Views:9 Author:zhangyun Publish Time: 2019-01-14 Origin:Site
Roll forming is a process of continuous shaping that makes it possible to obtain products of constant section, known as profiles, from sheet metal sheets or coil using a roll forming machine. These profiles can be divided into three main families:
Wide profiles: these are products of great width (600 to 1500 mm approximately) with several waves of equivalent shape or similar. This category includes roofing and cladding profiles;
Tubes: These are closed section products made by profiling with a continuous weld;
Narrow profiles: these are products with open or closed seamless section with no repetition of a waveform. This category includes, among others, structural sections, cable trays, guard rails, etc.
How roll forming works
The most important asset of profiling, compared to folding, is its high production rate.
How the roll forming process works:
Roll forming can be considered as continuous bending. During the process, the sheet is folded progressively by each of the heads, until the desired angles and shape. Each set of rollers (upper and lower) called profiling head. The shape of the metal coated steel sheet at each of the profiling heads or passes constitutes the profiling flower. This is a major feature because it defines the order of realization of the folds as well as the folding values of the angles. More generally, the profiling of a product on a defined machine is essentially characterized by:
1. Roll forming capabilities:
Roll forming is a very flexible process. This is reflected in its production capacities, in the forms achievable - even if they must remain of the constant section in the sense of the length - but also on the level:
Thicknesses: they can vary between 0.15 mm and 12 mm;
Widths: There is no minimum value due to the slitting capabilities of the coils. For the maximum value, the terminal is actually due to the achievable format of the coils, that is to say, 2060 mm according to our current program;
Lengths: there is no maximum for the length of the profiles except the one that exists for handling, transport, etc;
Steel grades: highly ductile grades with a low yield strength (around 150 MPa) are usable as well as very hard grades with yield strengths of 1000 MPa and more. With the right technology, it is possible to produce quality profiles in all existing grades;
The biggest restriction of roll forming is the fact that the product must be of a constant shape in its length - which does not exclude curved products.
2. The transversal deformations
To obtain a profile from a flat sheet, it is necessary to create folds and thus to locally laminate the sheet in its transverse direction. The level of these plastic deformations is mainly related to the geometry of the desired product. They can, therefore, be approximated by the following formula;
To avoid cracking of the coating and corrosion of the profile, when using it in the future, choose a geometry of the profile with the lowest possible e / R ratio: with large radii relative to the thickness of the material.
3. Longitudinal deformations
The main difficulty in profiling is to properly manage the twisted areas of the sheet in the profile use. These are intrinsic to the process. It is not a question of eliminating them - which is totally impossible - but of limiting them or even, in certain cases, of distributing them correctly. It is necessary that the longitudinal deformations caused by the kinking of the sheet in the profile use remain in the elastic domain of the material. If this is not the case, the material will laminate. The sheet will locally extend irreversibly in its longitudinal direction and twist at the exit of the profile use.