Additive manufacturing of metal parts: 7 steps (case study)

As additive manufacturing (AM) technology continues to evolve, increasingly complex parts are being 3D printed. However, every material has its own properties and thus requires its own manufacturing process. What about metal? Sirris put it to the test. We printed the world’s very first cylinder head for a new car engine. The best practices we’ve learned along the way can be summarized in these 7 steps.

The cylinder head is made of Ti6Al4V, a high-strength titanium alloy, and will be used in the engine of the EcoMOTION, a prototype car developed by the Higher Education Institution of the Province of Liège. The mission: to produce a complex metal part that is vital to today’s economy, with a minimal use of material and reduced design-to-manufacturing time.

1. Redesign

The original part was redesigned for two primary reasons: to reap the benefits of additive manufacturing, and to comply with the manufacturing specificities. First of all, the cylinder head was redesigned into a lighter version. At the same time, extra squares on the surface were added to decrease the melting region (see step 5) per layer. Some extra thickness was added as well, to allow a post-finishing step (see step 7).

The original part (left) and the redesigned part (right)

2. Technology

Choosing the right machine(s) is a crucial step. To make the cylinder head, we used an Electron Beam Melting machine. Based on powder bed technology and powered by an electron beam source, it melts metal into successive layers – hence the term ‘additive’.

3. Reorientation

In order to apply the perfectly precise amount of melted metal, the part should be oriented correctly in the 3D-space. After all, melting too much per layer can lead to defects.

4. Support generation

During the printing process, additional supporting structures are sometimes needed as a sort of scaffolding. When the part is finished, the supports can be removed. For the cylinder head, we made the supports serrated and fragmented, allowing easier manual removal (marked in orange).

5. Manufacturing

Printing the part is a fast process – we made two parts in 24 hours. Agglomerated metal powder in the machine can be easily recycled afterwards.

6. 3D scanning

If the orientation was not optimal (see step 3), thermal stresses during the manufacturing stage could cause deformations. In any case, an optical scan is recommended to check the part’s dimensions and to position the rough part correctly before machining.

7. Post-finishing

During the last step, we can treat specific surfaces to add particular properties. It is important to take this stage into account when redesigning the part (see step 1). An overthickness of 1 mm was added in all these areas. 
Finally, two steps of post-finishing were applied. First, a chemical polishing for internal pipes that are hardly accessible, followed by a necessary post-machining, of all the functional parts and tolerances.

Ready! The part was all set to be mounted in the motor. And we can proudly state that it works!

Learn all about additive manufacturing at our event
A thorough understanding of AM’s many benefits is a good start … but integrating this technology into your company is a whole different story. Interested in the ins and outs? Register for our event “Flexible and efficient manufacturing with additive manufacturing” on June 7.