Keeping the call-outs at bay
The use of industrial laser systems for material processing is growing rapidly, particularly for manufacturing applications in aerospace and automotive sectors. The transition of the automotive industry towards e-mobility, for example, is one driver behind an increase in industrial lasers used for welding, as the increased precision, flexibility and productivity they offer makes them ideal for joining the reflective and lightweight materials involved.
It is only possible to reap the benefits of laser technology, however, if laser systems are properly maintained, as any time spent awaiting and undergoing repairs impedes the efficiency of production processes relying on them.
Thankfully, there are several different housekeeping procedures that can be used on a regular basis to help keep the need to call out an engineer at a minimum.
Maintain a good environment
For example, there are some seemingly ‘common sense’ practices that can be adopted in a manufacturing environment when looking to prevent the need for laser maintenance. For starters, the temperature and moisture level surrounding the laser should be kept at the level recommended by the system’s manufacturer. In addition, any compressed air and gas lines should be free of leaks or contaminants, and the power supply has to be stable. It is also important to try to maintain as clean an environment as possible.
Chris Jacobs, owner of HPC Laser, a UK specialist in laser engraving and cutting machines, said: ‘Dust and debris are inevitably going to occur in every machine. However, it is important to minimise build-up by regularly cleaning your machine, particularly the inside of the cabinet, the bed and anywhere material often collects.’
The impact of different materials being cut are also worth taking into consideration. Jacobs said: ‘Some materials like acrylic, MDF and woods release more fumes, residue and potentially flammable oils, which can affect components of the machine and be a fire hazard if not managed properly. Be sure to check for the accumulation of dust and debris on the impeller on the extractor fan unit, as any build-up can impede its function, unless a fume filter is fitted.’
Check and check again
Other checks that can be undertaken include ensuring a laser system’s air-assist compressor is operating correctly. ‘Check for obstruction in any filtration elements that may be present, and also inspect the delivery hose from the compressor to the cutting head, to make sure there are no obstructions, so that a suitable supply of air is reaching the nozzle,’ said Jacobs. ‘Reduced airflow to the nozzle can increase the risk of a flame breaking out on some materials while the machine is cutting. In addition, lubricate runners and the rise and fall of the bed using light oil to ensure these run smoothly, if not, friction can cause wear on moving components.’
Other visual inspections and monitoring results, said Jacobs, can help to identify potential issues with performance before the machine becomes damaged. ‘Testing beam quality can be as simple as comparing cuts from today, with cuts from pieces when the machine was new,’ he said. ‘Poor cuts may indicate bad alignment, a weakening laser tube or dirty optics.’
Keep the optics clean
If optics do become dirty, this can reduce the beam’s strength. ‘You can visually inspect the optics,’ said Jacobs, ‘however you may already notice poor results such as blurry lines, not cutting as deep etc. If the optics aren’t cleaned, dirt can combust or burn into the surface of the optic, permanently damaging the lens or mirror.’ He advises cleaning optics every 10 to 40 hours of work, depending on what types of material are being processed. ‘It’s extremely important to clean these carefully, to avoid damaging them. You can use IPA solution or acetone, together with some gentle cotton buds for this.’
There is always the chance that things can go wrong or break-down. Oliver Meier, executive partner at German repair and maintenance specialist, Laser on Demand, concurs about the importance of maintaining optics. ‘Based on more than 20 years’ experience in industrial laser applications, one of the most common causes of breakdown is a damage of the optical fibre – either caused by dirt or back reflection,’ he said. ‘While diode and disc lasers always allow a plug-and-play exchange of the damaged fibre, fibre lasers often require splicing of a replacement fibre by a service technician. This can be done in the field, but very often the laser source needs to be sent to the manufacturer. Besides a number of advantages, that is the most significant disadvantage of most high-power fibre lasers.’
Laser maintenance often happens in a clean room, to ensure that delicate components, such as the optics, are kept in good condition during the repair. (Image: Laser on Demand)
Meier recommends that optical components such as the processing head and cover slide should be checked at least once a day or once a shift – and more frequently, if required. He also advises that, if changing an optical fibre, tilting the fibre connector horizontal to avoid dirt falling on the lens should be standard procedure.
‘A lot of significant and expensive issues could be predicted in advance by continuous monitoring of relevant machine signals, such as temperatures and scattering light, by experienced technicians. Laser manufacturers offer such services for the latest laser models. However, most lasers that are a few years old are not supported like that. That’s the reason we offer a manufacturer-independent monitoring service, “laser care”. This is based on a safe direct network connection, completely separated from the customer’s network environment.’
