In recent months, we have enjoyed an increasing number of enquiries for not just our speciality of chrome-plated automotive components, but injection moulded parts for a range of projects. But one issue that has cropped up is our choice of tooling material for injection moulding.

Although aluminium tools have attracted a lot of interest, it is largely based on price, not necessarily on the results achieved. We believe this is false economy given the long-term advantages offered by steel tooling and the narrowing gap in pricing.

Steel has been the tool material of choice here at Borough, it’s what we know and what we have used for 50 years, because volume parts require tools that are fully hardened.

We typically produce components for our automotive clients in tens or hundreds of thousands and often millions, so we feel steel gives us greater consistency throughout our long production runs.

In our experience, steel tools do not wear or bruise like aluminium, which can wear more excessively along the split lines.

Steel is also better for polishing, long-term dimensional stability and avoids ‘sinkage’, which can be a problem with some tools for some components.

Whilst some enquirers will ask us to consider using aluminium tools for their projects, we would only consider using them to produce a few hundred prototypes or very low production volumes – otherwise for us it has to be steel.

Despite a lot of noise about the low cost for aluminium, there is hardly any cost difference now, so we always recommend the better option, steel. For Borough, the components we produce and chrome-plate are typically highly visible ‘trim’ items under intense visual scrutiny, for which quality and consistency of replication is critical.

The Borough rule is OEM trim parts for automotive really do require steel tools for injection moulding components, particularly those that take advantage of our new 2-shot machine that allows for selective chrome-plating of components.

For larger mouldings produced by vacuum-forming, like roof linings and interior panels, it is possible to use aluminium tools, which are much more cost-effective than steel when made on this scale. Aluminium tools are also ideal for low quantity applications such as signage, etc., or when upfront costs and short lead times are critical to the success of a project.

Our more than 50 years’ experience of moulding and plating shows that aluminium tooling probably isn’t right for every application. It depends on the material, the part being produced, the volumes involved, and the number and kind of secondary operations being performed.

As with all mouldings to be chrome-plated, we would always recommend involving our design team at the earliest stage. There are critical differences required in the moulding of components specifically for chrome-plating, like avoiding thickness changes which will eliminate uneven cooling that could cause shrinkage and warping.

Unfortunately, the nature of the beast is that mould tools need complex precision mechanisms, with parts that constantly impact each during production of the moulded components. And that is why a steel mould tool is the most durable solution for projects with expected long production runs – even if we’re not chroming the parts afterwards.

So, our advice will always be, choose what works best, as production runs might exceed your expectations and then the false economy of aluminium tooling will really impact the quality and overall cost.