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The benefits of hybrid mould and core production with 3D sand printing

Hybrid production combines traditional sand mould making with 3D printing of complex sand cores and can give casting businesses competitive advantages. Learn how foundries are using this modern approach to quickly manufacture complex cores, offset labour challenges, improve part quality, and de-risk their supply chain – all while reducing production costs.

Foundries worldwide are increasingly adopting a hybrid production strategy that pairs the conventional production of sand moulds with 3D printed sand cores using binder jetting technology. The change is being driven by rapidly evolving global market conditions that are driving new levels of part complexity combined with the wide range of business and technical benefits offered by this modern approach. Despite the increasing adoption of this hybrid production strategy, many foundries may not be fully knowledgeable about the approach, how easy it is to integrate into conventional operations and how the strategy helps their business remain competitive and thrive in the future. 

ExOne, the pioneer and global leader in sand binder jet 3D printing technology, carried out an exploratory research, which investigated the market drivers and benefits of a hybrid production strategy. The company interviewed several foundries that have implemented the strategy and reviewed scientific literature that documents the benefits of hybrid mould and core production. This article briefly outlines the findings of ExOne’s exploratory work. To get the complete report from ExOne, please contact them direct. 

A modern approach: Hybrid mould and core production

It’s unclear when the hybrid production of conventional sand moulds and 3D printed sand cores became a more widely adopted strategy in the marketplace, but its growing use has been documented for years. Slightly different terms, such as hybrid moulding, hybrid production, and hybrid concept are used to describe this modern approach. In ExOne’s report, the term hybrid production strategy is defined as ‘the pairing of a conventionally produced sand mould with a binder jet 3D printed sand core.’

Virtually all sand 3D printing done today is executed with binder jet technology. Binder jetting is one of seven categories of additive manufacturing (AM) recognised by ASTM International. In binder jetting, an industrial printhead selectively deposits a liquid binding agent onto a thin layer of sand. After printing, another thin layer of sand is deposited in the build area. The process is repeated layer by layer using a map from a digital design file until the object is complete. The process is routinely used worldwide to build high value and ‘one of a kind’ parts and tooling.

 

Drivers of the hybrid production strategy

ExOne discovered that the shift to this manufacturing approach is being driven by several changing market conditions, foundry challenges, and inherent efficiency and quality benefits, such as:

  1. Increasing complexity of cast components

Modern products with increasing requirements for performance, sustainability, and innovation are driving increased demand for complex castings that are only expected to grow further in the future. One of the strongest drivers is the push for more sustainability and performance from virtually all transportation and machinery that uses traditional CO2 emitting fuel, which is leading to more complex designs.

  1. Labour challenges

At the same time part complexity is growing, finding labour to reliably assemble traditionally produced core segments has become more challenging. ExOne identified that nearly fifty per cent of foundries worldwide reported challenges finding and/or retaining workers who have the knowledge to assemble cores into quality sandcasting moulds. The high labour cost is also a key consideration.

  1. Demand for quality improvement with less scrap

Foundries strive to improve the quality of their complex cores. By eliminating hand assembly of complex core segments, quality improvements flow naturally as ridges formation or parting lines are reduced or eliminated, and every core is produced virtually identical to the next.

  1. Increasing demands for faster delivery

Time is money. For almost every foundry, promised delivery times can determine whether a job is won or lost. Speed matters for all volumes, from prototypes to the highest volumes. The speed advantage offered by sand 3D printing, especially with the hybrid core-printing approach, is often cited by users as a key justification for adoption.

  1. Disrupted supply chains

Manufacturing supply chains can be fragile. Whether it’s global pandemics, economic crises, wars, or even extreme weather events, complications for manufacturers can escalate and disrupt schedules quickly. Sand 3D printing can help de-risk the supply chain by enabling a decentralised manufacturing strategy. Indeed, several foundries reported that disruption in supply chains had accelerated its adoption of 3D printing.

  1. Sustainability improvements 

The foundry industry is energy intensive, which makes it a high CO2 emission industry as well. The challenges associated with this, coupled with rising energy and labour prices, require foundries worldwide to rethink their strategies. Both regulatory requirements and corporate responsibility make green foundry and sustainable manufacturing concepts indispensable.

  1. Ease of integration into existing operations

Foundries that have adopted sand 3D printing technology can continue to operate normally but simply send complex cores to the printer instead of through conventional processes.

 

The hybrid mould and core manufacturing processes

While traditional sandcasting requires permanent tooling for fabrications such as patterns or models, and core boxes, making cores via 3D printing is a digital process, thus eliminating the need for time consuming designing and manufacturing of core boxes as well as for assembling cores. With the aid of 3D design software, a virtual model of the core can be designed and rapidly iterated when needed. The digital file is used to 3D print the core.

Foundries reported that the total time needed for the hybrid production processes varies and can be difficult to generalise, but it’s undeniably faster. It can take a few days, one week, or a few weeks – depending on the size and complexity of the cast parts and the supply chain situation. However, the amount of time needed for the 3D printing process (right side of fig.3) is generally really fast, given that several steps are eliminated, although it also varies depending on factors like part size, the particle size of the print medium, and maybe the type of binder.

