With the launch of 10kW fibre laser cutting technology by Swiss firm Bystronic at the recent EuroBlech exhibition in Hannover, CO₂ laser cutting machines no longer have the advantage when it comes to processing thicker materials.

This is the view of Jon Till, joint owner (with technical director Steve Morgan) of Oldbury-based Accurate Laser Cutting (ALC), which has recently become a fibre-only sub-contractor.

1999, when ALC bought a Bystronic BySprint 3kW CO2 model; this was soon followed by 4kW and 4.4kW versions — and the first 6kW machine in 2002. June 2015 saw the introduction of fibre laser cutting at ALC, when the company installed a 6kW BySprint Fiber with 4 x 2m capacity (www.bystronic.com).

A 10kW ByStar Fiber for processing sheet up to 3 x 1.5m was added in November 2016 — the first machine with this level of power to be installed in the UK.

Based on his long experience, Mr Till provides a user’s view of the advantages of fibre over CO₂ laser cutting in terms of increased machine availability and productivity, lower running costs and greater versatility. He also argues that the demise of the CO₂ laser is nigh.

The first point he makes is that 6kW is the practical limit for CO2 laser cutting, as higher power would burn the optics. Even power sources below this limit take their toll on the lenses and mirrors in a machine, leading to frequent down-time to clean them, plus periodic — and costly — replacement.

“Clearly, it is financially detrimental for a manufacturer if a machine tool costing hundreds of thousands of pounds stands idle for extended periods.

“Furthermore, CO2 laser machines are difficult to maintain, due to not only the condition of the optics but also the tendency of the optical path to move out of alignment, necessitating time-consuming correction if quality is to be maintained.

“At the best of times, especially on machines with a 4 x 2m — or larger — bed, accuracy in one corner of a sheet can be hard to replicate at the diametrically opposite corner without operator intervention to correct any
discrepancy.”

Problem solving

Mr Till also bemoans the fact that one can spend hours identifying a problem with a CO2 laser cutting machine when quality or speed of cut declines.

“The first recourse is to tweak the parameters at the control, followed by taking off the head and cleaning the lens, and perhaps swapping the lens at a cost of £270 each time.

“Mirror alignment is then scrutinised and adjusted if necessary. Finally, if none of that works, it may be that the purity of the assist gas is too low, which is detrimental to beam quality. This is very difficult to predict and is the last thing that is checked, yet it will typically happen twice a year.”

Mr Till says that fibre laser cutting, on the other hand, avoids all of these problems. Because the solid-state technology directs the beam down a fibre-optic cable, there is no wear and tear on conventional optics and the laser beam does not degrade.

Furthermore, machine running costs are significantly lower, as electricity consumption is 60% less for a fibre machine — and there is no need to use costly nitrogen, helium and CO2 as laser assist gases. He also says that productivity is dramatically increased using fibre.

“Our new 10kW ByStar Fiber cuts 1mm mild steel at 60m/min, which is faster than our old CO₂ laser could position its head — 50m/min — to start cutting.

The speed — and hence productivity — advantage when processing thinner sheet is around three-times greater, although it is less for thicker materials.

Clean cutting, where nitrogen rather than oxygen is used as the cutting gas to prevent oxidation of the cut edge, is also much quicker.

When processing 5mm mild steel, for example, the fibre machine cuts at four-times the speed of our last CO₂ machine.”

Maintaining tolerances

Regarding the relative productivity of the two machine types, Mr Till says he would be reluctant to leave a CO₂ machine running unattended overnight, such is its tendency to drift out of tolerance.

“That said, I would have no hesitation running a ghost shift with the fibre laser.

Furthermore, the technology has de-skilled operation to the point where one simply presses a button on a fibre machine and it starts producing, whereas there is still a lot of ‘black art’ involved in operating a CO₂
machine.”

Cutting capacities of the 10kW Fiber laser source (those for the 6kW ByLaser CO₂ source are shown in brackets) are 25mm (25mm) in mild steel, 30mm (25mm) in stainless steel and 30mm (16mm) in aluminium.

“This shows that CO₂ technology has already been overtaken by fibre laser, which also copes with cutting reflective materials much better than CO₂, hence the superior performance in aluminium.

For the same reason, the 10kW Fiber can cut 15mm brass and 12mm copper, materials that CO₂ cannot process without the risk of back reflections damaging the optics.”

Mr Till’s final analysis brings in the cost of the two machines — typically £750,000 for a 10kW fibre laser cutting centre and £500,000 for a 6kW CO₂ machine.

In his opinion, the higher capital investment in fibre laser cutting is easily outweighed by the extra expense of running a CO₂ machine and the latter’s low residual value towards the end of its life.

He concludes by saying: “A fibre laser can cut everything that a CO₂ laser can process — and very much faster in the case of thinner gauges. It can also tackle a much wider variety of materials, which is perfect for a sub-contracting environment.

“Moreover, it achieves accurate and repeatable results economically with very little machine down-time. In my view, this latest 10kW machine is a game changer in laser cutting.”