Leifeld develops, produces and distributes tooling machines for chipless metal forming. We are one of the world’s leading providers for the technologies spinning, flow flow-forming, shear-forming, necking-in, and profiling.
Metal Spinning
Metal spinning pursuant to DIN 8584 consists of transforming a circular blank by chipless forming
with a roller into a rotationally symmetrical hollow body.
Metal spinning in detail
A preform is clamped against a spinning chuck and set in rotation. The spinning roller forms the
preform step by step until the material has been brought onto the spinning chuck. Rotating tools
generate a variety of surface lines on the work piece, which is also rotating, so that the final
form of the work piece is generated and the surface is smoothed.
A variety of other, additional machining processes can be performed in the same clamping setup, such as the subsequent
profiling of contour areas, the separation of marginal or base areas, the bordering of external edges, etc. In this way,
virtually any type of hollow body can be produced with complicated or complex geometries, very narrow tolerances and excellent surfaces.
Advantages of metal spinning
Metal spinning displays obvious advantages in terms of cost-effectiveness and flexibility.
Savings in material and the possibility of creating any kind of form changes at low tool cost
and in fast production runs make metal spinning one of the most competitive alternatives to
other processes, such as deep drawing.
The high work-hardening rate enables the use of more cost-effective materials, while nevertheless guaranteeing the
stability of the finished article and the required increased strength. This results in an enormous savings potential
in terms of material and weight.
Metal spinning tools (spinning rollers) are primarily not bound to the geometry of the work piece. This means that
changes in geometry can be made in virtually any areas of the work piece by implementing simple programming changes.
Flow Forming
With flow forming pursuant to DIN 8583, rotationally symmetrical hollow bodies are formed from a tube or bowl with a cylindrical, conical or curved surface line.
Flow forming in detail
A preform is slid onto the mandrel and clamped securely. As a rule, three or more rotating flow
forming rollers press radially onto the rotating work piece, such that the material spreads in an
axial direction. The wall thickness is thus reduced and the work piece is lengthened.
The process is also frequently referred to as cylinder flow forming or stretching, whereby a distinction is made between
forward and backward stretching. An essential criterion regarding the process to be used is the question of whether
the workpiece is solely of tubular form or if it has a bottom and can be clamped. In the case of forward stretching,
it is also possible to form teeth and so to produce a range of different internally toothed gear components.
Advantages of flow forming
The aim of flow forming is always to achieve a reduction in wall thickness. The final state is
attained by pure compressive loading. The pressure applied to the material first of all serves
to increase the work piece’s strength and also lengthens the material. The result is an extended
work piece with enhanced material properties, a higher load-bearing capacity and a longer
service life than components produced by metal cutting processes.
Profiling
Profiling consists of forming notches, grooves, etc. into a round blank or preform over several
stages. The most important variants are the splitting, bending and rolling procedures. Hub moulding
is also associated with profiling technology.
Profiling in detail
A preform or round blank is clamped between the main spindle and the tailstock spindle and set
in rotation. A variety of shear forming rollers are now applied in several consecutive work
steps and brought towards the work piece. The profiles of the rollers are coordinated in such
a way that they build on each other and ultimately generate the final contours of the work piece.
Advantages of profiling
Chipless profiling results in optimum material properties and narrow tolerances, which is
essential for safety-relevant parts in particular, such as brake components. The enormous
cost savings resulting from the low material input and very short cycle times should also
be emphasised.
Shear Forming
In shear forming, a round blank or preform is placed onto the external tool contours through
shear forming rollers. Shear forming is an incremental forming process that is related to metal
spinning.
Shear forming in detail
A round blank or preform is clamped between the spinning chuck and the tailstock pressure disc
and set in rotation. The round blank is formed parallel to the external contours of the tool by
the shear forming rollers and applied to the tool. In contrast to the gradual metal spinning
process, the material is applied in a single overflow: the metal is projected from one level to
another.
Advantages of shear forming
The advantages of shear forming lie in the simplicity of the process. All conically tapering
components with an angle of more than 18° can be made by shear forming in a single clamp. Since
the process consists purely of material displacement, the change in the wall thickness of the
finished part can be optimally calculated. While the shear forming roller moves parallel to the
spinning chuck, the wall becomes increasingly thin in relation to the cone angle (S1 = S0 * sinα).
The process results in narrow tolerances and polishable surfaces.
Necking-In
Necking-in consists of gradually reducing the diameter of the preform. The procedure is
particularly suitable for closing off pipes in pressurised vessels, gas cylinders or other metal
bottles. Necking-in is suitable for both vessel bottoms and necks, resulting in a permanently
gas-tight seal.
Necking-in in detail
The preform is heated in an induction unit outside the necking-in machine, clamped in the jaw
chuck of the machine by an automatic feeding facility, and set in rotation. A necking-in roller
installed on a 100° swivel support gradually moves material from the pipe to the centre of
rotation. The number of swivel steps determines the wall thickness of the evolving bottom or
neck of the vessel. A wall thickness bulge of up to 10x t0 is possible. To avoid slag inclusions
in the centre of rotation, an optional cutting torch can be used to ensure a homogeneous material
distribution and the vessel’s ultimate gas tightness.
Advantages of necking-in
Necking-in allows optimum determination of the wall thickness progression in the diameter
reduction zone. Short tooling and cycle times, process reliability in production and constant
material quality result in cost-effective manufacture.