Main benefits of hybrid mould and core production

Foundries adopting the hybrid production strategy and scientific studies alike have reported several benefits of the approach compared with conventional manufacturing alone. Moreover, it is found that one benefit leads to many other benefits, which are often interrelated.

  1. Complex core consolidation

For complex cast parts that require several cores, the design and assembly of those cores required in the conventional process are time, labour, and cost intensive. The more complex the cast part is, the more resources are needed in the production.

Thanks to the freedom of design in 3D printing, foundries are now able to create a virtual design of the complex geometry and 3D print it as one piece – a monolithic core – instead of producing many cores as in the conventional core process. The integration or consolidation of cores through 3D printing eliminates the need for complex core boxes and assembly of cores, which is extensive post processing that requires many resources and is prone to gas issues due to gluing cores.

GF Casting Solutions Leipzig GmbH in Leipzig, Germany, produces complicated sand cores for hydraulic rotary transmissions. Conventionally produced, twelve partial cores were needed to form undercuts and thin channels. With the aid of the ExOne S-Max® 3D printer, the iron foundry can produce the cores in one piece only. This core consolidation has significantly improved the quality of the hydraulic transmission cores and reduced laborious manual assembly and subsequent fettling work.

  1. Faster delivery time/accelerated lead time

Sandcasting often suffers from high lead times due to many aspects, such as the lengthy process of toolmaking and disrupted supply chains. A significant benefit of the hybrid production strategy is a much faster delivery time of cast parts due to several factors: 

  • The elimination of hard tooling requirements.
  • Elimination or reduction of hand assembly and other post processing.
  • The ability to consolidate core segments, often into just one piece. 
  • Elimination or reduction of time consuming and wasteful quality errors. 
  • The use of high speed binder jet 3D printing systems.

With the hybrid production strategy, Eisengiesserei Mezger in Kallnach, Switzerland, pairs a conventionally produced mould with a monolithic core printed with the S-Max® Pro. High quality cores are completed in just twelve hours, while a raw cast part is completed in around three to five days. The speed of the digital workflow and the S-Max® Pro allows the company to deliver cast parts to customers at top speeds.

Saudi Mechanical Industries (SMI) in Riyadh, Saudi Arabia, delivers cast parts for pumps, valves, and automotive parts. The foundry shared that it can provide the parts much faster with the hybrid approach as it saves a lot of time in its production through 3D printing. Fifty per cent of the lead time is saved by 3D printing as the foundry doesn’t have to make tooling anymore. 

  1. Reduced production costs

Given that 3D printing improves production time and eliminates expenses such as hard tooling and labour for core production, it stands to reason that it’s a cost saver. While no clear academic work has been done on this topic, previous research has identified the economic opportunity for 3D sand printing in comparison with conventional manufacturing of moulds and cores. Several foundries reported the process improves efficiency due to the following factors: 

  • The elimination of tooling (core boxes):
    • No design and fabrication costs for core boxes. 
    • No storage for core boxes. 
    • Easy and rapid iteration of virtual core design. 
  • Reduced labour needs through core consolidation. 
    • Reduced assembly labour and associated cost.
    • Reduced post-processing. 
    • Reduced scrap costs.

Aldo Randazzo, who leads the customers’ sand printing applications at ExOne GmbH pointed out: “The hybrid mould and core production has a huge potential to reduce overall production costs. But foundries must take into account the whole aspects and processes in the production, also the costs in the downstream processes, and not only count the production cost per core.”

Customers also save money. Not only do foundries reduce production costs through the hybrid approach, but ExOne’s study also found that the foundries’ customers can have the same benefit as well. According to Grede Iron Mountain in the USA, its customers save significant amounts of money by eliminating the capital cost for tooling, where some pours traditionally required multiple core boxes to be built.

  1. Better core quality

High quality cores contribute to high quality castings. The foundries in ExOne’s study and previous research have proven that the consolidation of multiple cores via binder jetting 3D printing technology enables better quality of cores in terms of scrap rates, surface quality, and precision or level of detail.

GF Casting Solutions Leipzig GmbH prints the cores for the hydraulic rotary transmission with ceramic sand and a cold hardening phenol (CHP) binder. The foundry exploits the good properties of the 3D printer’s single component binder system, such as high temperature resistance, good disintegration properties, and low core cleaning effort. Due to the long resistance at high temperatures compared to conventional cold box binders, high dimensional accuracy and clean interiors can be ensured for very thin channels.

Further benefits of hybrid mould and core production

Beyond the benefits specific to the hybrid production strategy, the foundries in ExOne’s study reported that the integration of 3D printing technology into their traditional ways of manufacturing has also given them several further advantages, such as driving business growth, localising manufacturing, improving productivity, and sustainable manufacturing. Download ExOne whitepaper to learn more about it: teamdm.com/X1-Hybrid-Production

 

Author

This article by Dr Nonni Sri Athari, ExOne GmbH, was originally published in CP+T International, Issue 1 (2024) and is reprinted here thanks to their kind permission. A further full printed version, including supporting imagery, is published in the Aug/Sept 2024 issue of Foundry Trade Journal.