One member is £35 million turnover Grainger & Worrall. Indeed, the installation at the company's Bridgnorth, Shropshire, headquarters of an Exone S-Print HHS (now renamed S-Print Phenol – UK supplier, John Burn, 0121 508 4144) was the first commercial installation in Europe, when the machine was delivered at the end of 2012. And today there are just four installations in Europe – two commercial; two non-commercial – for this £500,000 sand-printing equipment, which is used to rapidly produce sand cores, so avoiding the design and manufacture of hard tooling.

Established in 1946, as a pattern maker, by Vernon Grainger and Charles Worrall, under second generation Grainger family ownership (the Worralls exited early), the company, led by Pat Grainger (now chairman), moved into casting during the 1980s. Subsequently, the third generation of James, Matthew and Edward Grainger has driven further into the casting engineering, casting and casting machining total package area, targeting prototype and low volume series production at a global level. Today, the 500-employee company boasts representation in the USA, its largest export market, China, Italy and Germany.

"It was never a strategy to compete in the volume area. We had the opportunity to move into it, but didn't. It would have been a mistake, if we had. That work is best left to low-cost economies," offers executive manager, head of engineering, Keith Denholm, who, in underlining the nature of the company's work, adds: "For the most part, we're doing things that haven't been done before." And the measure of its global significance is that it typically competes with just two or three other companies when bidding for work around the world, much of which now emanates from China.

Grainger & Worrall's field of expertise centres on, but is not exclusively, automotive powertrain activity, including high grade cast iron 6-cylinder truck engine blocks at the heavy end of its work spectrum (about 400 kg). Most work is in aluminium, but stainless steel and cast iron, including compact graphite iron, feature, too. Some 60% of part numbers delivered are supplied fully machined, Mr Denholm reveals, adding that this is a reflection of the market's desire for single-source supply. Indeed, the company acquired a Telford machinist in 2006, although machining isn't all carried out in-house. As a matter of policy, some will take place overseas – "to maintain customer involvement and provide customer access", the head of engineering offers.

PREMIERE LEAGUE PLAYER

The list of its top-end clients, who inhabit the F1, supercar and premiere luxury automotive market segments, for example, plus its direct-to-line supply of series produced, assembled, fully tested and packaged aluminium engine blocks for a famous UK-headquartered luxury brand, offer strong proof of its premiere league credentials.

Image: Engine blocks for the Bentley Mulsanne is one of the prestige projects Grainger & Worrall is involved with

Outside of automotive powertrain, the company also makes structural elements for prototype automotive body-in-white duties, with 4x4 vehicles, for example, making use of complex 3D castings to give strength to the body, although they may be encased in sheet metal, so not visible. (For production, these would be pressure die-cast.) Says Mr Denholm: "There is a big growth in that market. Prestige vehicles have more castings beneath the skin than you might imagine." As for the move towards electric vehicles, while there may be fewer block and head castings, others will take their place, including those for in-wheel motors, complex driverless systems and challenging 4x4 technology. "There won't be fewer castings, but different castings. And the requirements might change: instead of having to deal with heat, they will have to be lightweight; instead of containing oil, they'll have to contain sound, for example."

The aerospace market is also a customer. Previously, this was jet engine ancillaries, but now includes light aircraft piston engines, which are similar in technology to automotive engines and need to be lightweight, well made and durable. In the defence sector, the company offers a lower cost one-piece option versus multi-part fabrications.

Grainger & Worrall's Bridgnorth factory is not a homogenous operation, but instead houses a number of "small and nimble" businesses that "remain focused and excel, attracting high value work". Indeed, there are three distinct, defined business units the Shropshire site – prototyping (which is Mr Denholm's area of responsibility), series production (batches of 500-5,000/annum) and motorsport (batches of 50-500/annum).

The proportion of business split across these three can vary, but, currently, the split is around one half in prototyping, with a fifth taken by motorsport and then series production accounting for the rest, the latter seeing 90,000 castings produced annually. The S-Print HHS investment supports the prototyping operation, which has also seen investment in a further prototyping foundry at Bridgnorth, bringing the total number of lines to six – one for cast iron and stainless steel parts; one for motorsport parts, using the Cosworth pressure-pumped method; and four gravity-fed aluminium lines, one of which is given over to prototype parts, the other three to small series production.

