FEATURE MACHINE BUILDING, FRAMEWORKS & SAFETY
Images courtesy of Griffon Hoverwork
For Griffon Hoverwork,
Britain’s only large-scale hovercraft maker, high pressure
waterjet cutting of
sheet and plate materials solves two important
WATERJET COLD-CUTTING: A cool technique when building customised hovercraft
A
s one of the world’s leading hovercraft manufacturers, Griffon Hoverwork offers a
wide range of craft for commercial and military purposes, building large and small hovercraft variations to suit customer’s specifications. For a mid-range craft the bill of materials
(BoM) lists over 100,000 items, a larger example more than 500,000. Besides off- the-shelf products, a variety of bought-in bespoke parts and panels represents a major percentage of each BoM. These parts and panels, outsourced for supply to manufacturing services contractor ICEE Managed Services, range from small, non-standard washers to strengthening gussets and formed brackets. In contrast, many large flat panels feature holes, slots, and simple or complicated profiles. The panels are welded together by the
hovercraft manufacturer at its factory adjacent to Southampton Water to form the hull and superstructure of the vessel, and to fit out the interior. The outsourced and usually bespoke
items are cut from 2mm thick sheet up to 20mm plate, mostly 5083-0 grade aluminium and 304L or 316L grade stainless steel.
PREVENTING HAZ To eliminate a major risk when building and welding hulls and superstructures from aluminium sheet and plate, Griffon Hoverwork specifies cold-cutting by waterjet. This process offers a valuable cost-saving benefit to minimise cleaning-up or fettling of cut edges. If a panel is profile-cut by fibre laser (or
another method that cuts metal by melting it) the intense heat generated forms oxides or heat- affected zones (HAZ) on cut metal surfaces – top, bottom and edge – along the length of cuts. If this oxide is not removed before the panels
are welded together it could contaminate a part or the whole weld. Entrapped oxide may weaken the weld’s strength and, over time, operational stresses could cause propagation of cracks leading to local or extensive weld
manufacturing issues: it eliminates the risk of inadvertently including impurities in welds, while
highly organised delivery of parts from ICEE Managed
Services helps to streamline the company’s fabrication and certification processes. ICEE’s Chris Arnold explains
breakage. This might result in catastrophic failure of a hull structure or superstructure – a major risk the hovercraft maker takes every precaution to eliminate. If HAZ are produced, operators would have to
carefully remove all oxide from cut edges prior to welding, adding considerable cost. It would also demand supervisory skill and more time after to check results met required standards. Waterjet cold-cutting solves the problem. Ideal
for aluminium and stainless steel, this results in a clean and accurate edge, wasting little material as the kerf, or cut itself, is narrow. On thick plate, no wandering or ‘tapering’ of the cut occurs, so the edge is always square and true for welding,
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60
