Development and history of punching
Punching is considered to be one of the oldest machining technologies in the field of metal construction. However, today modern presses are able to process metal sheets of different thicknesses at high speed, and cut them out of a piece of metal in just a single stroke. The technology is comparable to that of a hole puncher used for filing documents.
The early beginnings of punching
Punching, a technology still widely used today, was originally developed in the 19th century. At that time, bicycle production was in full swing, and punching became a suitable technology for mass series production. In the 1890s, bicycle production focused on cost-effectiveness and efficiency. Until this time, forged parts were used for manufacturing bicycles, and these parts actually stood out due to their high quality and stability. As far as these two latter aspects are concerned, punched parts could not keep up with forged parts; however, punching made it possible to enhance both the speed and cost effectiveness of production.
Germany exported its very first punched bicycle components to the United States. In the Country of Unlimited Possibilities, toolmakers developed the tools required for user-defined punching. West Rad, a prestigious manufacturer at that time, brought the largest number of punched parts to market. And with the automotive industry evolving at rapid speed, cost-effective solutions were also in great demand in this sector. That was when Henry Ford adopted the idea of punching. The Ford Motor Company thus became one of the very first auto makers to get involved in punching: The company used this technique to manufacture the necessary components. Punching advanced triumphantly; an ever growing number of manufacturers relied on punching and the number of punching machines grew accordingly. Today, the market is dominated by a small number of manufacturers of world-famous brands.
The development of punching goes on and on
Punching machines became more and more powerful, and punching convinced manufacturers all down the line. Forged parts were replaced by punched parts more and more. But in spite of its many advantages, it also became clear that punching in the form applied so far could not be the ultimate solution. The 1950s saw the further development of fineblanking, which had its origins in Switzerland. This punching technique enabled significantly higher precision, but was much slower. The advantage: With cut surfaces being provided with a so-called straight cut, the post-finishing of parts became a thing of the past. Punching, which was originally a rather unsubtle way of machining metal sheets of various thicknesses, thus enabled much finer machining operations.
Some background information: The thicker the metal sheets to be machined, the lower the number of strokes and consequently the number of parts per production cycle. The presses must achieve significantly higher forces in order to punch the thicker material. The problem: The stamp creates higher pressure, and thus greater resistance, inside the material. However, this resistance suddenly ceases to exist in the lower area of the material and the stamp exercises tremendous force to make its way through the remaining material. This so-called “cutting impact” causes the edges to tear off – and this, in turn, results in a rather fringed edge finish. To obtain precise cutting edges, the material must now be post-finished, which costs time and money. Fineblanking eliminates this problem because it enables chipless cutting. Simultaneous forming is also possible, to the extent that the production process requires this.
From fineblanking to precision punching
Fineblanking was not the ultimate solution either: It was succeeded by precision punching developed by Carl Wüst. Fineblanking was not the ultimate solution either: It was succeeded by precision punching developed by Carl Wüst. Precision punching is still very young: It was only developed in 2003. This technique enables the production of large quantities.
Today, the three punching techniques mentioned above are usually combined with each other. Conventional punching is the technique of choice for machining outer workpiece contours which are less important or fully covered. The cost benefit is maintained because traditional punching is still the most cost-effective solution for metal sheet manufacturing or machining. State-of-the-art precision punching tools stand out due to their intelligent design and in the course of the years, great importance was attached to designing different retractions, breakouts, and straight cuts. The quality which can now be achieved in this way equals that of fineblanking. However, the latter is still not the technique of choice when it comes to manufacturing large series. Fineblanking is possible, but only at speeds which are considered too low. Especially in automotive manufacturing, fineblanking is therefore not a good option wherever quantities of up to 12,000 parts per day must be achieved.
Cost effectiveness is the benchmark
During each step of the evolution of punching, the focus was on cost-effective production: from forged bicycle parts to punched parts to the development of fineblanking presses which have been built predominantly by companies like Feintool AG since 1958. Since these presses ultimately enable the processing of metal sheets of larger thicknesses, a range between 0.5 and 17 mm can now be machined with high precision. During the early days of precision punching, however, no more than just 50 strokes were possible per minute. With innovative presses nowadays even generating more than 100 strokes per minute, this number has already doubled! But the number of strokes has skyrocketed since servo control in linear technology became ready for series production in 2004. Furthermore, the development of the servo drive has contributed significantly to avoiding cutting impact. The speed is controlled with high precision within each power stroke. Wherever only slow cutting was predefined before, accelerating the speed is now also possible under full load. Today, the variably controllable speed can reach up to 140 strokes per minute, and this even during running production. However, with up to 2,000 strokes per minute being possible with punching, the number of 140 strokes still appears to be relatively low.
Combined advantages of precision punching
Considering its relatively short period of existence of 130 years, punching has developed at a rapid speed: from fineblanking to precision punching. But what is truly astounding is the fact that the original punching technique can still not be replaced by new technologies; instead, the advantages of punching are nowadays combined with those of fineblanking. The result is precision punching which represents the state of the art today and is possible at high speeds. However, the high level of cost efficiency enabled by punching cannot be achieved with the other two techniques. It is therefore understandable that companies which attach great importance to cost effectiveness, high machining speeds and superior quality still cannot do without conventional punching.
bmk Baumann is your specialist in Nuremberg for adiabatic cutting, CNC turning, CNC milling, machining, vibratory grinding, ball bearing cages, as well as for punching & forming.