Experimental and numerical investigation on micro deep drawing process of stainless steel 304 foil using flexible tools

Flexible forming technology provides significant application potential in various areas of manufacturing, particularly at a miniaturized level. Simplicity, versatility of process and feasibility of prototyping makes forming techniques by using flexible tools suitable for micro sheet metal forming. This paper reports the results of FE simulation and experimental research on micro deep drawing processes of stainless steel 304 sheets utilising a flexible die. The study presents a novel technique in which an initial gap (positive or negative) is adopted between an adjustment ring and a blank holder employed in the developed forming system. The blank holder is moveable part and supported by a particular spring that provides the required holding force. The forming parameters (anisotropy of SS 304 material, initial gap, friction conditions at various contact interfaces and initial sheet thickness) related with the forming process are in details investigated. The FE models are built using the commercial code Abaqus/Standard. The numerical predictions reveal the capability of the proposed technique on producing micro metallic cups with high quality and large aspect ratio. To verify these results, number of micro deep drawing experiments is conducted using a special set up developed for this purpose. As providing a fundamental understanding is required for the commercial development of this novel forming technique, hence the optimization of the initial gap in accordance with each sheet thickness, thickness distribution and punch force/stroke relationship are detected

Investigation of micro/milli flexible deep drawing process

Flexible forming technology provides significant application potential in the manufacturing of complex shaped components even at miniaturized levels. The most attractive characteristic of this technology is simplicity, and its feasibility for prototype processes and low-volume production. The main purpose of this study is to clarify the decisive characteristics of micro deep drawing of metallic foils by using flexible forming technology. In this work a new technique is adopted using rigid punch, rigid holder and rubber pad, so that a particular gap is allocated between the blank holder and a fixed plate to allow the rubber pad to expand through it. The key process parameters studied here are rubber hardness, rubber-pad dimensions, drawing velocity, and initial gap value. Stainless steel 304 foils are used with thickness of 0.1mm. To investigate the effect of soft material properties, urethane rubber with hardness of 20, 40 and 60 shore A is utilized. Also, the punch diameter used in this study is 4mm. Moreover, many drawing experiments are conducted with punch velocities range of (0.1mm/s-100mm/s) to show the effect of process velocity. FEA using the commercial software ABAQUS/Standard is used to simulate the drawing process at micro scale. A hyperelastic material model is adopted to define the flexible pad and an elastic-plastic model is defined for the blanks

Nano/microfabrication of three-dimensional device structures using a multilayered mould approach

There is growing interest in the development of fabrication techniques to cost effectively mass-produced high-resolution (micro/nano) three-dimensional structures in a range of materials. Biomedical applications are particularly significant. This work demonstrates how to fabricate simultaneously a sacrificial mould having the inverse shape of the desired device structure and also create the desired device structure using electrodeposition techniques. The mould is constructed of many thin layers using a photo-resist material that is dissolvable and sensitive to ultraviolet (UV) light. At the same time the device is created in the emerging mould layers using gold electrodeposition technique. Choosing to fabricate the mould and the three-dimensional structures in multiple thin layers allows for the use of UV light and permits the potential cost-effective realization of three-dimensional curved surfaces, the accuracy and geometric details of which are related to the number of layers used. An example is provided to explain the novel fabrication process and to outline the resulting design and fabrication constraints