Image: Pouring cylinder block castings

PROTOTYPING DEFINED

Prototyping sees batches of 1 through to 1,000 castings produced, with these made in any of the materials processed by the company. The majority of this prototype work is automotive-focused, with development driven by the push to reduce CO2 emissions, which means reduction in both size and weight, leading to a corresponding increase in unit loads, pressures, torque and power density, Mr Denholm explains. As a result, the prototyping area takes in much work that is effectively "R&D and risky".

To understand the pressures on automotive supply companies to support fast prototype development, the head of engineering offers that, 20 years ago, a project would take 36-48 months to take from drawing board to a design ready for production. "Today, you have 12 months to do everything, so we have deployed technology to help us achieve that." And the investment in the sand printer is a part of that.

"The technology isn't new. It has developed over the last 10 years, but it wasn't able to do what we wanted it to do. Then, in 2012, we considered that the technology had developed far enough and that it was now appropriate to our mixed needs, so we installed it, in Q4 2012." The company previously used a similar, but not identical, machine installed at CTI, which is located at the Advanced Manufacturing Park near Rotherham, on a subcontract basis.

THE CASTING PROCESS

Castings are produced using moulds and cores, assembled as core boxes into which molten material is poured. Sand moulds deliver the outside contours and are produced via patterns; sand cores deliver the cavities, bores and galleries. To produce both the patterns and cores, tools must be produced. At Grainger & Worrall, tools for both patterns and cores are designed in-house, with these made from one of three grades of plastic and machined on Hurco machining centres (some tooling is subcontract machined, too). The grade of plastic used depends on the volume of castings to be produced. For a cylinder head project, there may be 10 core boxes, and the company undertakes some 200 projects a year. So the number of tools required multiplies considerably.

The S-Print HHS is used for prototype core production (patterns for the external part contours, which are easier to make, are still produced via the traditional route). The machine, driven by CAD data, puts down layers of 0.2 mm thickness from, depending on requirement, a variety of sand mixes, with a layer put down every 40 sec.

The machine at Grainger & Worrall can employ a phenol bonding system, which remains strong at elevated temperatures (the CTI system is not a phenol system). The phenol system requires pre-heated sand, with cores subsequently cured to fully realise the high bond strength. While this is currently typically only required for steel parts (turbocharger and exhaust parts), with castings getting smaller and channel dimensions shrinking proportionately, Mr Denholm explains that the phenol capability will find wider use in the future, so this investment offers "future proofing in the area of high performance castings", while it also delivers "the lowest gas castings on the planet".

Image: Keith Denholm in front of the S-Print HHS, holding a core produced by the machine

Fundamentally, the system at Grainger & Worrall underpins very fast turn-around prototype casting manufacture, plus it offers a capability to produce complex cores that might otherwise demand multi-part cores. Multi-part cores obviously offer potential for misalignment errors and/or flash or witness at joints.

So, from receipt of CAD data, the company could be casting within 24 hours. For a steel turbocharger core, that is, say, two hours per core; 10 hours per completed box of five cores (the box measures 800 by 500 by 400 mm); plus 2 hours to cure. The traditional route, which would require the CAD-based design of tooling, plus its manufacture, would likely see cast parts not available within a week. "Now, we don't need to turn parts round in 24 hours, but part of our business requires us to be able to do so within two or three days," offers Mr Denholm, adding: "Before we couldn't do that; now we can." As at Machinery's visit, the company had undertaken some 150+ projects using the S-Print HHS, with heads, blocks and turbochargers the main focus of that.

Image: Complex cores such as this are more easily produced using the sand printer

NOT ALWAYS FASTEST

For repeat parts, however, tooling has the edge, since producing cores from hard tooling offers a faster production cycle. Instead of, say, five sets of cores in 10 hours, it would be possible to make 100 with tooling.

So 3D sand printing is not a major threat to established techniques, except in the area of rapid turn-around prototyping or very complex cores, although Mr Denholm does not rule out the possibility of the company having multiple sand printers in the future.

