Mogens Arentoft

Pulse reversal plating of nickel-cobalt alloys

Abstract Electroforming, as a versatile process for fabrication of durable tools, is experiencing an increasing interest with the start of commercial use of products with micro or nanofeatures. Electroformed tools can be utilised for polymer, glass and metal replication processes and, in addition, when extreme demands, in terms of tool accuracy, process temperature and tool wear, are requested. In order to meet these demands, electroforming of hard nickel alloys is an obvious way forward. This paper presents several electrolytes from which it is possible to deposit nickel–cobalt alloys with high hardness (>550 HV), low internal stress and easy maintenance. Moreover, different organic complexing agents – as well as alternatives to boric acid – have been investigated.

Measurements of Normal and Frictional Forces in a Rolling Process

Abstract To improve the quality of frictional data and to validate the simulations in rolling, a load transducer for measuring normal and frictional stresses in the deformation zone has been developed. The transducer consists of a strain-gauge-equipped insert embedded in the surface of the roll. The length of the insert exceeds the contact length. By analysing the output from the insert, the frictional stress and normal pressure in the contact zone can be determined. The new concept differs from existing pin designs by less disturbance of lubricant film and material flow and limited penetration of material between the transducer and roll. The transducer is tested at laboratory conditions and is expected to be running in industrial conditions in 2004.

Methods and devices used to measure friction in rolling

Abstract Friction at the workpiece-die boundary, in both bulk forming and sheet forming is, arguably, the single most important physical parameter influencing the processing of metals; yet it remains the least understood. Hence there is a need for basic research into metal-die interface mechanisms. To gain a good understanding of the mechanisms at the interface and to be able to verify the friction and tribology models that exist, friction sensors are needed. Designing sensors to measure frictional stress in metal working has been pursued by many researchers. This paper surveys methods that have been used to measure friction in rolling in the past and discusses some of the recent sensor designs that can now be used to measure friction both in production situations and for research purposes.

Accuracy of Transferring Microparts in a Multi Stage Former

Many fasteners used in electromechanical systems are micro metal parts which should be manufactured with high accuracy and reliability and in large quantities. Micro forming is promising to fulfill these demands. This research focuses on investigating a gripping unit in a multi stage former, as the positioning unit was discussed earlier. The parameters which play important roles in the gripping unit will be discussed and the precision and reproducibility evaluated to show the performance of the unit. This includes two different tests. The first test will show how accurately the unit can locate the parts and the second one is intended to depict how the unit transfers the parts with different diameters with respect to the front profile of the fingers. The experiments showed that the manipulator can handle the parts with 7 µm accuracy, 2 µm reproducibility and 9µm uncertainty for a 20mm distance between two adjacent stations.

Micro-bulk Forming

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.

A motion study of a manipulator for transferring microparts in a multi stage former

In the earlier studies, it was shown that a whole multi stage former can be divided into three major sub-sections, the positioning unit, the gripping unit and the forming unit. The two first units were investigated and related parameters and features of each were discussed. This research herein deals with the forming unit. For this research, the positioning unit and the gripping unit are applied to the forming unit including a micro press equipped with a die system. The analysis focuses on verifying the results already extracted from previous researches by implementing all mentioned units together. A motion study of the system gives an overview of different steps and movements inside the multi stage former. Significantly, increasing the production rate increases the acceleration and also causes the time frame tight. The time limitations put overlaps on the moving parts in terms of milliseconds. A high speed camera was used in the experiments with high resolution to show the details of the motion while enabling to detect any unwanted movement within milliseconds. Importantly, increasing the frequency of image capturing within the movement is another beneficial feature in the high speed camera in order to give sufficient information on critical movements where they may need sensors and enough time to ensure getting at the right position as programmed. In this research the production rate raised to 169 strokes per minute. The results show that the concept introduced for the manipulator works very well at a real process implementation. This significantly approves the techniques already were given to evaluate the precisio in the positioning unit and the gripping unit.Copyright

Tooling Process Chains and Concepts

This chapter introduces the concept of tooling process chains for micro-manufacturing. Two main approaches have been described: indirect tooling and direct tooling. The building blocks of tooling process chains can be combined in numerous ways and obtainable dimensions and geometries are dependent on specific choices of these building blocks. A tool is a component that can be used (preferably more than once) to make other components. Normally the tool will be a durable component with a well-defined geometry, but tools that are only used once can be envisaged, for example in casting. In most cases, the tool will be used to fabricate a large number of identical components before it is destroyed due to wear, corrosion and mechanical failure. Replication methods such as injection molding and cold forging belong to the preferred choice of macro-scale manufacturing methods when the focus is on mass production and high productivity and yield. The same processes are found in microscale manufacturing, now typically referred to as micro-injection molding and micro-cold forging.

Forming of polymeric tubular micro-components

This chapter is intended to provide an overview of three nontraditional shaping technologies for the forming of polymeric micro-tubes, which are hot embossing, blow molding, and cross rolling, as well as realization of a process chain and the integration of a modular machine-based manufacturing platform for the production of functional polymeric tubular micro-components. The chapter gives background on the current market and process development trends, followed by description of materials, process configuration, tool design and machine development for each processing technology as well as strategy for integration of the technologies and equipment into a common platform. Finally, potential applications of the technologies and facilities developed are highlighted.

Micro-mechanical Assembly

This chapter gives an introduction to micro-mechanical assembly and proposes a classification and characterization of micro-mechanical assembly methods. Firstly, main challenging issues concerning micro-mechanical assembly are introduced, followed by classification of the micro-assembly methods into snap fit, screwing, velcro, joinery, injection molding, riveting, folding, and clinching, for each of which a description is given. An application example—mechanical assembly of push button parts, is given as a demonstration of the methods and techniques described.