Additive Manufacturing

Improving products layer by layer

Text: Petri Seppänen and Atte Rättyä

The term additive manufacturing (AM), also known as 3D printing, has gained a lot of popularity in recent years. AM has increased the possibility to produce complex shapes without being restricted by traditional manufacturing constraints. As a result, the functional requirements of parts have become the primary focus of design efforts.

Additive manufacturing (AM) is a term used to describe a set of manufacturing processes that progressively adds layers of material to manufactured products. AM makes it possible to design complex structures and gives the designer full control over the internal structure of the component. Designers can design voids, lattices, and other hard-to-manufacture structural components that can help reduce material use and increase functionality. Other benefits of additive manufacturing include:

• Subassemblies that used to require multiple parts can be combined into a single component.
• Heat exchangers can be designed to be small with great efficiency.
• Creates cost savings and flexibility for production. There is no need for large batches.
• Minimises amount of wasted material.
• Possible to print moving assemblies.
• Ideal method for customisation. For example, manufacturer can produce personalised earbuds that are fitted to the shape of individual users’ ears.
• Complexity of structures does not increase manufacturing cost as with traditional/subtracting manufacturing.
• AM can reduce or completely eliminate tooling cost.

Table 1. Time saved in prototyping with inhouse AM versus other methods.

When discussing future trends, AM is often mentioned since it is something of a novelty. In the wildest dreams, AM will change the last two centuries of approaches to design and manufacturing with fundamental geopolitical, economic, social, demographic and environmental implications.

Even with a “keep your head in the clouds and your feet on the ground” mentality, AM has a lot of potential. There have been claims that AM can cut new product cost by up to 70% and the time to market by 90%. AM holds great advantages for companies. Table 1 provides a comparison between different manufacturing methods in different industries. The Aston Martin racing team, for example, succeeded in developing the LMP1 racing car for the Lemans in 2011 in just six months with the use of AM in the conceptual mock-up stage. This would not have been possible with traditional manufacturing methods.

A brief history

AM is not a new invention, it is almost 40 years old. In 1981, Hideo Kodama from Nagoya Municipal Industrial Research Institute published a rapid-prototyping system (photopolymers). The model was built up in layers, each of which corresponded to a cross-sectional slice of the model. In 1984, Charles Hull invented stereolithography (SLA). Stereolithography lets designers create 3D models using digital data, which can then be used to print an actual part. The world’s first selective laser sintering (SLS) machine was produced by startup DTM in 1992. This machine shoots a laser to power and does not use a liquid to build up the model, In the same year, the patent for fused deposition modelling (FDM) was issued to Stratasys. An FDM machine extrudes the print material, which is usually plastic. This is the most commonly used 3D printing method. In 1995, the Fraunhofer Institute developed selective laser melting (SLM).

Large-scale production with the use of AM is impeded by low productivity and the size of printers. Despite the limitations, there is potential for industrial scale production in the long run.

Redesigning intercooler air supply

In order to demonstrate the benefits of combining shape optimisation of structures and fluid channels, the authors of this article decided to redesign an intercooler air supply. The intercooler was designed for a high-performance motorsport application. The original intercooler is shown in Figure 1.

First, the original duct between the turbocharger and intercooler was simulated. The pressure drop in the duct was rather high and the velocity distribution at the intercooler inlet was not ideal. Thus, pressure drop reduction and better flow uniformity at the intercooler inlet were selected as the design objectives.

Before optimising the geometry, a few modifications to the structure were made. The enlargement was modified to be more symmetric. This was done to offer a better starting point for the optimisation. The rubber hose was also modified to fit the enlargement.

ANSYS Fluent was used in simulating the initial state of the setup and generating the optimised structure. In ANSYS Fluent, an adjoint solver was used to calculate sensitivity data for the defined design objectives. The geometry was then modified with design tools to achieve an improvement in terms of the defined design objectives. The flow solution was thereafter calculated for the new geometry. The procedure was repeated until the desired performance level was achieved.

After the final geometry modification, the pressure drop between the turbocharger and intercooler was reduced by 47 %. The flow uniformity at the intercooler inlet was also improved. The optimised intercooler air supply is presented in Figure 2. A comparison between the original and optimised structure is shown in Figure 3.

After improving the design, it is essential to consider what manufacturing method is feasible for the current case. The improved intercooler air intake could be manufactured by TIGwelding, casting or 3D printing. In most cases, the TIG-welded structure would be preferred. So, what is the role of 3D printing? In this case, the fluid volume could be printed, making it is easy to mould aluminium sheets into the optimal the shape.

If even better performance is desired, the whole intercooler could be redesigned. A 3D-printed intercooler could deliver a competitive edge in motorsport applications. The performance gains due to weight saving and improved air cooling will be significant, if the geometry is designed carefully. With more efficient cooling, it is possible to reduce the size of cooling air intake holes, which will improve vehicle aerodynamics. Efficient cooling also contributes to high intake air density, which is essential in high performance engines. Taking into account the structural strength of the intercooler in the optimisation phase, it is also possible to make tougher and more durable intercoolers.

Current state of AM

Additive manufacturing will not replace traditional manufacturing methods any time soon. It will, however, complement and coexist with traditional methods. Parts printed in metal often require machining before installation. When different manufacturing methods are skilfully combined, smart products that excel in competition are born.

It is not wise to print products only because it is possible. One should consider how printing can support manufacturing and what is needed to make the product printable. Printing will, however, change the way products are designed. Some companies have already introduced 3D printed parts in their products. Based on results, these companies will not be returning to traditional manufacturing methods. In that sense, the manufacturing revolution has already begun.