The consistent implementation of Industry 4.0 has a decisive influence on the factory of the future, which will develop into a smart factory. For a smart factory to work autonomously without human interaction, some criteria must be met for welding applications:
The welding know-how has to be digitised and prepared in such a way that a computer can make similarly correct decisions as an experienced welding technologist
The welding equipment must be equipped with high-performance information and communication technology and customised sensors so that all production-relevant information can be digitised and given the necessary real-time behaviour of the system
The need to transfer and store large amounts of data requires powerful network infrastructures & sufficient storage capacity
However, if the digitisation process in welding technology is not completed, humans will continue to play a central role in determining welding solutions. Accordingly, the communication channel between human & welding machine will continue to be one of the most important success factors.
Digitalised welding knowledge
A networked modular welding cell must be equipped with the right welding parameters and welding consumables, depending on the task assigned by the production control. Nowadays, the welding technologist holds responsibility for the right choice of welding parameters. If these tasks are to be supported by intelligent software systems in the future, it is necessary to digitise existing knowledge and make it automatically retrievable. This is probably the most difficult challenge of Industry 4.0 in welding technology, as all the existing knowledge is very difficult to quantify and therefore hardly comprehensible to digitisation. For autonomous cells, however, digitised knowledge is a prerequisite. At this point, the integrated networking of the smart factory must be effective, and all information has to be available at the right time.
Modern welding power sources
Modern welding systems consist of several microprocessors networked by means of bus systems and thus, already form a network internally. A welding power source is a complex power electronic device that must not negatively affect itself nor adjacent systems in any operating condition via electromagnetic interactions. In addition, the sensitive electronics must be reliably protected from the harsh, dirty and dusty industrial environment. To ensure this, innovative production engineering concepts are necessary, which also must be checked in intricate functional tests. But these tasks are necessary to ensure the functionality of the system for the customer.
One of the key words in Industry 4.0 is obviously ‘communication’. In the case of modern MIG/MAG power sources, the necessary in-machine communication can be estimated by a simplified calculation: Modern short arc processes, such as CMT operate at a droplet stripping frequency of up to 150 Hz, which means that one drop is removed approximately every 7 msec. In order to optimally control this drop by changing the current and voltage signal, it is necessary to intervene in the welding circuit 50-100 times during a drop separation cycle. This results in a remaining communication time between the arc and the control computer of about 30 μsec. During this interval a lot of signal processing steps have to be carried out, like - the physical data must be digitised and sent to various microprocessors, all necessary computations to determine the right control action must take place and all the derived control signals must be sent back to the systems actuator.
All these real-time demands concerning the data transfer and signal processing represent an enormous technical challenge. To overcome this, it is useful to distinguish between the internal data communication, on which the entire control technology is based on, and the external data communication via intranet and internet, which is mainly used for documentation purposes. Both networks meet completely different requirements in terms of real-time behaviour and data transmission rates.
Welding parameter selection & data storage
One of the most challenging goals of Industry 4.0 is the flexible, autonomously working manufacturing cell, which consist of different, but closely networked individual subsystems. Since the welding process is classified as a special process, it will take a long time before appropriate knowledge management systems are established. However, welding data storage is already becoming more and more interesting to the user – not just for documentation, but also for data analysis with regard to possible defects in the welded joint and for intelligent, predictive wear part management. However, it has not yet been precisely evaluated at which level of detail the data must be available for the creation of appropriate algorithms, there is currently a strong tendency on the user side to record and store the data at as high as possible resolution. Since the internet connection speed is often insufficient at customer sites and the topic of data security on cloud systems has not been finally clarified, such production data can also be stored and analysed locally. Specially designed server systems with coordinated system performance and intelligent evaluation functions are ideal for this.
Welding torch position identification
One of the main factors influencing weld quality is the timing of torch positioning relative to the part along the weld path. In the case of automated robot welding systems, the topographic measurement of the part surface and the position of the welding torch can already be reliably performed. In most cases, laser scanners are used, and the information obtained is used for the realisation of adaptive welding processes. Such processes respond to deviations in the part topology by means of the adaption of torch positioning and power source parameters. In addition, deviations of the actual robot movement from the taught default values, e.g. welding speed can also be considered.
Communication human / welding machine
The welding technologist and the welder will remain responsible for the welding quality of complex welding products in the coming decades. This requires the means of communication between human and welding machine continue to play an essential role. The current trends in the development of interfaces are significantly influenced by those devices that the welder also uses in his private environment. Smartphones and tablets are ubiquitous and can be used as a benchmark for reducing complexity for the operator. Abilities such as multilingualism, touch operation, voice control, etc are already making their way into the harsh workshop environment.
Before the autonomous Industry 4.0 welding cell manufactures a real part, it is necessary to create the welding program in off-line mode, to define and check the torch movement in order to avoid unnecessary rejects. This procedure is unavoidable especially if it comes to single piece production. For this purpose, special software systems will be needed in the future, which are able to represent the welding process virtually. The basis for their development will be those software programs that are already being used in the training of welders and robot programmers to virtually train the correct programming of torch holding.