Bar Straightening Machine

    The bar straightening machine is a device used to straighten metal bars such as steel wire ropes. The most common type of the bar straightening machines are the roll type straightening machines that are made up with rollers. The basic components of a bar straightening machine is actually quite similar to those of the pipe rollers except that the pipe rolling machines are used to achieve an opposite goal: to bend or to curve the metal tubing and piping. In addition to the components of the machine, the process of bar straightening and bending also has something in common.

    In a bar straightening process, a piece of metal bar has to undergo several stations, just like how it works in a pipe bending process. The bar straightening process is highly automated; the minimal human factor is involved in the process. From the feeding of the bar materials all the way down to the dissection of the straightened bars, it is all performed by the bar straightening machine. With the minimal human factor, the process can be done more efficiently and the errors take place during the process can be categorically reduced.

How It Works

    The most common type of the bar straightening machines are the roll type machines. There are a series of rollers on the machine. When the metal materials pass through the series of rollers, they will be straightened. However, the straightening of the metal bars is in fact carried out by bending the material on the opposite sides of it. The rollers on the machine are spaced in two rolls: the upper roll and the bottom roll. A piece of metal bar has to go through the space between the two rolls so that it can be bent.

    From where the metal bar enters the straightening machine, it passes a bottom roller, and then a top roller, and a bottom roller again, and so on. Each time it encounters a roller, it is bent. The top rollers and the bottom rollers are placed that way to make sure the bars can be bent evenly on both sides so that it can be straightened after the sequence of bending. Just like a tube bending process, the bar straightening process is also a cold forming process which is typically conducted at room temperature.

Straightening Mechanisms

    When straightening a bar material, one important factor to put into consideration is the inertia of the material. Since a piece of metal bar is usually shaped in round cross section, a bar can bend freely in three dimensions during the straightening process. As a result, the two planes that are created by the bottom rollers and the top rollers are important. The rotation of the bars makes sure the bending of the material is done evenly through the whole bar piece.

    On the other hand, in a cross roll straightening machine, the top rollers are the concave rolls and the bottom rollers are the convex roll. This design also allows the bars to rotate while being bent. As long as the distance between the rollers is larger than the diameter of the bar, the bar is able to undergo pure bending. This mechanism is primarily applied on a cross roll bar straightening machines. Other approaches such as stamping may be used in certain bar straightening processes.

The Bending Process

    The materials that can best work with a bar straightening machine are steel or steel-based alloys. Because a bar straightening process is a cold forming process, it relies on the ductility and malleability of the metal material to deform into a desired shape without breaking. Therefore, a straightening machine is used mostly for straightening steel wire ropes or other thin metal bars that are made of mild metals. The use of a bar straightening machine is highly automated. The only steps that a human operator is involved are probably the feeding of the material and the collection of the straightened bars.

The Feeding of the Bars

    The feeding of the steel bars is commonly done by an operator, or it can sometimes be done by other automated units. The feeding step is rather simple. The operator places one end of the steel bar into the straightening machine and the machine will pull the rest of the piece in. At this stage, what the operator has to do is to keep feeding the steel bars into the entry of the machine and the machine will take care of the rest.

    If the feeding of the process is done manually, the metal bars or wires are usually thin, light weighted, and short in length. This is the light duty application of a straightening machine and the cutting is not included as the last step in this process. As for the heavy duty industrial application, the bar material is usually long heavy metal wires. In this case, the feeding is a non-stop continuous process and the machine will have to cut the material into short pieces.

Straightening & Cutting

    No matter it is a light duty straightening machine or a heavy duty console style straightening machine, when the bar goes into the machine, the machine will pull the materials in and send it all the way out of the machine. The bar will go through rollers to be bent and straightened and when it is done, the material will exit the machine or send to the last station to be dissected.

    For the light duty machines, they process the bars that are already dissected into section and the cutting is not necessary. For the heavy duty straightening machines that process heavier and longer bar materials, the terminal station of the machine is a normally a cutting press where the materials will be cut into a predetermined length. After that, the straightened bars will be sent to a collector. This is the whole process of bar straightening.

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