Pressing (forming)
The press according to DIN 8584 (referred to in practice as metal spinning or pressing mold) is a manufacturing method of metal forming and, together with the projecting and pressing rollers to the group of spinning process, part of the tensile compressive forming. The spinning processes are used to manufacture mostly rotationally symmetrical hollow bodies with almost any surface line contour in small and medium quantities and are usually used in a combination of these processes.
Typical components that are manufactured by pressing are, for example:
- Pots, jugs and kettles for large kitchens
- Works of art and ornaments such as vases and cups
- Parts of the container and plant construction such as container bottoms or gas bottles ( dished bottoms, basket arch bottoms )
- Inlet rings and nozzles in aerospace engineering
- Lampshades and reflectors
- Car rims
When pressing, a circular sheet metal blank (the so-called round blank) is clamped in front of the face of a press chuck. The press chuck represents the geometry of the component as an internal shape (forming tool). The chuck is then set in rotation together with the round blank by the main spindle drive of the spinning machine or, in individual cases, by muscle power.
The actual forming of the round blank into the component takes place in several stages using a pressing tool (universal tool), which is moved step by step from the center of the round blank to the edge and back again. As this movement progresses in the axial direction, the round piece gradually approaches the geometry of the chuck. A pressure roller is used as a tool in industrial processes and the movement is computer-controlled. Rod-shaped tools with differently shaped ends are often used in the artisanal production of pressed parts. In this case, the tool is guided in a holder and moved using the human hand. Theoretically, the sheet metal thickness of the original round blank is retained during the forming process - due to the existing tension-compression-stress condition. Since the deformation is only carried out in a locally concentrated manner due to the geometry of the tools (in the partial deformation zone ), only small forces are required e.g. B. required compared to deep drawing . Because of the locally limited forming, which only encompasses the entire component as time progresses, it is also known as an incremental forming process .
The good shape and dimensional accuracy of the components often makes post- machining of the components unnecessary. As a rule, forming is carried out as cold forming (without additional external heating). Complicated components made of materials that are difficult to form, however, also require intermediate annealing (heat treatment in the furnace) or hot forming, in which the round blank is heated with a burner. Recent research also shows the possibility of performing the process with local, laser-assisted heating.
In addition to reshaping round blanks, already preformed components (e.g. deep-drawn or pressed preforms) can be further reduced in diameter by pressing. If this reduction in diameter only takes place locally on the component, it is referred to as pulling in . In this way, for example, pressurized gas cylinders are produced. Conversely, large hollow bodies can also be expanded from the inside outwards.
The process is very flexible and allows materials to be formed that are otherwise difficult or impossible to form. However, the manufacture of complicated components requires a great deal of experience and a high level of manual skill. Even today, the process is still heavily crafted and many components (lamps, ornaments, cups, musical instruments, etc.) are still made by hand.
The pressing is derived from the metal driving that used to be carried out by hand . Jakob Sokopp was the founder of the first trade union organization for Austrian metal printers .
The spinning processes are currently experiencing increasing industrial importance, especially in combination with spinning. With the production of internally toothed components in which hubs are formed in one clamping, gear components can be produced economically that could previously only be produced by cutting (clutch plate carrier, planetary gear ).
The process was used, for example, in the VEB metal handle in Halle .
literature
- M. Runge: Pressing and pressing rollers. Series: Library of Technology, Vol. 72, Modern Industry Verlag, Landsberg / Lech 1993