Akhtar Razali

Dynamics characteristics of a micro-sheet-forming machine system

Dynamic characteristics of a micro-forming machine system are of significant importance to be considered if high-precision micro-parts are to be produced. This is because forming tolerances may be within a range of sub-microns up to 5-15% of the thickness of a thin sheet-metal (e.g. <100µm) being used in micro-sheet-forming. Achievability of the quality parts often vary with the machine-system performance and process parameters being set, and it largely depends on the understanding of the machine and tool system’s dynamic characteristics and effectiveness of the control of the machine and the process. Nevertheless, there has been lack of the effort in this field of research. Significant number of the efforts in this field were focused mainly on discrete and/slow processes where the dynamic characteristics of the forming systems were often neglected. This paper presents the dynamic characteristics of an autonomous micro-sheet-forming machine system and its effect towards the produced parts’ quality. These have been studied by combining finite element analysis and forming experiment, with a particular focus on the combined effects from the machine, tooling system and the sheet-metal feeding system (the strip feeder). The results showed that, besides importance of the dynamic performance of the machine and the tool-system, dynamic characteristics of the material-feeding plays an important part in determining the parts’ quality produced.

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.

Development of a New High-Precision Feeder for Micro-Sheet-Forming

Feeding the raw material accurately is essential in microsheet-forming, especially in multistage progressive forming operations and also when in particular, a certain feeding rate has to be maintained. Research into the microforming of thin sheet metals (< 100 mu m) led to investigations of the performance of existing sheet metal feeders, regarding their feeding accuracy and repeatability. The results indicated that the pursuance of greater feeding accuracy and repeatability, which was aimed at 5-15% of the strip thickness, was difficult to achieve with commercially-available feeders. A new high-precision and high-speed feeder was, therefore, developed for microsheet-forming. The feeder design was supported by motion analysis and feeding simulations. The feeder was constructed in collaboration with industrial partners. The conducted feeding tests and forming experiments demonstrated that greater feeding accuracy and repeatability can be achieved, compared to those of existing commercial feeders. This suggests a promising solution for high-precision strip feeding in microsheet-forming where thin sheet metals are to be fed.

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.

Reconfigurable foot-to-gripper leg for underwater bottom operator, Hexaquad

This paper presents the development of a configurable leg-to-arm for configurable robot, named Hexapod-to-Quadruped (Hexaquad) robot, which is designed and developed for riverbed/seabed exploration and related works. Reconfigurable legged robot, one of robotics research areas, is generally focused on optimizing the usage of leg during locomotion. Until recently, most of the researches have emphasized on leg reconfigurable design in order to solve issues related to fault tolerant, stability, multitasking and energy efficiency. However, the emphasis of Hexaquad robot is on providing optimum leg usage, actuation configuration as well as satisfying the legged robot stability criterion in reconfiguration mechanism. Inspired by foot-to-gripper (FTG) transformation of crab chelipads, each leg of the proposed Hexaquad robot have mass affect avoidance. The minimum torque on each leg joint is calculated as well as FTG using static torque calculation on multi-link structure before selecting the actuator/motor. Performance tests are done by performing fundamental testing on optimum standing posture, stress and displacement analysis on FTG model, including gripping tests to several shapes of objects both in the air and underwater environment.

Parameter Optimization of AA6061-AA7075 Dissimilar Friction Stir Welding Using the Taguchi Method

In this study, the Taguchi method was utilized to determine the optimum process parameters for dissimilar friction stir welding between AA6061 and AA7075 aluminium alloys. The Taguchi L9 orthogonal array and optimization approach was applied on three levels of three critical factors, namely rotational speed, transverse speed and tool tilt angle. The optimum levels of process parameters were determined through the Taguchi parametric design approach. Through the parameter analysis, the predicted value of the dissimilar joint’s tensile strength was calculated to be 209.7 MPa, which is in close proximity to the experimental data (219.6 MPa) with 4.5% error. It can be concluded that a high tensile value of 219.6 MPa was achieved using 1000 rpm rotational speed, 110 mm/min travel speed and 3 ̊ tilt angle.

Machine and tool development for forming of polymeric tubular micro-components

This paper reports the work associated with the development of a desktop hot-embossing machine system and tools which would enable volume production of polymeric tubular micro-components for various applications. The development was undertaken by considering factors such as machine dynamic performance, precision guides to tools, tool heating and cooling, raw material feeding and end-part collection, control strategy. It was assisted with FE analysis and a series of forming experiment. An integrated machine system has now been constructed and tested with the forming of several demonstration-components. A good result was obtained from these tests.

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.

Size effects in thin sheet metal forming

Negligible factors in bulk materials, such as grain-size effects, have proven inappropriate to be neglected for micro-forming processes. Studies had shown that material behaviour varies greatly with the increasing of the scale in the micro-forming world. Therefore, in every micro-forming-related process, especially in micro-stamping, studies and analyses of each material used for the process have to be considered as indispensable in order to be able to understand their behaviour and to be able to correlate their behaviour with the process. Uniaxial tensile-testing experiments have been carried out to determine the strips properties, behaviour and its correlation with the feeding process in micro-stamping/micro-sheet-forming application. Based on the results of the uniaxial tensile-test experiments conducted, the flow stress was found to decrease with the decrease of the strip thickness and vice versa, due to the size/scale effect. A surface model was used to explain the findings.

Improvement of Overall Equipment Effectiveness (OEE) through Implementation of Total Productive Maintenance (TPM) in Manufacturing Industries

Today competitive manufacturing requires innovative approaches in the production management, as well as for customer satisfaction. Production management requires an effective and efficient maintenance management system. One approach to improve the performance of the maintenance system is through the implementation of Total Productive Maintenance (TPM). The key performance index to measure the effectiveness of TPM implementation is Overall Equipment Effectiveness (OEE). The TPM activities will eliminate equipment losses related to availability, performance rate, and quality rate. Hence, the TPM implementation will increase the OEE value. This paper outlines the theories of TPM and OEE. The paper also presents the studies carried out by different authors to show the improvement of OEE through implementation of TPM in manufacturing, such as electronic industry, steel manufacturer, as well as locomotive components manufacturer.