A smaller investment and adequate production capacity&#;the arguments for buying a second-hand machine are obvious. Is it that simple though? Particularly in the case of complex tube bending machines, many factors determine the efficiency of using a second-hand system. Beware that in the worst case, a second-hand machine can become a liability in the production sequence because the component
quality and output performance do not match those of your existing equipment.
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Who buys a used car without a test drive and without learning about its features? Investing in a second-hand system resembles this scenario more often than you would think. This can be especially troublesome if a complex bending machine from a niche area is bought without consulting the original manufacturer. In many cases, the machine is customer-specific, designed and built for
high-precision bending results by means of CNC, high-performance drives, and complex bending tools. It&#;s not a simple matter to dismantle and reconstruct such a machine to produce new components.
It&#;s critical to learn what the bender was designed to do&#;the component geometry, material, and output quantity are three main factors. A machine designed to process thin-walled exhaust pipes in mass production might not be suitable for bending thick-walled high-pressure tubes for plant construction. The machine manufacturer is in the best position to determine if the machine&#;s design and
drive concept can produce the intended components in sufficient volumes.
Taking Risks
The buying and selling of second-hand, special-purpose machines, usually again and again without consulting the manufacturer, is the result of economic considerations. It&#;s difficult to walk away from a bender offered at an attractive price. However, buyers of bending machines frequently take excessive risks. Machines often are purchased without any testing. Under these conditions, it is
impossible to verify that the system has the required capacity.
A thorough evaluation is necessary before making the purchase. The control must show no errors, the mechanics must not be worn, and the machine must be complete in terms of its components. Every axis must work properly.
However, this is just the minimum; many more aspects need to be evaluated. Even small things can tip the balance. For example, if incorrect hydraulic filters are used, the result is a problem in the hydraulic pumps after a short time.
Again, this evaluation is best carried out by the equipment manufacturer.
Check the Records
Sellers sometimes exploit uninformed buyers: old machines are repainted and, in some cases, the capabilities are exaggerated, and accordingly the machine is sold for an inflated price.
The manufacturer can look up the serial number to determine the details, such as the delivery condition, age, and whether the machine has undergone regular maintenance by the manufacturer.
A related problem concerns improper repairs. In the event of production problems, even the original manufacturer&#;s fitters are sometimes baffled, because they cannot repair nonstandard parts. It is a good idea to contact the manufacturer before making the decision to invest.
If the machine has been altered, restoring it to its original condition is possible only if all the original parts are still available. Generally, only the machine manufacturer can determine if vital components are still available. Here again, the manufacturer&#;s database has the necessary information.
Keep in mind that if the manufacturer reconditions the machine, it will replace all of the obsolete components. Moreover, a service contract provides a measure of assurance that the machine will have a sufficient service life.
Focus on Safety Technology
Of course, these indicators aren&#;t a guarantee. The ideal way to purchase a second-hand machine is to buy it from the original manufacturer. Many equipment manufacturers provide reconditioned and factory-tested second-hand machines.
Reconditioning gives the manufacturer an opportunity to restore the machine to original condition by completely dismantling and reconstructing it from scratch, and including the latest control, electrical and electronic devices, hydraulics, and so on. It&#;s also an opportunity for the manufacturer to install the latest safety features. In the U.S., this means bringing the machine into
compliance with the latest standards, such as the American National Standards Institute (ANSI); in Europe, the machine earns the CE mark. If the machine doesn&#;t display a CE marking and its safety technology is incomplete, it must not be operated. In some cases, even the lack of operating instructions might be enough for a second-hand machine to be out of compliance with the safety
regulations.
You should also inquire about the machine&#;s warranty when considering a reconditioned machine.
Better Brand-new?
When should a second-hand machine be avoided? The product range and intended use of the machine are critical considerations.
A second-hand machine is a candidate if no series parts are to be produced and sufficient time is scheduled for maintenance and repair. On the other hand, if production is dependent on a high level of availability, and you want the advantages of the latest controls, a new or reconditioned machine is a better choice.
Resolve These Questions Before Buying a Second-hand Machine
Resolving a handful of questions will go a long way in ensuring the machine is a good choice for the application, and that the machine will provide the necessary reliability and output.
- Is the rating plate in place and does it match the machine?
- When was the machine last used?
- Are complete operating instructions pertaining to the machine present, including all maintenance documentation and wiring diagrams? Are they written in the language used by your company&#;s operators and maintenance personnel?
- Are all the current safety regulations completely fulfilled?
Answering the following questions completely and accurately requires a machine evaluation by the manufacturer.
- Is the machine suitable for the required component specification? Can the machine achieve the output demanded at maximum load?
- Does the machine control show errors in test mode?
- Does the mechanical system seem stable in test mode (no play, unusual noises, or signs of excessive wear)?
- Can all spares be obtained easily?
- Have any structural alterations been made to the machine?
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.
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Criteria Checklist for selecting the right tube bending machine
The main parameters to take into consideration when choosing a tube bender are:
Diameter
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.
Various models of the ALL ELECTRIC, ELECT series of machines and the recommended range of tube diameters for each of them.
Wall thickness
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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 by SIEMENS on our ALL ELECTRIC tube bending machine.
Material
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 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.
Bending 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
All-electric In-process LHS and RHS Bending machine E-TURN.
Conclusion
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.
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