Spring Back Compensation

Last updated

'Spring back compensation is used in metal forming to ensure that the final shape assumed by a piece of metal after being removed from a forming tool is the shape desired. Typically, when metal is being formed at room temperature, it will undergo both plastic and elastic deformation. After the metal workpiece is removed from the tool or deformation implement, the elastic deformation will be released and only the plastic deformation will remain; thus, the workpiece will "spring back" to a position between its original position and the position into which it was formed. Usually, spring back compensation is realized by over-bending the material by an amount corresponding to the magnitude of the spring back.

Contents

When bending metal, spring back compensation is done by pushing the workpiece further into the die. For other sheet metal forming operations like drawing, it entails deforming the sheet metal past the planned shape of the part so that when the part's elastic deformation is released, the plastic deformation in that part delivers the desired shape of the part. In the case of complex tools, spring back must be considered in the engineering and construction phases. Complex software simulations are often used, but frequently this is not enough to deliver the desired results. In such cases practical experiments are done, using trial-and-error and experience to correct the process. However, the results of the process are only stable if all influencing factors are the same. [1] These include such things as yield strength, chemical composition, aging processes, and structure of the workpiece; tool wear; and temperature and deformation rate during the forming process.

Spring back assessment of final formed products is a difficult problem and is affected by the complexity of the formed shape. The NUMISHEET 93 conference benchmark problem involves the draw bending of a U-channel using three measured parameters. Parameter-less approaches have been proposed for more complex geometries but they need validation. [2]

Practical example: electronic bending tools with spring-back compensation

Electronic bending tool with integrated angle measurement and spring-back compensation Bending tool for Standard bending EHRT.jpg
Electronic bending tool with integrated angle measurement and spring-back compensation

Manufacturing of electrical assemblies produces components that are flat, using copper and aluminum. The mechanical properties of copper and aluminum are very different and require different programmable inputs in order to achieve the same dimensional characteristics.

Bending technology for flat material which measures each bend angle and provides spring back compensation is required. This gives the bend angle of flat materials true accuracy. This is attained by using bending prisms with electronic angular measurement technology. While bending two flat bolds supporting the material turn around. The bolds are directly connected to the angular sensors. A computer or rather the machine control then calculates the required final stroke. The spring back of every bend is compensated regardless of material type.

If the measuring accuracy is 0.1º, a high angle accuracy of +/- 0.2º is achieved instantly with the first workpiece without any rework. Because no adjustments are required, material waste amounts and setup times drop considerably. Even inconsistencies within a single piece of material are automatically adjusted.

See also

Related Research Articles

<span class="mw-page-title-main">Metalworking</span> Process of making items from metal

Metalworking is the process of shaping and reshaping metals in order to create useful objects, parts, assemblies, and large scale structures. As a term, it covers a wide and diverse range of processes, skills, and tools for producing objects on every scale: from huge ships, buildings, and bridges, down to precise engine parts and delicate jewelry.

A die is a specialized machine tool used in manufacturing industries to cut and/or form material to a desired shape or profile. Stamping dies are used with a press, as opposed to drawing dies and casting dies which are not. Like molds, dies are generally customized to the item they are used to create.

<span class="mw-page-title-main">Grinding machine</span> Machine tool used for grinding

A grinding machine, often shortened to grinder, is any of various power tools or machine tools used for grinding. It is a type of material removal using an abrasive wheel as the cutting tool. Each grain of abrasive on the wheel's surface cuts a small chip from the workpiece via shear deformation.

<span class="mw-page-title-main">Sheet metal</span> Metal formed into thin, flat pieces

Sheet metal is metal formed into thin, flat pieces, usually by an industrial process.

<span class="mw-page-title-main">Work hardening</span> Strengthening a material through plastic deformation

Work hardening, also known as strain hardening, is the process by which a material's load-bearing capacity (strength) increases during plastic (permanent) deformation. This characteristic is what sets ductile materials apart from brittle materials. Work hardening may be desirable, undesirable, or inconsequential, depending on the application.

<span class="mw-page-title-main">Shot peening</span> Cold metal working process to produce compressive residual stress

Shot peening is a cold working process used to produce a compressive residual stress layer and modify the mechanical properties of metals and composites. It entails striking a surface with shot with force sufficient to create plastic deformation.

<span class="mw-page-title-main">Drawing (manufacturing)</span> Use of tensile forces to elongate a workpiece

Drawing is a manufacturing process that uses tensile forces to elongate metal, glass, or plastic. As the material is drawn (pulled), it stretches and becomes thinner, achieving a desired shape and thickness. Drawing is classified into two types: sheet metal drawing and wire, bar, and tube drawing. Sheet metal drawing is defined as a plastic deformation over a curved axis. For wire, bar, and tube drawing, the starting stock is drawn through a die to reduce its diameter and increase its length. Drawing is usually performed at room temperature, thus classified as a cold working process; however, drawing may also be performed at higher temperatures to hot work large wires, rods, or hollow tubes in order to reduce forces.

