Small, hydroformed aluminium part.
concave shapes). The final shape can be achieved in fewer steps and with less manual correction. Heavy gauge and difficult materials can also be formed into complex shapes with close tolerances. The metal fabrication and forming process enables the shaping of metals such as steel; stainless steel; copper; aluminium and brass. Internal highpressure forming( hydroforming) is, in fact, a methodology for the manufacture of hollow metal components( a process that has grown enormously since the mid- 1990s). There are numerous applications for the process in various industry sectors to manufacture lighter, stronger as well as rigid, one-piece structures. The process is suitable for industries that require intricate and high-quality components( such as automotive, aerospace and electronics). It is also a sustainable process, producing little to no scrap. In sheet hydroforming, a metal sheet is placed over a die before highly pressurised water forces it down and makes it conform to the shape of the mould. In tube hydroforming, a preexisting tube is set between two dies, and water pushes the interior of the tube to expand and conform to the new shape. Both processes allow for the seamless forming of new shapes and parts in common metal alloys without welds.
Sheet hydroforming
Image: Jones Metal Products.
“ Sheet hydroforming operates using one tool instead of two, which reduces die cost when compared to other cold forming processes. Rolled sheet metal, cut to size, serves as the blanks in the sheet hydroforming process, the size and shape of which is be determined by the results of simulations which will be conducted to determine process parameters to optimise material flow,” said press specialist, Macrodyne.
“ Sheet hydroforming is typically performed using a cavity die or a punch. Punch hydroforming is also known as hydromechanical deep drawing. To determine whether a punch or a cavity will be used, the geometrical complexity and draw depth of the part being formed will have to be considered,” it continued.
“ Sheet hydroforming can also be performed using a flexible bladder, to prevent the fluid from contacting the blank, or using fluid that is in direct contact with the material, which often leads to the need for secondary processes and results in better surface quality. Bladders prevent lubricant from mixing with the working fluid and enables the use of certain forming techniques, such as circular pressure intensifiers that can tighten radii,” it added.
Sheet hydroforming is a metal forming process that uses pressurised hydraulic fluid in a flexible diaphragm to shape sheet metal against a single, un-mated tool. The process can create a wide range of complex geometric shapes from a variety of materials including aluminium; steel; stainless; titanium; niobium; Inconel; copper; composites and more.“ Sheet hydroforming presses can combine or even replace different metal forming processes including spinning; press brake forming; traditional draw forming; rubber pad forming; progressive die forming and more. These machines can also consolidate multiple steps into a single cycle, virtually eliminating secondary finishing processes such as polishing, annealing or welding,” added press manufacturer, the Beckwood Corporation.
Hydroformed parts.
Image: Helander.
The two primary types of sheet hydroforming presses are fluid cell and deep draw. Fluid cell presses create shallow parts with open corners while deep draw presses are used for taller parts with closed corners. Deep draw hydroforming machines use pressurised hydraulic fluid( either water or oil) to force sheet metal into or around a single solid mould. The hydraulic chamber is sealed by a flexible rubber diagram, which acts as the female portion of the tooling and can be paired with any mould.
Rubber pad forming is a deep drawing technique that is suitable for the production of small and medium-sized batches.
The uniform pressure exerted by the diaphragm in sheet hydroforming is suitable for creating complex geometric
FOCUS ON HYDROFORMING
Sheet hydroforming benefits
■ Complex and irregular shapes can be formed.
■ Accurate and repeatable forming.
■ Reduced reliance on skilled labour.
■ One comprehensive tool( no mating part is needed).
■ Uniform elongation of material.
■ Thinner materials can be used for the blank, resulting in a lighter end product.
■ Multi-directional force to reduce stretching or thinning.
■ Complex, net-shape parts formed in a single cycle.
■ Short set-up times and reduced waste.
■ Eliminates multi-step processes.
■ Supports sustainable manufacturing processes.
■ Smooth finishes, with little to no secondary processing.
shapes which are difficult using traditional forming methods. Parts that normally require multiple steps or expensive progressive dies can often be formed in a single cycle through sheet hydroforming. Cans, boxes or parts with curved flanges, which tend to wrinkle, also benefit greatly from the controlled flow of material.
Tube hydroforming
Tube hydroforming( THF) is a cold forming process to form a hollow part with different cross sections along its length by applying an internal hydraulic pressure and forcing the tubular blank to conform to the shape of a given die cavity. It is a specialised type of coldforming technique that uses a highpressure hydraulic fluid to press tubes into a die at room temperature. This method makes it possible to manufacture hollow components with a complex external shape and especially favourable strength properties.
“ Tube hydroforming is extremely advantageous because it allows manufacturers to create precise replications of the same part without needing to weld or join the two halves of the tube. Hydroforming also leaves the part with a high-quality finish that reduces
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