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Criteria Checklist for selecting the right tube bending machine

Dec 10, 2020 10:30:00 AM

If you are considering buying a tube bending machine, this checklist will help you to select the most suitable machine to satisfy your requirements. This is a basic guideline that explains the important parameters involved.


The main categories of the tube bending machines

Before going into detail about the tube bending machine selection process, let’s review the types of tube bending machines. We can divide them in three main categories:

  • Manual tube bending machines are normally used for bending tubes with small diameter and lower wall thickness. These are used for applications where accuracy, repeatability and cost per piece are not important and the production volumes are also low. In short, these are ideal for artisanal applications.
  • Hydraulic tube bending machines are capable of bending large diameter and thick-walled tubes but have limitations in terms of repeatability. This technology consumes a lot of power, is slow, generates a lot of heat and noise, is not easy to use, require an experienced operator for set up, and require a lot of maintenance.
  • All-electric tube bending machines can bend a broad range of tube diameters and wall thicknesses, are fast, and are extremely repeatable. The set-up is much simpler, power consumption and maintenance is much lower, and the control over the bending process is much higher compared to the hydraulic machines. Hence these machines are most suitable when high productivity, easy change of production and repeatability over time is desired (these machines do not suffer performance variation due to change of oil temperature intrinsic to hydraulic machines).

For more than 60 years, BLM GROUP has been developing innovative solutions for processing tubes, solid bars and special profiles. The wide range of all-electric bending machines can process tubes from a coil or cut to length pieces, are configurable for left-hand or right-hand bending, and some models are capable of in-process left-hand and right-hand bending.



Criteria Checklist for selecting the right tube bending machine

The main parameters to take into consideration when choosing a tube bender are:




Diameter capacity is surely the first criteria to be taken into consideration while selecting the tube bending machine. The maximum diameter capacity is a distinguishing feature of a tube bending machine, and many times, it is included in the name of the machine model.

In selecting the machine, it is important to define the range of tube diameters to be bent and choose the machine accordingly.

Consider purchasing a bending machine that has adequate capacity to process your entire range of tube diameters. Make sure it is not too large as it would result in excessive and expense tooling as well as lower productivity and increase energy consumption.

The chart below shows the recommended diameter range for each model of the ELECT series of tube bending machines. You will see that larger machines can be used to bend much smaller diameter tubes compared to the maximum diameter capability. In fact, it is common to use larger capacity machines to bend thick-wall, small diameter tube or tube made of hard metals.


Machine models and range of diametersVarious models of the ALL ELECTRIC, ELECT series of machines and the recommended range of tube diameters for each of them.




Wall thickness

The tube wall thickness is another important parameter to be considered while selecting a tube bending machine.

As discussed earlier, if the wall thickness of the tube is high, then the required bending force would be greater and a larger capacity (diameter capacity) machine would have to be selected.

On the contrary, if the wall thickness is thin, although the bending torque is limited, there is a risk of tearing or wrinkling at the bend location.

In such a case, control of the bending process plays a fundamental role. For this reason, electric tube benders are the most suitable solution with the correct management of the axes, it allows you to control force, torque, and the positions of the various elements of the machine


CNC of an ALL ELECTRIC tube bending machineCNC by SIEMENS on our ALL ELECTRIC tube bending machine.





Ductility of the material is important in bending process. The more ductile the material is, the easier it is to bend. Materials like Copper, Aluminum or low carbon steel are bent easily, with lower bending force.

Bending is much more difficult on hard materials like high carbon steel, alloy steels, titanium alloys, etc.. Here one must use draw bending process. One can also obtain bends with large CLRs using push bending. Since these materials have higher elasticity, spring-back compensation becomes necessary.


An example of compound bending tool setAn example of compound bending tool set: bending of a 60 mm dia tube with 4 mm wall thickness on an ELECT 80 machine.



Number of Tool Stacks

The number of tool stacks is the capability to install multiple bending dies on the machine. The benefit of stacked tooling is that having multiple dies allows for a job with multiple radii to be completed in one setup better improving part accuracy and reducing material handling.

A machine that can accommodate multiple bending tools automatically allows the user to have higher design freedom in terms of bending different CLRs and the distance between two bends can be reduced to zero.

Another potential advantage of having a machine with stack tooling capability is that you can keep the machine partially tooled and reduce the time required for production changeover by only switching the collet and/or mandrel.



Tube Shape

If you are bending non-standard shaped tube, you may require a machine with different characteristics in terms of bending force, dimensions of the tools, and special accessories to properly bend the non-standard profiles.


Special profile tube bendingBending of a special profile used on tractor cabin on an ELECT 130 machine.



Bend quality

Quality of bend can’t be defined in absolute terms because it has many aspects and one of them is the final utilization of the part in question.

In some cases, the precision and the repeatability of the bend angle or the accuracy of the length of the straight areas is important. Components produced for the automotive, aerospace, industrial vehicles, and HVAC industries commonly meet this criteria. In these sectors, the bent component is part of an assembly in which the overall geometry of the final part is important.

In other cases, like in furniture or motorcycle exhaust sector, the aesthetic aspects, like roundness of the bend area as well as absence of clamping marks and wrinkles, are important because these parts are visible in the final product.

Some of the applications would require all these attributes while not limiting the freedom of the form of the bent component.

The capability to bend complex shapes also reduces child parts and process steps such as welding.

Find out how a tube bending machine can transform a tube into an object that is also a piece of artistic expression


In-process LHS and RHS BendingAll-electric In-process LHS and RHS Bending machine E-TURN.



In conclusion, tube bending is complex technology and consideration of any one of the parameters discussed above is not sufficient to make the decision; all factors should be considered collectively.

Not only the diameter, CLR, wall thickness, material, surface finish considerations but also the type of production, production quantities, application sector, and future opportunities must be taken into consideration. With BLM GROUP, with over sixty years of bending experience, you can count on a reliable partner that will help you make the decision quickly and select the right machine for your production criteria.