Berk Korucu - 030080104 - 3rd Week

1) B spline (Modelling)


Previous Definition 


B spline surface

The same tensor product method used with Bezier curves can extend B-splines to describe B-spline surfaces. A rectangular set of data (control) points creates the surface. this set forms the vertices of the characteristic polyhedron that approximates and controls the shape of the resulting surface. 

(CAD/CAM Theory and Practice, İbrahim Zeid, McGraw Hill. 1991, p300.)

New Definition (Better)

B-Spline Curves

Most shapes are simply too complicated to define using a single B´ezier curve. A spline curve is a sequence of curve segments that are connected together to form a single continuous curve. For example, a piecewise collection of B´ezier curves, connected end to end, can be called a spline curve. Overhauser curves are another example of splines. The word “spline” can also be used as a verb, as in “Spline together some cubic B´ezier curves.

We know from basic structures theory that the bending moment M is an infinitely continuous function along the spline except at a duck, where M is generally only C 0 continuous. Since the curvature of the spline is proportional to M (κ = M/EI), the spline is everywhere curvature continuous.

While C 1 continuity is straightforward to attain using B´ezier curves (for example, popular design software such as Adobe Illustrator use B´ezier curves and automatically impose tangent continuity as you sketch), C 2 and higher continuity is cumbersome. This is where B-spline curves come in. In practical terms, B-spline curves can be thought of as a method for defining a sequence of degree n B´ezier curves that join automatically with C n−1 continuity, regardless of where the control points are placed.

Whereas an open string of m B´ezier curves of degree n involve nm + 1 distinct control points (shared control points counted only once), that same string of B´ezier curves can be expressed using only m + n B-spline control points (assuming all neighboring curves are C n−1 ). The most basic operation you need to understand about B-splines is how to extract the contituent B´ezier curves. That understanding will provide you with a good working knowledge of B-spline curves.

(W. Sederberg, An Introduction to B-Spline Curves, p1)


2) On Machine Inspection (OMI) (Quality)


Previous Definition

In recent years there has been a significant growth in the use of tactile probes as on line inspection systems in CNC machining center applications. Called ''On Machine Inspection'', the probes in these systems are mounted in toolholders, inserted into the machine tool spindle stored inthe tool drum, and handled by hte automatic tool changer in the same way that cutting tool are handled. When the probe is mounted in the spindle, the machine tool is controlled very much like a CMM. sensors in the probe determine when contract has been made with the part surface. Signals from the sensor are transmitted to the controoller that performs the required data processing to interpret an utilize the signals.

( Automation, production systems, and computer-integrated manufacturing, Mikell P. Groover, p.678)

New Definition (Better)

 After a machine tool cuts the part, a laser will scan it for dimensional informa t ion  tha t   i s   c aptur ed  and downloaded to the CNC. Within the CNC will be an interfaced statistical process control software program that downloads the dimensions. If any of the part’s dimensions are trending away from preset tolerances, the program will make the necessary offsets to the cutting program or alert the operator. Then the SPC program will command
the machine’s CNC program to check the tooling to make sure it isn’t broken or experiencing excessive wear. Also, if needed, the SPC data will be shared with a central computer and sent throughout the plant or even to a location thousands of miles away. This is all done within seconds, making onmachine QC inspection the most efficient way to check a part.


( C. Russell, Controlling Quality, p7)




3) Process-Focused Production System: (Management)


Previous Definition (Better)

The term process-focused is used to describe a form of production in which production operations are grouped according to type of processes. In other words, all production operations that have similar technological processes are grouped together to form a production department. For example, all production operations throughout a factory that involve painting are grouped together in one location to form a painting department.

Process-focused production systems are also sometimes known as intermittent production or job shops. They are referred to as intermittent production because is performed on products intermittently, that is, on a start-and-stop basis. Product-focused production systems are also commonly referred to as job shops because products move from department to department in batches (jobs) that are usually determined by customer orders.

(Production and Operations Management, Norman Gaither, Page 132) 





New Definition



The fundamental integration phase in the design of productive systems is the layout of  production facilities.  A working definition of layout may be given as the arrangement of machinery and flow of materials from one facility to another, which minimizes materialhandling costs while considering any physical restrictions on such arrangement. Usually this layout design is either on considerations of machine-time cost and product availability; thereby making the production system product-focused; or on considerations of quality and flexibility; thereby making the production system process-focused. It is natural that while product-focused systems are better off with a ‘line layout’ dictated by available technologies and prevailing job designs, process-focused systems, which are more concerned with job organization, opt for a ‘functional layout’. Of course, in reality the actual facility layout often lies somewhere in between a pure line layout and a pure  functional layout format; governed by the specific demands of a particular production plant.


(M. Khoshnevisan, Optimal Plant Layout Design for Process-focused Systems, p2)






4) Acceptance Sampling (Quality)


Previous Definition (Better)

Acceptance sampling consists of taking only a few random samples from a lot and inspecting them to judge whether the entire lot is acceptable or whether it should be rejected or re-worked. Developed in the 1920’s and used extensively during WW2 for military hardware (MIL STD 105), this statistical technic is widely used valuable.

Acceptance sampling is particularly useful for inspecting high-production-rate parts where % 100 inspections would be too costly. There certain critical devices, however (such as pace makers, prosthetic devices, and components of the space shuttle), which must be inspected %100. (Kalpakjian, Smith; Manufacturing Engineering and Technology 4^thEdition; pg. 991)

New Definition

A large supermarket sells prepacked sandwiches in its food department. The sandwiches are bought in large batches from a catering firm. The supermarket manager wishes to test the sandwiches to make sure they are fresh and of good quality. She can test them only by unwrapping them and tasting them. After the test it will no longer be possible to sell them. She must therefore make a decision as to whether or not the batch is acceptable based on testing a relatively small sample of sandwiches. This is known as acceptance sampling.

( A. Fuller, Sampling Techniques, p167)

5) Use Value

Previous Definition

Use value is the ability of an object to satisfy a human want. In Larocque's case, the two individuals with whom he traded probably set different use values on horses, as well as on the trade goods they were to recieve in exchange.

( Charles E Orser Jr., A Historical Archaelogy of The Modern World, Plenum Press, 1996, p.114 )

New Definition (Better)

Use value: It is the lowest cost of providing for the reliable performance of a function.

( T. Wilson, S. Jantrania, Understanding the Value of a Relationship, p60)