Finite Element Analysis in Roll Forming Applications

This contact creates the loading on the strip. The strip will deform (the nodes will move) as it passes through the surfaces of the rolls. One can visualize and quantify the results in the nodes as it passes through the rolls (see Figure 2).

An analogy can be made by applying the circle grid technology to roll forming. If one were to scribe a grid onto the surface of the strip and feed the strip through the forming rolls, one can see how the intersection of the grid displaces and moves around as it forms. FEA will allow the engineer to see how the strip progresses through the forming mill, how the material feeds from the forming stand to forming stand, and how the edge of the material strip strains as it progresses through the mill.

FEA also allows the engineer to see the stretch and thinning of radii and analyze hole features (see Figure 3). Typically, for this case, the mesh density would be increased around the feature and any distortion of the feature can be viewed and measured as it progresses through the tooling.

The software will also allow one to toggle and view the roll tooling in an “on” or “off” state. This allows one to virtually see what is happening to the strip as it leads into a forming pass or view the “forming footprint” (what is happening underneath the forming pass). In the past, this would happen at the mill. One would need to take the time to disassemble the roll pass in order to cut out the required samples. This is time consuming, inefficient, and non-value added.

When used by an experienced designer, FEA will allow one to develop a ideal roll design. Roll problems are discovered and solved before the tooling is made. When combining FEA with design experience several iterations of tool tryout can be removed from the development process.

PROCESS BENEFITS
When it comes to producing quality roll-formed parts, there is no substitute for experience. In experienced hands, FEA is a powerful tool that increases efficiency, quality, uptime, and profitability for manufacturers, clients, and end users alike. To discover development problems and make necessary design changes after production has started can add weeks to a project and considerable expense for both the manufacturer and the client.

The manufacturer has to pull the job, reschedule it, and redesign the rolls. As a result, the client’s project is delayed, valuable floor capacity is wasted, and profitability for both parties is diminished. FEA helps to avoid this scenario with roll and product models that give manufacturers the ability to optimize uptime and productivity with designs that have been pre-tested and verified for quality before they ever hit the production floor.

For end users, value is enhanced as these savings are passed along and the quality of parts is improved. FEA is a helpful training aid and when reviewing the results, experience can be shared among engineers. This allows the opportunity to sharpen skills without the danger or expense of disassembling actual production lines to gain firsthand knowledge. In addition, FEA provides an unbiased, fact-based view of design performance and effectiveness so manufacturers and clients can easily document needed engineering changes.

OTHER CONSIDERATIONS
Because FEA modeling assumes “ideal” manufacturing conditions and homogenous materials in its calculations, the results it generates are only as good as the data entered. This is why it is most effective in the hands of experienced roll-form engineers who have the practical and technical knowledge necessary to fully utilize FEA’s strengths as well as the ability to apply real world expertise to the interpretation of its findings.

CONCLUSIONS
Finite Element Analysis is a valuable and effective tool for experienced roll-form engineers to verify process and product quality from roll development all the way to part finishing. While FEA modeling cannot completely eliminate the need for traditional research and development with physical prototypes, it can greatly enhance the process and make it much more cost-effective.

The ability to perform FEA is a great asset for any roll-form manufacturer and provides enhanced value for clients and end users that benefit from the cost savings, quality improvements, and shorter lead times made possible by this powerful modeling method.