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The application of Van der Waals forces in micro-material handlingMatope, S., Van Der Merwe, A. January 2010 (has links)
Published Article / This paper investigates the challenges of employing Van der Waals forces in micro-material handling since these forces are dominant in micro-material handling systems. The problems include the creation of a dust-free environment, accurate measurement of the micro-force, and the efficient picking and placing of micro-work pieces. The use of vacuum suction, micro-gripper's surface roughness, geometrical configuration and material type are presented as alternatives to overcome the challenges. An atomic force microscope is proposed for the accurate measurement of the Van der Waals force between the gripper and the micro-work piece.
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Manipulation of Van der Waals' forces by geometrical parameters in micro-material handlingVan der Merwe, A., Matope, S. January 2010 (has links)
Published Article / This paper explores the manipulation of Van der Waals' forces by geometrical parameters in a micro-material handling system. It was observed that the flat-flat interactive surfaces exerted the highest intensity of Van der Waals' forces followed by cone-flat, cylinder-flat, sphere-flat and sphere-sphere interactive surfaces, respectively. A conical micro-gripper proved to be versatile in manipulating the Van der Waals' forces efficiently in a 'picking up' and 'releasing' mechanism of micro-work parts. It was deduced that the pick-up position should be rough and spherical, and the placement position should be smooth and flat for an effective 'pick-and-place' cycle to be realised.
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Application of Van-der-Waals forces in micro-material handlingMatope, Stephen 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2012. / This doctoral dissertation focuses on the application of Van-der-Waals’ forces in micromaterial
handling. A micro-material handling system consists of four main elements, which
include: the micro-gripper, the micro-workpart, the picking up position and the placement
position. The scientific theoretical frameworks of Van-der-Waals’ forces, presented by Van
der Waals, Hamaker, London, Lifshitz, Israelachvilli, Parsegian, Rumpf and Rabinovich, are
employed in exploring the extent to which these forces could be applied in a micromanufacturing
situation. Engineering theoretical frameworks presented by Fearing,
Bohringer, Sitti, Feddema, Arai and Fukuda, are employed in order to provide an in-depth
synthesis of the application of Van-der-Waals’ forces in micro-material handling. An
empirical or pragmatic methodology was adopted in the research.
The Electron Beam Evaporation (e-beam) method was used in generating interactive surfaces
of uniform surface roughness values. E-beam depositions of copper, aluminum and silver on
silicon substrates were developed. The deposition rates were in the range of 0.6 – 1.2
Angstrom/s, at an average vacuum pressure of 2 x 10-6 mbar. The topographies were analysed
and characterised using an Atomic Force Microscope and the corresponding rms surface
roughness values were obtained. The Rumpf-Rabinovich equation, which gives the
relationship of the exerted Van-der-Waals’ forces and the rms surface roughness values, is
used to numerically model the results. In the final synthesis it is observed that the e-beam
depositions of copper are generally suited for the pick-up position. Aluminum is suited for the
micro-gripper and silver is suited for the placement position in an optimised micro-material
handling system.
Another Atomic Force Microscope was used in order to validate the numerically modelled
results of the exerted Van- der-Waals’ forces. The aim was to measure the magnitude of Vander-
Waals’ forces exerted by the e-beam depositions and to evaluate their applicability in
micro-material handling operations. The measurements proved that Van-der-Waals’ forces
exerted by the samples could be used for micro-material handling purposes on condition that
they exceeded the weight of the micro-part being handled.
Three fundamental parameters, ie: material type, geometrical configuration and surface
topography were used to develop strategies of manipulation of micro-materials by Van-der-
Waals’ forces. The first strategy was based on the material type variation of the interactive surfaces in a micro-material handling operation. This strategy hinged on the fact that materials
have different Hamaker coefficients, which resulted in them experiencing a specific Van-der-
Waals’ forces’ intensity during handling. The second strategy utilised variation in the
geometrical configuration of the interacting surfaces. The guiding principle in this case was
that, the larger the contact area was, the greater the exerted Van-der-Waals’ forces would be
In the analytical modelling of Van-der-Waals’ forces with reference to geometrical
configuration, a flat surface was found to exert more force than other configurations. The
application of the design, for purposes of manufacturing and assembling (DFMA) criteria,
also proved that flat interactive surfaces have high design efficiency. The third strategy was
based on surface roughness. The rougher the topography of a given surface was, the lesser the
Van-der-Waals’ forces exerted were. It was synthesised that in order for a pick-transfer-place
cycle to be realised, the root-mean-square (rms) interactive surface roughness values of the
micro-part (including the picking position, the micro-gripper, and the placement position)
should decrease successively. Hybrid strategies were also identified in this research in order
to deal with some complex cases. The hybrids combined at least two of the aforementioned
strategies.
