Andrew Brockett

Design considerations for developing a new, ultra-high precision feeder for micro-sheet-forming applications

A recent review of micro-forming research and technological development suggested that the trend of the development is focused more on the manufacturing processes, machines and tooling, with efforts on the precision material handling being insufficient. Most of the developed machines were based on stand-alone concepts that do not support efficient integration to make them fully automated and integrated. Material feeding, in most cases, was not of sufficient precision and reliability for high throughput manufacturing applications. Precision feeding is necessary to ensure that micro-parts can be produced with sufficient accuracy, especially in multi-stage forming, while high-speed feeding is a necessity to meet production-rate requirements. Therefore, the design of a new high-precision and high-speed feeder for micro-forming is proposed. Several possible approaches are examined with a view to establishing feasible concepts. Based on the investigation, several concepts for thin sheet-metal feeding for micro-forming have been generated, these being argued and assessed with appropriate applied loads and force analysis. These form a basis for designing a new feeder.

Micro-sheet-forming and case studies

Various analytical rules of mixture are commonly used to take into account heterogeneous features of a material and to derive global properties. But, with such models, one may not be able to fulfil the requirements for separating appropriately the different lengthscales. This might be the case for some issues such as strain localisation, surface effect, or topological distributions. At an intermediate lengthscale, which we refer to as the mesoscopic scale, one can still apply continuum mechanics. So why not perform calculations using the finite element method on volumes of material to obtain the response of Representative Elementary Volumes (R.E.V.). The construction of digital microstructures for such calculations is performed in two steps. First, a series of R.E.V.s with statistics of features of real materials should be defined. Then, finite element meshes should be produced for these R.E.V.s and updated when calculations involve large strains. Powerful automatic three-dimensional mesh generators and remeshing techniques prove necessary for this latter task. This strategy is applied to create digital R.E.V.s which match statistical features of forgings. Measurements provide micromechanical parameters of each subvolume. As an example of calculations, numerical simulations provide the anisotropic fatigue properties of forgings.

Chapter 8 – Forming of Micro-Sheet-Metal Components

Sheet metal components are used extensively in various applications such as vehicles, aircraft, electronics products, medical implants and packaging for consuming goods, typical parts/components including car panels, aircraft skins, cans for food and drinks, frames for TV/computer screens/monitors/displays, etc. Basic process configurations for the forming of macro-products include shearing, blanking, bending, stamping, deep drawing (including mechanical and hydromechanical), hydroforming, stretching forming, super-plastic forming, age forming, spinning, explosive forming, and incremental forming. Some of these processes may be equally applied to the forming of miniature and even micro-products, if the issues related to “size effect” can be handled successfully. The manufacture of micro-sheet metal products, such as those used in electronics products and MEMS (micro-electric-mechanical systems), often needs bending to produce 3D profiles/sections. Typical applications include micro-electric contacts/fingers/switches, 3D profiles for mechanical and thermal-mechanical sensors and 3Dsheet metal frames/housing for optical devices and micro-sensors.