Metin Atmaca 030080007 2nd week definitions

1. Bill of Materials (BOM) (Organization):

Previous Definition:

Since manufacturing cost estimation is fundamental to DFM, it is useful to keep this infotmation well organized. Exhibit 11-6 shows an information system for recording manufacturing cost estimated. It basically consists of a bill of materials (BOM) augmented with cost information. The BOM is a list of each individual component in the product. Frequently the BOM is created using an indented format in which the assembly "tree structure" is illustrated by the indentation of components and subassembly names.

The columns of the BOM show the cost estimates broken down into fixed and variable costs. The variable costs may include materials, machine time, and labor. Fixed costs consist of tooling and other nonrecurring expenses (NRE) such as specialized equipment and one-time setup costs. The tooling lifetime is used to compute the unit fixed cost (unless the tool's expected lifetime exceeds the product's lifetime volume, in which case the lower product volume is used). To compute total cost, overhead is added according to the firm's accepted cost accounting sheme. Note that additional fixed costs, such as depreciation of capital equipment used for several products, are often also included in the overhead charge.

(Kalpakjian S., Schmid S.R., Manufacturing Engineering And Technology, p. 215)

New Definition (better):

The bill of material (BOM) is a list of the materials (including quantities) needed to make a product. The BOM for a 500-pound batch of the NRG-A or NRG-B bars is shown in Figure 4-16.

Figure 4-16

The BOM for Fitter Snacker’s NRG bars is fairly simple because all ingredients are mixed together to form the dough; there are no intermediary steps. To produce many other products, however, component parts are joined into subassemblies that are then joined to form the finished product. It is obviously more complicated to calculate the raw material requirements for products with more complex BOMs.

The BOM can be used to calculate how much of each raw material is required to produce a finished product. Determining the timing and quantity of purchase orders, however, requires information on lead times and lot sizing.

For example, if a manufacturer orders a make-to-stock item, the lead time is the cumulative time required for the supplier to receive and process the order, take the material out of stock, package it, load it on a truck, and deliver it to the manufacturer. The manufacturer might also include the time required to receive the material in its warehouse (unloading the truck, inspecting the goods, and moving the goods into a storage location).

(E. Monk, B. Wagner, Concepts in Enterprise Resource Planning, p. 97)

2. Agile Manufacturing (Organization of Manufacturing)

Previous Definition:

Agile Manufacturing is a term indicating the implementation of the principles of lean production on a broad scale. The principle behind agile manufacturing is ensuring agility (hence flexibility) in the manufacturing enterprise, so that it can respond rapidly to changes in product demand and customers needs.

(Kalpakjian S., Schmid S.R.,Manufacturing engineering and technology, p. 37-38)

New Definition (Better):

Agile manufacturing is an emerging concept, which is adopted to improve the competitiveness of firms. It is more pragmatically defined and closely associated with quick response. Manufacturing enterprises adopting the agile concept are characterised by customer−supplier integrated processes for product design, manufacturing, marketing and support services. This requires stable unit cost, flexible manufacturing, easily accessible integrated data, modular production facilities and decision making at functional levels. Agility connects the interface between the company and the market. Essentially, it is a set of abilities for meeting widely varied customer requirements in terms of price, specification, quality, quantity and delivery. Agility has been expressed as having four underlying principles:

1. delivering value to the customer;

2. being ready for change;

3. valuing human knowledge and skills; and

4. forming virtual partnerships.

(Lihui Wang, S. C. Lenny Koh, Enterprise Networks and Logistics for Agile Manufacturing, p. 209)

3. Optical Detectors (Automation):

Previous Definition:

Before any evaluation of the information that the received light carries can start, it has to be transformed into electrical signals. All processes in which light incident onto a surface produces a current or a voltage are therefore processes around which optical detectors can be designed. The most important of these processes is the photoeffect upon which the working principles of different types of detectors are based.

(Jörg Haus, Optical sensors: basics and applications, Weinheim : Wiley-VCH, c2010 pg27)

New Definition (Better):

BASIC INFORMATION ON LIGHT DETECTORS

When light strikes special types of materials, a voltage may be generated, a change in electrical resistance may occur, or electrons may be ejected from the material surface. As long as the light is present, the condition continues. It ceases when the light is turned off. Any of the above conditions may be used to change the flow of current or the voltage in an external circuit and thus may be used to monitor the presence of the light and to measure its intensity.

