Furniture design incorporates a lot of features and processes, and it has to take several factors into account as well. Sheet metal is one invention that has made furniture design and manufacturing much easier. This has also led to highly durable and cost-effective results.
However, the forming of sheet metal isn’t confined to just one process itself. There are several steps involved in the manufacturing of parts that may be on display or remain hidden in the final product. Sheet metal has a very high surface area with respect to its volume and is hence usually formed in rolls or coils.
The testing of sheet metal is definitely a highly important factor when it comes to furniture design. If the sheets are not up to par, the resulting furniture would come with many issues.
Not sure about how this is done?
Let’s take a look below!
The Standard Checks
When manufacturing the sheet metal, it’s important to check its mechanical behavior. It’s actually desirable for surface metals to have a large plastic deformation before the necking process.
In general, diffused necking is preferable to localized necking. Before the fracture process, it’s also preferred that the sheet metal shows a high elongation in total. Point elongation is usually found in metals like alloys of aluminum and magnesium or steels of the low carbon variety.
When the metal yields unevenly, those in the know would be able to detect stretcher strains on the sheet. These are also known as Leuder’s bands. Mostly seen as lines running over the sheet metal, these inconsistencies are depressions within the material. Hence, sheet metal with such markings isn’t acceptable where you desire a smooth finish for your furniture.
Other aspects to consider in the quality of sheet metal during necking include the grain size, the orientation, and the structure of that sheet metal piece. Too high a grain count will affect both the surface finish of the final product as well as the properties of that particular metal. Therefore, it may respond differently to outside elements and treatments.
Tests For Formability
Along with tension tests and grain tests, sheet metal should also undergo certain tests for their formability level. These tests can be specific to the kind of sheet metal involved, or some general ones that are applied to just about every type available.
The Cupping Test
The cupping test is one of the common ones, which companies like 3ERP perform on their prototypes before releasing them on the market. In this test, a specimen of the sheet metal is bound over a round die depression or cavity. A steel ball is then pressed or pushed into the sheet metal sample until the material eventually fractures.
The distance of plastic deformation for the sheet metal is calculated before the fracture is measured. The greater this distance is, the higher the sheet’s formability would be. Naturally, we want as much distance as possible before a fracture occurs.
Determining Anisotropy In Sheet Metal
One highly essential factor in the forming of sheet metal is anisotropy. This is the measure of the sheet metal’s mechanical properties. In layman’s terms, this factor measures how the sheet metal reacts when stress is put on it from one angle against when the same amount of stress is applied upon it from a different angle.
Anisotropic sheet of metal will have properties that are almost identical from any direction and angle possible. Cupping tests will determine anisotropy if another sample from the same stock of sheet metal is tested when flipped in the opposite direction.
The anisotropy is determined by looking at the kind of fracture that occurs when a steel ball finally manages to break a specimen. If the fracture that results is circular in shape, you can be fairly sure that the whole stock consists of isotropic sheet metal.
If the fracture is straight, the stock is labeled as anisotropic.
Changes In Sheet Metal
The testing for the sheet metal after its production is all well and good. However, you also have to take into account the changes it undergoes during the many work processes that are inflicted upon it. These operations could result in a highly complicated distribution of forces upon the sheet metal.
For instance, the material can be exposed to different levels and frequencies of bi-axle force, strain, or pressure depending on how they’re being processed.
There may also be several kinds of bi-axle forces at work. A sample may be tested with these forces and a grid printed on this particular specimen. This grid has a number of circles inscribed upon it so that you can observe how they deform along with the metal when under process.
Testing For Sheet Metal Manufacture
After the tests outlined above, the sheet metal may be tested further under different combinations of the same strains. These tests may include safe zones, failures, major and minor direction combinations, and many more.
To display this information in a convenient and graphical manner, manufacturers and tests of sheet metal often make use of forming limit diagrams. This proves to be an excellent way of showcasing the excellence of their product to clients.
If a certain batch of sheet metal proves to be exceptionally strong, manufacturers can replicate it and use it as a base for future projects.