Material removal by traditional machining operations has always been the workhorse of manufacturing industry. In this video lecture we will learn how to analyse a single point orthogonal cutting operation.
Detailed description of above video lecture is given below.
Cutting Force and Thrust Force During Cutting
During an orthogonal cutting operation material is removed from the work piece with help of cutting force. Along with that, a thrust force, which is normal to cutting direction is also induced. The thrust force could be either upward, or downward.
|Fig.1 Cutting force,Fc and thrust force,Ft induced in an orthogonal cutting operation|
Material Removal by Shearing - Shear Plane Theory
If you take a close look at cutting operation it will be evident that, material is getting removed from work piece by shearing action. Where different layers of atoms slip one another to form chip. This is why there is a change in chip thickness from uncut to cut chip. In actual case this shearing mechanism happens in a region called shear zone.
|Fig.2 Material removal happens because of shearing action happens in shear zone|
|Fig.3 According to shear plane theory shearing action occurs all of a sudden at shear plane|
Determination of Shear Angle - Merchant Analysis
But what is the orientation of shear plane ?. That is the big question in machining analysis. It could be at any angle during a particular machining operation. As explained in this figures. As shear angle decreases thickness of the chip increases.
|Fig.4 Increase of chip thickness with decrease in sear angle for same cutting operation|
Since material flow before, and after cutting operation is same we can write.