A. Role of an optical detector

Many photonics applications require the use of optical detectors to measure optical power or energy. In laser-based fiber optic communication, a detector is employed in the receiver. In laser materials processing, a detector monitors the laser output to ensure reproducible conditions. In applications involving interferometry, detectors are used to measure the position and motion of interference fringes. In most applications of light, one uses an optical detector to measure the output of the laser or other light source. Thus, good optical detectors for measuring optical power and energy are essential in most applications of photonics technology.

Optical detectors respond to the power in the optical beam, which is proportional to the square of the electric field associated with the light wave. Optical detectors therefore are called “square-law detectors.” This is in contrast to the case of microwave detectors, which can measure the electric field intensity directly. All the optical detectors that we will describe have square-law responses.

Detection and measurement of optical and infrared radiation is a well-established area of technology. This technology has been applied to photonics applications. Detectors particularly suitable for use with lasers have been developed. Some detectors are packaged in the format of power or energy meters. Such a device is a complete system for measuring the output of a specific class of lasers, and includes a detector, housing, amplification if necessary, and a readout device.

B. Types of Optical Detectors

Optical detectors are usually divided into two broad classes: photon detectors and thermal detectors. In photon detectors, quanta of light energy interact with electrons in the detector material and generate free electrons. To produce free electrons, the quanta must have sufficient energy to free an electron from its atomic binding forces. The wavelength response of photon detectors shows a long-wavelength cutoff. If the wavelength is longer than the cutoff wavelength, the photon energy is too small to produce a free electron and the response of the photon detector drops to zero.

Thermal detectors respond to the heat energy delivered by light. These detectors use some temperature-dependent effect, like a change of electrical resistance. Because thermal detectors rely on only the total amount of heat energy reaching the detector, their response is independent of wavelength.

(Jack Ready, Optical Detectors and Human Vision, p. 214)

4. Reverse Engineering (Manufacturing Process)

Previous Definition:

Reverse engineering is the process extracting the knowledge or design blue-prints anything man-made. The concept has been round since before computers or modern technology, and probably dates back to the days of the industrial revolution.

(Reversing: Secrets of reverse engineering, p. 3)

New Definition (better):

Reverse engineering (RE) is a process of measuring, analyzing, and testing to reconstruct the mirror image of an object or retrieve a past event. It is a technology of reinvention, a road map leading to reconstruction and reproduction. It is also the art of applied science for preservation of the design intent of the original part.

Reverse engineering is a practice of invention based on knowledge and data acquired from earlier work. It incorporates appropriate engineering standards and multiple realistic constraints. The part produced through reverse engineering should be in compliance with the requirements contained in applicable program criteria.

(Wego Wang, Reverse Engineering: Technology of Reinvention, p. 1)

5. CMM Coordinate Measuring Machine (Manufacturing Tool):

Previous Definition:

The coordinate measuring machine (CMM) is the most prominent example of the equipment used for contact inspection of parts. When used for CIM these machines are controlled by CNC. A typical three-dimensional measuring machine consists of a table, which holds the part in a fixed, position, and movable head, which holds a sensing, probe. The probe can be moved in three directions corresponding to the X, Y and Z Coordinates. For manual operation, the control unit is provided with joysticks, or other devices which drive X, Y and Z servo motors (AC/DC).

(CAD/CAM/CIM Radhakrishnan P., Subramanyan S., Raju V., 3rd edition, p510)

New Definition (better):

A coordinate measuring machine (CMM) is an electromechanical system designed to perform coordinate metrology. A CMM consists of a contact probe that can be positioned in three-dimensional (3-D) space relative to the surfaces of a workpart; and the x, y, and z coordinates of the probe can be accurately and precisely recorded to obtain dimensional data concerning the part geometry.

To accomplish measurements in 3-D, a basic CMM is composed of the following

components:

• probe head and probe to contact the workpart surfaces

• mechanical structure that provides motion of the probe in three Cartesian axes and

displacement transducers to measure the coordinate values of each axis

In addition, many CMMs have the following components:

• drive system and control unit to move eaeh of the three axes

• digital computer system with application software

(Gavriel Salvendy, Automation, Production Systems and CIM, p. 724)