ROLL FORMING APPLICATIONS FOR AUTOMOTIVE INDUSTRY :
Roll forming is a continuous profile production process to form sheet metal progressively into the desired shape with closer tolerances. The process offers several advantages such as complex geometrical shapes, high strength, dimensional accuracy, closer tolerances, and good surface finish. Several parts in the automobile body are produced with this process.
Roll forming process can easily be implemented to current production lines and synchronized with other stamping units. The pipe-shaped thin-walled cross-sections and complexly shaped profiles which are difficult to produce by other methods can be produced by roll forming. In some applications roll formed profiles have more inherent strength than those produced by other methods. Nowadays roll forming technology draws more attention than before in the automotive industry.
In this study, the roll forming process has been investigated in automotive applications and the latest developments according to the existing sheet metal forming techniques are discussed. The roll forming process is more rapid and takes less energy than extrusion. However, it requires large quantities to justify the investment cost
INTRODUCTION OF ROLL FORMING APPLICATIONS :
The roll forming process is a sheet metal forming process, which produces a more consistent part than other forming methods. It is preferable for large quantity production and long length parts. Dimensional accuracy and tolerances of the rolled parts much better than regular stamped parts. Numerous studies have been performed on the new forming technologies for car bodies such as hydro-forming, hot press forming, and roll forming. Roll forming (or roll forming) is a continuous bending process in which a long strip of coiled sheet metal moves in the sequence of rolls progressively to produce the desired shapes. Each roll sequence deforms only a shape of the bend and it continues up to reaching the desired cross-section. Roll forming is suitable for producing constant-profile parts in continuous forming with long lengths-large quantities and coil feeding and exit cutting to length held to close tolerances. Besides, notching, slotting, punching, embossing, and curving operations can easily be combined with the roll forming process to produce finished parts for manufacturing lines.
Even though, the flat steel products are approximately 35–40% of total production in North America [, the roll forming is not a common forming method. It is still considered as a new method in the automotive industry. While conventional roll forming machines produce parts whose cross sections are uniform in the longitudinal direction, nonetheless, the integrated structural skin can be designed in the vehicle body through 3D flexible roll forming techniques. In these techniques, both constant and variable cross-sectional sized profiles are produced. Nowadays, the roll forming process is capable of producing a wide range of cross-section. The 3D roll forming has overcome the constant cross-section limits on production. Basic roll forming applications are applied on as follows:
- Car body and bumpers
- Rail body
- Ship construction
- Transport and loading/unloading equipment
- Electric racks, control cabinets, and storage
- Electric racks, control cabinets, and storage
- Construction industry
- Beam members
In the roll forming operation, tensile and compression stresses are effective in the transition zone occurred during changing in cross-section areas in the deformation. These areas are critical regions because of excessive tensile and compression stresses
cause defects called as tearing and wrinkling, respectively. Holding force and stand movements are the main factors affecting the occurrence of failure modes; wrinkling, tearing in sheet metal parts. Improvements on defects are based on the control of material flow in the forming. Strain distribution at the transition zone was investigated for High Strength Steel (HSS) and Ultra High Strength Steel(UHSS).
A multi-stand roll forming simulation was developed for a large cross-section of the channel by using a method based on the Lagrange method in the deformable bodies mechanics . In recent years, the automotive, aerospace, electronics, medical industries have used the small-diameter pipes and tubes significantly. A modified roll forming process making welded tubes with discontinuous cross sections has been realized through forming stands equipped a feedback unit with a control system.
Forming process can be in the cold, warm, and hot conditions with respect to heat requirements. The small-diameter pipes or tubes have been produced from pre-notched sheet plates using a cold-roll forming technique. The starting temperatures of warm forming process are also above room temperature but below the recrystallization temperature.
Forming above recrystallization temperature is called as hot forming. When feedback devices are added to the roll forming process stand movements can be controlled separately. In this type of control case, critical regions like excessive tensile forces are sensed by the feedback devices and it is possible that the controller can manipulate trajectory of the stands to eliminate error between desired and current profile during the process synchronously. Through a cost calculation tool in the designing progress, comparisons on the production methods of the structural body parts in the automotive industry show that roll forming has a high potential to meet the continuously increasing demands on safety, comfort, ecological performance, high flexibility, and low-cost requirements with novel approaches.
Roll forming is useful due to the fact that the whole forming processes are in a single forming operation. An automobile wheel fabrication is obtained in single step operation using Russian AVT alloy, a 6010 aluminum alloy equivalent. In this context studies on the new profile developments produced with lightweight materials by roll forming are covered with analytics, experiments, and FE analysis. The microstructure is also important on the strain and stress distributions and the displacements. The UHSS steel is another widely used material in the automotive industry and the roll forming is a suitable method on the UHSS.
The roll forming is an efficient, reliable process on the bumper impact bars, associated brackets, and fascia supports less than 1 mm thick UHSS. Spring back is one of the likely defects caused by bending in the roll forming. A comparison was performed on the samples of automotive steels to be able to select suitable material.
Low plasticity and ductility of materials are serious limitations on forming. These limitations constrain the usage of the HSS but it is overcoming partially through a hot roll forming process. For a roll forming design process, a roll flower pattern and proper stand sequences are important to make fine tuning on parameters that affect quality. It is possible to determine through longitudinal strain and deformation analyses. A successful roll forming technique different from the conventional roll forming to manufacture automotive bumpers from the HSS steel was described with desired formability parameters. In recent years, materials for automotive components have been gradually changed from steels to aluminum for reducing the total weight of a car but fracture or buckling are other defects encountered in the roll forming of the aluminum alloys. Optimization methods are popular to make process parameters improved and preferred frequently in the designing process. Optimization of the forming process minimizes the number of stands to be used and residual stresses in the final product. Sheet metal stamping is a common forming process to produce structural parts for the automotive body.
Hydroforming is also used to produce some of the automotive parts. The roll forming is an alternative method to these methods owing to the fact that it is cost effective in high volume production and highly flexible. The roll formed parts used in the transportation industry are auto bodies, rail profiles, highway barrier profiles, roof liner, and door rafters. denotes the common shapes of roll formed parts at vehicles. Roll formed and stamped regions on a vehicle’s space frame are seen in bellow.
Roll formed cross-sections for automobiles/commercial vehicles The Advanced High Strength Steel (AHSS) tubes are principally applied as side impact door beams, seat structures, and IP beams in the automobiles. The shapes of the tubes may become circular, square, oval, and tapered tube sections and are produced in subsequent stages.
CONCLUSION OF ROLL FORMING APPLICATIONS FOR INDUSTRY
the roll forming process for the automotive industries was investigated. Their advantages and limitations were evaluated. Current trend reveals that the process in the automotive industry will be very common in the near future. When the precise, long, and high strength body parts are required in large quantity, the roll forming process will be the ultimate choice.