Christopher Ogden, founder of Laser Partners UK Limited, based in Sheffield, explores the plastic industry’s hesitancy to introduce laser technology and why it could be something to consider.
The uptake of industrial laser processing since its inception into the mainstream industry in the 1970s has been nothing short of phenomenal, with $5.7BN worth of lasers sold in 2018 and a prediction that this will increase to $14.5BN by 2026. Laser Cutting Engraving Machine
So, what can laser technology offer the plastics industry? In summary, quite a lot.
Here’s a brief list of the laser process options available today:
Probably the most popular and widely used of these technologies is Laser Marking – where laser systems with different wavelengths can be used to mark almost all plastic materials. Fast marking times of just a few seconds are achieved for most basic marking applications. Companies typically use laser marking systems to mark company logos, part numbers, date codes, serial numbers and machine-readable codes such as 1D barcodes and 2D barcodes such as QR and DataMatrix.
‘The wide range of plastic materials and their different colour additives and glass fibre content can make it difficult to mark some materials with a high contrast mark. But by using the right laser technology, almost all of these can be marked with a really good quality mark - whether the plastic is dark, light or colourless,’ stated Masahide Okano from laser system supplier Datalogic.
Most people are aware of laser cutting for steel-based applications, but using longer wavelength CO2 lasers also gives good results on thermoplastics. ‘With the right setup and laser parameters a cut edge with little or no discolouration can be achieved on most plastics, and on plastic material thicknesses of up to 25mm. With less dense materials thicker sections can also be cut’, states Lee Popplewell of Luxinar - a UK-based company specialising in CO2 laser technology, based in Hull.
CO2 laser technology creates a long wavelength of 10.6µm, by electrically charging gas contained within a sealed tube. Mirrors and lenses allow the system to build up sufficient power that can then be focused to perform different tasks. The longer CO2 laser wavelength means that it is readily absorbed by most polymers. Acrylic is one material where a neat, almost polished edge quality, is generally achieved, and many other materials will also give excellent results. With laser de-gating, the simple application of laser cutting eliminates the need for mechanical cutting blades, that eventually wear and require scheduled maintenance. As with many laser processes, there is no mechanical load resulting from the laser beam, so parts don’t need to be clamped in position for laser processing.
Laser welding is used for the repair of steel injection mould tools, with many tool makers using laser welding with filler wires to repair worn edges, cracks and fractures on mould tools, to extend the life of mould tools.
These systems are surprisingly simple to use with filler wire options available for most steel grades, including wires that leave a hardened deposit.
The use of pulsed laser technology, with a low flow rate shield gas, means that thermal damage and discolouration of the repaired surface is minimised, with results vastly superior to conventional welding processes, although deposit rates with laser welding are typically quite low.
A less well-known process is the use of lasers for ‘laser plastic welding’. Techniques are different to metal welding and this technology is not suited to all plastics and part designs, so careful consideration needs to be taken. A common approach is to use two different plastics (sandwiched together), one that’s absorbent to laser and one that is not. By focusing the laser beam through the non-absorbent plastic, the underlying absorbent plastic will then melt forming a welded seal between the two plastics. This can be a fast and effective process if material selection and part geometry is carefully considered at the design stage.
(left) Mould before laser cleaning, (right) mould after laser cleaning
One technology with a huge future is laser cleaning, which allows parts to be cleaned without damaging the underlying material and without the need for chemicals or abrasive media. Fast, effective, and consistent results are achieved by using pulsed lasers to break the bonds between the top surface layer and the substrate. Whilst not a new technology, laser cleaning is finding new applications for many industrial cleaning requirements including coatings, rust, and oxidation removal, as well as paint and contaminant removal.
Like all laser processes, care needs to be taken to use the laser safely, but UK manufacturer Woodrow Scientific have a big advantage with their patented eye-safe laser cleaning system, which can potentially be used without the need to fully enclose the processing area. These laser cleaning systems can be supplied and used as either a handheld system, or integrated as part of an automated or robotic setup. The use of different laser powers, optics and scanning devices can allow the laser to clean significant surface areas in a host of different applications with mould cleaning a popular application.
Changes to more technology-based solutions can seem a daunting task when compared with more conventional methodologies. Due to using a ‘light beam’ instead of mechanical parts, fixturing and work holding requirements are often quite simple, with no mechanical load exerted on the parts from the process itself. However, safety needs to be carefully considered too, with some level of protection required for all laser processes to prevent harmful exposure.
But surprisingly with lasers their integration can be quite simple. Power requirements are usually met by a standard 3-pin plug socket which helps keep costs low. The need for consumables with laser processes is usually low, or non-existent too. Lasers might be worth a look!
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