Non-Traditional machining process and its classification

 Non-Traditional machining process?

Non-Traditional machining, also known as “non-conventional machining” or “modern machining method”, generally refers to the machining method of removing or adding materials with energy of Electricity, Heat energy, Light energy, electrochemical energy, chemical energy, sound energy & special mechanical energy, so as to realize material being removed, deformed, changing properties or being plated.

Ø Classification of Non-Traditional machining process?

Abrasive Jet Machining:

In Abrasive Jet Machining (AJM), abrasive particles are made to impinge on the work material at a high velocity. The jet of abrasive particles is carried by carrier gas or air. The high velocity stream of abrasive is generated by converting the pressure energy of the carrier gas or air to its

kinetic energy and hence high velocity jet. The nozzle directs the abrasive jet in a controlled manner onto the work material, so that the distance between the nozzle and the work piece and the impingement angle can be set desirably. The high velocity abrasive particles remove the material by micro-cutting action as well as brittle fracture of the work material.

 

AJM is different from standard shot or sand blasting, as in AJM, finer abrasive grits are used and the parameters can be controlled more effectively providing better control over product quality. In AJM, generally, the abrasive particles of around 50 μm grit size would impinge on the work material at velocity of 200 m/s from a nozzle of I.D. of 0.5 mm with a stand off distance of around 2 mm. The kinetic energy of the abrasive particles would be sufficient to provide material removal due to brittle fracture of the work piece or even micro cutting by the abrasives.

 

AJM Process Capability

• Material removal – Typical cutting speeds vary between 25 -125 mm/min

• Dimensional Tolerances – Typical range 2 - 5 µm

• Surface Finish – Typical Ra values vary from 0.3 - 2.3 µm

 

Ultrasonic Machining (USM):

Ultrasonic machining is a non-traditional machining process. USM is grouped under the mechanical group NTM processes. In ultrasonic machining, a tool of desired shape vibrates at an ultrasonic frequency (18 ~ 40 kHz) with an amplitude of around 15 – 50 μm over the workpiece. Generally the tool is pressed downward with a feed force, F. Between the tool and workpiece, the machining zone is flooded with hard abrasive particles generally in the form of a water based slurry. As the tool vibrates over the workpiece, the abrasive particles act as the indenters and indent both the work material and the tool. The abrasive particles, as they indent, the work material, would remove the same, particularly if the work material is brittle, due to crack initiation, propagation and brittle fracture of the material. Hence, USM is mainly used for machining brittle materials {which are poor conductors of electricity and thus cannot be processed by Electrochemical and Electro-discharge machining (ECM and ED)}.