Ricoh develops Binder Jetting process for aluminium part production

December 1, 2020

Fig. 1 Binder jet sample parts incorporating internal channels (Courtesy Ricoh)

With metal Binder Jetting (BJT) systems now offering the potential for the high-volume, cost-effective Additive Manufacturing of complex parts, there is a growing demand to broaden the range of material options available. Aluminium is one such metal that could offer the potential to produce a variety of new parts; however, the metal can be difficult to process in the sintering stage.

To alleviate this problem, a team of researchers at Ricoh Company Ltd, based in Kanagawa, Japan, has developed a unique binder material that, when combined with a suitable debind and sinter stage, offers the potential to use typical aluminium powders in the Binder Jetting process. Furthermore, the use of a liquid immersion technique developed at Ricoh for removing excess powder is said to make it possible to form complex internal channels during the process – an option the company says is not possible with conventional processes (Fig. 1).

For the development of this new binder system, the team used an AlSi alloy powder with an average particle size of 35 µm, coated with what is described as a resin. The main objective of the resin coating, explains Ricoh, is to allow bonding through a mutual interaction with the binder liquid, as well as reducing the risk of explosion. The binder liquid used incorporates an organic solvent and an additive to ensure the cross-linking of the resin-coated powder particles.

Ricoh used a prototype Binder Jetting machine, developed in-house, to create a powder layer thickness of 84 µm with a binder liquid drop resolution of 300 x 300 dpi. The resulting green body was said to be resistant to specific solvents due to the cross-linking. Immersing the parts in a solvent for a set time therefore enables the efficient removal of excess powder, particularly from small internal channels.

Following a solvent drying stage, the parts undergo a liquid-phase sintering operation. A target liquid phase amount of approximately 20–30% is required, with the parts maintaining a temperature appropriate for elution of the liquid phase amount for between two and five hours.

Fig. 2 The tension test specimen, for which mechanical processing was performed on a resulting sintered body (Courtesy Ricoh)

The researchers reported that tensile strength testing, thermal conductivity testing, cross-section structure observation, and X-ray CT internal observation were performed on the resulting sintered parts. The tensile strength and stretch values of the test sample seen in Fig. 2 were reported to be 100 MPa, equivalent to that of a typical pure aluminium material. Using a xenon flash analyser, thermal conductivity was determined to be 188 W/mK, equivalent to AlSi die-cast products.

Fig. 3 X-ray CT of the sintered sample, approx.15 x 15 mm (Courtesy Ricoh)

An X-ray CT image of a sintered block, measuring roughly 15 mm per side, is shown in Fig. 3. The sample’s relative density reached 98.4%, and it was confirmed that sintering was accomplished well, with no large pores. The results of microstructural observations (Fig. 4, overleaf) found that grain sizes were approximately 50 µm, equivalent to a typical cast structure.

Fig. 4 Grain sizes were approximately 50 µm, equivalent to a typical cast part (Courtesy Ricoh)

The relationship between the amount of powder coating resin and the minimum ignition energy is highlighted in Fig. 5, showing that when the resin amount exceeds 2 wt.%, the minimum ignition energy increases, greatly stabilising the coated powder in comparison to uncoated powder. The researchers state that the resin coating appears to suppress the transfer of explosive energy between particles.

Fig. 5 Resin coating amount / minimum ignition temperature (Courtesy Ricoh)

This testing confirmed that it was possible to form 90 mm long internal channels with diameters of 2 mm. The company states that it is now working on the creation of a prototype with a larger build chamber and even thinner internal channels. The team is also working to expand the range of alloys that this method can be used with.

Download the latest issue of Metal AM magazine

Our latest issue is now available to view online or download in PDF format.

As well as an extensive AM industry news section, this 168-page issue includes articles and reports on:

  • Metal Additive Manufacturing and the new Space Race: The inside track with Launcher and AMCM
  • Falcontech: The journey from materials engineering to large-scale metal Additive Manufacturing
  • Strategies for advancing the automation of metal Additive Manufacturing
  • Machine Learning and Additive Manufacturing: What does the future hold?
  • System 3R: Bridging critical gaps in the Additive Manufacturing workflow to enable serial production
  • Metal AM in South Africa: Research and commercial initiatives bring the benefit of AM to the African continent
  • CFD simulation for metal Additive Manufacturing: Applications in laser- and sinter-based processes
  • > More information

Latest news


    Sign up to our e-newsletter, sent weekly to AM professionals and end-users around the world. We'll also let you know each time a new issue of Metal AM magazine is available.

    Discover our magazine archive…

    The free to access Metal Additive Manufacturing magazine archive offers unparalleled insight into the world of metal Additive Manufacturing from a commercial and technological perspective through:
    • Reports on visits to leading metal AM part manufacturers and industry suppliers
    • Articles on technology and application trends
    • Information on materials developments
    • Reviews of key technical presentations from the international conference circuit
    • International industry news
    All past issues are available to download in PDF format, in either single page format or as double-page “spreads” for viewing on large monitors. All downloads are free of charge. Go to archive...

    Connect with us

    Visit our social media channels and sign up to our e-newsletter

    Copy link
    Powered by Social Snap