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Product Development of Material Supply : Implementation of Karakuri KaizenPorteiro Paraponiaris, Yanni, Mateos Rodríguez, Arturo January 2019 (has links)
The industry 4.0 is continuously aiming to produce faster, increasing quality, and strictly using what is necessary to achieve efficiency enhancement. Within the wide list of methods used to reach this target, robot automation is usually used, although is expensive and rigid. Alternatively, a Japanese cheap automation philosophy called "Karakuri", is being introduced by Volvo GTO to manage this goal. This thesis relies on this philosophy, which takes profit of the existing energy, like gravity, to put in motion mechanisms, in order to reduce costs and improve the production efficiency by developing a semi-automated material handling system. The design method followed, the Scrum, divides the thesis in several phases of development, presenting a fully developed solution at the end of each one and iteratively increasing the level of definition along the process, to finally provide a solution suitable to be implemented.
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Load Carriers; Optimized Solution to Improve Performance of Roll containers : A Case Study at VGR-WESTMA OrganizationAlimohamadi, Bardia January 2009 (has links)
Roll containers are widely used in transportation and delivery operations due to the high level of flexibility and agility they offer to supply chains. However, there is a negative side to the application of roll containers in industry which can be removed or minimized by proper ergonomic and technical considerations. In this thesis work, the safety problems, economic issues and environmental effects associated with roll containers being used in VGR-WESTMA organization are reviewed in order to come up with alternative solutions to the current way of using old roll containers in their supply chain. The analysis of the problem resulted in ergonomic, safety and technical recommendation on using roll containers within their associated supply chain. The appropriate technical design of roll containers that fits the organization facilities are introduced with the aim of streamlining the supply chain flow within the organization. However, cost is considered as a limiting factor for this organization. Hence, proper ergonomic awareness and use of appropriate accessories to the roll containers are considered as a contemporary alternative solution to replacing roll containers being used in this supply chain.
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Concurrent design of facility layout and flow-based department formationChae, Junjae 17 February 2005 (has links)
The design of facility layout takes into account a number of issues including the formation of departments, the layout of these, the determination of the material handling methods to be used, etc. To achieve an efficient layout, these issues should be examined simultaneously. However, in practice, these problems are generally formulated and solved sequentially due to the complicated nature of the integrated problem. Specifically, there is close interaction between the formation of departments and layout of these departments. These problems are treated as separate problems that are solved sequentially. This procedure is mainly due to the complexity of each problem and the interrelationships between them. In this research, we take a first step toward integrating the flow-based department formation and departmental layout into comprehensive mathematical models and develop appropriate solution procedures. It is expected that these mathematical models and the solution procedures developed will generate more efficient manufacturing system designs, insights into the nature of the concurrent facility layout problem, and new research directions.
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Analytical Approach to Estimating AMHS Performance in 300mm FabsNazzal, Dima 07 July 2006 (has links)
This thesis proposes a computationally effective analytical approach to automated material handling system (AMHS) performance modeling for a simple closed loop AMHS, such as is typical in supporting a 300mm wafer fab bay. Discrete-event simulation can produce accurate assessments of the production performance, including the contribution by the AMHS. However, the corresponding simulation models are both expensive and time-consuming to construct, and require long execution times to produce statistically valid estimates. These attributes render simulation ineffective as a decision support tool in the early phase of system design, where requirements and configurations are likely to change often. We propose an alternative model that estimates the AMHS performance considering the possibility of vehicle-blocking.
A probabilistic model is developed, based on a detailed description of AMHS operations, and the system is analyzed as an extended Markov chain. The model tracks the operations of all the vehicles on the closed-loop considering the possibility of vehicle-blocking. The resulting large-scale model provided reasonably accurate performance estimates; however, it presented some computational challenges.
These computational challenges motivated the development of a second model that also analyzes the system as an extended Markov chain but with a much reduced state space because the model tracks the movement of a single vehicle in the system with additional assumptions on vehicle-blocking.
Neither model is a conventional Markov Chain because they combine the conventional Markov Chain analysis of the AMHS operations with additional constraints on AMHS stability and vehicle-blocking that are necessary to provide a unique solution to the steady-state behavior of the AMHS.
