What Is a Cold Drawing Machine?
Cold drawing machine is a process of cold working metal that involves forcing the lead end of a bar or coil of steel through a die to reduce its cross section and shape it. The result is an elongated, slender product with a desired mechanical properties. Several passes through the die may be needed to manipulate the material into a specific size and profile, and the final product is often annealed to remove internal stresses and ensure its ductility. The energy-power parameters of the process are determined by mathematical models based on technological factors such as mechanical properties of the metal, its tendency to harden during cold deformation, the single degree of deformation, friction coefficient at the metal-wire contact point, design characteristics of the die and the drawing speed [42].
The first step in this process is to sharpen the lead ends of the bar or coil to reduce their diameter, which allows them to pass through the dies. The lead ends are also swagged to reduce their length and make them easier to grip by the mandrel. This step is known as pointing and it usually occurs on both sides of the bar.
Next, the rod is forced through a series of dies that shrink its cross section. The smallest section that is drawn is called the final ductility, and it must meet the customer’s specifications. For example, the ductility of the steel must be high enough to allow for a specific radius to be formed in the rod. In addition, the rod must be able to support a specified weight and must not have any gaps or holes. For these reasons, the final ductility is often measured by measuring the tensile stress in the rod and calculating its ultimate tensile strength.
During the drawing process, a certain amount of radial stresses are generated in the rod due to the friction between the dies and the material being drawn. In order to minimise these stresses, the optimum die angle is selected for each rod size and drawing operation. Generally, higher angles tend to thin the wall of the tube and lower ones to thicken it. In addition, the optimum die angle varies according to the diameter-to-thickness ratio.
In order to optimise the conditions for each drawing machine and wire size, a number of computer simulations of the process are used to predict performance by estimating the ratio of drawing stress to ultimate tensile stress, the drawing force, back tension and heat generated. The resulting values can then be adjusted to achieve the desired results.
Manufacturer of custom & standard wire drawing machinery including dies. Capabilities include CNC machining up to 4000 mm dia. & 1000 mm between centers, lathe cutting up to 500 mm dia. & 450 mm dia., swaging, surface & cylindrical grinding, band & circular sawing, EDI using AutoCAD(r) & inspection. ISO 9001:2000 certified.