Of course, rapid prototype core production is no good without a comparably fast method of checking parts, it is suggested. So complementing the sand printer investment has been additional spend on metrology kit, housed in an adjacent area. Grainger & Worrall now boasts two Yxlon CT machines (Aegleteq, 01234 240729) – these take X-Ray slices through castings – which are able to measure at a rate of 19 sec/mm or 42 sec/mm, depending on the desired resolution of measurement. There is a limit, in terms of dimensional size and weight, so a GOM vision system is also available (02476 639920), as are more traditional CMMs (DEA Scirocco [01952 681300] and Mitutoyo Crysta models [01264 353123]).

Already an established global player, Grainger & Worrall clearly has its sights set on maintaining a leading position at the forefront of castings technology; a traditional and established process for sure, but where the knowledge to engineer and manufacture high performance castings on shortest possible lead times is a skill very much of today and, indeed, tomorrow.

Extended online version from here

Box item 1

Ceramic cores

Grainger & Worrell has worked with Southwest Research Institute based in San Antonioto, Texas, to develop the application of hybrid ceramic-sand core casting technology. The interest level in this will grow over coming years, suggests My Denholm, as the push to smaller, lighter castings gathers further pace. Ceramic-sand remains stable at higher temperatures and thinner sections than does normal sand, but its drawback is a lower rate of heat transfer.

The project looked to see what, for example, would be the smallest cast passageway achievable with ceramic-sand would be for a cast iron part. It turned out that, unexpectedly, a passageway of just 1 mm width (requiring a core of 1 mm cross-section) can be produced via this technique - Mr Denholm says that this was thought doubtful at the outset. He adds that this technique, for which the company is a joint patent holder on, will find its way into use at Grainger & Worrall, but that it is not yet fully industrialised. When it is, very few companies will be able to offer the service, however.

Box item 2

Export recognition

Grainger & Worrall was included in this year's Sunday Times Fast Track International 200 survey, which ranks companies using the last two years of available accounts. A typical company in this table has sales ranging from £25 million to £200 million; has international sales ranging from £5 million to £100 million; has average two-year international sales growth ranging from 25% to 500% per annum; has between 50 and 1,000 staff; and is in the engineering or consumer goods sector.

Box item 3

UK castings industry

According to the Cast Metals Federation, the UK makes around a billion metal castings every year. Some weigh over 300 tonnes, while others are less than one gramme. The UK foundry industry has bounced back after the extraordinary dip in all manufacturing in the2008-10 recession, with the expectation that 2013's output will be around pre recession 2008 levels of turnover by both tonnage and value. The headline figures for 2012 output are that there are 400 Foundries in the UK producing 523,000 tonnes of castings, with a turnover of £2.2 billion and employing 17,000 people.

Averaging the figures for all companies means that each company employs 42 and turns over £5.5 million, which puts Grainger & Worrall at the top end of the industry, with 500 employees and £35 million respectively.

Box item 4

About Exone and sand printing

The ExOne Company was founded in 2005, as a spin-off of Extrude Hone Corporation, a global supplier and developer of precision non-traditional machining processes and automated systems for more than 40 years.

Three-dimensional printing and laser micro-machining became the core technologies for The ExOne Company, which currently supplies services, systems and solutions for manufacturing in the digital age, including 3D printing in sand, metal and glass, and laser micro-machining.

Digital part materialisation for the sand printing business began in 1999, when a group of engineers at a start-up company called Generis in Augsburg, Germany, developed the prototype 3D printer for making sand casting moulds and cores. The first printing system was sold to BMW AG in 2001.

Generis was focused on the development of machines and processes for sand and investment casting before it was divided in 2003 into ProMetal RCT for sand and Voxeljet for investment casting.

As a division first of Extrude Hone Corporation and then ExOne, ProMetal RCT developed a worldwide market for sand printing, with dozens of machine installations. A smaller printer was developed in 2004 for printing with different materials and binders.

With the introduction of the S-Max in 2010, ExOne now offers the largest 3D sand printer in the world, redesigned for production flexibility and efficiency. The development and production facility in Augsburg, Germany, has been renamed ExOne GmbH.

ExOne's 3D sand printing business has grown from a handful of engineers to a worldwide team, with operation and support facilities in Germany, the United States and Japan.

First published in Machinery, January 2014