FOCUS ON HYDROFORMING
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 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 have a tendency to wrinkle , also benefit greatly from the controlled flow of material .
Parts that normally require multiple steps or expensive progressive dies can often be formed in a single cycle through sheet hydroforming
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 cold forming technique that uses a high-pressure 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 the need for most secondary processes . The parts can be as thin or as thick as the design demands , and it can have complex joints , threads and formations ,” commented spinning and hydroforming specialist , Helander HQ + Forming in the U . S .
Tubular hydroforming is used when complex components , such as curved sections , are needed . Examples include truck / car door handles and bicycle frames etc .
“ The main advantage of hydroforming is that it allows complex shapes with concavities to be formed , which would be difficult or impossible with standard stamping ,” commented stamping specialist , Gestamp . “ Tube hydroforming technology is vital for some key parts of chassis and body in white , even more now with so many electric vehicle projects entering the market . This technology allows us to manufacture lighter parts which have better performance and stiffness , because its application transforms different sections along the length of the tube .”
Making the choice
Hydroforming technology is well suited to structural items , from small and shallow to large and deep parts in various materials ( such as aluminium alloys , stainless steel and titanium ). It is used , for example , for engine components including deep drawn parts , in high-strength , heat-resistant materials . It is also employed for the expansion forming of tubes , ducts and other irregularly shaped parts .
Complex , close-tolerance parts can be produced , often in one operation . The process also offers higher productivity levels , as multiple parts can be processed in a single cycle . Faster lead times also result , with quick tool set-up .
If electrodes are used to vaporize the fluid explosively in an arc , this describes a similar process known as electro-hydraulic forming . For large parts , explosive hydroforming can generate the forming pressure by
Above and left : Inside a 50,000kN hydraulic hydroforming press ( image : LOIRE Gestamp ). simply exploding a charge above the part ( complete with evacuated mould ) which is immersed in a pool of water . The hydroforming-into-a-mould process also works using only a shock wave in air as the pressuring medium . “ Hydroforming ’ s broad design freedom ; high material utilisation ; reduced part weight ; high
A hydroformed stainless steel handle for a high-end coffee machine ( image : Inoxveneta SpA ).
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 .
■ Eliminate multi-step processes .
■ Smooth finishes , with little to no secondary processing .
mechanical strength and improved dimensional accuracy contributes to its popularity as the chosen manufacturing method for many [ industry sectors ] such as automotive , lighting and appliance industries ,” concluded Metalcraft Spinning and Stamping . n
EDITOR ’ S NOTE
A video of a Gestamp tube hydroforming process can be viewed on https :// youtu . be / glNKQey7Gw4
36 | ismr . net | ISMR March 2024