Buğra Çetinkaya 030070094 2nd week definitions

1-FMEA (Failure Mode & Effect Analysis) (previous answer) (Group: Manufacturing)

Failure mode and effect analysis (FMEA) is an important technique that is widely used in industry, including the big three auto manufacturers for continuous product quality improvement to satisfy the needs of the customer. FMEA can be described as a systemized group of activities intended to:

- Recognize and evaluate the potential failure of a product/process and its effects

- Identify actions that could eliminate or reduce the chance of potential failure occuring

- Document the process

To implement FMEA, the following steps may be taken:

a- Identify problems.

b- Use flow process charts for understanding the problem.

c- Collect data.

d- Prioritize the problems to be studied. The ranking of priorities is based on the following:

RPN (risk priority number) = occurence x severity x detection

- Occurence: how often the failure occurs

- Severity: how serious the failure is

- Detection: how easy or difficult it is to detect the failure.

e- Use appropriate tools to analyze the problem.

f- Implement the suggestions.

g- Confirm and evaluate results

h- Repeat FMEA periodically.

[Nanua Singh; Systems approach to computer-integrated design and

manufacturing,1996 ; pages 368-369-370]

FMEA (Failure Mode & Effect Analysis) (new answer) (Group: Manufacturing)

The FMEA process is applied to each new product and to any major change of an existing product. The FMFA documents become an integral part of the product design documentation and are as such continuously updated.

The FMEA process is used to ensure that all problems that could possibly occur in the design, procurement and servicing of a product have been considered, documented, and analyzed.

In this regard, the Product Engineering organization has the responsibility for product performance criteria establishment, and product design and development, which includes consideration of manufacturability. Service-ability, and the user's potential misuse. The Manufacturing organization has the responsibility for the fabrication or purchase of a product to an engineering drawing and specification. The marketing. sales. and Service organization have the responsibility for technical support of the product after sale.

Accordingly, there are three independent FMEA documents dealing with the three different aspects of the process. The Design FMEA lists and evaluates the failures which could be experienced with a product and the effects these failures could have in the hands of an end user. The Manufacturing FNMA lists and evaluates the variables that could influence the quality of a particular process. The Service FMEA evaluates service tools and manuals to ensure that they cannot be misused or misrepresented. In the following, we deal with the Design FMEA procedure only.

Definition and FMEA Forms

The following definitions apply:

Failure mode: The manner in which a part or system fails to meet the design intent

Effect of failure: The experience the owner encounters as a result of a failure mode

Cause of failure: An indication of a design weakness

Cause prevention: The in place and scheduled design verifications and quality assurance inspections

Severity ranking: A subjective evaluation of the consequence of a failure mode on the end user

Occurrence ranking: A subjective estimate of the likelihood that if a detective part is installed it will cause the failure mode with its particular effect

Detection ranking: A subjective estimate of the probability that a cause of a potential failure will be detected and corrected before reaching the end user

Risk Priority Number: The product of severity, occurrence, and detection rankings

(Fred K. Geitner,Heinz P. Bloch, Maximizing Machinery Uptime, p.136)

 

2-CONWIP (Constant-Work-In-Process) (previous answer) (Group: Manufacturing)

Spearman et al. (1990) described a pull-based production system called constant work-in-process (CONWIP). In contrast to kanban cards, which are part number specific, CONWIP production cards are assigned to the entire production line. The advantage of this system over the kanban system is that it can be used in environments where the kanban system is impractical because of a large number of part types or significant setup times.

(Nanua Singh; Systems approach to computer-integrated design and manufacturing,1996)

CONWIP (Constant-Work-In-Process) (new answer) (Group: Manufacturing)

CONWIP is a "long-pull- production model that controls the WIP by control-ling orders released to the shop floor. This is an extension of the Kanban model. Instead of assigning a set of cards to each station, cards are introduced only at the beginning of the line in the CONWIP model. Furthermore, the total amount of work is upper bounded since a new part (or lot) is allowed to enter the system only if a part (Or lot) of the same type is completed, which results in releasing a card that is made available at the beginning of the line. Indeed, the total WIP is constant when the system is sufficiently loaded to work non-stop (thus the name CONWIP).

Consider an order arriving in the shop floor, see Figure 4.14. If they are enough available cards in the bulletin board located at the beginning of the production line, then the required cards are attached to the order and the product is processed by visiting all the stations successively.

Figure 4.14: A CONWIP model

 

Cards are released when the finished product leaves the last station and they are sent back to the bulletin board. In other words, the basic rule assigned to each station in a Kanban model applies to the whole line in the CONWIP model.

Once raw material enters the system, the material flows freely and naturally accumulates in front of the bottleneck station. In real-life situations, CONWIP systems are used for mixes of parts having different operation times on stations, and thus there are different bottleneck stations. It is easy to understand that there may be an opportunity to better balance the system than in a Kanban environment.

