The Awesome CNC Tube Bending Machine

Posted on Nov 6, 2020

CNC Tube Bending Machine

The CNC tube bending machine is a machine developed specifically for the bending parts at a fast pace with variable configurations for ultimate use. These machines are able to cost-effectively bend individual parts as well as small batches with the same precision and efficiency as series-produced parts.

Some bending machines offer a simple setup and configuration and require minimal setup time for many types of bending operations. The simple plug and play operation provides fast setup times and very minimal tool change parameters.

The basic CNC tube bending machine consists of a numerically controlled side stop, a workbench, and programming and operating software. Its modular design provides an affordable entry into bending technology as after the initial investment, the machine can be adapted and later expanded without any conversion. This means that the basic machine performs the bending stroke and the tool determines the bending type.


Common Tools and Shapes for Bending

The 90 'bending tool is a popular type of bending tool in a CNC tube bending machine. In the case of bending tools, by type of turns generated. This design can be set to a bend angle for referencing a part. Then the stroke variable and bend angle measurement.

CNC machines usually refrain from the reference part. They ensure high bending accuracy from the very first workpiece. Another type that is quite common is the standard bending on the universal bending machine.

All arcs without unusual geometry are standard arcs. The distance between the fold and the end of the material is quite large, providing a suitable bearing surface. Same thing with one curve to the other.

Typical tools are so-called prism-coupled benders with electronic angular measurement or a simple prism. The u-shaped bends where the very high angle and small tight shapes narrow bends are necessary. The bending template is replaced with a bending mandrel.

In this case, The mandrel utilizes a tight shape. The other ancillary tools can be used to assemble two bends. This can be made with a small gap in just a few steps. Complex edge bending molds will be recommended as the axis bending is placed parallel to the right side of the workpiece.

Edge bending tools can include electronic angular measurements for high bending accuracy. Swivel tools can rotate the workpiece on the longitudinal axis. An alternative are complex assembly groups with standard bends.


Angle measurement and spring back compensation

When producing single pieces as well as small batches with the similar accuracy and efficiency as series-produced parts, spring back compensation is helpful. A bending accuracy of +/- 0.2 ° from the first workpiece is achieved through calculated springback compensation and the use of electronic tools. In some cases, the operating mode angle is measured.

Bending prisms with electronic angular measurements are equipped with two flattened bending bars. This part rotates during bending, giving a signal to measure the angle. The accuracy of the measurement is approximately 0.1º.

The computer then calculates the required final stroke and the springback of each turn is compensated for regardless of material type. High angular accuracy of +/- 0.2º is achieved immediately on the first workpiece without adjustment.

Compared to reference control, the amount of material waste is reduced because even non-conformities within one piece of material are corrected automatically.

Stroke measurement in operating mode

Wherever bending prisms with electronic angle measurements are not suitable, the reason may be a small distance between bends, bending prisms without electronic angle measurement are used. In this case, you can switch the control unit from angular measurement to stroke measurement.

This method allows you to pre-select the stroke of the bending ram in mm, and thus the depth of immersion of the punch in the prism. The setting accuracy is +/- 0.1 mm.

Usually, no final jump is required. The further development of the impact system enables the user to define the angle from which the stroke is calculated using the stored stroke functions.

CNC tube bending machines are for any metal forming process used to form tubes or tubes permanently. Tube bending can be shape-related or any shape bending procedures, and it can also use hot or cold forming procedures. Usually, round material is used to bend pipes.

However, square and rectangular tubes and pipes can also be bent to meet the operating specifications. Other factors related to the bending process are the wall thickness, tools and lubricants needed by the tube and tube bender to best shape the material, and the different ways in which the tube (tubes, tubing wires) can be used.


Tube Bending Geometry

The pipe can be bent in many directions and angles. Typical straight bends consist of forming elbows, which are arcs, and U-shaped bends, which are 180 ° bends. More complex geometries include many two-dimensional (2D) and three-dimensional (3D) bends. The 2D pipe has holes in the same plane; 3D has holes on different planes.

A two-plane or compound bend is defined as a compound bend that has a bend in the plan view and a bend in the elevation. When calculating a two-plane bend, you need to know the bend angle and the rotation (dihedral angle).

One of the side effects of bending a workpiece is changes in wall thickness; the wall along the inner radius of the tube becomes thicker and the outer wall becomes thinner.

To reduce this, the pipe may be internally and/or externally supported to maintain the cross-section. Depending on the bending angle, wall thickness, and the bending process, the inside of the wall may wrinkle.


Key Process Characteristics on CNC Tube Bending Machine

The tube bending process begins with loading the tube into the CNC tube bending machine or pipe bender and securing it in place between the two dies, the clamp block and the forming die. The tube is also loosely held by two other dies, the wiper and the pressure die.

The process of bending pipes is the use of mechanical force to press the raw pipe or tube against the die, forcing the pipe or tube to conform to the shape of the die. Often the tube is held firmly in place while the end is rotated and coiled around the die.

Other forms of processing, including forcing the material through rollers that bend it into a straight curve. [2] In some pipe bending processes, a mandrel is placed inside the pipe to prevent it from collapsing. The tube is held taut by the squeegee to prevent kinks when tensioned. The doormat is usually made of a softer alloy such as aluminum or brass to avoid scratching or damaging the bent material.

Much of the tooling is made of hardened steel or tool steel to maintain and extend the life of the tool. However, if there is concern about scratching or gouging the workpiece, a softer material such as aluminum or bronze is used.

For example, a clamp block, rotating mold block, and pressure die are often formed from hardened steel because the pipe does not slide past these machine parts. The pressure die and wiper die are made of aluminum or bronze to maintain the shape and surface of the workpiece as it slides.

CNC Tube bending machines are typically hydraulic, electric or air-driven, maybe hydraulically assisted, hydraulically driven, or with an electric servo motor.


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