We want to publish a useful and interesting article about big thickness bending that we can show to our potential customers. Without the necessity to explain every time, we decided to make this article with all the important notes.
This way, we will speak about bending of big thicknesses or bending of special steels like Hardox®, Raex®, Domex®, Weldox®, DOCOL®, Raex®, Optim®, Ramor®, and other high-resistant, hardened, wear-resistant steels with a high tensile strength value.
One time, we had a case:
The customer asked us for some bending tools to bend special steel. Moreover, he already had the quotation on his hands for punch and die, and he requested from us just the competitive offer for the same positions. During the conversation, we discovered that he has an ordinary press brake of around 200 tons for 3 meters, but for his bending work, he needed around 300 tons per meter. So for us, it was impossible to offer any tools, and we told the customer that there was no solution. Also, it was really strange that our competitor, a very well-known company, made such an irresponsible offer.
And the problem is very common: customers do not understand the possibilities and limits of their press brakes, and they do not understand what the main problem is for us to decline the request.
Steps by steps for big thickness bend
The most important detail of the press brake is the available tonnage. Let us make the example that the machine is 100 tons for 3 meters. It is a very typical bending machine in production.
The first question that the customer should understand is the tonnage for the requested length. During any study, we operate with the value of tonnage per meter. And the first question that we can ask is: if you have 100 tons for 3 meters, can you have on your machine 100 tons for 1 meter? Or 100 tons for 500 mm, if necessary? It could be an unanswered question, and there are really limitations with the old machine. So the customer should know what tonnage per length he can achieve.
The second point comes from the model of the press brake. Each tooling system has its limitations. If you overload the limitations and have strong bending tools for high tonnage, you have the risk of damaging the holders.
Press brake tonnage for the length
Let us set an example. The standard Promecam tooling system has a limit of 100 tons per meter for punch holders. If you make more, you will destroy the intermediates. If you have no intermediates, you can damage the beam. The reason is simple: the force is transferred through the piece with a width of 13 mm. It is not so big to transport the bigger tonnage.
The customer, let us consider, has the press brake of 220 tons for 3 meters. Maybe he can bring 220 tons even for 1 meter, and the manufacturer of the press brake confirms this possibility. But he cannot because his holders are limited to 100 tons per meter!
It is absolutely important that if the bending is not done at full length and requires a large tonnage, it be done strictly at the center of the machine. Otherwise, you will have the risk of the beam inclination, which leads to unparallelity.
So what do we have? A lot of customers think that their machine tonnage is their possibility for everything, even for 50 mm, and they can do everything. It is a completely wrong position, which could lead to a lot of risks for the machine and the operator itself.
To avoid risks at all costs
Even if the customer wants it, it is more appropriate to decline the project if we have doubts and see the risks. One more time, overtonnage could lead to:
- Punch deformation and damage
- Die deformation and damage
- Holders damages
- Beam damages
Let us just imagine that it is good if the punch during the overtonnage is just a little bit compressed and the machine is stopped after. But damage to the holder could lead to the risk of misplacement of the punch, and it could also hit the operator. So we are not talking only about the risks of the machine but also about the health and even the life of the operator.
We also do not know how the particular customer is prepared. Sometimes we have a lot of basic questions, and we can decide that the customer is not prepared at all. So we cannot be sure that he understands all the risks and takes all the measures and actions to prevent any problems.
But in a lot of cases, there is one big risk: there is no solution. The customer will not make the bend what he wants. He doesn’t have the proper capacity to do the job, so even if he is ready to invest, he probably needs to invest in the new press brake. There is no alternative solution!
There is one common risk as well: the customer declines to believe that he did something wrong. It is very easy to deform the gooseneck punch due to the overtonnage. It will just bend more. But for customers, it is easy to think that it is just the poor quality of the tool itself. So for us, it is better to decline the job near the limits.
Problems of design for the part
The design of the part becomes highly important if there are big thicknesses and small sizes together! For 1 mm thickness, you have a lot of freedom, and you can send the production drawing now to any machine to perform the bending. But if we are talking about critical values, the additional preparations are very important.
One case from our experience: the customer brang the part drawing to supply the tooling with special steel bending and a very small flange size. If you have in your workshop the press brake of 1000 tons for 6 meters, you are probably free to design what you want. But if you go to the weaker machines, you can see that such a part is just impossible to do! To respect the dimensions, you need incredible big tonnage, or you need to change the dimensions completely!
Moreover, it is important for special steels. A lot of steel manufacturers have their own recommendations and restrictions for bending. It is the minimal radius to have, and it is the recommended opening of the die to proceed. If the recommended radius is 3S (where S is the thickness of the part) and you have a drawing of 1S, you are automatically going against the recommendations of the steel producer. And any suggestions from the tool supplier are useless because the producer of steel didn’t confirm such a way of bending. So it is recommended for all special steels to have and to verify with the correct technical requirements from the steel producer.
Our recommendations for the customer for big thickness bend
The bending with high tonnage has a lot of risks. There could be a reputable risk that you take on the bending work and cannot do it. But there are a lot of risks to damaging your press brake as well. And problems with the beam could lead to very serious repairs and very big losses for service technicians.
Moreover, the factories do not have press brakes in perfect condition, as they came yesterday from the manufacturer. All the machines are used, all the machines passed intervals from the last service, and all the parts are in used condition with some wear. It means that it is probably better not to use the complete tonnage of your machine but not to overrun up to 80% of its capability.
To bend the thick material, you need to know your machine and its limits perfectly. You need to know the limits not only for the capacities of the press brake but also how the tooling system is made and what the risks are to it. Just for interest, you can see on YouTube how thick materials and special steels are bent. What press brakes are used, and what do the bending tools look like.
Factories buy very expensive high-tonnage press brakes not because they want to throw the money away but because they are necessary for their applications. But sometimes customers with ordinary low- and medium-tonnage machines think that they can also try to bend the same parts. And sometimes it could be possible, but it requires very careful study of everything. Moreover, we recommend also inviting the engineer for such projects because sometimes it is quite important to make modifications to the size of the final part.