Tag Archives: Canmaking

Soudronic Welder

British Steel’s PACS Centre had various pieces of kit for making different types of can, one of which was a Soudronic welder, which takes a rectangular piece of tinplate, forms it into a cylinder and then welds the overlapping edges of the cylinder to make the body of a 3-piece can.

Although the machine was often used to produce feedstock for other purposes (e.g. can performance tests or filling tests), the main trial it was used for during my time at Tinplate R&D was the welding of lightgauge can bodies from tinplate produced in Ebbw Vale. The standard gauge of commercial cans used to be 0.16 mm, although some had already gone as far as 0.14 mm.

Ebbw Vale had first trialled out the rolling of a 0.12 mm gauge material, followed by a 0.10 mm gauge. These we had then cut up into blanks of the correct size for a standard size 3-piece can – the 0.12 mm material we could do in-house, but for the 0.10 mm material we had to call in the help of Impress in Grantham. Even then we had to sort the blanks by hand so that we could feed batches of the exact same size into the welder; unfortunately there was such a size variation in the unsorted material that the welder couldn’t handle the changes in overlap.

And that’s when the welder started to misbehave, so we had a technician brought across from Switzerland to give the machine a good looking into. Turns out that the only thing the machine really needed was a proper oil service: what we didn’t know was that a Soudronic welder only starts to lubricate itself after extended runs, something that over all these years had never happened. Meaning that we were basically running the welder without any lubrication for the best part of 10 years. No wonder it started to misbehave.

Once this obstacle was out of the way, the machine managed to weld can bodies from 0.10 mm feedstock, thereby successfully completing that part of the project. Shortly afterwards I left Tinplate R&D for Ebbw Vale and ever returned. I don’t know what happened to the Soudronic welder – was it moved to IJmuiden or sold off ? It definitely was in good enough condition to handle the production of run-of-the-mill cans, but maybe there were other, more capable machines available by then, so I don’t know.

All I know is that when Welsh Labs shut down, the two main people of the PACS Centre moved to its equivalent in IJmuiden, but their forte was more DWI can making, so I don’t know whether the Soudronic followed them or not.

rBS Can

an rBS can, still in good shape after nearly 20 yearsThe rBS (or redicon / British Steel) Can was an attempt to produce the equivalent of the Japanese TULC can, using Ferrolite1 as its feedstock. The Ferrolite process in Trostre took a coil of ECCS (electro-coated chromium steel, or steel coated with a chrome-chrome oxide layer, also called TFS, or tin-free steel) substrate and fed it into contact on both sides of the strip with a film of usually polypropylene or PET. That way you can make aerosol cans or food cans which is in essence a coated product.

The only problem being that you can’t weld Ferrolite, at least not with your standard Soudronic welder. For starters, and unlike the tin coating of standard Tinplate, the chrome oxide of TFS does not conduct electricity well, and neither does it melt the way tin does. So you either prepare the welded edge by removing the coating (in which case you have to apply a protective coating of the bare edge after welding the can) or you have to make your can without any welding by using the DRD (draw-redraw) process or a similar drawing process.

The rBS can was one step beyond the DRD process, with drawing ratios more akin to that of the DWI (draw and wall-ironed) process, which first of all was a challenge to the integrity of the Ferrolite coating, but raised issues with lubrication. When you draw and iron a Tinplate DWI can, the tin acts as a lubricant and the lubrication fluid is there more in the capacity of a coolant rather than contributing much to the actual lubrication.

Clearly this is totally different for a Ferrolite feedstock, where the substrate does not contribute to the lubrication process at all, hence the lubricant really has to do the job of lubricating the process and carrying away the excess heat. The latter is especially important since otherwise the PET coating could easily start showing micro-cracks which would, when filled with liquid, lead to rapid corrosion of the underlying steel substrate and spoilage of the drink.

In short, that’s really what happened anyway: it proved possible to produce a can, which when left to its own devices was corrosion resistant when exposed to the atmosphere. However, the PET coating, which initially proved to be intact, started to exhibit micro-cracks after subsequent heating cycles (the latter simulating preparation of the can prior to filling). Brian Bastable, who was our Ferrolite expert, brought this major flaw to the attention of David Jones, who decided to go ahead anyway.

It even went as far as trials in China, where John S Williams, head of the PACS Centre, went to oversee the production of trial batches in Shanghai. And then fate stepped in, in the form of a Japanese company who bought up the company where we were doing the trials, and immediately stopped any further developments in favour of adopting the well-established TULC can.

Opportunity missed, or saved by the bell ? I suppose we’ll never know, because after that the rBS can died a quiet death, and as far as I’m aware we aimed our subsequent efforts on 2-piece aerosol cans, where a drawn can body would replace the welded can body cum domed bottom piece of steel aerosol cans.

But that’s a different story. Meanwhile, I still have an rBS can in my possession, which I have used over the years as a pen holder at work. The smudges you can see are just plain dirt from being handled in a mucky environment, but it’s still free of any rust, unlike a DRD can that I had retained but discarded once it was too rusty.

However, I suppose we’ll never known how it would have held up to containing aggressive drinks such as cola or mineral water.

(1) From “Canmaking: The Technology of Metal Protection and Decoration”, p.129
T.A. Turner, Crown Cork & Seal, Wantage, UK
Springer Science + Business Media, LLC – 1998

The first lamination line of this type was installed by Metal Box in their Neath (South Wales, UK) factory in 1985 and ran at speeds of up to 65-70 m/min, depending on steel gauge and the laminate structure being manufactured. A second line was installed by British Steel Tinplate in their Trostre plant (South Wales, UK) two years later, based on technology licensed from Metal Box.

Ferrolite has been converted, on a commercial basis, into a variety of products, for example aerosol components (cones, domes and valve-cups), easy-open ends and drawn containers for food.