Where casting and AM converge and a look at some example of businesses adopting the technology.
One of the oldest manufacturing processes is that of casting, which, generically, refers to pouring a liquid material into a mould. Subsequently, the liquid material solidifies in the desired shape and is ejected or broken out of the mould. The resulting part can then be used or subjected to further post-processing to achieve the required finish.
Some sources date casting as a manufacturing method as far back as 6000 years, and yet there is some commonality with the much more recent additive manufacturing (AM) processes that have emerged in the last three decades.
The general term of casting can be further categorised according to a diverse range of processes and/or according to the cast materials of choice.
Dominant Casting Processes
- Gravity Die
- Low Pressure Die
- High Pressure Die
- Chemically Bonded Sand
- Lost Foam
Casting materials can vary extensively, from metals to various curable materials, such as epoxy resins, concrete, plaster or clay.
The same further categorisation can be applied to additive manufacturing, or the more popular term 3D printing. There are actually seven recognised AM / 3D printing categories as well as a range of materials that can be processed – including metals, polymers, ceramics and composites. More recently, multiple materials within a single part are now also possible.
The 7 AM processes:
- Vat polymerization
- Material Jetting
- Binder Jetting
- Material Extrusion
- Powder Bed Fusion
- Sheet lamination
- Directed Energy Deposition
Overview of the UK Casting Industry
The most recent and accurate snapshot of the casting sector in the UK was provided by the Casting Metal Federation (CMF) with its 2017 census. The results from this survey found that there are around 480 foundries operating in the UK, which collectively employ just under 17,000 people. Sales revenue from the sector are estimated to be “at least £1.89bn.”
Indeed, casting foundries are active in a wide range of manufacturing supply chains, typically contributing at a tier one or two level. However, it is also pertinent to recognise that the term “foundry” is another general term that covers a diverse scope of businesses from large, highly automated operations through to traditional manual foundries as well as small niche focused foundry businesses. Moreover, UK based foundries serve a broad range of vertical manufacturing sectors, including but not limited to automotive, aerospace, construction, oil & gas, nuclear, renewable energy, water, engineering, rail, mining / mineral extraction, chemical, steel, defence and creative / fine arts.
Where Casting and AM Converge
It is probably an understatement to say that the casting sector, in general, exhibited a cautious reaction to the emergence of AM. For various reasons, not least the way in which AM was presented by some as a new manufacturing technology that would solve many of the world’s problems, traditional manufacturing firms viewed AM as a threat to their business. It was often billed as a replacement technology, that could potentially decimate the output of traditional foundries. In actual fact the very opposite is proving to be true, but this did not alter the slow rate of adoption over the last two decades.
However, this is starting to change and there are a significant number of casting companies in the UK that are now embracing AM / 3DP processes as complementary to their business. When adopted in the right way they are proving to enhance business activities and are demonstrably adding value to their business and making them more competitive.
This is not to say that all casting processes will benefit from all AM / 3D printing processes. Rather, there are some categories of casting where there is a great deal of synergy with some categories of AM. It is in identifying where this overlap occurs that is producing significant opportunities advancement with casting applications.
At this point, it is perhaps relevant to highlight that there is somecompetition between casting and AM, notably when AM is applied as a production process. However, these applications are still in a minority compared with the prototyping and tooling applications of AM. These latter two are where AM fits most comfortably within the casting sector and is utilized as a facilitator for manufacturing, that is to say as a tool within the end-to-end process of manufacturing.
The dominant polymer AM processes, namely material extrusion (commonly referred to as FDM1or FFF2) and vat polymerization (SLA3and DLP4) have been associated with investment casting applications for more than a decade. These processes were among the earliest to be developed and commercialized, and have become as established method for economically producing investment casting patterns with much shorter lead times than traditional methods.
Subsequently, the binder jetting AM process, which has the capacity to produce very large, complex parts, has been developed and utilized for a significant number of sand casting applications.
More recently, notable advancements with metal AM processes, specifically the metal PBF process, have seen a real convergence with the more demanding discipline of high pressure die casting (HPDC).
Some examples from across the UK
Investment Casting with AM at Lestercast
Lestercast, founded more than 40 years ago, operates an Investment Casting Centre near Leicester. The company utilizes advanced manufacturing process, including additive processes, to produce bespoke, high quality, precision engineered components in various metals and alloys. According to the company, “additive manufacturing offers several advantages for the Investment casting process.” This includes the ability to eliminate moulds (and their associated costs) and directly print patterns with extremely fine details. This reduces the process steps involved in the entire process and speeds it up considerably, making it more efficient.
In addition, it reduces material waste, energy and subsequent machining. Lestercast can produce components for both industrial and commercial applications and has supplied bespoke parts to a wide range of sectors, including the automotive, rail, motorsport, oil and gas, architectural, valves and pumps, marine and medical industries.
Sand Casting with AM at Grainger and Worrall
With almost 75 years or operations under its belt, Grainger and Worrall overs a range of casting, engineering and machining services from its facilities in Bridgnorth, Shropshire. As the company states, the foundry is just one part of the business, albeit a crucial one. Central to this is Grainger & Worrall’s specialist prototype aluminium foundry and its Digital Sand Printing with High Heat Strength (HHS) binder technology specifically aimed at Iron and Steel castings.
Grainger and Worrall cites a novel approach that contributes to its growth and success, which includes adding value in the delivery of high integrity precision sand castings for engine, vehicle, aerospace and industrial market.
High Pressure Die Casting with AM at CastAlum
Located in Welshpool in Mid Wales, CastAlum has established a stellar reputation for high pressure die casting (HPDC) for the automotive industry since it was founded in 2000.The company supplies complex die castings to clients in the UK and across the world, with 80% of all production exported. Over the past five years CastAlum has invested heavily in the development of new products through improved processes, including an Innovate UK funded project for R&D into metal AM for producing metal tool inserts.
The metal laser PBF process has demonstrably been proven to produce fully-dense metal components and thus opened up opportunities to apply the technology for the manufacture of HPDC tool inserts. This is a demanding application, by any standard, as during the HPDC process, the die is unique to each component to be produced and usually complex in nature, particularly if conformal cooling is used. Moreover, the die cavities are subjected to extreme and varying conditions, such as cyclic heating caused by the introduction of molten aluminium at over 650°C, followed by cooling in water-based die release medium at temperatures around 25°C. Besides cyclic heating, the die cavities are also exposed to pressures exceeding 1500 MPa during the injection of molten aluminium into the cavities. Part of the CastAlum Innovate UK project has been to test how metal AM parts withstand this process. To date, the results are encouraging and have already confirmed that these demanding requirements can be met while also bringing the advantage of reducedlead times.
After an initial exposure to the potential benefits of the process, CastAlum considered AM as an alternative, with the goals of bringing the knowledge and expertise in-house, reducing overall costs and increasing productivity. The development programme to replace traditional steel cores with an additive manufactured solution, has resulted in a new and innovative cooling channel design that has subsequently reduced downtime as well as mitigated the problem of solder in HPDC. Moreover, CastAlum has also realized significant productivity gains with ever increasing tool life through higher quality castings. Other advantages that have also resulted are faster cooling rates, and tighter grain structure, according to the company, a benefit that could lead to significant light weighting in future products. Its capabilities and expertise has seen the company look to expand into other sectors.
There is a significant and increasing range of opportunities for AM and 3D printing within the UK casting sector, where the two process sets intersect. However, these opportunities require companies to be open them with a view to developing innovative casting solutions that can set the sector apart – nationally and on a global stage.