Greg Blackman investigates the art of laser system design and integration
The laser as a cutting tool might not be as straightforward as a mechanical blade say, but it is now a reasonably well accepted, robust and reliable piece of industrial processing equipment. The beam itself can be tuned and tweaked to make a precise cut or to create a strong weld, but it is often the surrounding infrastructure – the part handling, or the fixtures in the case of welding – where the real complexity in designing a productive laser cell or machine lies.
As Tony Jones, managing director of UK laser system builder Cyan Tec Systems, noted ‘the laser source is the relatively easy bit’ and that how the part and the beam are manipulated is the complex aspect.
Around 65 per cent of Cyan Tec Systems’ work is building bespoke laser systems, according to Jones. Even customers buying a standard machine typically want a variant of it. ‘I often say, “we make six standard machines and eight million variants of each of them”, because everyone wants something different,’ he added.
Cyan Tec Systems’ main clients are automotive, aerospace, R&D and nuclear, closely followed by the consumer goods industry. The company’s systems range from a 500cm3 machine costing about £40,000, to those measuring 10 x 8 x 8 metres priced at £3 million.
‘A good integrated laser cell is simple to operate,’ Jones said. ‘There are systems out there that are just so complex for the end user that they aren’t used to their full capability. We try and ensure “green button operation”, so the machine does what it’s supposed to at the press of a button without too much intervention.’
Jones also noted that the machines have to be flexible, in that they have to be able to be adapted to suit small changes in task. ‘Even in the automotive industry, where manufacturers are making thousands of vehicles, there’s always a slight model variation,’ he said. Therefore, equipment should be able to handle minor changes, whether that is a programming change or different tooling. ‘Trying to think ahead is the best way of looking at that,’ he added. Around 70 per cent of Cyan Tec Systems’ laser cells use robotics, which gives a certain degree of flexibility, according to Jones, because changing the cutting path is a program change, rather than having to alter the mechanics.
Around 65 per cent of Cyan Tec Systems' work is building bespoke laser systems
Working on welding
Jones said that, on an average project, the company would spend around four weeks working with the customer at the front end, before the machine is designed to make sure the engineers understand the process requirements, on both sides, the end-user and the integrator. ‘The customer has to fully understand their process and to understand the advantages of the laser, but also its limitations,’ he said. ‘For instance, for a welding project, we’d really stress to the customer how important it is that the two parts fit together well, or how well they can be held together with tooling. If they don’t, it’s quite difficult to laser weld and more traditional welding processes like MIG or TIG might be better.’
The disadvantage of using traditional welding methods is that they put a lot of heat into the part, which can cause distortion. ‘If you can get the fit-up of the parts correct, you can use a laser to weld it and there’ll be virtually no distortion in the parts. Plus, it gives a much neater weld requiring minimal finishing,’ Jones said.
In automobile production, remote laser welding, whereby the laser is scanned over the surface of the workpiece from a distance, is now a more popular method of joining car parts, because of its processing speed. The technique requires specialist knowhow and there are now integrators that concentrate almost purely on these types of system. One of these is German system maker Bergmann and Steffen, which was one of the first companies to integrate a remote welding system, installing it in 2000. Since 2005, Bergmann and Steffen has focused on laser welding, especially remote laser welding. The company works purely on automotive integration projects and, in 2011, it established its own application lab specially for remote laser welding.
Uwe Bergmann, managing director of Bergmann and Steffen, emphasised the importance of the fixture to hold the parts in place in remote laser welding applications, where components are joined by anywhere between 50 and 200 welds.
‘You’d need 100 standard toggle-level clamps for remote laser processing, which would be a very complicated clamping fixture,’ Bergmann said. The firm has developed its own fixtures with a patented design consisting of pneumatic, hydraulic or spring-loaded pins. They are made of two plates, a lower plate with telescopic pins and the upper side with some fixed pins and holes in it to weld through. The part is clamped between the fixed pins on one side and telescopic pins on the other.
