Selection of optimum cutting parameters for CNC machining

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By M. KRISHNAMOORTHY

Role of cutting tools and optimum machining parameters:

Right selection of cutting tools and cutting parameters is extremely important in CNC Machining.  Today CNC machine tools come with host of features like high spindle power, higher spindle speed (RPM), re circulating ball screws for accurate & fast movements, powerful CNC controller, etc.., In similar lines, latest cutting tools are able to sustain toughest cutting conditions based on their material, geometry, etc.,

However, majority of CNC machines are under utilised due to various reasons including fear of machine abuse, failure of machine sub systems, breakage of cutting tools, etc., This leads to poor productivity and improper resource utilisation. Knowledge in types of tools, insert geometry, selection criteria of tools, selection of cutting parameters, optimising parameters in actual machining will help in enhancing productivity as well as optimum resource utilisation.

Machining parameters:

Basic machining parameters in CNC machining are the spindle speed, feed and depth of cut. Though the rule of thumb is to choose the maximum depth of cut, highest possible feed and optimum spindle speed, selection of these parameters has to be based on the following factors:

  • Work piece material viz. Steel, cast iron, Al alloy, etc.,
  • Tool insert material viz. carbide, ceramics, CBN, PCD, etc..,
  • Spindle power available in machine tool
  • Insert shape viz. round, rhombus, tri angular, V type, etc.,
  • Insert geometry viz. positive rake vs negative rake, etc.,
  • Tool holder type and rigidity
  • work holding method

Knowledge in each of the above is essential for arriving at the right combination of machining parameters for a given set of machining conditions.

System approach for CNC Machining:

Thus the entire machining needs to be considered as a system or chain where multiple elements are closely interlinked viz. CNC Machine tool, cutting tools & holders, CNC Programme, work holding & fixturing, measuring equipment. User needs to be thorough in each area with a holistic approach towards CNC machining in order to get optimum output. Today, effective utilisation of resources is the key to realise ever growing need for higher productivity, Quality, Cost and Delivery (PQCD). 

Training at IMTMA:

Indian Machine Tool Manufacturers’ Association (IMTMA) is organizing an exclusive hands on course “FINISHING SCHOOL IN PRODUCTION ENGINEERING at IMTMA Technology Centre, Bangalore & Pune to enhance skill sets of engineers and supervisors from manufacturing industries. This 4 weeks duration course is totally practical oriented with Hands on practice in production CNC machines, CAD/CAM, Metrology equipment, Tooling & work holding systems and other accessories.

This course enables engineers to achieve Productivity and Quality improvement in their own projects, with in say 3 months by implementing some of the key learnings.