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In this study the application of a simulative sliding friction test at micro scale is suggested. Two work piece specimens are upset against opposing sides of a flat tool element. The tool element is then pulled out while the resulting friction force F is measured. The test principle offers several advantages when compared against the DEC-test, including easy visual inspection of tool and work piece surfaces, continuous measurement of friction coefficient over the complete sliding length and less sensitivity to mechanical tolerance deviations of work piece and tool elements.

The tool surface topography is often a key parameter in the tribological performance of modern metal forming tools. A new generation of multifunctional surfaces is achieved by combination of conventional tool manufacturing processes with a novel Robot Assisted Polishing process. This novel surface texturing method allows for a large degree of freedom in specifying surface characteristics and facilitates a high degree of reproducibility between samples surfaces. A series of strip reduction tests, equivalent to a metal forming ironing process, are conducted to benchmark the tribological performance of 15 generated tool surfaces.

The industrial demand for micro mechanical components has surged in the later years with the constant introduction of more integrated products. The micro bulk forming process holds a promising pledge of delivering high quality micro mechanical components at low cost and high production rates. This work describes a number of prototype system units, which collectively form a desktop sized micro forming production system. The system includes a billet preparation module, an integrated transfer system, a temperature controlled forming tool, including process simulation, and a dedicated micro forming press. The system is demonstrated on an advanced micro forming case where a dental component is formed in medical grade Titanium.

A novel artefact for calibration of the height in 3D microscopy is presented. The artefact comprises three steps having a common vertical axis, which allows z-coordinate calibration at different magnifications without requiring repositioning. The artefact is suitable for transferring traceability to 3D techniques at the micrometer and nanometer scale, e.g. 3D SEM, confocal microscopes etc. Two different series of samples were fabricated using EDM with three steps of 2–5–7 μm, and 20–50–70 μm, respectively, from a 3 mm diameter carbide wire. The artefact steps were calibrated on a stylus instrument according to ISO 5436 and measured on 3D microscopes.

Bulk metallic glasses have enormous potential for use in small-scale devices such as MEMS and biomedical components. Thermoplastic forging of free standing components poses challenges unlike those seen when forging crystalline materials. Central to these challenges is the simultaneous advantage/disadvantage that BMGs flow readily into small features and asperities in the dies and molds. Whilst useful for replicating patterned surfaces, this quite often makes non-destructive removal of components quite difficult, with disproportionate extraction forces and specialized tools required to overcome friction and mechanical locking. Several solutions to this extraction problem were explored, including high temperature extraction, lubrication and the use of materials with low coefficients of thermal expansion (CTE) as die/mold materials. We show that the use of appropriately chosen low CTE die materials offers a superior method to remove BMG components from dies/molds at room temperature. The criteria for selecting the appropriate die material, cavity size and extraction temperatures are outlined.

A comparative friction study of tooling dies with a simple internal cylindrical geometry has been performed. The purpose of the experiment consist of studying the influence of the surface characteristics of tooling dies on the frictional behaviour in a micro bulk forming operation. This research will seek to contribute with knowledge in the field of the category of structural size effects. By evaluating and benchmarking three different surface topographies, in an O1 and an O2 millimetre cylindrical forming-die, it is expected that frictional performance and forming limits can be evaluated, with the option of extracting general guidelines for evaluation of surface characteristics for dies utilized for micro-forming. The DCE test will be supported by numerical analysis in order to determine the friction factor.

Titanium is a popular material for medico components, primarily due to its excellent properties as regards strength, resistance to corrosion and biocompatibility. The disadvantages are mainly the low formability at room temperature and the material cost. As an alternative to conventional machining, the component can be plastically formed by a number of warm forming operations. Commercial pure titanium, grade 1, 2 and 4, is tested in 4 dimensions to investigate the size effect as function of temperature and strain rate. From these tests, a heat treatment procedure is derived and reliable data for a numerical model is acquired. The concept is validated by forming a dental implant. Due to the high aspect ratio of the tool inserts, a segmented die design is proposed. A two-step process design with pre-stressed die inserts is realized; following from the high yield strength of the titanium material that causes internal pressures above 2500 MPa under forging. The design phase is supported by numerical modeling.

