16-05-2012, 04:23 PM
ORTHOGONAL MACHINING
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BACKGROUND:-
Machining can be defined as the process of removing material from a workpiece in the form of chips by a sharp cutting to leave the desired part shape. The predominant cutting action in machining involves shear deformation of the work-piece to form a chip; as the chip is removed, a new surface is exposed. A typical machining process is illustrated figure below.
Orthogonal cutting uses a wedge-shaped tool in which the cutting edge is perpendicular to the cutting direction. As the tool is forced into the material, the chip is formed by shear deformation along shear plane oriented at an angle Φ (shear angle) with the surface of the workpiece. Along the shear plane, plastic deformation of the work material occurs.
Orthogonal machining is not used for commercial purpose. It is rather used for research and study process in machining. In commercial machining purposes its counterpart, Oblique Machining is used.
APPPLICATIONS:-
The most common use is to machine straight, flat surfaces, but with ingenuity and some accessories a wide range of work can be done. Other examples of its use are:
Keyways in the boss of a pulley or gear can be machined without resorting to a dedicated broaching setup.
Dovetail slides
Internal splines
Keyway cutting in blind holes
Cam drums with toolpaths of the type that in CNC milling terms would require 4- or 5-axis contouring or turn-mill cylindrical interpolation
It is even possible to obviate wire EDM work in some cases. Starting from a drilled or cored hole, a shaper with a boring-bar type tool can cut internal features that don't lend themselves to milling or boring (such as irregularly shaped holes with tight corners).
AIM:-To understand the basic mechanics of chips formation. Study the effect of rake angle, material system and the depth of the cut on the process.
METHOD DESCRIPTION:-The method of orthogonal machining will be performed using shaper ont two types of materials, that are, Aluminium and Plastic.
Mount the aluminium work piece in the vise and set to cutting tool angle (rake angle) to 10º.
Bring the tool in touch to the surface of the work piece. And set this mark at zero on vertical scale.
For a given rpm of ram vary the depth of tool for three divisions.
Vary the rpm of ram for three different speeds.
Collect the chip and measure the thickness with the vanier calipers.