‘We don’t normally use standard clamps,’ Bergmann continued. ‘Our clamps just need to be closed around the part, the hydraulic mechanism switched on, and then the part will be clamped at 200 positions at the same time.’
A second important consideration when designing remote welding cells is air management, Bergmann noted. Remote welding needs clean air – the air needs to be changed at least 60 times per hour, according to Bergmann, which is much more than for standard laser welding or other welding processes. ‘There is a big standoff distance between the scanner optics and the workpiece in remote laser welding, and the environment between the optic and part has to be clean – there shouldn’t be any dust, spatter or smoke between optic and part, because this would defocus and absorb the laser beam,’ he said.
Bergmann and Steffen has also developed its own systems for air management that are now standard in remote welding cells installed at OEMs and Tier 1 suppliers. The air management system consists of blowers and extraction points to keep air clean.
‘Customers are asking for cost-efficient systems. They ask for low energy consumption and systems that are easy to maintain,’ said Bergmann. ‘Running cost for remote laser welding is important.’
The company has developed the Tornadoblade to help reduce the operating costs of remote laser welding cells. ‘The main costs of running a remote welding system are electricity, compressed air and shield glasses,’ said Bergmann. Compressed air is necessary to cover the optics and prevent them from getting damaged by spatter or dust and dirt. The Tornadoblade uses a blower instead of compressed air, which improves cost efficiency and reduces the running cost of the cell.
‘Remote laser welding is now fully established in the automotive industry, and it’s still growing,’ observed Bergmann. He said that remote processing used to be mainly overlap welding for steel applications, whereas today the firm has to make systems to weld lightweight car designs using aluminium and magnesium, as well as high-strength steels, which are more difficult to weld. ‘The main questions we get from our customers involve process monitoring and seam tracking for remote welding. There are new materials, new applications, and new seam shapes that all need to be investigated. So, remote laser welding is still growing.’
Bergmann and Steffen uses scanning optics from German supplier Blackbird Robotersysteme, owned by Scanlab. One of Blackbird’s innovations, which will be launched at Laser World of Photonics in Munich in June, is a new scan head with an in-built distance sensing system based on interferometry for process control, technology that aims to meet the types of demand for seam tracking that Bergmann mentioned.
The interferometer beam can be steered around the welding beam to capture high resolution and high sample rate measurements of the distance between the scan head and workpiece. The new product offers seam tracking to detect edges of the weld seam, and is able to scan the welded surface to give a high-resolution 3D image of the weld. ‘This, from our perspective, is going to be the next step to extend our solutions to not only cover scanning and scanning control, but to also provide a deeply integrated solution for sensing, so scan systems can track geometric contours and record the seam profile during the welding process,’ said Dr Wolfgang Vogl, CEO of Blackbird Robotersysteme.
‘We don’t want system integrators to worry about additional measurement technology,’ he continued. ‘We want them to be able to choose a scanning solution that already comes with a powerful and flexible tracking mechanism and one that offers a better way of tracing the quality of welds.’
Blackbird Robotersysteme works with different robot makers – ABB, Comau, Fanuc, Kuka and Yaskawa – and laser makers – like IPG, Laserline, Rofin, Trumpf and nLight – to make sure the components are compatible.
Bystronic's ByTrans Cross system offers automatic unloading and unloading
Making automation pay
Turn to laser cutting and the story is similar to welding, namely that the laser source is only one aspect of the system and that quite a lot of the innovations to increase productivity are to do with part handling, sorting, and automatic loading and unloading.
‘Customers are talking about high performance and automation,’ stated Guido Wahl, head of laser development at system supplier Bystronic.
The company’s high-end-system ByStar Fiber is equipped with 10kW of laser power, which can process parts very quickly. This means that automation is important to maximise production throughput and to exploit the full potential of the machine. ‘If you can cut faster there is also a need to remove the parts from the machine quickly, which means an automatic loading and unloading mechanism,’ explained Wahl. Bystronic’s ByTrans Cross system is designed for this, and fits with the ByStar Fiber.
