Drawing (manufacturing)
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- This article is about the manufacturing technique. For the art form, see Drawing.
Drawing is a manufacturing process for producing a wire, bar or tube by pulling on a material until it increases in length. This is typically accompanied by a thinning out of the material, usually through a reduction in the girth.
This technique has long been used to produce flexible metal wire by drawing the material through a series of dies (holes) of decreasing size. These dies are manufactured from a number of materials for wire drawing, the most common being Tungsten Carbide and Diamond. Diamond dies can either be synthetic or natural, synthetic diamond is usually used in the early stages of the drawing process, whereas natural diamond dies are used in the final stages. More recently drawing has been used with molten glass to produce high quality optical fibers.
Drawing can also be used to pull metal over a die (male mold) to create a specific shape. For example, stainless steel kitchen sinks are formed by drawing the stainless steel sheet metal stock over a form (the die) in the shape of the sink. Beverage cans are formed by drawing aluminium stock over can-shaped dies. By comparison, hydroforming forces metal into a female mold using pressure.
The success of forming is in relation to two things. Flow and stretch of material. As a die forms a shape from a flat sheet of metal, there is a need for the material to move into the shape of the die. The flow of material is controlled through pressure applied to the blank and lubrication applied to the die or the blank. If the form moves too easily, wrinkles will occur in the part. To correct this, more pressure or less lubrication is applied to the blank to limit the flow of material and cause the material to stretch or thin. If too much pressure is applied, the part will become too thin and break. Drawing metal is the science of finding the correct parameters between wrinkles and breaking to achieve a successful part.
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