As part of this regular monitoring, Meier believes that there should be a yearly maintenance of the system’s power supply and water chiller, as these can be the biggest causes of breakdown. He said: ‘Two more reasons for laser systems to fail are a breakdown of the cooling system (internal circuit or external chiller) and a failure of the laser power supply. Chiller problems can usually be avoided by a exchanging the water, filter and coolant at least once a year. While a power supply failure nearly always cannot be foreseen or prevented.’
Jacobs takes the importance of the water chillers a step further. ‘Water chillers are an effective method of keeping the water temperature down to ensure the tube doesn’t overheat. It is therefore important to keep a close eye on chiller performance and monitor any temperature indication on the chiller display.
‘Every few weeks, locate the air filter in the chiller and remove any build-up of material. Use this time to check for water contamination and change if required. Use de-ionised or distilled water as the impurities in regular water can encourage bacterial growth, clogging piping, protection devices and filters in the water circuit.’
In addition, said Jacobs, particular care must be paid during the cold season. He explained: ‘The drop in temperature during winter months means your machine needs extra attention and TLC. There are a few pointers to effectively maintain your laser throughout winter. For example, ensure the room in which the machine is in is kept above 0°C, preferably 5°C.
Laser users should ensure that the room in which their machine is kept is continuously above 0°C, preferably 5°C. (Image: HPC Lasers)
‘Take extra care in rooms susceptible to a plummet in temperature overnight. If you struggle to maintain this temperature, use an approved anti-freeze. It is important that only an approved anti-freeze is used in the coolant circuit, and the use of coloured automotive coolant is avoided, as some formulations can rust coils and damage the seals of the chiller.’
As part of a healthy regular maintenance routine, it is helpful for users to keep to a recommended schedule that is followed by everyone, and ensure a log of any maintenance activity is kept up-to-date. Having one or more trained, internal points-of-contact is recommended to help with diagnostics, or liaise with third party repair or maintenance professionals remotely and follow their advice. This could help reduce the need for downtime and potentially costly call-outs.
Maintenance contacts should be aware of what key performance indicators are tracked, such as time spent on improvements of equipment or procedures, elimination of root causes, elimination of waste, and effectiveness of planned maintenance.
A visual board on the shop floor can afford employees a greater understanding of what these indicators are and why they are important, which helps them take greater ownership of maintenance procedures. Feedback should be sought from the maintenance contacts and they should be included in continuous improvement tasks. For users of laser cutters in particular, it is a good idea to keep a small collection of essential spare parts. It is also worth checking that the supplier stocks parts locally, and can deliver on a quick turnaround.
Keep replacement parts handy
Meier explained: ‘For critical components that are likely to fail and would lead to a stop of production, the user needs to have replacement components on stock. This typically includes cover slides for optics, a spare fibre and a spare diode module. Sometimes, especially small companies, try to save on costs for spare parts. This is quite surprising if you imagine some components – especially optical fibre cables – may have a lead time of multiple weeks.’
When it comes to what can go wrong with laser systems, it can depend on what type of laser is used. Meier explained: ‘For industrial laser materials processing, diode-pumped solid state lasers (disc or fibre lasers) and direct diode lasers are most relevant.’ Diodes can cause laser breakdown as these are the wearing components of modern laser sources. On the one hand, this can mean power losses due to degradation during the lifetime, which can lead to a power reduction that cannot be compensated and thus to a process or systems failure.
‘On the other hand, secondary issues such as misalignment of fast axis collimation (micro-lenses) or water leakage of micro-channel cooled diode bars, are common towards the end of the lifetime. Sometimes, the latter mentioned occur even before a power drop, which is painful, as the diodes themselves could still be used.’
Looking at the trends the company has seen in the number of call-outs and the reasoning for them, Meier said: ‘During the last decade the number of calls for diode replacement or repair increased significantly.
‘On the one hand, this is due to the fact that diode-pumped laser sources replaced the lamp-pumped sources. On the other hand, a considerable number of service calls is related to some outpriced after-sales strategies or discontinued sources and spare parts.’
In terms of addressing some of these problems, diode issues can typically be solved by replacing complete modules, according to Meier. ‘However, this is fast but can be relatively costly,’ he said. ‘The refurbishment of pump modules or diode stacks can be a cost-efficient alternative. As a real repair/refurbishment of critical components – instead of replacement by new modules – requires some key-enabling facilities and jigs, it hardly makes sense to offer repair of all laser types and brands.
‘Moreover, a concentration on specific types allows us to offer an economic and efficient repair solution. Therefore, we currently concentrate on repair and maintenance of high-power disc lasers and diode-pumped solid-state nanosecond pulsed lasers in an in-house cleanroom.’
Meier concluded by comparing the care of laser sources to that of cars.
‘It’s no problem,’ he said, ‘as long as spare parts are available at moderate costs. Repair and refurbishment of used lasers can be a cost-efficient and sustainable solution, even for many years after the end of a manufacturer’s warranty period.’
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