Page 19 - MetalForming November 2022

high-torque, low-speed servo motor, designed for heavy metal stamping applications. It also includes zero-clearance roller slide guides, which create a lubri- cation-free die space and prevent cross-contamination of die and press lubricant, according to Aida officials. The press also includes a communications port for remote diagnostics via eWon connectivity.
Slawek provides another under- the-radar advantage of servo-dri- ven presses: stopping time.
“Everyone focuses on slide velocity and energy, which are important, but stopping time also is critical,” he says. “Compared to our traditional mechanical press- es, stopping time on our two ser- vomechanical presses is signifi- cantly quicker. Traditionally, we would try to finish our material feeding at top dead center in case something was out of position in the press. Now, as these presses stop more or less instantaneously, we can have material feed and use an extra 30 or 40 deg. of timing to speed up the stroke.”
Fine-tunability of these servo- mechanical presses, notes Slawek, also allows for better matching with movement of auxiliary equip- ment such as a transfer and servo- driven tapping unit, delivering
“We had run the first genera- tion for this spindle part at 16 strokes/min. on our 400-ton mechanical straightside,” Slawek recalls. “Our engineering manager
and I, in converting part produc-
tion to the servomechanical press, began playing with slide velocities.
One benefit of the servomechan- ical: It offers unlimited energy, especially at exceedingly slow slide velocities. We ran design experi- ments at different forming veloc-
ities checking if dimensional sta- bility improved, didn’t improve or stayed the same, and what happens if we hit harder or softer. For this part we ended up finding a sweet spot.”
The three speed segments men- tioned above reflected the need to slow velocities for transfer movement, increase dwell time to ensure sensor readings and optimize for forming.
“We did this before we even got into the details of pendulum motion,” Slawek says. “Overall, we increased production from 16 to 20 strokes/min. with the servomechanical press over the mechanical.”
Second Servo Buy Yields Greater Gains
Pleased with its initial foray into servomechanical press technology, in 2021 Omex purchased another 630-ton DSF-M2, identical to the first save for a longer 168-in. bed. Omex teamed this press with a transfer from Linear Automation. At the same time, the company decided to outfit both ser- vomechanicals with coil-feed systems from Colt Automation, designed for feeding high-strength steel and boast- ing four-over-five roller configurations
16 MetalForming/November 2022
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An Omex die-alignment innovation as shown on its newest 630-ton servomechanical press. Note how press- bed grooves matched to die-block grooves and blocks (center of photo) are used to place tooling quickly and accurately.
for powered straightening. With two servomechanicals inhouse, Omex has discovered all manner of advantages this technology offers.
“We are fine-tuning our servo presses, especially in pendulum mode,” Slawek offers. “For example, we’ve just finished trialing an automotive-part program that previously ran at 25 strokes/min. We monitored the energy when forming at that rate, and by using pendulum motion to significantly cut back the dead (nonforming) cycle, we easily reached 40 strokes/min. Tool life remains the same, but output increases.
“Of course, this brings new chal- lenges,” he continues, “such as dealing with quicker bin filling due to the increased output. With this logistics issue, we had to slow down a bit, rearrange resources and rethink how we remove these parts from the press.”
Press-stroke control inherent in servo-driven presses also comes in handy for stamping lighter-gauge material, “which tends to dance,” says Slawek. “Now we can lift softly, so that when the stripper or lifter plate raises, it does not stop abruptly and cause the strip to bounce.”
greater accuracy.
Bringing in servomechanical presses
did require a learning curve, acknowl- edges Slawek, but that has smoothed out, “and we’re very comfortable quot- ing jobs because we have inhouse expertise that knows how to get the most out of this technology,” he says. “At first, we almost quoted as a tradi- tional stamping job and then had to learn the process. Now, given a tool design, we are confident in quoting based on how we can adjust and cal- culate the energy and motion.”
One challenging takeover job calling for Omex’s servo press capabilities: a seatbelt housing from 3.5-mm-thick 480-MPa high-strength steel. Another stamper had stamped and extruded, then tapped—one hole Imperial, a sec- ond hole metric—via a secondary process. Omex, in its 630-ton servome- chanical press and with assistance from Aida to set up the process, coil-feeds a two-out die that forms the part and extrudes on vertical sides, then punches four tab holes on the horizontal. A servo-tapping unit then taps the two extruded holes. Integrated part transfer and the plug-in servo tapping operate