Sheet metal fabrications

I would like to try and illustrate some of the modern production methods used to manufacture sheet metal work and sheet metal fabrications today in the UK. I have used examples of sheet metal components manufactured in our factories in Fareham, Hampshire, UK. They illustrate the range of component design features that can be created and some of the machines that can be used produce them.

If you can arrange that a design for a new sheet metal fabrication you are designing can be produced in one continual homogenous part you will always have the best solution for the easiest manufactured and cheapest purchased component. That’s fine in an ideal world but you may have to design sheet metal fabrications that are created from more than 2 different thicknesses of metal, for instance a 1mm mild steel chassis with 2mm mounting angles, perhaps profiles that would be materially inefficient to cut from one metal part (such as crosses), impossible to manufacture in one component (such as overlapping areas or features that would need the same sheet material taken twice from a developed blank) or perhaps a design where water/air tight joints will be required after fabrication has been completed. In a similar way to spot welding fabrication assemblies; tungsten inert gas welding (TiG), metal inert gas welding (MiG) or gas fuel welding various metal alloy grades allows us to join these sheet metal components together into one continual “fabricated” assembly. This could be a 3mm mild steel base plate with 1.5mm locating angles or a mild steel housing with spot welded stiffening rails, the options are endless. Of course, you may be aware that visible witness marks of the welding process (either spot welds or seam/tack welds) will be seen as an area known as the heat affected zone (H.A.Z.) which may be visible to the naked eye as a burn / oxidisation mark along either edge of the welded joint on both sides of the sheet material (this is not so obvious in aluminium welding but still present). The welded joint area can be cleaned down to the parent sheet metal surface if sufficient penetration has taken place, so that the strength of the original weld joint is maintained. If the component is then required to be painted or polished / grained the final welded joint in the fabrication can become invisible in the finished sheet metal component.

If you are looking to achieve a stronger joint than a simple spot welded fabricated joint in sheet metal assemblies then one of the industry standard welding processes maybe needed. There are three main welding processes you can think about; these being tungsten insert gas (TiG), metal inert gas (MiG) and gas welding / brazing. They all need an insert gas or flux to help shield the weld pool during fusion of the parent metal to help reduce imperfections and impurities in the final weld joint. All three weld processes can be applied to various sheet metal material alloys including steels, stainless steels and aluminium alloys. These welding processes apply more heat to the weld zone than spot welding, are slower to perform and inevitably more expensive but have some important advantages over simple spot welding.

1. They can be used to good advantage where a waterproof joint is required in say the corners of a simple sheet metal drip tray or water tank.

2. If strength is important then welding techniques should be used for any sheet metal fabrication in preference to spot welding as the length and depth (of height) of the welded joint is superior.

3. The cosmetic appearance of the seam welded joint will be better and if cleaned up after welding an invisible joint can be achieved.

The exact welding method needs to be selected with care and will differ from design to design depending on the mechanical and cosmetic requirements needed in the final sheet metal fabrication.