Smart Devices and Machines for Advanced Manufacturing

Although parallel structures have found a niche market in many applications such as machine tools, telescope positioning or food packaging, they are not as successful as expected. The main reason of this relative lack of success is that the study and hardware of parallel structures have clearly not reached the same level of completeness than the one of serial structures. Among the main issues that have to be addressed, the design problem is crucial. Indeed, the performances that can be expected from a parallel robot are heavily dependent upon the choice of the mechanical structure and even more from its dimensioning. In this chapter, we show that classical design methodologies are not appropriate for such closed-loop mechanism and examine what alternatives are possible.

The balancing of parallel mechanisms is addressed in this chapter. First, the notions of static balancing, gravity compensation and dynamic balancing are reviewed. A general mathematical formulation is then developed in order to provide the necessary design tools, and examples are given to illustrate the application of each of the concepts to the design of parallel mechanisms. Additionally, some limitations of the techniques currently used for the balancing of parallel mechanisms are pointed out.

In this chapter, a new family of PKM structures based on the Tau concept is described. It is shown that the non-symmetrical Tau link structures solve the problem of obtaining a large accessible workspace in relation to the footprint of a PKM and examples of large workspace of Tau PKMs are given both for rotating and linear actuators. Some results are presented from an investigation of the SCARA Tau manipulator with respect to its workspace and elastodynamical properties, showing its potential for applications with high performance requirements. The main part of the chapter is about the Gantry Tau manipulator, which is based on the same non-symmetrical link structure as the SCARA Tau manipulator. It is shown that this manipulator will get a large accessible workspace, that it can be reconfigured to increase the workspace further, that it can be calibrated to non-parallel linear guide-ways and that it can be designed for very high stiffness and bandwidth. The nominal kinematics as well as the kinematics with non parallel linear guide ways are derived and the stiffness is calculated using the duality between the statics and the link Jacobian for a PKM. The mechanical bandwidth calculations are based on a new method with mass-spring-damper link models. With the promising performance results obtained with the Tau family of manipulators, the potential for the use of these in industry is discussed.

This chapter discusses the layout and force optimisation in cable-driven parallel manipulators (CPM). These manipulators need to be redundantly actuated to be fully constrained in their workspace. This can be achieved by having redundant limbs applying forces on the mobile platform to generate tension in the cables. The layout of the redundant limbs can be optimised such that they generate the desired tensile forces in the cables to keep them taut against any external and dynamic loads without excessively tensioning the cables. The optimisation of the redundant limbs is formulated as a projection onto an intersection of convex sets. This chapter also discusses the benefit of having multiple redundant limbs to minimise the cable tensions required to balance an external wrench during the operation and demonstrates this with a numerical example. In addition, the calculation of the optimum redundant-limb forces using the Dykstra’s projection algorithm is demonstrated.

In this chapter, a new polishing/deburring machine developed at Ryerson University is presented. This machine consists of two subsystems. The first subsystem is a five-axis machine for tool/part motion control. The second subsystem is a compliant toolhead for tool force control. Both subsystems are designed based on the tripod principle. For motion control, a motion planning software package is developed that includes axis motion planning based on the tripod inverse kinematics; and tool motion simulation and part profile measurement based on the tripod forward kinematics. For force control, a parameter planning method is developed for planning tool pressure and tool spindle air flow rate according to the part geometry, based on the Hertzian contact model. A force control method is also developed that utilises the active compliance toolhead to deal with the parts with large geometry deviations. Two test examples are provided to demonstrate the effectiveness of the developed machine.

This chapter introduces a reconfigurable tripod-based machine system. The objective is to develop such a machine system that is capable of performing different machining tasks with the same set of system modules. The tripod system can be applied to different light machining operations, such as deburring and polishing. It consists of core modules and customised modules. The core modules, such as linear actuators, spherical and universal joints, are essential to all tripod machines, whereas the customised modules, such as base, end-effector platforms and support legs, can be changed and optimised for a specific task. This chapter focuses on the design methodologies of the reconfigurable machine system, and the theoretical model development for analysing and synthesising machines with alternative configurations. An integrated toolbox has also been implemented to support the system reconfiguration design processes.

The arch-type reconfigurable machine tool (RMT) is a full-scale reconfigurable machine tool, designed to provide customised flexibility in milling and drilling operations for a part family, i.e. V6 and V8 engine cylinder heads. The designed machine not only has to achieve the required kinematic task, but should also exhibit similar dynamic characteristic across all members of the part family to ensure specified productivity and quality levels in the manufacturing environment. This chapter begins with a brief introduction to reconfigurable manufacturing systems and reconfigurable machine tools, and later delves into the various RMT design considerations e.g. part family, machine specifications, workspace, and accuracy. The detailed design and construction of the arch-type RMT is described. This section also describes the research activities carried in the area of RMT design. The later part of this chapter discusses the variations in dynamic performance of the arch-type RMT across the various reconfiguration positions. The dynamic performance of the arch-type RMT is measured in terms of frequency response functions and stability lobe diagrams. It is observed, that for the arch-type RMT, the dynamic characteristics are similar across the part family, because the dominant frequency where chatter occurs comes from the tool-tool holder-spindle assembly. The machine dynamics is similar to many other industrial machines used for milling and drilling operations on similar sized workpiece, which are not designed to be reconfigurable. Thus, the arch-type RMT successfully demonstrates the concept of reconfiguration and its application in the machine tool industry.

