Abstract
Piston-based material extrusion enables cost savings for metal injection molding users when it is utilized as a complementary shaping process for green parts in small batch sizes. This, however, requires the use of series feedstock and the production of sufficiently dense green parts in order to ensure metal injection molding-like material properties. In this paper, a methodological approach is presented to identify material-specific process parameters for an industrially used Ti-6Al-4V metal injection molding feedstock based on the extrusion force. It was found that for an optimum extrusion temperature of 95 °C and printing speed of 8 mm/s an extrusion force of 1300 N ensures high-density green parts without under-extrusion. The resulting sintered part properties exhibit values comparable to metal injection molding in terms of part density (max. 99.1%) and tensile properties (max. yield strength: 933 MPa, max. ultimate tensile strength: 1000 MPa, max. elongation at break: 18.5%) depending on the selected build orientation. Thus, a complementary use could be demonstrated in principle for the Ti-6Al-4V feedstock.
Highlights
Metal injection molding (MIM) is a production technology that is primarily suitable for high production volumes since molds are required that only amortize with increasing quantities [1,2]
An industrially used Ti-6Al-4V MIM feedstock was processed with piston-based material extrusion with the aim of producing sufficiently dense green parts to enable complementary use of PEX in already established MIM process chains
It was found that an extrusion force of 1300 N at a maximum printing speed of 8 mm/s in combination with an extrusion temperature of 95 ◦C resulted in sufficiently dense green parts
Summary
Metal injection molding (MIM) is a production technology that is primarily suitable for high production volumes since molds are required that only amortize with increasing quantities [1,2]. The additive manufacturing (AM) of green parts can lead to time and cost savings in metal injection molding when it comes to functional prototypes, custom-made or complex parts with hollow structures since no molds are required [5] For this field of application, piston-based material extrusion (PEX) was introduced as a new complementary AM process for MIM users by combining the main advantages of the polymer-based AM processes fused filament fabrication (FFF) and fused granular fabrication (FGF) [6]. With the help of this in-process measured value, a methodical approach is presented which allows materialspecific process parameters to be derived for a granular Ti-6Al-4V feedstock that is used in industrial MIM process chains The aim of these material-specific process parameters is to produce dense green parts without rhomboid voids in order to achieve comparable material properties in the sintered state. The resulting sintered parts are analyzed in terms of part density and tensile properties and compared to corresponding MIM values
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