System provider Trumpf has gone along similar lines with its TruLaser Center 7030, launched at Euroblech in Hannover at the end of October 2016. The machine is able to speed throughput by 53 per cent and reduce processing costs by 30 per cent compared to standard 2D laser cutting systems, according to the company. The list of automation built into the machine includes its ability to eject and sort small parts; dispose of residue and slag; sort and stack larger parts during machining; load itself with blank sheets; stack scrap skeletons; and the programming is also largely automatic.
Wahl at Bystronic observed that laser cutting systems are becoming higher power. ‘We recognise we are not at the end of increases in laser power for cutting systems,’ he said.
Automation is another trend he noted, and a third trend is Industry 4.0 and the demand for digital services to optimise productivity.
Bystronic introduced its ByCockpit product at Euroblech which, as of summer 2017, will be available as an app for mobile devices. It collects, analyses, and visualises process data from the connected Bystronic cutting and bending systems.
‘Bystronic’s software doesn’t just support the laser cutting machine, but the wider production process,’ Wahl said. ‘The laser cutting machine might get an order directly from the enterprise resource planning system. In addition, when parts are cut with a machine with ByCockpit, the user gets feedback on how the machine is working, and it can recognise where bottlenecks in production might occur and how to solve those.’
In addition, Wahl noted: ‘Service and training is very important and is still required, because there are so many different parameters involved in laser processing. We have customers that want to cut very fast with lower accuracy, and those that want higher accuracy; the training is there so we can offer the best solution for the application.’
It’s also important to fix a machine quickly to minimise any potential downtime. In line with Industry 4.0, Bystronic machines offer predictive maintenance so that the customer knows when components are nearing the end of their life and need changing.
Jones at Cyan Tec Systems commented that ‘the biggest change for us as an integrator and as an end-user is the cost of lasers.’
Lasers used to be expensive to buy and run. ‘With the introduction of the fibre laser over the last five to ten years, laser technology has become a lot cheaper to buy and run, and the maintenance is virtually zero,’ he added.
‘With lower costs, the laser is now a lot more viable for projects where it wouldn’t have previously been considered – because the cost is more realistic, we can do a lot more with the laser.’
Jones went on to say that diode laser technology is now suitable for industrial processes. ‘People are realising that they can do a lot with diode lasers,’ he said. ‘The beauty of a diode is that it has a long life, is inexpensive to make, and is scalable to higher powers. Costs will continue to come down with diode lasers, and with that there will be more applications using laser technology.’
With automation now high on the agenda of laser system providers, the design of safety equipment must also take this into consideration.
Lasermet’s interlock systems are built with automation in mind. To enable certain laser processing systems to become even more productive whilst maintaining safety, the company has further developed its laser safety cabin to incorporate interlocked turntables. As the Laser Castle is built from modular components, additional laser safety walls can be added to the cabin’s external structure so that workpieces can be delivered and retrieved safely.
For installations where a turntable is required, the laser can only be enabled once the turntable has stopped moving and the workpiece is inside the laser cell. When the interlocked switches on the rotating table are open, the laser safety input to the laser is isolated. This is particularly necessary while the turntable rotates, as there would otherwise be a risk of exposure through the gaps produced either side of the moving turntable. Once in place, the contacts on the dual channel interlock switch are made and the interlock allows the laser to be fired.
To enable safe visual monitoring of the workpiece while the laser is operating, Lasermet has developed the Glaser Jailer active filter window system. If any window is struck by the laser or a powerful reflection, the interlock controller isolates the laser safety input within 50ms, thereby switching off the laser beam. This principle of operation extends to the Laser Jailer active laser guarding system, which can be installed throughout the whole of the inside structure of the cabin. Again, if any of the detector tiles – which line the inside of the cabin – are struck, the laser is switched off by isolating the laser safety input, also within 50ms.