Page 23 - MetalForming Magazine May 2022

Rebuild or Retrofit?
At the heart of older press technology likely is a control panel with limited func- tionality and with monochromatic keypad displays, which provides a slow update time for viewing critical data. Conversely, state-of-the-art controls (as shown here), working in concert with the newest generation of programmable- logic controllers, also boast touchscreen panels and allow easy changing of all press-setup points—including those for top stop, slowdown and reversal.
Aging pumps, motors and even hydraulic fluids are not as efficient by today’s standards, wasting power and money. As shops grow and add larger presses, the amount of facility power is increased unnecessarily. Updating older equipment can reduce the need for major facility-upgrade projects.
Last but not least, metal formers must address safety and update their older presses as needed. Upgrading to ANSI B11.2-2013 and adding light cur- tains allow a press to be run by an aux- iliary piece of equipment such as a feeder or foot switch, to reduce cycle time. In the event of a valve failure, monitored valving stops hazardous motion mid-stroke, reducing risk to personnel and equipment. Secondary load-holding systems eliminate the need for stop-blocks during tool changeover and protect operators from potential hazards. Implementing new safety features in the right ways can boost reliability and productivity.
Pressing Ahead
Today’s hydraulic presses are faster and more reliable than ever. In the last decade, the technology has continued to improve. PLCs and other electronic controls have improved speed and flex- ibility, improving cycle times and part quality. Better valves and high-perfor- mance PLCs provide faster valve shift speeds and excellent positional accu- racies. Servo-quality proportional valves offer fast response times, even in larger-size valves that can handle high flows for faster cycle times. Pro- portional valves offer more reliable control over older servo valves, without the sensitivity to contamination that leads to maintenance issues. And, today’s PLCs have scan times fast enough to achieve ±0.001-in. positional accuracy with a high-flow D08-size valve. High-speed monitoring of linear transducers helps achieve the tight reversal/positional accuracy of the
press, and the controller’s more advanced functions provide the ability to smooth- ly manage the increased pressing speed.
Using today’s valves and PLCs, cycle times can be improved with simpler and easier-to-troubleshoot cir- cuits. Variable-displacement piston pumps allow flow and pressure to be controlled directly at the pump, simpli- fying the hydraulic circuit and optimizing horsepower to improve the circuit’s efficien- cy. And, as efficiency improves the press will experience less wear to the oil and hydraulic components, reducing the maintenance burden.
To reduce cycle times and
improve part quality, a press
rebuild can include installing servo-quality proportional
valves and high-performance
PLCs to offer faster response
times and improved positional accu- racies. Advanced control packages can take existing equipment and dramati- cally broaden their capabilities, open- ing new opportunities for manufac- turers.
Using touchscreen press controls, all press-setup points—including those for top stop, slowdown and reversal— easily can be changed. This eliminates the need for time-consuming manual adjustments, and such a closed-loop system adjusts itself to match process parameters. A control’s safeguards even can reject incorrect settings, preventing costly accidents. In addition, ram posi- tion is tracked by a linear transducer, which rarely needs calibrating. The control can be integrated with a pre- cision digital control system, which enables actual position accuracies of ±0.001 in. and reversal at ±1 percent of specified tonnage.
Repeatability has improved dramat- ically thanks to the use of new PLCs and valves. Metal formers can store multiple programs or recipes in the controllers, which can be accessed as needed—a big advantage compared to manually entering program parameters each time a new job runs. This auto- matic process can eliminate the need for a setup operator, requiring only the press operator to call up the program already loaded with values that have been checked by performing qualifying runoffs. Depending on PLC memory capacity, hundreds of recipes can be stored, enabling the press operator to change programs in just seconds and ensuring that parts are produced pre- cisely and repeatedly every time they run. Modern PLCs also are flexible enough to allow the use of multiple programming languages to best suit the current requirement.
20 MetalForming/May 2022
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