Principle

In machining or metal cutting, relative velocity between cutting tool and workpiece is mandatory in order to cut (shear off) excess material from workpiece to get desired shape, size, finish and tolerance. Every machining process requires three relative motions namely cutting velocity, feed rate and depth of cut. Such motions are imparted in several ways in various directions depending on the process and requirement. For example, in straight turning operation in Lathe, cutting velocity, feed rate and depth of cut are given in three mutually perpendicular directions.

Estimating and determining the performance of machining operation for a particular combination of work-tool material under specific set of process parameters and working conditions are indispensably necessary in order to check the feasibility of machining as well as to plan a process as per the requirement. There exist a number of parameters to judge one machining process; however, all of them may not be applicable for every case. A list of various responses that determine overall performance is enlisted below.

  • Cutting force
  • Specific cutting energy
  • Power consumption
  • Material removal rate
  • Surface finish and surface integrity
  • Level of burr
  • Cutting temperature
  • Type and color of chip
  • Tool wear
  • Tool life
  • Machining time

Cutting parameters – speed, feed & depth of cut

Process parameters in machining are all those parameters that are inherent to any machining operation and should have a suitable finite value to smooth and efficient removal of materials. Such parameters directly affect machining performance. In machining, three process parameters are (i) cutting speed or cutting velocity, (ii) feed rate and (iii) depth of cut. Their functions, effects, calculation, typical values, units, etc. are provided here. Difference between cutting speed and cutting velocity is also explained here. Browse all articles.

Quality of machined surface

Characteristics of a machined surface are defined by three features – surface roughness, surface finish and surface integrity. Overall quality of machined surface depends on a large number of factors. This section gives a topic list for assessing quality using mathematical expressions, direct measurement using instruments, possibility of improvement and several differences. Browse all articles.