Explosive forming
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The explosive forming process
In general, a metal sheet is placed on a die. The die cavity is vacuumed and the assembly is placed in water. An explosive charge is detonated under water pushing the sheet in the die in about 2 milliseconds.
example of explosive forming (video)
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Advantages
Explosive forming offers unique solutions because explosives can be applied in any shape and mass. We have no restrictions in product size, shape, material and thickness.
Sizes range currently up to 10x2 meters, thicknesses from 0,3 mm aluminium to 60 mm stainless steel and many types of aluminium, titanium, stainless steel and nickel have been successfully formed by explosive forming. These ranges are not limits.
The shape of the blank material can be optimized for any product shape. Sheets can be formed from flat or bent condition, or from a conical or cylindrical shape.
An extreme example of applying an optimized blank shape is an explosive formed lobe mixer. A disk is folded and explosive formed in a segmented die. The result is a seamless shape while the conventional method is to weld the shape from many pressed segments.
Sheets and tubes can be formed in welded condition, even when the welded sheets have different thicknesses. Good results have been achieved in steel (MIG and electrode welding), stainless steel and nickel alloys (laser and TIG welding) and aluminium (TIG and friction stir welding).
The tooling for explosive forming is relatively simple. One die half is needed without a mating part. Low cost tooling concepts decrease costs further.
Prototypes can be delivered quickly. The tooling is relatively simple and can normally be manufactured quickly. The tooling does not need to be installed in a machine so that production can be started immediately.
Engineering
We are highly experienced in 3D CAD and CADCAM operations.
We have a FEM simulation software (Autoform) for simulating our processes. This enables us to advise in developing new products and predict the product properties (e.g. thickness, remaining elongation of the metal).
example of FEM simulation (video)
Link to product (Smedinghuis)
History of explosive forming
Explosive forming was applied in the 1960's in the USA and the USSR for aerospace and space applications. But in the 1980's applications were hard to find due to the development of other metal forming technologies that can be applied in a workshop jointly with other processes without the safety measures that come with applying explosives.
Also, the technology of explosive welding was developed in the 1970's. Companies that operated explosive forming focused to explosive welding large plates of e.g. titanium or aluminium to steel.
Several factors contributed to the re-introduction of explosive forming. Products with more complicated shapes were required in smaller quantities. The time-to market decreased and companies became used to subcontract specialized work.
TNO started a research program in 1995 that resulted in the spin-off company Exploform B.V. in 1998 in order to make explosive forming commercially available to the industry.