<span class="mw-page-title-main">Rolling (metalworking)</span> Metal forming process

In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is similar to the rolling of dough. Rolling is classified according to the temperature of the metal rolled. If the temperature of the metal is above its recrystallization temperature, then the process is known as hot rolling. If the temperature of the metal is below its recrystallization temperature, the process is known as cold rolling. In terms of usage, hot rolling processes more tonnage than any other manufacturing process, and cold rolling processes the most tonnage out of all cold working processes. Roll stands holding pairs of rolls are grouped together into rolling mills that can quickly process metal, typically steel, into products such as structural steel, bar stock, and rails. Most steel mills have rolling mill divisions that convert the semi-finished casting products into finished products.

In the context of machining, a cutting tool or cutter is typically a hardened metal tool that is used to cut, shape, and remove material from a workpiece by means of machining tools as well as abrasive tools by way of shear deformation. The majority of these tools are designed exclusively for metals.

<span class="mw-page-title-main">Bending (metalworking)</span> Metalworking to produce a V-, U- or channel shape

Bending is a manufacturing process that produces a V-shape, U-shape, or channel shape along a straight axis in ductile materials, most commonly sheet metal. Commonly used equipment include box and pan brakes, brake presses, and other specialized machine presses. Typical products that are made like this are boxes such as electrical enclosures and rectangular ductwork.

<span class="mw-page-title-main">Press brake</span> Machine for bending sheet and plate material

A press brake is a type of brake, a machine used for bending sheet metal and metal plate. It forms predetermined bends by clamping the workpiece between a matching top tool and bottom die.

In metallurgy, cold forming or cold working is any metalworking process in which metal is shaped below its recrystallization temperature, usually at the ambient temperature. Such processes are contrasted with hot working techniques like hot rolling, forging, welding, etc. The same or similar terms are used in glassmaking for the equivalents; for example cut glass is made by "cold work", cutting or grinding a formed object.

<span class="mw-page-title-main">Burnishing (metal)</span> Deformation of a metal surface due to friction

Burnishing is the plastic deformation of a surface due to sliding contact with another object. It smooths the surface and makes it shinier. Burnishing may occur on any sliding surface if the contact stress locally exceeds the yield strength of the material. The phenomenon can occur both unintentionally as a failure mode, and intentionally as part of a metalworking or manufacturing process. It is a squeezing operation under cold working.

<span class="mw-page-title-main">Tube bending</span> Metal forming process

Tube bending is any metal forming processes used to permanently form pipes or tubing. Tube bending may be form-bound or use freeform-bending procedures, and it may use heat supported or cold forming procedures.

<span class="mw-page-title-main">Friction stir processing</span>

Friction stir processing (FSP) is a method of changing the properties of a metal through intense, localized plastic deformation. This deformation is produced by forcibly inserting a non-consumable tool into the workpiece, and revolving the tool in a stirring motion as it is pushed laterally through the workpiece. The precursor of this technique, friction stir welding, is used to join multiple pieces of metal without creating the heat affected zone typical of fusion welding.

<span class="mw-page-title-main">Roll bender</span> Machine that produces a circular arc shape from sheet metal or bars

A roll bender is a mechanical jig having three rollers used to bend a metal bar into a circular arc. The rollers freely rotate about three parallel axes, which are arranged with uniform horizontal spacing. Two outer rollers, usually immobile, cradle the bottom of the material while the inner roller, whose position is adjustable, presses on the topside of the material.

<span class="mw-page-title-main">Metal spinning</span> Metalworking process

Metal spinning, also known as spin forming or spinning or metal turning most commonly, is a metalworking process by which a disc or tube of metal is rotated at high speed and formed into an axially symmetric part. Spinning can be performed by hand or by a CNC lathe.

In metalworking, forming is the fashioning of metal parts and objects through mechanical deformation; the workpiece is reshaped without adding or removing material, and its mass remains unchanged. Forming operates on the materials science principle of plastic deformation, where the physical shape of a material is permanently deformed.

<span class="mw-page-title-main">Bending machine (manufacturing)</span>

A bending machine is a forming machine tool. Its purpose is to assemble a bend on a workpiece. A bend is manufactured by using a bending tool during a linear or rotating move. The detailed classification can be done with the help of the kinematics.

Rule based DFM analysis for forging is the controlled deformation of metal into a specific shape by compressive forces. The forging process goes back to 8000 B.C. and evolved from the manual art of simple blacksmithing. Then as now, a series of compressive hammer blows performs the shaping or forging of the part. Modern forging uses machine driven impact hammers or presses that deforms the work-piece by controlled pressure.

References

  1. Optimierung der Produkt- und Prozessentwicklung. ETH Zürich. 1999. p. 67. ISBN   978-3728126962.
  2. Raghavan; et al. (September 2013). "Numerical assessment of springback for the deep drawing process by level set interpolation using shape manifolds". International Journal of Material Forming. 7 (4): 487–501. doi:10.1007/s12289-013-1145-8. S2CID   255585418.