Please note – this is not commercial article. So we use some other info and publications with reference links for general purposes. The header picture is from here
We have already been told a lot of times that the traditional technology of bending which is used in press brakes today has been well known almost more than 70 years. All right, that time it was not the traditional press brake machine but mainly presses with force with top and bottom bending tooling installed similar to the punch and die which is used on bending machines today. For sure works were much more simple and bending punch geometry was mainly the straight one to perform the simple bend.
The photo from here. According to the source it is dated by 1957 year. It is an interesting picture because you can have radius bending here (several strokes) and die with 2-V openings so you can rotate it to install another V-groove.
This is maybe the oldest picture we found – it informed that Pacific Press company started to produce press brakes during WW2 which means the early forties. Internet knows everything but it is hard to find something about the real history of press brakes so we don’t know who invented the first classic machine with 2 shoulders for the length of several meters like the construction that is widely used today.
We also tried to look for some patents and it seems that there is the oldest patent we can see is 2,456,749 issued December 21, 1948, to J. Steibel but unfortunately no information on what it was. About patents there are really very interesting things about some press brake units and functions, for example US3214955A of 1961. We never encountered such things but very useful for research – the lower tooling (die) there was made as a round shaft with grooves and rotation with fixation by the level.
So finally. The bending is possible with the hydraulic press, it was made 70 years ago and is possible even today and used somewhere as one more function to make small length parts as brackets. But the real work with sheet metal required the bending with a big length and a more technological solution than the standard press which is mainly high tonnage, complicated to install the tools, and quite expensive equipment for the factories. So the invention led to the classical press brake construction – the machine with 2 shoulders and a beam installed on 2 sides to perform the parallel travel up and down. Such construction allows to go with more length, easier access to the working zone, and parallelity of the beam from the sides. And hydraulic system is mainly used as an easy and good source to provide the necessary force for the press brake. Mechanical (clutch) press brakes have been presented in the past and somewhere available as new even now (for example in India) but do not have a big amount on the worldwide market.
So let us speak about the general view and the construction of modern press brake which has been well-known for more than 50 years. We already made an article about press brake typology in the past but maybe now we can renew something of it.
The welded bed is connected with 2 shoulders from both sides of the machine. Mainly the table (low part) is fixed and non-movable (there were some machines in the past with downstroke so with a movable table but it is better to ignore it because their percentage on the market is very low). The upper part – traverse is moveable and goes up and down according to the request of the operator. It is driven with 2 hydraulic cylinders from the sides of the machine. There are some variations – for example, only one forcing unit at the middle (hydraulic or servo drive) for small length or hydraulic cylinders are replaced with electric drives. Press brake works with the proper bending tools: dies are installed on the table. Punches are installed on the beam to go down and to perform the bend. To tell the truth, the base of kinematics and movements is a quite simple construction with one stroke – up and down.
Picture from here
A small note because it affected the market in the 1950s-1960s. The small company “Promecam” which was later purchased by Japan company AMADA in the mid-80s was the real leader in press brake production these years and Promecam in a lot of talks was even just the synonym of press brake. Their first main presses (which we can consider as “key products” because they were sold in thousands of units in the world) were upstroke which means that the upper beam was completely fixed and the table with the installed die was moveable with all power units of the machine placed at the bottom. Promecam machines are widely used in production even though they are incredibly old and have been at work for dozens of years. Promecam was also the first manufacturer (based on the materials we have found) who made the promotions not only of press brakes as machine tools for sale but for the solutions of bending, different ways, different applications, and different tools to explain the widest range of possibilities which could be interested in the potential customers.
Now we are starting the story by explaining the complete press brake machines’ evolution and differences. As we told before the machine is simple with one movement so on the machine today and on the machine 70 years before the movement was the same. The difference is only with regulations and how it was performed. The final distance between the beam and table in old machines was regulated with mechanical jacks, screws, stoppers, then with hydraulic pistons, etc. Together with the becoming of the era of digitalization numerical controls were invented and adapted to the regulation of the position of the ram through the numerical panel which allows precise movement and comfort working for the operator. So, the installation of digital controls, digital outputs, and inputs, digital guides with the reading of the actual position of the beam made a big jump to the machine which we see normally today in production worldwide.
The back gauge is one of the additional and most important elements of the construction. What does the back gauge of the press brake? According to the requirements it is positioned with the finger stop where you should place and position of the part. So back gauge makes the operator the assistance for precise part positioning. Can the bend be performed without a back gauge? Yes. Can the bend be performed with the use of a manual back gauge like a simple metal fixator? Yes. So back gauge makes nothing for the bend itself. But it allows the positioning of the part BEFORE bend so the bending will be precise, exactly on the line where it should be. So like the main function of the press brake (beam movement to perform the bend) back gauge provides not only additional functionality but provides the availability of quick and precise bending operations.
When press breaks in the world became to be “numerically controlled”? At first, we are talking about beam digital input to get the real positioning and the system to compare it with the desired position. According to the patents database, we can refer to the patent N US3874205A for Hurco Manufacturing Co Inc. company. It is hard to understand who was first but the timing is quite realistic: the 70s were the years when a lot of types of fabrication and metalworking machines were developed with new systems of numerical controls. But for sure as we said it is quite hard to search and to find the real picture and mainly this is ignored in all books about press breaks because they are written by engineers and not detectives or searches for historical passes. Anyway it is interesting to see – we found an ad for sale of 75 Ton x 10′ Chicago Dreis & Krump 810-C Press Brake, 1972. As you can see the machine has already a numerical panel and numerical control for the back gauge as well.
Picture of press brake from website of Revelation Machinery
It is interesting to note the fact that even historical machines are “touchable” today and still on the market, even after 30-40 years of work. There are many reasons and some of them are simple construction, simple service, no difference in bending (if we are not talking about real precise parts and a big bending cycle with a lot of steps), and for sure the money if we are talking about a high tonnage machine. A new big tonnage or big length press brake machine costs a lot so maybe it is easier to save investments and to care for old machines already installed in the factory.
We will continue this topic in the second part so keep in touch!