Cold drawing machine is a specialized forming process for metal rods, bars and tubes. It is used to achieve greater dimensional accuracy and surface finish for a wide variety of industrial applications. The cold drawing process realigns the molecules in steel to increase strength, while also reducing brittleness and increasing the accuracy of shapes and sizes. The procedure can be accomplished through a combination of piercing, ironing, necking, rolling, and beading.
In order to achieve this, the steel is drawn (pulled) through a series of dies that gradually reduce the diameter of the rod or bar. The resulting material is work hardened and has a lower tensile strength than the original unformed rod or bar, but it retains high ductility. It can also be strengthened through a post drawing anneal that increases its yield strength and toughness.
The first step in the drawing process is to procure raw stock, which is typically delivered from a hot mill as pre-annealed bar or rod coils. This material must meet strict dimensional and softness tolerances, and it should be free of scales and oxidation. It is also important that the chemistry of the steel be consistent throughout the batch of coils.
Once the raw stock has been procured, it is cleaned and coated with a drawing lubricant to prepare it for the drawing process. The lubricant will help to minimize the friction between the draw die and the steel, which can lead to excessive stress in the bar or rod. The lubrication will also help to reduce the amount of drawing force needed.
After the lubricant has been applied, the drawing machine can begin the operation by drawing the rod or bar through the dies. During this stage, the drawing speed can be quite high and large area reductions are possible. However, it is important to monitor the drawing forces and back tension to ensure that these parameters do not exceed allowable limits.
At the same time, it is important to note that the drawing process can alter the plastic properties of the metal. This can be a significant problem in some cases, as it can increase the tensile and yield strengths of the alloy while decreasing its plasticity. Consequently, it is essential to understand these changes in order to develop an accurate energy-power mathematical model of the drawing process.
This can be done experimentally using a laboratory drawing machine. The drawing machine can be equipped with strain gauges that can measure the actual drawing forces and power consumed. This data can be processed with well-proven simulation programs, such as QForm and ABAQUS, to estimate the energy-power parameters of the process. The results of these calculations can be compared to the measured values and used to determine the correct set-up for the drawing machines. This can improve the quality of the resulting wire and increase productivity. This is especially true for large-scale production processes. The more accurate the model is, the more reliable it will be.