Oğuzhan Paçal, 030070031, 10th week

Laser Hardening: 00:17 14.04..2011
In conventional methods of heat treatment, the component is heated to the required temperature and then quenched in oil or water to achieve the desired hardness at the surface. In most industrial applications, wear occurs only in selected areas of the component. Rapid advances in laser technology in the past decade have made it possible to perform various operations such as heat treating, glazing, alloying, and cladding on surfaces of materials, resulting in better physical properties of the surface and improved performance in a given enviroment. Because a laser is an expensive source of energy, it is used only in cases where it offers some technical or economic benefits compared to conventional methods. The advantage of using a laser for surface processing results from its highly directional nature and from the ability to deliver controlled amounts of energy to desired regions. In laser heat treatment, which involves using a laser as a heat source, the beam energy is applied to harden a surface with the rest of the component acting as a heat source, the beam energy is applied to harden a surface with the rest of the component acting as a heat sink. Because ferrous materials are very good heat conductors, the high heal fluxes generated by laser are most suitable to heat surface layer to austenitization levels without affecting the bulk temperature of the sample. The ensuing self-quenching is rapid enough to eliminate the need for external quenching to produce the hard martensite in the heated surface.Thus a highly wear resistant surface with the desired core properties of the component can be obtained.
(Joseph R. Davis, Surface Hardening of Steels: Understanding the Basics, p. 264)


Ancillary equipment 19:05 18/04/2011

Ancillary equipment is used to support primary plastics processing equipment. Typical ancillary equipment includes:

· Plenum hoppers

· Material loaders

· Material dryers

· Magnet systems

· Mixing systems

· Robots and part pickers

· Conveyors

· Granulators

· Mold temperature contorllers

While much has been written about primary processing of plastic materials to create plastic parts, very little has been written about ancillary equipment. Similarly, when manufacturers evaluate primary processing equipment for potential puchase, they usually conduct a through and extensive study; however, when it comes to purchasing ancillary equipment, too often few or no studies are conducted.

(Edward A. Muccio, Plastics Processing Technology, P.9)

Honing against a faceplate: 19:36 20/04/2011

Many parts have bores which cannot be honed to the required tolerances by any of the techniques like stacking, clapping or honing free hand. These parts may have extremely short bores (too short for honing one or two at a time), or may not have parallel ends to
allow stack honing. A good percentage of this work may have a flat face at one end of the bore and can be honed one part at a time while being pressed against a faceplate. This technique has been used for honing the straight, narrow sizing lands (at the ends of the tapered approach angles in drawing dies) square to the die base surface.Short blind holes are usually honed against a faceplate to hold squareness to the workpiece end and to increase stability. Any relief that can be premachined in the bottom of a blind hole will greatly facilitate honing; the longer the relief, the easier the honing. Relief allows over-stroking the blind end of the bore and avoids leaving a radius in the blind corner.

Preconditions for honing against a faceplate:

1. Suitable Honing Machine.

2. Workpieces must be "short", with a flat face.

3. Capacity to Eliminate Conical Mandrel Runout.

(Sunnen Procuts Co., Sunnen Honing Techniques, p.6) gh

Biomachining: 19:52 20/04/2011

Simple metallic components of prostheses can be machined from bar stock. Titanium and Co-Cr-Mo alloys are more difficult to machine than stainless steel, şn terms of cutting tool wear. The stock is usually obtained from forging, to achieve good internal properties, including strength, toughness and fatigue resistance. Intricate shapes such as the condyle of knee joint can be more economically produced by investment casting process, though internal porosity may reduce their reliability owing to lower strength and fatigue resistance. This may be improved by Hot Isostatic Pressing, which may however, take the cost to the same levels as that involved in machining.

The most important polymer used in medical applications is UMHWPE (ultra high molecular weight poly ethylene). These components for the knee are manufacture in one of two ways: machining from bar stock, or direct compression molding. The machining process can result in areas of high stress, which may eventually lead to breakdown of the polymer component. Direct compression molding provides a more uniform and harder surface, and gives a more durable component, but is economical only when the requirement is significant.

(Bopaya Bidanda, Bio-Materials and Prototyping Applications in Medicine, p.201)