Forces experienced by a tool during cutting is detrimental in design of mechanical structure of cutting machine, predicting power consumption, determining the tool life and increasing the productivity. In this video lecture we will analyse how to predict cutting forces using Merchant's circle analysis.
Summary of above lecture is described in following sections
Why Cutting Force Analysis is Important ?
Most of the time cutting force acting on a tool is measured experimentally. But it is also important to predict quantity of cutting force and how different cutting parameters are affecting cutting force even before setting up the machining operation due to following reasons.
- In order to design of mechanical structure of cutting machine which will withstand cutting force and thrust force effectively.
- To determine power consumption during machining process. This will help in selecting suitable motor drive.
- To predict tool life.
- To increase productivity
The following figure describes important terminologies used in cutting force analysis.
|Fig.1 A tool under orthogonal cutting operation|
Forces Acting on the chip
If you make a free body analysis of the chip, forces acting on the chip would be as follows.
|Fig.2 Forces acting on the chip on tool side and shear plane side|
Merchant's Circle Analysis
Steps involved in Merchant's circle analysis is as follows. Since we know angle of resultant force at tool side, draw a line parallel to this. On one end of this line draw shear force(Fs), magnitude and direction of which is known. Now draw a line perpendicular to shear force line, it will meet resultant force line at one point. You can draw a circle assuming the intersected line as diameter of the circle, this is known as Merchant's circle. It is shown in figure below.
|Fig.3 Construction of Merchant's circle|
|Fig.4 Determination of cutting force and thrust force using Merchant's circle diagram|