became more prevalent and they

realized that they could use servo’s controlled slide velocity and motion to vary speed and dwell. Then they discovered how quickly and repeat-able die setup was and that the slide-to-bolster parallelism could be main-tained automatically.

Although today servo press capa-bilities are more widely understood and used more widely than they were before, the dynamic global market is applying cost pressures that are prompting stampers to get more cost and productivity advan-tages from the technology.

Therefore, stampers should fully exploit all the fl exibility of servo tech-

nology to enhance their overall man-ufacturing processes. Today stampers need to look at a servo press as part of a manufacturing system rather than just a stand-alone machine.

Servo Presses in a System

Automation Equipment. One way stampers can optimize a servo press as part of a system is to inte-grate the programmed slide motions with the automation equipment (see lead image). This optimizes the total operation because it increases strokes per minute (SPM) and elimi-nates secondary operations. This results in more throughput.

Stampers can optimize a servo press as part of a system by integrating the programmed slide motions with the automation equipment. In this example, the slide never stops; it coasts over top dead center and speeds up through the working part of the stroke. Notice how close the die is to the grippers on the down stroke. The grippers are still moving back when the upper dies starts to engage. To see a video of this, read the online version at www.thefabricator.com

Servo press serves best as a system

Servo press serves best as a systemHow to capitalize on the technology’s cost-saving opportunities

Transfers. Stamping manufac-turers first realized the benefits of coordinating the press slide motion with transfer automation in transfer applications. In a non-servo-driven mechanical press, the stroke typi-cally has to be long enough for the slide to travel high enough to clear the transfer fingers or grippers as they move the parts from station to station. This is especially true when a 3-axis motion (lift) is used.

In the past, to maximize through-put, stampers used to run the presses in a continuous operation mode, with a typical maximum transfer speed of 14 parts per minute (PPM) for class A parts. Today, using servo technol-ogy, stampers can coordinate the slide motion with the motion of the trans-fer bars and fingers to increase speed.

For example, if the slide decreases speed slightly as it engages the mate-rial, similar to link motion at bot-tom dead center (BDC), then at 185 degrees (just beyond BDC), the slide increases to full velocity and main-tains this speed until it reaches 359 degrees (see Figure 1).

Then the slide slows down to an operator-programmed speed through top dead center (TDC)—just slow enough to allow the trans-fer fingers to clear the interference zone. After the fingers are clear, the slide speed increases through the working part of the stroke again.

The slide never stops moving through the stroke, thus eliminat-ing wasted motion and optimizing throughput. The press and transfer are working together as a system.

An additional way to capitalize on the controlled slide motion in this transfer application is to reduce the stroke length. The traditionally long press stroke of a mechanical trans-fer press is typically not required. The actual stroke length needed will be based on the application. It is not uncommon for the press stroke to be reduced to only 24 inches. The obvi-ous outcome is better process optimi-zation, but this also lowers initial press cost and reduces overall press height.

Multistroke. Another capabil-ity unique to servo technology is called multistroke. In this mode, the slide can make multiple strokes or “stages” before reaching BDC. This can be especially useful for striking and restriking materials with high

springback, such as thin titanium and advanced high-strength steels.

Typically, performing restrikes in a progressive-die application requires multiple stations. In a servo press, the restrike can take place in the same die station using the multi-stroke feature. This reduces tooling costs (fewer stations). It may even allow the die to run in a smaller foot-print (shorter bolster left to right).

After the final stroke, the press returns quickly to TDC and signals the material automation equipment to enter the die space and move or remove the part via robotic arm pick-up, coil line feed progression, shuttle device, and so forth.

Some multistroke applications require specific coordination with the coil feed. For example, in one application with a two-stage die, the coil line feeds to the first die station for the first two strokes so the part can be partially formed and a hole punched for a fastener. Then the coil is fed backward to allow clearance for fastener insertion. The next coil is fed forward again to the second

Today stampers need to look at a servo press as part of a manufacturing system rather than a stand-alone machine.

die stage for the third press stroke to crimp the fastener and actuate the cutoff. All three press strokes are done in one press cycle at a rate of 35 PPM before hitting BDC.

Inserting the fastener in the initial setup eliminates a secondary opera-tion, allowing the now finished part to be stacked and packed after it leaves the press. This may increase the rate of parts shipped per shift by up to 40 percent.

Control signals from the insertion device, coil line, and press are coor-dinated to make this efficient process system (see Figure 2).

Today’s servo presses make coordi-nating press slide motions with auto-mation equipment, such as transfers, coil feeds, and part insertion devic-es, easier. But when a part quality problem arises, stampers still ask the perennially debated question: Is it the press or the die? Exact digital control of press motion combined with BDC accuracy and automatic parallelism of slide face to bolster face—measured in microns—has stabilized the press variable. Now attention can be focused on the remaining aspects of the process, typically the tooling and material.

The way to make process improve-ments with servo technology is to make the press, tooling, and automa-tion work as a system. For most, pro-cess references are based on the past technologies, so it’s easy to say what can’t be done; but servo technologies empower stamping manufacturers to explore what can be done.S

Jim Landowski is vice president, Komatsu America Industries LLC, 1701 Golf Road, Roll-ing Meadows, IL 60008, 847-437-3750, jland owski@komatsuna.com, www.komatsupress.com.

0° (TDC)

180° (BDC)

Slid

e Po

sitio

n

Time

FeedForward

FeedForward

FastenerInsertedFeed

Backward

PressStroke #1 Press

Stroke #2

PressStroke

#3

0°

90°

180°

270°

1. ReducedVelocity

Full Velocity

2. WorkingSpeed

1. Velocity Programmed to Allow Transfer Grippers to Clear Interference Zone

2. Working Speed Determined by Part-Link Motion, No Speed Reduction, Dwell, etc.

Figure 1

The servo drive allows press speed to vary, reducing velocity from 0 to 120 degrees, then operating at the designated working speed and accelerating to full velocity on the upward segment of the stroke.

Figure 2

Servo press technology allows not only variability in speed, but also direction. In this example, the coil is fed forward, stamped, then moved backward to prepare for fastener insertion, then moved forward again. Automated transfer equipment must synchronize with this motion.

Reprinted with permission from STAMPING JOURNAL®, May/June 2014. Visit our website at www.stampingjournal.com.© FMA Communications Inc. All Rights Reserved. Foster Printing Service: 866-879-9144, www.marketingreprints.com.

Eprinted and posted with permission to Komatsu America Industries LLC from STAMPING JOURNAL®

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