Designing a Tool System for Lowering Friction during the Ejection of In-Die Sintered Micro Gears

Abstract

The continuous improvements in micro-forging technologies generally involve process, material, and tool design. The field assisted sintering technique (FAST) is a process that makes possible the manufacture of near-net-shape components in a closed-die setup. However, the final part quality is affected by the influence of friction during the ejection phase, caused by radial expansion of the compacted and sintered powder. This paper presents the development of a pre-stressed tool system for the manufacture of micro gears made of aluminum. By using the hot isostatic pressing (HIP) sintering process and different combinations of process parameters, the designed tool system was compared to a similar tool system designed without a pre-stressing strategy. The comparison between the two tool systems was based on the ejection force and part fidelity. The ejection force was measured during the tests, while the part fidelity was documented using an optical microscope and computed tomography in order to obtain a multi-scale characterization. The results showed that the use of pre-stress reduced the porosity in the gear by 40% and improved the dimensional fidelity by more than 75% compared to gears produced without pre-stress.

Material Flow in Ultrasonic Orbital Microforming

“…They also refer to the internal structure [14][15][16], which affects the quality of the surface and cracking mechanisms [17,18]. Scale effect concerns even the construction of machines [19], tooling [20,21], and tools [22][23][24][25][26], as well as the design of the technological process plan [27,28]. Materials and friction tests using microsamples are also created because their results differ from those obtained in macrotests [29,30].…”

Ultrasonic Orbital Microforming—A New Possibility in the Forming of Microparts

“…The size of the grain affects the geometric characteristics of the product, such as the shape and quality of the surface [17], but above all affects the functional properties [18][19][20][21]. The scale effect is also applied to the construction of machines [22], instrumentation [23,24], tools [25][26][27], and technological plans [28][29][30]. Materials and friction tests using microsamples are also created because their results differ from those obtained in macrotests [31,32].…”

Micro/Nano Manufacturing

“…(1) Process developments of micro-scale fabrication methods. Cannella et al [1] developed a novel tooling system for in-die sintering of micro metal gears; Martinez-López et al [2] investigated xurography and laser ablation processes for the rapid fabrication of micromixing arrays; Obikawa et al [3] demonstrated ultrasonic-assisted incremental microforming for the rapid prototyping of thin shell metal pyramids. (2) Micro/nano manufacturing technologies based on electrochemical processing.…”