Elif Naz Aladağ 1st week

The Bill of Materials

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)

Robust Design

A robust design, process, or system is one that continues to function within acceptable parameters despite variabilities (often unanticipated) in its environment. In other words, its outputs (such as its function and performance) have minimal sensitivity to its input variations (such as environment, load, and power source). In addition, robustness refers to a product or machine performance being insensitive to tolerance changes that should not deteriorate significantly over its intended life.

For example, in a robust design, a part will function sufficiently well even if the loads applied (or their directions) go beyond anticipated values.

As a simple illustration of robust design, consider a sheet-metal mounting bracket to be attached to a wall with two bolts (Fig. 36.1a.). The positioning of the two holes on the bracket will include some error due to the manufacturing process involved. This error then will prevent the top edge of the bracket from being perfectly horizontal.

(Kalpakjian S., Schmid S.R., Manufacturing Engineering And Technology, p. 1116)

Total Productive Maintenance

The management and maintenance of a wide variety of machines, equipment, and systems are among the important aspects affecting the productivity of a manufacturing organization.The concepts of total productive maintenance (TPM) and total productive equipment management (TPEM) include continued analysis of such factors as (a) equipment breakdown and equipment problems; (b) monitoring and improving equipment productivity; (c) implementation of preventive and predictive maintenance; (d) reduction of setup time, idle time, and cycle time; (e) full utilization of machinery and equipment and the improvement of their effectiveness; and (f) reduction of product defects. Teamwork is an important component of this activity and involves the full cooperation of the machine operators, maintenance personnel, engineers, and the management of the organization.

(Kalpakjian S., Schmid S.R., Manufacturing Engineering And Technology, p. 1153)

Holonic Manufacturing

Holonic manufacturing is a new concept describing a unique organization of manufacturing units. The word holonic is from the Greek holos (meaning whole) and the suffix on (meaning a part of). Thus, each component in a holonic manufacturing system (at the same time) is an independent entity (or whole) and a subservient part of a hierarchial organization. We describe this system here because of its potential beneficial impact on computer-integrated manufacturing operations.

Holonic organization systems have been studied since 1960s, and there are a number of examples in biological systems. Three fundamental observations of these systems can be stated as:

1. Complex systems will evolve from sipmle systems much more rapidly if there are stable intermediate forms than if there are none. Also, stable and complex systems require a hierarchial system for evolution.

2. Holons simultaneously are self-contained wholes to their subordinated parts and the dependent parts of other systems. Holons are autonomous and selfreliant units, which have a degree of independence and can handle contingencies without asking higer levels in the hierarchial system for instructions. At the same time, holons are subject to control from multiple sources of higher system levels.

3. A holarchy consists of (a) autonomous wholes in charge of their parts and (b) dependent parts controlled by higher levels of a hierarchy and (c) are coordinated according to their local environment.

(Kalpakjian S., Schmid S.R., Manufacturing Engineering And Technology, p. 1224)