Bending (metalworking)

Bending is a forming manufacturing processes. In this case, a bending moment is introduced into the semi-finished product ( the starting material prior to forming ), and thus brought about a plastic, i.e. permanent set.

Bending of sheet metal ( folding, crimping )

Bending metal sheets, called bending or flanging is effected, in principle, by the folding of a sheet member with respect to the remaining surface part of a metal sheet. Depending on the coming to apply small-scale tools or industrial processes and machines on the workpiece -related characteristics such as the bending edge, the bending angle or the bending radius is more or less exactly defined and reproducibly. For accurate processing while the flexural shortening is einzuberechnen and plan ahead with the flat pattern.

A sheet bending with a bend angle of 180 degrees for producing a fold is referred to as an envelope.

In the modern industrial manufacturing processes are divided into swivel bending, roll bending and flanging. When swivel bending the sheet is stretched by an upper beam and bent by a pivoting movement of the bending beam. In addition to stand-alone folding machines are powerful bending centers for flexible production of large amounts of bending parts, especially for complex bending shapes, up to individual pieces used. Typical products are: electric cabinets, casings, furniture, doors, cassettes, etc. See also: Kant part.

The roll bending is a patented special form of the swivel bending, in which the bending beam during the pivoting movement controlled by the plate moves away. Hence no any relative movement between tool and sheet, which can result in scratch marks on the sheet surface. This is important as the bending of stainless steel and metal sheets with pre-painted or pre-coated surface. With the controlled driving away of the bending cheek also programmable bending radii can be achieved. The roll bending comes with some bending centers are used.

More common in the artisanal and industrial sheet metal processing is flanging. The machines used for this purpose is called a press brake, press brake, press brake.

The bending of sheet metal are also comparable

• Align ( manufacturing process )
• Deep drawing
• Roll Forming

Bending of profiles

Curved pipes are used in many industrial fields such as the automotive, aviation, chemical, construction, or the food industry. They allow the construction of pipeline systems with lower material and labor used to angular pieces (fittings ). In addition to cold-formed metal profiles, for example, steel, copper, aluminum, brass or bronze and plastic profiles made ​​of fiber- reinforced thermoplastics are bent with the help of local heat input increasing.

For easy and fast, but also comparatively inaccurate bending of profiles (for example, for plumbing work in the heating and pipeline construction ) mobile, hand-operated tube bending devices are often used. For precision bending of profiles CNC bending machines are used. Depending on the bending task different bending processes are used. To bend very tight bend radii, in which the ratio of bending radius is to profile height between 0.7 ... 2.5, the so-called shape-related rotary- used. Rotary draw bending when the contour is dictated by the bending mold. The profile is stretched between the inner and outer clamping jaw. The bending moment will be induced by the rotation of the bending template, together with the clamping jaws. The counter holder tool serves as an abutment for the introduction of the bending moment. For demanding bending tasks with a ratio of bend radius to profile height less than or equal to 1.5 the tool elements mandrel and wiper die are used. The mandrel is inside the tube in the bending zone ( deformation zone ), and supporting the profile cross section in order to counteract cross-sectional deformation. The wrinkle is positioned on the inside of the bend or straight side of the tube and extends to the point of contact of the tube with the bending mold. He leaves no room for wrinkles. The wrinkles on the inner arc is a typical failure case for profile bending especially for very thin-walled sections. Another typical case of failure is the cracking on the outer arc. Cracks occur, when the elongation in the outside bend exceeds the maximum allowed strain for the transformation. As a rough guide, the uniform elongation of the profile material is used as the maximum allowable elongation at Section bending often.

For bending conditions of the bending radius for profile height greater than 2.5 freeform bending method must be used. When free-form bending the bending contour is not bound tool, but is also influenced by the tool kinematics. The best known and most widely used free-form bending process is the so-called three-roller thrust bending. In this method, the profile between the bending roller and the support roller (s) is guided and fixed in the transport unit. By delivering the forming roller transversely to the longitudinal axis profile and subsequent or simultaneous profile feed on the transport unit, the profile is curved. For changing the bending plane and the production of three-dimensional contours of the bending profile of the rotating unit around its longitudinal axis can be turned. To form a spline ( bending line / function of nth degree ) or a variable radius profile with continuous transitions between the radii, the delivery of the forming roller have to (and hence the bending radius ) during the bending process at the same time profile feed continuously in accordance with the curvature of the bending line be varied.

The plastic bending of profiles has always a permanent deformation of the profile cross-section the result. In the case of bending of a circular tube, the round tube ovalized in the bending zone ( deformation zone ). The size of the ovalization depends on the complexity of the bending task. The smaller the ratio of bend radius to pipe outside diameter, the greater the ovalization. Ovalization can not be avoided, they can be reduced ( made ​​of metal or elastomer materials mandrels ) during bending only through the use of any tools or aids in the tube interior.

Bending wood

In boat building, furniture making, glulam ( glued laminated timber ) and musical instruments are also curved wooden components. This is usually done with the aid of steam and heat ( bentwood ); in instrument with bending iron. For the production of curved components also veneers, which are bonded in presses to form plywood suitable.