Welding with Building Blocks
The use of lasers in production is considered modern and advanced. And it is. But there’s fierce competition among the various technologies, particularly in production. What counts isn’t a great image; it’s the levels of quality and economic efficiency that can be achieved. Bosch researchers take the measure of these techniques.
To use sports terminology, Bosch researchers are similar to trainers and Olympic judges in one: They “train” the various contestants for a certain task and then evaluate their performance. In welding, for example – a standard technique for joining metal parts in the production of car bodies or precision equipment – the competitors standing in the arena are the laser, classic resistance welding and electron beam welding. And this is where the researchers choose the appropriate technology for the welding task at hand. If they opt for the laser (which is increasingly the case), the technique is adapted to the production step and, if necessary, developed further with industry partners until it is suitable for use in series production.
The high-pressure storage tube known as the “rail” in common-rail diesel injection systems, for example, which operates at pressures of up to 1,800 bars and is supplied in dozens of customer-specific variants, is no longer forged as one piece. It’s welded together using a laser. In this instance, engineers chose the proven CO2 laser, which delivers the four-kilowatt output and beam quality that’s needed to achieve the weld depth of up to four millimeters in steel. New generations of lasers, such as the diode pumped solid-state laser, are not yet economical enough when used in this output range.
The main consideration that must be taken into account in laser-welding the rail is that it no longer has to be given its final form with expensive forging tools in the first step and then subjected to elaborate machining operations in succeeding steps. Instead, the rail is put together from individual elements according to the “lego” building-block principle, and the connection points are welded.
In a rail for a four-cylinder engine, there are twelve such welds. If the customer wants an eight-cylinder engine, there are eight more welds. If the rail will be mounted on the engine in a different way, the fastening elements are welded onto the appropriate spot.
There’s also tremendous interest in laser welding when it comes to electrical contacts. Laser spot-welding is particularly valuable for control units. These units are increasingly moving closer to the scene of the action in the engine compartment or transmission, and this is a result of the integration of sensor technology, actuators and electronic components.
This type of welding guarantees contacts that are more stable thermally and mechanically than those that have been created using soldering, and it’s also more flexible in production than classic resistance welding. But that’s not all: The rapid laser pulses make it possible to run very brief production cycles.
The high-pressure storage tube known as the “rail” in common-rail diesel injection systems, for example, which operates at pressures of up to 1,800 bars and is supplied in dozens of customer-specific variants, is no longer forged as one piece. It’s welded together using a laser. In this instance, engineers chose the proven CO2 laser, which delivers the four-kilowatt output and beam quality that’s needed to achieve the weld depth of up to four millimeters in steel. New generations of lasers, such as the diode pumped solid-state laser, are not yet economical enough when used in this output range.
The main consideration that must be taken into account in laser-welding the rail is that it no longer has to be given its final form with expensive forging tools in the first step and then subjected to elaborate machining operations in succeeding steps. Instead, the rail is put together from individual elements according to the “lego” building-block principle, and the connection points are welded.
In a rail for a four-cylinder engine, there are twelve such welds. If the customer wants an eight-cylinder engine, there are eight more welds. If the rail will be mounted on the engine in a different way, the fastening elements are welded onto the appropriate spot.
There’s also tremendous interest in laser welding when it comes to electrical contacts. Laser spot-welding is particularly valuable for control units. These units are increasingly moving closer to the scene of the action in the engine compartment or transmission, and this is a result of the integration of sensor technology, actuators and electronic components.
This type of welding guarantees contacts that are more stable thermally and mechanically than those that have been created using soldering, and it’s also more flexible in production than classic resistance welding. But that’s not all: The rapid laser pulses make it possible to run very brief production cycles.
The individual elements of a rail for a four-cylinder common-rail direct injection system are welded together using a CO2 laser. Twelve joints are passed over and welded — and each must later be able to withstand the effects of a maximum internal pressure of 1,800 bars.
