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Straightening machine is used to remove defects in rolled materials such as gnawing, up and down bending, side bending, torsion and correction marking. It does so by applying compressive and tensile forces to the material until it becomes straight.
Most standard powered straighteners are rated to process relatively mild steel with yield strengths below 340 MPa. AHSS requires greater forces to be applied, which significantly influences equipment specifications.
After the product is bitten by the rollers, they continue to make linear or rotary motion and bear various aspects of compression, bending, flattening, etc. This is where the power requirements of the machine become very important. The work rollers must be able to withstand a large amount of force and have to be dimensioned accordingly.
The work rolls are supported by precision guiding slide block assemblies which are driven with either single or double drive motors. When using two or more drive motors, the system must ensure that each set of work rollers is powered equally to avoid overstretching or other damaging effects on the product. The work rollers are usually made of case-hardened, hardened steel with every surface being ground. They also run on needle bearings and are lubricated by an oil circulation system. For heavy duty applications, the rollers may be equipped with a forged ring. This provides better protection against abrasion, wear and corrosion.
Power for straightening is supplied by a drive motor for each set of work rollers or for the whole machine. Regardless of the method used to drive the rolls it is important that the sets revolve at similar speeds – within about 1 to 2 rpm at maximum machine speed. This enables an even and consistent load to be applied to the tube. In the event that the roll set rpm is not closely matched then tube straightness will suffer and rapid wear will occur. It is normal for the manufacture to incorporate an electronic system that ensures the work loads are shared equally between the drive motors.
With the possible variation in material types, thicknesses and widths the power requirements for a given application are widely variable. It is therefore critical that careful attention is paid at the equipment specification process. The correct combinations of pinch roll pressures, drag brake strength and work roller depth settings will determine the level of effectiveness for a particular material.
The controls of a straightening machine are critical to the success of any operation. It is important to have control of the work to avoid deflections and bending, which can lead to inaccurate final size tolerances of the metal product. Whether it is an off-line application that requires precise manual control or an in-line operation with high speed, Turner has the designs and expertise to supply the equipment to your needs.
Developed in 1988, the CASAM system is recognized as a world leader in computer control of straightening machines. CASAM allows the operator to set up the machine with recorded, known to work roll positions, which ensures consistent tube quality from batch to batch.
Having backup rollers in the straightening machine is essential to reduce excessive work roll deflection. Excessive deflection can create undesirable side effects such as edge waves, increased journal stresses and premature gear failure. Adding backup rollers helps to keep the bending moment to a minimum and improves the performance of the straightening machine.
All straightening machines require trained and experienced personnel to operate them properly. This is particularly true of rotary tube straightening machines, where precise adjustments and knowledge of metal forming techniques are essential to the operation of the machine.
A rotary tube straightening machine uses a set of power-operated rolls to straighten the edges of a round or rectangular steel or nonferrous metal product. These machines are typically used to straighten welded or cold-rolled metal tubes in the hot or cold state, primarily for applications such as automotive manufacturing.
To ensure that a rotary straightening machine works correctly and efficiently, it is usually designed with one or more back-up rollers to support the work roll. These back-up rollers prevent the work roll from excessive deflection, which can result in poor straightening and damage to the work roll. They can also help maintain a consistent contact between the work and back-up rollers. This ensures that the straightening machine produces accurate results across the width of the material.