Forming Presses (Hydraulic, Mechanical, Servo)
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Forming Presses (Hydraulic, Mechanical, Servo) Konrad Wegener* Institut f€ ur Werkzeugmaschinen und Fertigung (IWF), ETH Z€urich, Z€urich, Switzerland
Synonyms Press machines
Definition Forming presses are forming machines with linear relative movements of the two main parts of the tools. Presses have a drive system, which generates a linear movement of at least and in most cases one ram carrying the first main part of the tool, which is bound by the linear guiding system. To counterbalance the press forces, presses have a stout frame, supporting the drive system for the ram(s), supporting the linear guides of the ram, and supporting some kind of table for the fixture of the second main part of the tool. The frame also supports all kinds of auxiliary systems as transfer, ejectors, die cushions, material infeed, lubrication and coolant, and systems for the exchange of tools and tool parts. Presses are subclassified in path-driven, force-driven, and energy-driven machines, depending on the drive system. In path-driven machines, the drive system defines the path of the ram, while the forces are defined by the feedback from the forming process. Typical realization of such machines is the mechanically driven presses. Force-driven machines define by their drive system the force at every position of the ram, while the path is defined by the feedback from the forming process. Typical realizations of such machines are hydraulic presses, where the pressure and the cross section of the piston define the press force. Both machines suffer from energetic limitations of their drive system, which influences accelerations and thus speed. If only the energy for the process is defined by the machine, the machine is classified as energydriven press machine. Typical realizations are hammers and flywheel spindle presses. A servo press is a press machine with a closed-loop control of the position and/or force. Those machines can be operated in a path-driven, force-driven, or energy-driven mode and thus mark a fourth class of press machines. But those machines can only be operated in one of those modes, which is decided by the control system. A path-driven mode in servo presses requires a position feedback loop, a forcedriven mode, and a current feedback loop, while the energy-driven mode does not require any feedback loop. All kinds of presses are further subdivided in metal-forming, bulk-forming or sheet metal-forming, and polymer-forming presses by the kind of raw material to be processed and in cold, hot, and semi-hot forming machines, depending on the temperature at which the material is fed in. Those criteria define the design specification of the whole press. Forming presses are press machines that are designated and utilized to deform some kind of material, mostly metals, which means that the main operations within the machine are processes from the second main group of processes of DIN 8580. Forming presses therefore introduce energy into the workpiece during the travel of the tool under acting process forces, which distinguishes them, e.g.,
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