Case study: 3D printing enables efficient production of marine diesel outboard engine

Cox marine diesel outboard engine

M Di-Vito demonstrates serious serial production capabilities with additive manufacturing (AM) for its client Cox Powertrain.

Over the past 20 years, M Di-Vito, based in Birmingham in the UK, has established a solid reputation as a foundry operation. However, the result of a recent restructure has seen this family-run business expand and evolve its capabilities with the introduction of additive manufacturing (AM) and win a number of impressive contracts as a result. One of the most recent is a production application for a major client in the marine sector, one that takes advantage of M Di-Vito’s expertise with the digital sand printing process from ExOne together with its dedicated casting facility. 

M Di-Vito’s client is Cox Powertrain, a company founded in 2007 that has developed a radical and innovative new lightweight diesel marine outboard engine platform. The main drivers behind the considerable interest that this Cox engine is generating for many critical marine applications comes from the unprecedented weight to power ratio that it enables together with the improved safety of employing diesel over gasoline in a marine environment on smaller (10–20 foot) vessels. 

Traditionally, gasoline engines have dominated the outboard marine sector where power and reduced weight were required, at the expense of fuel efficiency and engine longevity, not to mention safety. Cox is changing that and has already attracted the attention of UK and US military and government agencies with its engine, which will go into pre-production next year and full production in 2019, according to the company. In the second half of 2018 and throughout 2019, Cox will undertake a demonstration program alongside its rigorous durability testing, supported by leading boat builders and operators worldwide to showcase the CXO300.

The uniqueness of the CXO300 engine is that it is able to generate 300 horsepower (HP), achieving the highest power diesel outboard engine ever. Moreover, the engine weighs just 330 kg, which matches equivalent gasoline outboard weights with the advantages of more readily available diesel fuel and an increased life expectancy of the engine—up to three times longer than a gasoline engine. 

As a result, there is huge market interest, including from navies and coastguards around the world, as well as a host of other parties for whom gasoline increases risk, such as around oil rigs and taxi boats. 

As a Tier 1 supplier to Cox, M Di Vito’s considerable expertise with AM and casting processes is critical to the production process of four key components of the CXO300 outboard engine, specifically: the transmission casing, which sits in the water and houses the propeller and gears; the exhaust housing; the shift guider slide; and the shift slider cover. One core is additively manufactured per part and to date 52 sets of components have been produced. 

By far the largest part is the transmission casing, with overall dimensions of 800 x 200 x 600 mm (X, Y, Z). Working in collaboration with Cox, M Di Vito developed and designed a complex sand core for the transmission casing that could be manufactured additively in one single core on the ExOne S15 platform, adding in functional features that were previously not possible and eliminating the need for assembly and additional machining operations. Moreover, the cores can be nested within the build platform to print nine of them in a single build. 

The core is then cast in aluminum 9 (to meet EU regulations) at M Di Vito’s in-house facility to produce the final transmission casing, weighing in at 14.777 kg—1 kg lighter than would be possible with any alternative production methods. All of these advantages are gained with an overall cost saving of 25 percent and faster turnaround times compared with competitive products. 

Cox has already demonstrated the advantages of its innovative R&D, and the 300 model is only the first in a family of new diesel powered outboard engines. M Di-Vito’s role in the full production process for the four components listed above has now been confirmed, and it will be serially producing sets of the four components using the proven AM and casting process from 2018 to meet Cox’s production schedule. 

This is also a marker for the AM industry in terms of increasing serial production volumes with industrial 3D printing. Although it may not fit some people’s narrow view of production AM, this application is a testament to how the additive sector is enabling previously impossible production activities in ways that are reducing costs and improving efficiency and functionality, all while achieving shorter lead times.


About Rachel Park

Rachel is a passionate advocate of additive manufacturing/3D printing technologies and the industry that has sprung up around it. However, as the hype and hyperbole has gathered momentum, her aim is always to offer a reasoned voice in the midst of inflated expectations and to cut through the noise in order to provide a realistic outlook of how things are.