08-12-2012, 03:38 PM
Advanced Manufacturing Choices
Advanced Manufacturing.ppt (Size: 9.52 MB / Downloads: 614)
Manufacturing Types
Manufacturing dominates world trade. It is the main wealth creating activity of all industrialized nations and many developing nations. A manufacturing industry based on advanced technologies with the capability of competing in world markets can ensure a higher standard of living for an industrial nation (McKeown, 1996).
Where primary manufacturing processes involve casting* and molding*, secondary manufacturing processes constitute the main mechanical removing techniques involving turning, drilling and milling. Abrasive processes to super-finish a work-piece are called tertiary manufacturing processes. Casting*/molding*: The act or process of making casts or impressions, or of shaping metal or plaster in a mold; the act or the process of pouring molten metal into a mold.
Mechanical Machining
In mechanical removal processes, stresses induced by a tool overcome the strength of the material.
The process produces complex 3D shapes, with very good dimensional control, and good surface finishes.
The method is wasteful of material, and expensive in terms of labor and capital.
How well a part made from a given material holds its shape with time and stress is referred to as the dimensional stability of the part and the material.
Mechanical Energy Based Removing
What is milling? The use of a rotating multi-point cutting tool to machine flat surfaces, slots, or internal recesses into a work-piece.
Milling is one of the more versatile machining processes. There are three degrees of freedom associated with milling. The tool can move up and down, left to right, and front to back. In this process the tool spins while the part remains stationary. Although milling is a more versatile process than turning or grinding, it is not as accurate and tends to leave a rougher surface finish than the other two processes.
What is turning ? Turning is the machining operation that produces cylindrical parts. In its basic form, it can be defined as the machining of an external surface with the work-piece rotating and with a single-point cutting tool.
Mechanical Energy Based Removing
Grinding is a finishing process that is used to remove surplus material from the work-piece surface. It is usually used on almost any surface that has been previously rough machined and is among the most expensive process for it is generally quite slow in removing material.
Precision Machining
Mechanical engineers define precision machining as machining in which the relative accuracy (tolerance/object size) is 10–4 or less of a feature/part size
For comparison, a relative accuracy of 10–3 in the construction of a house is considered excellent. It is important to realize that, while IC techniques and silicon micro- and nano-machining can achieve excellent absolute tolerances, relative tolerances here are rather poor compared to those achieved by most mechanical machining techniques.
The decrease in manufacturing accuracy with decreasing size is rarely mentioned in discussions of Si micro-machines; this probably is because Si micromachining originated from electrical engineering practice rather than mechanical engineering.
Ultra Precision Machining-Nanotechnology
Taniguchi coined the term nanotechnology and in 1974, used the term to define ultra-precision machining.
Taniguchi defines ultra-precision machining as “the process by which the highest possible dimensional accuracy is achieved at a given point in time.”
Norio Taniguchi predicted accuracies along with the processes or tools used to achieve it (next page)