Pressing force

For presses: Force with which the pressing power is exerted on the workpiece.

Units

Typically, the pressing force is given in t. Although this is physically incorrect, it is adequate in practice because one ton corresponds to a weight force of about 100 kN. The pressing force is independent from the surface. Thus, always the same force is exerted independent from the load of the press. However, the specific pressing power on the workpiece decreases the more the press is loaded. This plays a key role especially for veneer presses.

Other terms

Operating pressure (max.) in bar: The total operating pressure of the hydraulic system. Without additional information, this information cannot be used to determine the pressing power or the pressing force.

Pressing power kg/cm², specific pressing power in kg/cm².

Generation of pressure

Following possibilities of pressure generation are used for presses in woodworking:

Manually

  • Pressure generation with toothed rack, which is clamped by a hand crank and locked via clamping device
  • Advantages:
  • low acquisition costs, no maintenance costs
  • independent from energy grid and compressed air supply of the company that enables a fast relocation within the workshop
  • Disadvantages:
  • the pressure must be generated manually and in each pressing element separately, so the cycle time increases with an increasing number of cylinders

Pneumatically

  • Pressure generation via pneumatic cylinder
  • Peumatic cylinder is supplied with compressed air from the compressed air network of the enterprise
  • Advantages:
  • relatively inexpensive production of the presses
  • usage of air hoses enables the manufacture of workpieces with a curved contour, for example steps
  • Disadvantages:
  • only limited pressure generation possible
  • Fields of application
  • pneumatic pressure cylinder: framing presses, carcase clamp
  • horizin* air hoses: laminating presses in staircase production, compact veneer presses, for example JOOS Junior
  • perforated plate presses, drawer clamps

Manual hydraulic

  • Pressure generation with hydraulic cylinder
  • Pressure build-up with hand lever pump at each separate cylinder
  • Advantages:
  • independent from energy grid and compressed air supply of the company that enables a fast relocation within the workshop
  • possibility of building up high pressures
  • relatively inexpensive
  • Disadvantages:
  • the pressure must be generated manually and in each pressing element separately, so the cycle time increases with an increasing number of cylinders
  • pressure can not be metered using a manometer
  • Fields of application:
  • framing presses
  • laminating presses
  • hole plate presses, drawer clamp, for example SCHÖBERL drawer clamp horizontally
  • carcase clamp, for example BARTH RP

Electrohydraulic

  • Pressure generation via hydraulic cylinders
  • pressure build-up with electrically driven hydraulic pump
  • Advantages:
  • possibility of building up high pressures
  • construction of presses with many cylinders possible because of own hydraulic aggregate
  • Disadvantages:
  • higher acquisition and maintenance costs
  • Fields of application:
  • veneer press, throughfeed veneer press
  • industrial gluing press, throughfeed gluing press
  • automatic framing press for high-volume production, for example HESS Hydrolux

Electromotive

  • Pressure generatiom via clamping bars, which are moved by electromotive driven threaded spindles
  • Advantages:
  • determining the clamping bar and build-up the pressing force in a single process step with one aggregate (automatic pressing)
  • Fields of application:
  • carcase clamps, for example COMIL Cosmo NK

Images

Rahmenpresse, manuell
BARTH, 2012
Schubkastenpresse, pneumatisch
GRASS, 1993
Verleimpresse, schlauch-pneumatisch
COLUMBUS, 1997
Rahmenpresse, elektrohydraulisch
S+S, 1997
Bedientafel für Elektrohydraulik
S+S, 1997
Furnierpresse, elektrohydraulisch
STETON, 2003