A driving method named “walking drive” is introduced in this chapter. The method is suitable to feed an ultra-precision table continuously over a long stroke by utilising piezoelectric actuators. The table is driven smoothly in a similar way to walking motions of animals. Ultraprecision positioners and their control algorithms have been developed, and it is confirmed that ultra-precision positioning can be realised by combining a laser-feedback system. The positioners driven by the walking drive have advantages such as high positioning resolution, smooth continuous motion, a long stroke, high stiffness, 3-axis motion, direct drive without conventional guides, high load capacity after positioning, and no need for lubricant.

This chapter describes a surface motor-driven XYθ_Z stage system. The surface motor consists of two pairs of linear motors. The magnetic arrays are mounted on the moving element (platen) and the stator windings of the linear motors on the stage base. The platen can be moved in the X and Y directions by the X-linear motors and the Y-linear motors, respectively. It can also be rotated about the Z-axis by a moment generated by the X- or Y-linear motors. In the controller of the stage, a decoupled controlling element is employed to reduce the interference errors between the in-plane motions. A cascaded notch compensator is applied for dealing with the stage resonance. A disturbance observer is implemented to estimate and eliminate the influence of disturbance forces. A surface encoder is also developed to replace the conventional laser interferometers for XYθ_Z motion measurement.

In this chapter, we discuss the important new class of machine tools, the micro/meso-scale machine tool or mMT, which is now addressing the exploding marketplace for miniature components with high relative accuracy requirements, true 3D features, and made in a wide range of engineering materials. These mMTs fill the gap created by the inability of the common MEMS processes to meet the aforementioned needs. In particular, we review a number of research efforts of the late 1990s and early 2000s that have been directed toward the development of the “mMT” and “microfactory” paradigms. We then provide in-depth discussions of efforts by Northwestern University (3-axis mMT) and the University of Illinois at Urbana-Champaign (5-axis mMT), introducing both the design principles used and technologies adopted in creating prototype mMTs. A machine tool calibration methodology specifically developed for mMTs is then presented. Finally, we will discuss recent efforts in Japan, Europe and the US to commercialise the mMT paradigm.

A high precision Micro-CMM (Coordinate measuring machine) is introduced for the 3D measurement of part dimensions in meso to micro scale. Expected measuring range is 20×20×10 mm and the resolution is 1 nm. In order to enhance the structural accuracy, some new ideas are integrated into the design, such as the semi-circular shape bridge for better stiffness and the co-planar stage for less Abbé error. The ultrasonic motor and linear diffraction grating interferometer are used to drive the stage and feedback the position to the control. Some problems due to current techniques are also addressed.

Mechanical micro-cutting methods such as micro-grooving, micro-turning, and micro-milling are emerging as viable alternatives to lithography based micromachining for applications in optics, semiconductors and micro moulding. However, certain factors limit the range of workpiece materials that can be processed using these methods. For difficult-to-machine materials such as mould and die steels and sintered ceramics, limited cutting tool and machine stiffness and/or strength pose significant barriers to the efficient use of mechanical micromachining methods. In addition, when cutting at the microscale, the effect of tool/machine deflection on the dimensional accuracy of the machined feature can be pronounced. This chapter describes a novel hybrid mechanical micromachining process called Laser-Assisted Mechanical Micromachining, or LAMM, that is designed to overcome the aforementioned limitations of mechanical micro-cutting methods. The chapter describes the basic idea behind LAMM and the development of a LAMM-based prototype system for micro-grooving, experimental characterisation and modelling of the laser assisted microgrooving process, and concludes with a discussion of future directions of this technology.

Micro assembly refers to assembling micro size objects, such as integrated electronic circuits, micro mechanical components, and micro fluidic components. These objects are usually no bigger than 10 mm. Moreover, high accuracy (e.g. 1 µm) and high speed (e.g. 1 m/sec. or 10 m/sec²) are often required. In general, a micro assembly system is made of two parts: grasping and positioning. This chapter gives a review on the newly developed technologies with a focus on our own research. For grasping, it includes pneumatic grippers, capillary force grippers, and bio-inspired grippers. For positioning, it includes servomotors, linear motors and piezoelectric motors. Force feedback controls and image based feedback controls are also discussed. A practical micro assembly system is included.