Based on the throughput capacity model, an approach is developed to approximate the expected response time of the AMHS to move requests. The expected response times are important to measure the performance of the AMHS and for estimating the required queue capacity at each pick-up station. The derivation is not straightforward and especially complicated for multi-vehicle systems. The approximation relies on the assumption that the response time is a function of the distribution of the vehicles along the tracks and the expected length of the path from every possible location to the move request location.
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Concurrent design of facility layout and flow-based department formationChae, Junjae 17 February 2005 (has links)
The design of facility layout takes into account a number of issues including the formation of departments, the layout of these, the determination of the material handling methods to be used, etc. To achieve an efficient layout, these issues should be examined simultaneously. However, in practice, these problems are generally formulated and solved sequentially due to the complicated nature of the integrated problem. Specifically, there is close interaction between the formation of departments and layout of these departments. These problems are treated as separate problems that are solved sequentially. This procedure is mainly due to the complexity of each problem and the interrelationships between them. In this research, we take a first step toward integrating the flow-based department formation and departmental layout into comprehensive mathematical models and develop appropriate solution procedures. It is expected that these mathematical models and the solution procedures developed will generate more efficient manufacturing system designs, insights into the nature of the concurrent facility layout problem, and new research directions.
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Analytical models to evaluate system performance measures for vehicle based material-handling systems under various dispatching policiesLee, Moonsu 29 August 2005 (has links)
Queueing network-based approximation models were developed to evaluate
the performance of fixed-route material-handling systems supporting a multiple
workcenter manufacturing facility. In this research, we develop analytical models for
fixed-route material-handling systems from two different perspectives: the
workcenters?? point of view and the transporters?? point of view. The state-dependent
nature of the transportation time is considered here for more accurate analytical
approximation models for material-handling systems. Also, an analytical methodology
is developed for analytical descriptions of the impact of several different vehicledispatching
policies for material-handling systems. Two different types of vehicledispatching
policies are considered. Those are workcenter-initiated vehicle
dispatching rules and vehicle-initiated vehicle dispatching rules. For the workcenterinitiated
vehicle dispatching rule, the Closest Transporter Allocation Rule (CTAR)
was used to assign empty transporters to jobs needing to be moved between various
workcenters. On the other hand, four different vehicle-initiated vehicle dispatching
rules, Shortest Distance Dispatching Rule (SDR), Time Limit/Shortest DistanceDispatching Rule (TL/SDR), First-Come First-Serve Dispatching Rule (FCFSR),
Longest Distance Dispatching Rule (LDR), are used to select job requests from
workcenters when a transporter is available. From the models with a queue space limit
of one at each workcenter and one transporter, two different types of extensions are
considered. First, the queue space limit at each workcenter is increased from one to
two while the number of transporters remains at one. Second, the number of
transporters in the system is also increased from one to two while maintaining the
queue space limit of one at each workcenter. Finally, using a simulation approach, we
modified the Nearest Neighbor (NN) heuristic dispatching procedure for multi-load
transporters proposed by Tanchoco and Co (1994) and tested for a fixed-route
material-handling system. The effects of our modified NN and the original NN
transporter dispatching procedures on the system performance measures, such as WIP
or Cycle Time were investigated and we demonstrated that the modified NN heuristic
dispatching procedure performs better than the original NN procedure in terms of
these system performance measures.
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Scheduling of Generalized Cambridge RingsBauer, Daniel Howard 14 October 2009 (has links)
A Generalized Cambridge Ring is a queueing system that can be used
as an approximate model of some material handling systems used in modern
factories. It consists of one or more vehicles that carry cargo from origins
to destinations around a loop, with queues forming when cargo temporarily
exceeds the capacity of the system. For some Generalized Cambridge Rings
that satisfy the usual traffic conditions for stability, it is demonstrated that
some nonidling scheduling polices are unstable. A good scheduling policy
will increase the efficiency of these systems by reducing waiting times and by
therefore also reducing work in process (WIP). Simple heuristic policies are
developed which provide substantial improvements over the commonly used
first-in-first-out (FIFO) policy. Variances are incorporated into previously
developed fluid models that used only means to produce a more accurate
partially discrete fluid mean-variance model, which is used to further reduce
waiting times. Optimal policies are obtained for some simple special cases, and
simulations are used to compare policies in more general cases. The methods
developed may be applicable to other queueing systems. / text
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