A CNC press brake is a modern machine for sheet metal deformation. There are different types on the...
Press brake: what it is and how does it work?
The press brake is an extremely versatile machine, yet at the same time complex. The technology on which operation is based is only trivial in appearance, however it hides remarkable developments in the mechanical and technological field.
In fact, if we compare a modern press brake to one from fifty years ago, on the outside it seems that little has changed. However, the truth is that they are two completely different machines; the external elements may also have remained stationary with the typical design that we all know, but mechanics and electronics have evolved in a silent and inexorable way.
Conceptually, between a bending machine from the past and a modern one, there are no changes in the process; both, in fact, share the same purpose: to bring a punch to a matrix up to a certain altitude in the most precise and repeatable way possible.
Yet, the modern press brake is the result of constant evolution. Just as happened with cars, which from a simple and almost rudimentary means of transport have become truly high-tech machines, the bending machine is also now a concentration of technological and mechanical innovation. However, both in the case of the car and the press brake, the basic mechanical components have remained the same, but over time they have been improved and refined.
To understand the fundamental stages of sheet metal bending and know the best technology that combines efficiency, effectiveness, operating costs and versatility, you need to take a trip back in time and know a little history of press brakes.
Among the pioneering countries, there is undoubtedly Italy.
In an area surrounding Brianza, businesses have flourished that have enhanced Italian products and continue to do so to this day, within the bending press brake sector. Our country is renowned worldwide for great tradition and quality in the construction of press brakes.
Big names like Mariani and many others have literally invented this technology
Let’s now take a short journey through the systems that have followed one another, focusing on today’s non plus ultra: the hybrid hydraulic press brake.
Press brakes: types and characteristics
1) Mechanical press brakes
Mechanical press brakes are still used in many workshops to do marginal work, even if they are now considered to be illegal machines from a safety point of view and, therefore, cannot be used by employees.
In the past, the best known mechanical press brakes were Mariani or Omag branded; they were characterised by extremely fast movement and great pressure strength.
2) Promecam "RG" hydraulic press brakes
Originated in France thanks to the intuition of the Italian-French Roger Giordano, RG Promecam hydraulic press brake machines are compact and low.
Their most obvious feature is movement of the bench, different from all other press brakes.
In fact, if it is usually the upper part - called the "beam"- that lowers, in this case the bench goes up.
Movement is obtained by pushing a central hydraulic system. Simple and very reliable, they have practically made the history of Italian press bending and more besides.To date, they no longer comply with safety regulations as they do not have a speed change point and are not equipped with modern safety systems.
They can, therefore, only work if they are adapted with specific kits.
They were widespread for quite some time and it is not rare to still find them in many workshops and still operational; in the post-war period they represented a real revolution, as the bench contrasted the natural bending of the beam.
The latter, being rather low and compact, allowed large, closed profiles to be obtained, which could "embrace" the upper part of the machine.
3) Hydraulic press brakes with torsion bar
They are the forerunners of the synchronised ones that look very similar in appearance. Movement is via the beam that descends through a pair of hydraulic pistons.
They usually have two or three axes:
- X for the rear carriage;
- Z for the height of the rear carriage;
- Y for the descent of the beam.
The characteristic of these machines is that the two cylinders are mechanically connected through a bar that couples movement up to the "lower dead centre".
The latter is regulated through movement of two nuts that lower or lift to adjust the height of the end of stroke of the cylinders and the beam.
The machine is controlled by a simple positioner, often without internal memory.
4) Synchronised hydraulic press brakes
To date, the synchronised hydraulic press brake is the most widespread modern machine.
It includes movement of the upper beam by means of two independent hydraulic cylinders and regulated by appropriate proportional valves.
By doing so, the machine is more versatile and allows the operator to work on both cylinders independently to change the descent of the beam and counteract any irregularities of the sheet.
It can happen frequently, in fact, that a piece bends more on one side than the other because of the aforementioned variables of the raw material.
The numerical control of a synchronised hydraulic press brake is much more advanced than the positioner of the torsion bar press brake.
The CNC allows the operator to make many adjustments: from the parking time to the "lower dead centre", from the bending speed to decompression. Fig. 4.4
5) Electrical press brakes
They represent the latest evolution of press brakes and continue today to be considered a border line solution for some specific needs.
They guarantee speed and repeatability, combined with low consumption, however they are less versatile and have much higher costs than synchronised hydraulic press brakes.
There are basically two techniques to operate an electrical press brake: with ball screws or by means of special belts.
The future of press brakes: the hybrid press brake
Synchronised hydraulic press brakes are the breeding ground for technological innovations and improvements with very important results.
VICLA has grasped the occasion with much commitment, specialising in hybrid technology.
This solution allows the best to be got from the system, combining it and making it into an advanced solution, which is distinguished for:
- energy consumption;
- quality-price ratio.
VICLA hybrid presses guarantee millesimal positioning of the beam, always ensuring precise and constant bends: all possible irregularities should be exclusively attributed to natural factors due to the variability of the raw material.
This surgical precision is possible thanks to use of less oil compared to traditional hydraulic press brakes.
Simply think, for example, that a 110-ton VICLA .SUPERIOR hybrid synchronised hydraulic press has a double tank with just 50 litres per chamber (compared to 200 litres used by a hydraulic press brake).
Less oil means fewer ducts, smaller tubing, less heat and expansion and reduced clearance and wear. Two powerful electric motors work exclusively and directly on the minimum quantity of oil necessary.
Repeatability is a direct result of the lesser quantity of oil used.
Heating litres of oil that flow within metres of tubing causes considerable side effects, first and foremost, loss of precision. This becomes more and more obvious as the machine is used after numerous work cycles and the inconsistency becomes more visible with each bend.
Thanks too to a smaller tank, a compact circuit that allows you to have little oil that changes its volume as the temperature changes, VICLA press brakes maintain bending precision on each work cycle.
Repeatability is also guaranteed by precision and the constructive sturdiness par excellence. Without these basic qualities, no electronics or new technology could express its real potential.
Energy savings up to 78%
If we compare the performance of a hybrid bending machine to a conventional synchronised hydraulic press brake, the results are really impressive: energy savings, in standard conditions, are equal to 55%.
But even better limits can be achieved: if the standard hybrid technology achieves 55% energy savings, with the Hybrid Plus option, a sophisticated exclusive hydraulic component, energy savings up to as much as 78% are achieved!
This is possible thanks to a simple and effective use philosophy: consume only when the press brake is bending.
In a traditional synchronised hydraulic press brake. there is always a large three-phase motor that is never switched off, even while the operator equips the machine, programs the numerical control, organises the pieces near the workstation or, simply, looks at the drawing of the item to work.
Instead, the highly coefficient motor of a VICLA hybrid press brake only switches on when the operator activates the machine by pressing the descent pedal. It is a huge advantage in financial terms, even in the short term.
In terms of cost, the benefit of hybrid technology is even more obvious.
This is because, on comparing the VICLA hybrid system with an electrical press brake that however allows energy savings, the purchase cost is still favourable to hybrid technology.
But there’s more: electric hydraulic press brakes, especially if they use a belt system, have a very different structure that makes them generally less versatile.
In fact, it is impossible to bend particular parts such as hoppers, tanks of a certain depth or chutes, because their closed structure on the sides and the widespread use of casings creates numerous occasions for collision between the parts and the machine.
On the other hand, the hybrid hydraulic press brake allows, like any hydraulics, to work even "leaving" the machine sideways, with greater use versatility.