Yellow goods laser

Citation

(2002), "Yellow goods laser", Assembly Automation, Vol. 22 No. 3. https://doi.org/10.1108/aa.2002.03322caf.006

Yellow goods laser

Keywords: Lasers, Cutting

In 1951 the late Basil Thwaites unveiled his first "dumper-truck". Fifty years on the company which continues to bear his name is still the world's leading producer of such vehicles – exporting them to more than 70 countries.

In the late 1990s, some time after most manufacturers of off-road vehicles had already embraced laser technology, two factors emerged to alter this situation – one general, and one specific. In general, more powerful lasers were now available – these enabled both the cutting of thicker materials, and the cutting of medium gauges of material much faster than before. Also in Thwaites' particular case a new Unigraphics CAD system had been installed, in preparation for the design of a new product range. These new products could be designed from the outset with laser profiling in mind. The production freedom offered by laser-processing would allow Thwaites' designers to realise more of the potential of their new CAD system than any other cutting process would.

Further benefits factored into their justification included an improved material utilisation – needed to offset rising material costs. The "flying-optic" approach to cutting did not necessitate sheet clamping. It also enabled the cut-widths and skeleton web-thicknesses on sheet nests to be reduced compared with their old Plasmapress and oxy-propane cutting nests. Additionally, the tool-free nature of the process enabled them to place lower batch size orders onto the shop – leading to inventory and other production-control benefits. A further production advantage over their existing facilities was provided by an automatic pallet-exchange system, combined with the ability to run a laser machine unmanned into the night at the end of a late shift (Plate 5).

Plate 5 Thwaites choose Trumpf's L3030

The idea of using "tongues" and slots in respective components to enable "jig-free" assembly is far from new. But at Thwaites they have taken this idea to new heights or should one say depths – by "cashing-in" on a Trumpf laser's ability to produce "narrow" slots in their thick plate components. In many instances welding jigs have been eliminated, but even the remaining jigs are now much simplified, by using this tongue and slot technique – particularly in the area of vehicle sub-frame assembly. Jig elimination, although most noticeable among the major sub-assemblies, is by no means confined to this area. According to John Tebaldi, it is also significant in the detail production area. On older machine models, any components thicker than about 10mm were profiled on their gas-cutting machine. This meant that any holes needed in them had to be subsequently drilled. Also, even on thinner parts, if any "small" holes were required – i.e. holes smaller in diameter than plate thickness, then they also had to be drilled rather than punched. However, on their new model, holes and slots as small as 40 per cent of plate thickness are now produced by laser, at the same time as the larger profiles. Not only has this eliminated "second-ops" – with all their extra handlings, setups, and machining times – but it has also eliminated literally dozens of drilling jigs on this one new model alone.

Another envisaged benefit, which Thwaites can now confirm, is a reduced manning requirement when compared with their other machines. One feature of the L3030 which they do exploit is its ability to run unmanned into the night, without any operator involvement, and without any of the other control and management resources usually associated with running an FMS or "lights-out" facility. At the end of the late shift the operator makes sure that the machine is loaded with two fresh sheets of raw material. One goes into the cubicle for cutting, and one onto the second pallet ready for use. On completion of the first sheet, the pallets exchange and the second job is cut. On completion of the second job, the machine shuts itself down in a controlled and safe manner – ready for unload next morning. Obviously, when working in this lights-out mode they only load proven work, but by choosing long-cycle jobs – usually in their slower-profiling, thicker materials of up to 20mm – they can often obtain two or three hours per night of "free" production: in fact up to six hours has been achieved.

For more information contact: Trumpf Limited, President Way, Airport Executive Park, Luton, Beds, LU2 9NL, UK. Tel: +44 (0) 1582 725335; Fax: +44 (0) 1582 399250.