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PBF-SW Sheet Stretch Forming Machine

Aircraft Wing Skin Manufacturing

Longitudinal and transverse are the two basic types of stretch forming machines. Longitudinal stretch formers stretch the workpiece along its length, while transverse stretch formers stretch the workpiece along its width.

In both types of stretch forming machines, the jaws or grippers hold and stretch the metal sheet or extrusion while it is formed over the die table. The die table provides the shape for the metal to be stretched and formed over, and the hydraulic system provides the force needed to control the stretching process.

Sheet Stretch Forming process

Sheet stretch forming is a manufacturing process used to shape sheet metal into complex three-dimensional forms. It involves stretching a sheet of metal over a die, causing it to deform and take on the shape of the die.

Sheet Stretch Forming is commonly used by aircraft builders to manufacture fuselage skin sections from special aerospace aluminum alloy sheets. During the metal stretch forming process (also known as ‘wrap forming’), in which a sheet of metal is wrapped around a mandrel or a form, using tension to create a three-dimensional shape. Stretch forming(wrap forming) typically involves wrapping the metal over the form and then pressing the metal onto the mold using a mechanical or hydraulic press. This process is commonly used in the aerospace industry to create complex curved or contoured parts for aircraft and spacecraft.

The process typically begins with a flat sheet of metal, which is clamped around its edges and held in place. The sheet is then forced to stretch and deform by applying controlled forces or pressure. This stretching causes the metal to thin out in some areas and stretch in others, allowing it to conform to the shape of the die.

Which metals can be used for the sheet stretch forming process
  • Any ductile metal can be shaped by this method.
  • The process is mainly applied to aluminum alloys for aircraft skins.
  • Magnesium alloys are stretch-formed while hot.
  • Stainless steel and titanium are stretch-formed on a commercial scale.
  • Thinning and strain hardening are inherent in the processes. It is important to know the elongation values for the metal being used. Large elongations are best. Thickness reduction should not exceed 5% of the original thickness.