Manufacturing Complex parts from Metal/Polymer Feedstocks

Blended metal/polymer feedstocks with high loadings of fine metal powders (>50 vol%) can be used for near net shaping of complex bodies. The first technology to take advantage of this concept commercially was ‘Metal Injection Moulding’ (MIM), commonly used for fabricating complex steel shapes, but more recently used, especially by TiTeNZ and its partners, for shaping of complex titanium alloy parts. This capability is being built on within TiTeNZ to develop novel shaping technologies that are being seamlessly integrated with state-of-art Additive Manufacturing (AM) methods.

Medium Pressure Injection Moulding (MPIM)

Conventional high pressure MIM processing uses commercial feedstocks which are available for many common alloys, enabling high accuracy, repetitive manufacture of components. MPIM provides us with a flexible variant on MIM processing enabling ‘in-house’ feedstock formulation and application to a wide range of materials. MPIM is ideal for prototyping and small volume production. One feature of the flexibility of MPIM is the ability to use mould inserts, reducing and managing the (occasionally) prohibitive cost of complex die manufacture. Figure 1 shows a ‘parent’ die with a replaceable machined aluminium metal insert. Successful prototyping trials have also been undertaken using polymer inserts. Figure 2 shows a selection of parts made from this die set in 316L Stainless Steel. Other materials trialled include alumina ceramic and alloy steels.

MIM - AProf Peng Cao

Fig.1.  MPIM die set with machined aluminium metal inserts

Fig.2. MPIM parts fabricated in 316L Stainless Steel.

AM assisted MPIM

The TiTeNZ team has developed new and world leading capability in the fabrication and use of 3D Printed Soluble Moulds. The process involves using ‘in house’ designed and manufactured 3D printed moulds, as shown in Figure 3. This gives ultimate flexibility in mould design for prototyping and ‘proof of concept’ especially where sequential small changes in mould design may be needed to fine tune a particular design characteristic.

Fig.3.1. AM Mould

Fig.3.2. AM Mould with MPIM injected feedstock

Fig.3.1. AM Mould

AM with metal- polymer feedstocks

FFF (Fused Filament Fabrication) extrusion printing technology has been trialled for fabrication of mouldless ‘MIM-equivalent’ parts, using a Metal–Binder composite filament with >80 wt% loading of metal. The technology operates from any open source FFF printing platform, including simple benchtop devices. Successful prototypes have been printed using 316L SS filament (Figure 4) and trials are active with alumina and zirconia ceramic filaments.

Fig.4.1. FFF technology - CAD model

Fig.4.2. FFF technology - Printing head

Fig.4.1. FFF technology - CAD model

In all the shaping technology examples discussed above, the common - and critical - processing capability is TiTeNZ’s knowledge and facilities with respect to polymer debinding and sintering of the printed parts. Integration of state-of-art thermal analysis with a high degree of controlled atmosphere management in customised debinding and sintering furnaces, fully dense parts can be fabricated that meet or exceed recognised materials standards. The vacuum furnace laboratory at Callaghan Innovation is shown in Figure 5.

Further details on start-of-art methods for the manufacture of complex parts from metal/polymer feedstocks can be seen in the linked pdf file.

Fig.5. Sintering and debinding furnaces in Callaghan Innovation’s Titanium Laboratory, Lower Hutt