Two fundamental questions are at stake:

• How to manage the orders waiting at the entrance of the system (backlog) due to the fact that demands temporarily exceed the production capacity? A simple solution consists in applying a FM'S (first arrived. first served) policy, except if other priorities are imposed by management.

• How many cards of each type should be introduced at the beginning of a line? This number depends mainly on the following factors: the demand (forecasted if not steady), time spent by the lots in the stations (manufacturing time), the priority policy that applies between the first and the last station.

(Alexandre Dolgui,Jean-Marie Proth, Supply Chain Engineering: Useful Methods and Techniques, pp.154-155)

3-The Open System Interconnection (OSI) (previous answer) (Group: Design)

The open system interconnection (OSI) reference model proposed by the International Standard Organization (ISO) provides a framework for modeling communication protocols. This permits interoperability between dissimiliar systems. The ISO/OSI model divides the communication process into seven layers: the phsical layer, the data link layer, the network layer, the transport layer, the session layer, the presentation layer and the application layer.

[Nanua Singh; Systems approach to computer-integrated design and

manufacturing,1996 ; page 587]

The Open System Interconnection (OSI) (new answer) (Group: Design)

The OSI network model developed by the International Standards Organization (ISO) consists of seven layers of services. Each layer is responsible for handling a different aspect of network communication.

When sending data, each layer performs its processing on the data and passes it to the next lower layer. When receiving data, each layer performs its processing on the data and passes it to the next higher layer.

This layered approach allows different types of processing (services) to be developed without having to develop all layers of the model. The new service is linked into the "stack of layers" or protocol stack at the appropriate layer.

-Physical Layer: The first layer is concerned with the physical interface between devices. It controls the transmission of a hit stream over the physical medium and deals with the mechanical and electrical characteristics of the physical medium.

-Data Link Layer: The second layer provides error detection and control. It adds reliability to the physic-al layer by grouping bits into frames and providing svnchronization, error control, and flow control over the frames. Basically, it controls the transfer of data across a network media.

-Network Layer: The third laver is responsible for determining a path through the network between systems that want to communicate. It understands the data communication and switching technologies used to interconnect systems.

-Transport Layer: The fourth layer provides end-to-end error recovery and flow control. These services ensure that the data is delivered with-out errors and in sequence without duplication. -Session: 'Die fifth layer provides a control structure for communication between applications. It is responsible for establishing, maintaining, and terminating connections. 

-Presentation: The sixth layer is responsible for handling the differences in data representation or syntax. This layer maps data between formats so that the application can understand the data.

-Application: The seventh layer provides utilities used by humans including functionality such as remote 'wins, file transfers, and so on.

(Darrell Ambro,Ed Tittel, Solaris 9 System Administrator Certification, pp.220-221)

 

4-SQL (Structured Query Language) (previous answer) (Group: Design)

SQL is the standard query language for data manipulation in relational databases. The results produced by various operations are also represented as tables. The operation select chooses rows of a table based on criteria that is a condition expressed over the values of attributes in the table.

(Nanua Singh; Systems approach to computer-integrated design and manufacturing,1996 ; pg 604)

SQL (Structured Query Language) (new answer) (Group: Design)

SQL is a nonprocedural database programming language used to create databases, manipulate and retrieve data, and provide security to relational database structures. SQL is often referred to as nonprocedural because of the way it processes instructions. In contrast to high-level procedural computer languages such as Visual Basic and C+ +, which process instructions based on how to perform an operation, SQL processes instructions based on what operation to perform. For example, "what to retrieve", "what to insert," or "what to delete."

(Cecelia L. Allison,Neal Berkowitz, SQL for Microsoft Access, p.16)

 

5-Hierarchical Coding (previous answer) (Group: Design)
The structure of these codes is like a tree in which each symbol amplifies the information provided in the previous digit. The major advantage of hierarchical coding is that it captures a great deal of information in a relatively short code. The hierarchical nature of the code makes it useful for storage and retrieval of design-related information such as part geometry, material and size. The applicability of these codes in manufacturing is rather limited, as it is difficult to capture information on manufacturing sequences in a hierarchical manner. The disadvantage of this type code is that it requires expertise to conceive such a coding system for a part spectrum.
(Nanua Singh, Computer-Integrated Design and Manufacturing, pg:480)

Hierarchical Coding (new answer) (Group: Design)

It is also called monocode. In this code the interpretation of each succeeding digit depends on the value of preceding digit. Each symbol amplifies the information contained in the preceding digit. Therefore a digit code cannot be interpreted alone. The main advantages of this system are a short code contains large amount information. But it is complicated to apply in a computerized system.

 

(C. Elanchezhan,G. Shanmuga Sundar, Computer Aided Manufacturing, p.24)