Sinan Sever 030070127 - 4th Week Definitions

VIBRATORY BALL MILLING

Old:

The use of vibratory ball mills for MA has been promoted predominantly by Kuhn. The vibratory ball mill is a long closed tube containing grinding balls and powder. The mill agitates the charge in three mutually perpendicular directions. Impact forces acting on the powder in a vibratory mill are a function of rates of milling, amplitude of vibration and mass of the milling medium. High energy milling forces can be obtained by using high frequency and high amplitude of vibrations. These mills normally operate at frequencies of the order of 200 Hz and a high amplitude of about 12 mm. It is estimated that the maximum acceleration of the grinding balls work out to be 24 g, where g is the gravitational force.

(Soni P.R.,Mechanical Alloying: Fundamentals and Applications, page 9 )

New:

Vibratory ball milling uses a vibratory action transmitted into the mill containing powders, liquid, and grinding media (fig.) Vibration causes a cascading action as well as local impact and friction and reduces the particle size effectively. The mill chamber is usually lined with rubber or plyurethane. This method yields finer particles compared to those achieved by ball milling.

(Engineering Ceramics, Murat Bengisu, page 86)

SOLVENT

Old:

There is no old definition.

New:

In a limited sense solutions are homogeneous liquid phases consisting of more than one substance in variable ratios, when for convenience one of the substances, which is called the solvent and may itself be a mixture, is treated differently from other substances, which are called solutes. Normally, the component which is in excess is called the solvent and the minor component(s) is the solute. When the sum of the mole fractions of the solutes is small compared to unity, the solution is called a dilute solution.

A solvent should not be considered a macroscopic continuum characterized only by its macroscopic physical constants such as boiling point, vapour pressure, density, cohesive pressure, index of refraction, relative permittivity, thermal conductivity, surface tension etc. From the molecular-microscopic point of view, a solvent is a discontinuum which consists of individual, mutually interacting solvent molecules, characterized by their molecular propertiessuch as dipole moment, electronic polarizability, hydrogen-bond donor (HBD) etc.

(Solvents and Solvent Effects in Organic Chemistry; Christian Reichardt, Thomas Welton; page 7)

CAPACITY PLANNING

Old:

CP comprises the information that is required to accomplish the production goal, such as identifiying the number of machines, persons, material handling resources, tooling and so on. The availability of shifts per work day, the work days per week, overtime, subcontracting, and machine/tool/material-handling device requirements, are fed back to the MRP control unit, which adjusts the work orders, purchase orders, and schedule notices.

(Computer Aided Manufacturing Second Edition, Chang T.C., Wysk R.A, Wang H., 1998, Pages: 7,8

New:

Capacity plannning deals with specifying the capacity level of recources such as workforce level, equipment, and facilities to support the organization’s production strategy. Capacity planning desicions are classified into three main categories bsed on time durations.

1.       Long Term – relating to overall capacity such as facility size, aquisition or disposal of wquipment, buildings, and facilities.

2.       Medium Term – relating to setting workforce levels and subcontracting

3.       Short Term – relating to production schedules, overtime, etc.

Capacity may be defined as an upper limit on the load that an operating unit can handle, and in general sense, it can be defined as the capability of the organization to meet future demands for products or services; operating costs can be reduced if capacity is matched with demand; and planning involves long-term commitment of recources. Capacity planning involves: measuring capacity, determining requirements, evaluating capacity alternatives.

(Production and Operations Management; Sai Kolli; page 27)

ENTITY GROWING

Old:

Entity growing methods have been developed to generate volumetric features from surface features that have already been recognized. There are a number of methods developed. The edges of a face, other than the face that belongs to the surface feature, are extended to generate volume(s) through creating new edges and vertices. Feature volumes may also be created by adding half spaces corresponding to feature faces.

(Xun Xu, Integrating Advanced Computer-Aided Design, Manufacturing, and Numerical Control: Principles and Implementations, p.99)

New:

The need for feature extraction arises most often in manufacturing applications, where features correspond to areas that must be machined from a blank piece. This case is depicted in figure 9.6. As shown, the feature extraction results in a volume decomposition of the original model, which is directly useful for manufacturing planning applications.

The basic problem encountered in feature extraction is entitiy growing. Recall that a feature recognizer is only capable of locating some of the surfaces of a volumetric feature. For instance, when we reorganize a slot in the first step of the case in 9.6, we find three of the six faces of the slot volume. Somehow the three missing ones must be found as well. Moreover, after the three slot faces gave been removed from the model, the ramaining gaps must be filled.

(Parametric and Feature-Based CAD/CAM: concepts, techniques and applications; Jami J. Shah, Martti Mantyla; page 327)

BACKWARD GROWING

Old:

The backward growing approach reverses the machining/removal process by growing properly machined volume/feature back to other machined face(s) (Figure 5.6). Basic cavity features were generated, and compound and protrusion features were decomposed into basic ones by adding surrounding materials. During the growing procedure, manufacturing parameters, such as types of basic elementary machined shapes, tool approach directions, precedence between recognized features, refined features, and intermediate work piece specifications/shapes may also be determined.

(Xun Xu, Integrating Advanced Computer-Aided Design, Manufacturing, and Numerical Control: Principles and Implementations, p.98-99)

New:

Wang developed the concept of backward growing by reversing the process of machining operations. To determine the cavity shape, the method looks for a set of concavely connected faces, oblique faces, or circular faces that are machined faces. Because each machined face is the result of the machining operation on the part, these faces can be the candidate of the growing bse faces. This method uses a set of concave faces of a depression feature to create the feature volume in order to decompose the delta volume as well as protrusion feature into the basic feature.

(Engineering Design and Rapid Prototyping; Ali K. Kamrani, Emad Abouel Nasr; page 241)