Unconventional Machining Processes 14AU9132- Fast Track Course Unconventional Machining Processes Dr.Karthick Jayaram Associate Professor, MCET

Introduction Manufacturing Technology I Metal casting (Sand casting and other casting processes) Bulk deformation (Metal Forming – Forging, Rolling, Extrusion) Manufacturing of plastic materials (Injection molding, etc). Manufacturing Technology II (Material removal process) Metal Cutting or Mechanical Abrasion Shaper, Planer, Slotter, Milling, Drilling, Broaching, Gear cutting, etc. Grinding, Honing, Lapping, etc. CNC and DNC

Introduction – Contd. Machining – produces finished products with high degree of accuracy. Conventional machining Utilizes cutting tools (harder than workpiece material). Needs a contact between the tool and workpiece. Needs a relative motion between the tool and workpiece. Absence of any of these elements – makes the process a unconventional or nontraditional one. Big boon to modern manufacturing industries. The need for higher productivity, accuracy and surface quality – led to combination of two or more machining actions, called hybrid machining processes.

History of Machining In ancient days – hand tools (stones, bones or stick). Later – hand tools of elementary metals (bronze or iron) Till 17th Century – tools were either hand operated or driven mechanically by very elementary methods. Wagons, ships, furniture, etc. – were produced. Introduction of water, steam and electricity – power driven machine tools Caused a big revolution in 18th and 19th centuries. 1953 – Numerical control machine tools – enhanced the product productivity and accuracy.

Traditional or Conventional Machining

Metal Cutting Processes

Abrasive Machining Cylindrical grinding Flat surface grinding

Abrasive Machining Centreless grinding

Machining Accuracies 100 -1 microns 1 -0.01 microns 0.1 -0.001 microns Micro-turning and Micro-Milling M/C 0.1 -0.001 microns

Classification of all Material Removal Processes Area of interest

Need for Unconventional Machining Greatly improved thermal, mechanical and chemical properties of modern materials – Not able to machine thru conventional methods. (Why???) Ceramics & Composites – high cost of machining and damage caused during machining – big hurdles to use these materials. In addition to advanced materials, more complex shapes, low rigidity structures and micro-machined components with tight tolerances and fine surface finish are often needed. To meet these demands, new processes are developed. Play a considerable role in aircraft, automobile, tool, die and mold making industries.

Need for Unconventional Machining Very high hardness and strength of the material. (above 400 HB.) The work piece is too flexible or slender to support the cutting or grinding forces. The shape of the part is complex, such as internal and external profiles, or small diameter holes. Surface finish or tolerance better than those obtainable conventional process. Temperature rise or residual stress in the work piece are undesirable.

Unconventional Machining Processes - Classification Electrical 14 14

Mechanical Based Processes AJM WJM AWJM USM Working principles Equipment used Process parameters MRR Variation in techniques used Applications

Electrical Based Processes Working principle Equipment used Process parameters Surface finish & MRR Electrode/Tool Power & Control circuits Tool wear Dielectric Flushing Applications Electrical EDM WEDM 16 16

Chemical & Electrochemical Based Processes CHM ECM ECG ECH Working principles Etchants & Maskants Techniques of applying maskants Process parameters Surface finish & MRR Electrical circuits in case of ECM Applications 17 17

Thermal Based Processes LBM PAM EBM Working principles Equipment used Types Beam control techniques Applications 18 18

Mechanical based Unconventional Processes USM – thru mechanical abrasion in a medium (solid abrasive particles suspended in the fluid) WJM – Cutting by a jet of fluid AWJM – Abrasives in fluid jet. IJM – Ice particles in fluid jet. Abrasives or ice – Enhances cutting action.

Thermal based Unconventional Processes Thru – melting & vaporizing Many secondary phenomena – surface cracking, heat affected zone and striations. Heat Source: Plasma – EDM and PBM. Photons – LBM Electrons – EBM Ions – IBM Machining medium: different for different processes.

Chemical & Electrochemical based Unconventional Processes CHM – uses Chemical dissolution action in an etchant. ECM – uses Electrochemical dissolution action in an electrolytic cell.

Classification of UCM Tip Remember

Mechanical Based Processes AJM WJM AWJM USM Working principles Equipment used Process parameters MRR Variation in techniques used Applications

Introduction to Abrasive Jet Machining (AJM) In AJM, the material removal takes place due to impingement of the fine abrasive particles. The abrasive particles are typically of 0.025mm diameter and the air discharges at a pressure of several atmosphere.

AJM

Waterjet and Abrasive Waterjet (AWJ) Cutting

Abrasive Waterjet and Waterjet examples

Mechanics of AJM Abrasive particle impinges on the work surface at a high velocity and this impact causes a tiny brittle fracture and the following air or gas carries away the dislodged small work piece particle.

Ultrasonic Machining

Ultrasonic grinding https://www.youtube.com/watch?v=fEvo5jarIW4 https://www.youtube.com/watch?v=-fLz4B8vg20

Basics of the USM process The basic USM process involves a tool ( made of a ductile and tough material) vibrating with a very high frequency and a continuous flow of an abrasive slurry in the small gap between the tool and the work piece. The tool is gradually fed with a uniform force. The impact of the hard abrasive grains fractures the hard and brittle work surface, resulting in the removal of the work material in the form of small wear particles. The tool material being tough and ductile wears out at a much slower rate.

Classification of UCM Tip Remember

Schemes of UCM Process Tip Remember