In micro forming, the increased surface to volume ratio makes ejection of an extruded component to an often complicated process. The aim of this work has been to demonstrate the possibility to reduce the force required to eject the component, by controlled pre-stressing of the die, before, during and after the forming process. The level of required prestress has been evaluated by FE analysis of the interaction between the forming process and the elastic deflection of the tool-system. A test rig has been designed containing four piezo actuators mounted symmetrically around the circumference of the die cavity. Mechanical amplification has been used to increase the pressure created by the piezo actuator to reach the level required for prestressing of a bulk forming tool.

This chapter firstly introduces the background of micro-bulk forming, backed by the description of conventional cold forming processes based on which fundamental issues concerning micro-bulk forming such as size-effects, work materials, and tool materials are discussed. These considerations are considered in a press and tool system design which is described in detail in this chapter, especially on machine precision, tool-guide, and handling system design. Finally, micro-tribology and process analysis of micro-bulk forming are described.

Publisher Summary Bulk forming is used extensively in a wide range of industrial applications. Within the production of transmission elements for the automotive industry, the bulk forming process is the standard. A typical forming process requires multiple forming steps and comes in a wide range of variants. The industrial popularity of the bulk forming process still relies on the underlying theory of material flow and behavior, something that has not changed since the early days of forging. Micro-bulk forming is the utilization of the bulk forming process to form micro-components. Material knowledge is central for the bulk forming process, which fundamentally relies on differences in flow stress between two materials. These two materials are often termed “workpiece material” and “tooling material,” relating to their respective functional purpose in the bulk forming process. In micro-bulk forming the geometrical tolerances of the tool are very narrow and deflections of the tool during heat treatment often exceed the total allowable tolerance deviation of the tool.

For production of micro components in large numbers, forging is an interesting and challenging process. The conventional metals like silver, steel and aluminum often require multi‐step processes, but high productivity and increased strength justify the investment. As an alternative, bulk metallic glasses will at elevated temperatures behave like a highly viscous liquid, which can easily form even complicated geometries in 1 step. The strengths and limitations of forming the 2 materials are analyzed for a micro 3D component in a silver alloy and an Mg‐Cu‐Y BMG.

The central part of the metal forming processes are the forming tools. In the macroscale, these tools are manufactured by means of machining‐ and drilling operations and subsequently hardened. Due to the required precision, this approach is not possible in the microscale. An investigation of alternative tool manufacturing techniques has been carried out, including μ‐EDM, electroforming and machining operations. A series of universal forming tools for simple microcompoents has been manufactured using different techniques, allowing side‐by‐side comparison. A series of ejectors and punches have also been manufactured using a combination of grinding and μ‐EDM processing. Critical tooling parameters including geometry, yield strength, surface roughness and production time has been recorded. A silicon replica method has been utilized to measure the internal geometry of the microforming tools.

Manufacturing techniques for production of small precise metallic parts has gained interest during recent years, an interest led by an industrial demand for components for integrated products like mobile phones, personal digital assistants (PDAs), mp3‐players and in the future for spare parts for the human body. Micro components have also found several applications within the medical, audiological and dental industry, applications that impose increased demands for biocompatible and corrosion‐resistant materials and cleanness. So far these micro components have mainly been manufactured by traditional machining techniques or chemical etching. However, these traditional machining and etching techniques are generally not well suited for mass production of advanced micro components, due to handling problems, waste of expensive material and long machining times. This calls for development of a novel production system that can meet the demands for high productivity, high reliability, low cost, while being environmental acceptable. Bulk metal forming meets these demands to a great extent, but the technology cannot directly be transferred to the micro scale. A flexible machine system for bulk micro forming has been developed and used to form a number of industrial micro parts in aluminium and silver, with ongoing work on forming of titanium. Manufacture of billets by cropping has been examined using a simple test rig and an automatic cropping device has been designed, manufactured and tested.

Current manufacturing of precision tools for machining typically requires processes such as grinding, EDM or laser processing in order to comply with high requirements on tolerances. However even tools manufactured by these processes come short, when a new batch of workpieces are supplied, and their tolerances are not compliant. This approach presents a precision broaching tool for adjusting the inner diameter of an external broach. The tool compensates for the manufacturing tolerance chain of tool and workpieces by up to 37 μm. The approach is based on conventional shrink fitting of cold forging tools. A numerical and analytical model of the compression is compared with experimental results.