NIBBLE, PUNCH AND SAVE

Lowering the Total Cost of Ownership: The newest technology in punching cylinder axes promises metal fabricators they can maximize their nibbling, punching, engraving, soft punching and deep drawing – all while lowering their energy consumption.

When pursuing development work targeted on high-efficiency punching cylinder axes, energy demand patterns in punching and nibbling machines were first ana­lyzed under real-world conditions. The findings revealed that the ma­chinery actually calls for peak energy during just ten to twenty percent of the total cycle time. Only the punch movement itself de­mands full energy output, while secondary periods that involve tool changing, loading or removing workpieces and other kinds of handling place almost no load on the hydraulic power unit.

The newest standardized punching cylinder axes from Rexroth (Lohr am Main, Germany) are particularly suitable for notching and perforating machines, cutting presses, hole and copy punches, slot and turret punching machines, as well as em­bossing machines with high stroke rates that are used in applications associated with nibbling, punching, engraving, soft punching and deep drawing.

Since they incorporate demand-driven energy generation, these modules save an enormous amount of energy. There are three versions to choose from – standard, advanced and high-performance – that deliver 200 kN and 300 kN of rated power and typically achieve punch rates ranging from 600 cycles per minute to 1,500 cycles per minute at stroke lengths of four mm (and up to 4,000 strokes in the engraving mode).

Two pressure ranges and an accumulator charging circuit reduce the installed power level from the very outset and, as a consequence, cut consumption by up to fifty percent. Augmenting the high and low-pressure system (itself an energy saver), an adjustable axial piston pump with electrohydraulic pressure regulation brings about further energy reductions. Savings potentials are exploited through eighty to ninety percent of to­tal running time without restricting productivity. Above all, boosting efficiency lowers the total costs of ownership and reduces the user’s CO₂ emissions.

Whereas a constant-speed pump, even in an optimized high and low-pressure system, generates the full volumetric flow all the time, a Type ER adjustable pump with electrohydraulic pres­sure regulation will lower energy consumption during idling pe­riods. Those periods can account for eighty to ninety percent of total time, depending on the specifics of the cycle.

To execute the punch movements themselves, the adjustable pump works in concert with the electrohydraulic controls to dynamically fill the accumulator in the high and low-pressure system. The software for the integrated and thrifty pressure modula­tion solution is stored in a Motion Control HNC100-3x that matches pump output to the process, responding to momentary need and doing so steplessly.

An A10VSO axial piston pump is used in this configuration to cover an extremely broad perform­ance spectrum, with rated pressure of up to 315 bar and dis­placement from 18 cm³ to 140 cm³. Hysteresis in all the models is less than three bar. The residual pressure function, designed for safety, protects the machine in case of a power failure and extends the service life.

The integrated func­tion libraries in these units, laid out for highly dynamic operat­ing modes, use fast and easy parameter specification instead of programming. Decentralized intelligence facilitates integration into any of a variety of control environments. The HNC100-X supports not only PROFIBUS DP, SERCOS III and CANopen, but PROFINET RT as well, and also incorporates an Ethernet serv­ice interface.

As a universal vendor supplying every type of drive and control technology, Rexroth augments the punching cylinder axes with shock-tested servo motors and IndraMotion MTX, an open CNC control concept. Time to market is shortened by a common en­gineering environment for project work, commissioning and di­agnosis for all the PLC-based electrical and hydraulic drives, in accordance with IEC 61131-3.

The system solution includes all the electromechanical, hydraulic and pneumatic components required, all obtained from a single source. Regarding the hydraulics, only four hoses need be laid. And to avoid wiring errors, a preassembled cable harness is offered. Inter­faces coordinated with each other reduce complexity and boost productivity.