Sheet metal working
Deep drawing, spinning & rounding
Besides bending, deep drawing, spinning & rounding are other non-cutting forming processes. These highly productive processes are also among the core competencies of the SwissFactory.Group.
Hydromechanical deep drawing of sheet metal (up to 900 t pressing force)
Conventional deep drawing of sheets
(63–230 t pressing force)
Automatic metal spinning
(centre height: ‑750; centre width: ‑1450 mm)
Manual metal spinning
(centre height: ‑500; centre width: ‑900 mm)
(L 1040 x D 100 or max. width 1020 mm)
Deep drawing is the tension-compression forming of a sheet metal blank into a hollow body open on one side, or of a pre-drawn hollow body into one with a smaller cross-section without deliberately changing the sheet metal thickness. In many cases, the part geometry is rotationally symmetrical, but it can also have almost any shape — with gradations.
As a rule, a deep-drawing consists of three components, deep-drawing punch, deep-drawing, and blank holder (also called sheet holder). The purpose of the hold-down is to prevent the undesirable formation of wrinkles due to tangential compressive stresses in the flange. An important characteristic value (material conditional), which describes the extent of a forming, is the deep drawing ratio ß, which is defined as the quotient of round diameter d0 and inner diameter d1 of the cup (punch diameter) at the initial drawing. For the onward pull, the deep-drawing ratio is determined from the decrease in the internal diameter of the cup.
There are many possible areas of application for deep drawing. One reason for this is that very many metals can be formed using this process, starting with aluminium, brass, copper, sheet steel, rust and acid-resistant alloys, but also heat-resistant and various other metal alloys.
Deep-drawn parts can be found in vehicle construction, mechanical engineering, space technology, solar technology, household, energy technology, chemistry, and many other places.
Picture: Can (slotted pipe) for pump motor
approx. 12 forming steps
Besides deep drawing, metal spinning is also a very economical process. Metal spinning is a very old craft. Thin sheet metal was used to make everyday objects at an early stage. In recent decades, thanks to Improvement of technology (automation) from it an efficient manufacturing method. Especially for the production of rotationally symmetrical parts — small and medium quantities — metal spinning is superior to other processes. In metal spinning, a sheet metal round plate is pressed centrally — with the pre-setter — against the spinning die and set in rotary motion. The spinning roller reshapes the rotating round blank step by step until the material is in contact with the spinning form. The forming process is controlled by means of two axes. With perfect control of the process, the wall thickness of the material remains almost constant. Since the parts have a good shape and dimensional accuracy, there is usually no need for machining. In addition to the forming of circular blanks, components that have already been preformed, such as deep-drawn blanks, can also be further reduced in diameter by spinning. The forming takes place very locally due to the process, therefore only low forces are required, in contrast to deep drawing.
In addition to automatic spinning, hand spinning is still indispensable today for prototypes/sample parts and small series for the most diverse areas, such as technical products, lights/reflectors, household articles, but also high-quality design products.
Projection stretch spinning is a special form of spinning, it is a precise process that uses a projection spinning roller to “project” the molecules of material on one plane into another. Conical workpieces are produced by moving the projection roller (spinning roller) parallel to the projection mould (spinning mould). Under its pressure, the material (circular blank) shifts axially, whereby the wall becomes thinner (s0 times sin α) and the part of the circular blank that has not yet been machined is perpendicular to the axis. The surface is very highly compressedby this process and also exhibits — on the projection mould side — a very good surface quality.
Graphic: Projection stretch press
Hydromechanical deep drawing
Hydromechanical deep drawing with our Dieffenbacher allows higher drawing ratios to be achieved than with conventional drawing processes.
- complex geometries
- expanded tubes
- Intersections in the shaping
- Parts with high surface quality
- Parts made from multilayer sheets
- Small and medium batch production
To hydromechanical deep drawing
As one of the leading suppliers of hydroforming in Europe and Switzerland, our partner company Egro Industrial Systems AG has a 900 ton press with 1’000 bar Hydromec pressure. With this press, the range of services can be covered up to a part size of 1’400 mm x 1’600 mm. Conical and parabolic drawn parts are produced in one go with this process.
In the production of demanding deep-drawn parts with larger drawing ratios, more complex shapes or increased demands on surface quality, it is often advantageous to use the hydromechanical deep-drawing process in — one — stage instead of the conventional deep-drawing process in — several — stages.
The principle of hydromechanical deep drawing is based on the high hydraulic pressure in the drawing area (see graphic step 1 — 3). The sheet metal blank to be formed (blank) is pressed against the immersing drawing punch from the beginning with an appropriate, adjustable pressure in the water box, and thereby receives the exact shape of the punch. This hydraulic pressure, which also acts directly on the sidewall of the drawn part, causes additional compressive stress there. With the help of this additional compressive stress, the process is facilitated in the drawing direction. In concrete terms, this means that the drawing ratio can be increased by up to 40% (depending on the material) without difficulty. The limits of this method are the sealing possibilities between the sheet metal blank and the drawing ring.
As a customer, you can thus benefit from higher capacities, greater mechanical flexibility and more economically efficient solutions.
Graphic: Principle of hydromechanical deep drawing in three steps
Advantages of hydromechanical deep drawing
- Higher limiting draw ratio, the achievable draw ratio is much more favourable (up to 40%).
- Conical and parabolic drawn parts are produced in one go. In the classical drawing process, depending on the geometry, it may require 5 to 6 drawing operations and 1 to 2 annealing operations.
- Lower tooling costs thanks to the more direct path to the finished part geometry.
- Different materials and different sheet thicknesses can be processed in the same tool.
- Better surface quality due to the reduction of friction in the area of the die infeed radius (sheet metal blank is drawn over a “water bead”).
- Less sheet thickness reduction in the bottom radius and the possibility of smaller bottom radii.
- Less residual stress in the component.
Image: Inverter hood
Solar system principle of hydromechanical deep drawing with active medium in three steps.