Highly automated small parts production
Workpiece clamping in the cycle of intelligent connectivity
In large companies, the conversion of traditional machining processes to Industry 4.0-compliant processes has long been underway. The aim is to utilise the potential of digitally networked production. This includes individual process participants making decisions autonomously on the basis of digital data. At Krones Nittenau, this is achieved by a production concept that works with clamping technology from Gressel.
Krones, headquartered in Neutraubling, is recognised as the global market leader in the planning, development and production of process, filling and packaging technology as well as intralogistics. Every day, tens of millions of bottles, cans and moulded containers are processed worldwide using Krones systems, primarily in breweries, the soft drinks industry, wine, sparkling wine and spirits producers, but also in the chemical, pharmaceutical and cosmetics industries.
Three-stage plan for the production of large parts
Krones has around 9,000 employees at five production sites in Germany. One of these is Nittenau in the Upper Palatinate, where large and small parts of machines and lines for the main plant are manufactured. To ensure long-term competitiveness, Nittenau invested in a modern large-scale machining centre for turning and milling in 2021. The investment was part of a reorganisation of the entire production area launched in 2018, which comprises three stages as an investment programme. Krones Nittenau completed the first stage of the programme at the end of 2020 with the commissioning of a new laser welding system, which included the optimisation of upstream and downstream processes and the reorganisation of the material flow. In the coming years, phase three will see the commissioning of further turning and milling systems.
Investment with foresight
Parallel to the programme for large parts, Krones Nittenau also invested heavily in small parts production from 2021, where components between 5 and 1,250 mm in size are manufactured. These investments are linked to far-reaching automation and digitalisation measures, which are intended to ensure the on-time supply of high-quality parts in the future as well. As with the production of large parts, this will take place in several stages in the production of small parts. “We have drawn up a plan up to 2028 that consists of several steps,” says department head Vitali Schmidt, outlining the scenario. “Implementation has started with a highly automated production concept, the key components of which are milling machines, clamping devices and driverless transport systems. One of the reasons why we decided in favour of Gressel clamping systems is because of the next step. Here we will be moving in the direction of turning with the same clamping systems. In this respect, they are an investment with foresight.”
A chain of strong links
Before the modernisation, production in the milling area at Krones Nittenau was classic: “We pre-set up on pallets, brought them to the machine and lifted them in by crane,” explains Schmidt. In the meantime, the output hours had been recorded and the number of hours had been increased with a separate set-up station and optimised processes, but the concept had now been exhausted. The company was looking for a process that would mean even less set-up at the machine and that employees would no longer be tied up with set-up. This was only possible through automation. This approach ultimately resulted in a concept consisting of ten “G550” 5-axis machining centres from Grob, a fleet of “Agilox” automated guided vehicles (AGVs) for workpiece and tool handling and a whole range of clamping systems from Gressel. “This means we no longer have the traditional operator at the machine,” says Schmidt. He continues: “There have also been drastic changes in work preparation. Today, everything has to be 100 per cent prepared. The programmes have to be 100% correct, every screw, every vice has to be drawn in advance. That’s a huge challenge for the programmers.”
Two fifths more output
In addition to the set-up, Krones Nittenau wanted to achieve two main objectives with the changeover. First of all, the machine running time is to be significantly increased. “In the first step, an increase from 3,500 to 5,500 hours is planned,” specifies the department manager. “In the second step, we want to achieve 6,000 hours, almost 40% more output and a considerable reduction in costs in order to keep up with the international competition.” The second point arises from staff turnover and a shortage of skilled labour. As in the old manufacturing world, Krones will also work in three shifts in the new one. “We may be running night shifts without staff as early as next year,” announces Schmidt. “Initially, there will still be an employee on site to handle the parts, but a line operator will no longer be required. In this way, we want to reduce the costs per hour – in addition to increasing the output at the machine.”
First cycle: Tools
Today, orders are started from a delivery point for sawn parts. A control system then checks whether all the required tools are in the machine. If this is not the case, the set is put together. For example, from another machine that is not currently using the tool. An Agilox then fetches this tool to the first machine in the same way as other tools from the central presetting. This is where the remaining requirements had previously been placed automatically. As soon as an AGV has picked up the preset tools and brought them to machine 1, tool loading is complete. “Production itself is monitored for tool life, for which the system also takes into account the remaining service life of tools that have already been used,” explains Schmidt. “Depending on the machining time of an operation, the system automatically orders a Duplo tool to ensure the remaining machining time. It also checks whether a tool can be taken from another machine or whether a new one from the tool presetting is required.” Once the order has been processed, the tools normally remain in the machine for two days. Finally, a new order may come in, perhaps even for the same part for which the tool is required. Tools that are not required for more than two days are gradually removed from the machine and returned to the presetting by an AGV with a note of the remaining tool life.
Second cycle: Workpieces
In a second cycle, another Agilox fleet handles the workpieces. Once they have been clamped at the set-up station, an AGV takes the pallet to machine 1. “Here, it is stored in a buffer with nine slots and simultaneously added to the internal system,” explains Schmidt. “The system then makes it possible to finish parts from the buffer with different priorities depending on when they are needed.” After processing, the part goes to the inspection department. If everything is OK here, the system starts up again and brings the pallet with the next part. How many parts are checked in which cycle can be flexibly defined. All parts that can be handled in terms of travel and clamping options are manufactured in this way, whether they are made of aluminium, brass or stainless steel. Batch sizes between 1 and 50, often between 1 and 30, are produced on the machines. “We don’t want to run more than that, which is due to the throughput time,” emphasises the department manager. “Because the number of dissimilar parts that are fed through is very high, simple, fast reclamping is the be-all and end-all.”
Great variability mapped
“The clamping devices that we have used reflect this great variability,” emphasises sales engineer Sokha Hem from Gressel. “In addition to pyramids, ‘C2’ centric clamps and ‘Gredoc’ zero-point modules and plates, these include ‘SC5X’ 5-axis clamps, ‘S2’ fixed-jaw clamps, clamping tombstones and ‘D2’ double tombstones.” The collaboration, in particular the development of the clamping tasks, was extremely constructive and based on partnership. The first effect that Krones Nittenau achieves with the systems is the intended set-up efficiency, which goes hand in hand with features such as quick jaw and spindle change or quick adjustment of the clamping range. “Added to this is the high stability of the clamping devices, which, together with the stability of the machine, is essential for precision,” says Hem. Schmidt explains the necessity of this: “A machine is only as good as its clamping device. But we manufacture many parts in the hundredths range. This requires the high stability and repeat accuracy of the Gressel systems as well as the high pull-in forces that ensure secure clamping.” Finally, the price was also right for the overall package, reveals the head of department.
Another decisive factor for Krones is the standardisation that goes hand in hand with the clamping devices. Nittenau has now defined the Gressel systems as the standard for milling. Turning is soon to follow, which means that the zero-point clamping system in particular will be used on all machines. In addition, the clamping devices will also be used for production at the main plant in Neutraubling in future. “We want to be able to machine parts that are produced there at the touch of a button. However, this is only possible if the clamping devices are the same.” Standardisation also plays a role abroad. For America, for example, where it influences the spare parts business. By rolling out identical production equipment internationally, parts can be manufactured abroad without any problems. This brings Schmidt back to the basic approach: “The entire concept is designed for automation. The focus is therefore on the smooth interaction of the individual, digitalised components. The systems from Gressel are a bank for this.”
