What is the meaning of the term formability in the context of sheet metal design ? Why is it important while designing sheet metal components ?
When designing sheet metal components there are two major types of processes
While Bending is like folding paper, forming is a lot more complex but also opens up a lot more design possibilities for design engineers.
Forming cannot be done on all type of metal sheets . There are some material grades which are more formable than others.
This formability is a vital factor in design of stamping parts like Automotive doors, roofs, chassis brackets etc. Good design with a formable material results in a durable design of a sheet metal assembly maintaining structural integrity .
Formability is basically how intricately can we form or shape the sheet metal into desired shapes without the material fracturing .
Key factors which affect formability
Measuring Formability: Formability is often quantified using tests like the tensile test, the bend test, and the Erichsen cupping test. These tests help in understanding how the metal behaves under different types of strain and stress.
Importance in Design and Manufacturing: Understanding formability is crucial for designing sheet metal parts. It helps in selecting the right material and forming processes, which in turn affects the tooling design, the production speed, and the cost-effectiveness of the manufacturing process. Additionally, good formability reduces the risk of defects such as cracks, wrinkles, or tears, ensuring high-quality end products.
Forming tests are carried out as shown
The strains are then measured and plotted .
Due to deformation and stretching the thickness of the sheet reduces locally . While in some areas material accumulates and there is thickening . Both extremes of excessive thinning and thickening are not desirable . Thinning being more critical in terms of load bearing applications.
Forming limit diagram showing Minor strains and Major strains.
Forming limit diagrams are characterized for each sheet metal material grade and the design engineer selects materials which are suitable for good formability . The decision of good formability or bad formability is based on the Forming limit diagrams.
Using software tools like “ One step formability” we can get a basic idea of the thinning of material in forming
Forming simulation of a simple cup showing the thinned area in red.
With available forming Limit diagram from the manufacturer , the major and minor strains obtained from a forming simulation are plotted on the graph
To learn about Sheet metal design in deep here is a course which can help :
Basics of Sheet metal design for Mechanical design engineers
For more content on sheet metal design have a look at the list of articles here :
How to Stiffen Sheet metal design
Categories: : Sheet metal