ABRASIVE JET MACHINE

INDEX Introduction to AJM Component of AJM Working Parameter of AJM Conclusion

INTRODUCTION OF AJM Abrasive jet machining (AJM) is a process in which the material is removed from the work piece due to impingement of fine grain abrasive by a high velocity gas stream. The stream of abrasive mixed gas is directed to the work piece by suitably designed nozzle. This process differs from the conventional sand blasting in that the abrasive used is finer and the process parameters and cutting action is carefully controlled.

BLOCK DIAGRAM

COMPONENT OF AJM The following components are used in Abrasive jet machine, Compressor Mixing Chamber Nozzle Regulator And valves

SCHAMATIC LEYOUT

WORKING OF AJM Abrasive jet machining is a process in which material removal takes place due to erosive action of a stream of fine-grained abrasive particles impacting at high velocity on the work surface. Fine-grained abrasive particles mixed in suitable portion with high pressure carrier gas, usually air, are directed through a suitably designed nozzle. The nozzle used imparts high velocity to the carrier gas and thereby to the jet of abrasive particles at the nozzle exit. This is directed onto the work surface to be machined The erosion of a surface by solid particles entrained in a fluid stream has received consideration attention from many investigators in the past. The theory of erosion phenomena in such situation is not fully understood and adequate data of its governing parameters are not available; some of these parameters are interdependent and difficult to control.

The first phase involves the determination from fluid condition, of the number, direction and velocity of abrasive particles striking the work surface. The first phase is essentially a two-phase (solid-gas suspension) flow problem and is beyond the scope of present work. The discussion will, therefore, be confined to mechanism of material removal or erosion rate. The erosion of materials by surface impact of hard particles is a complex phenomenon, consisting of several simultaneous and interacting, typically involving mechanical, chemical and material parameters as well as complex mechanism

The first phase involves the determination from fluid condition, of the number, direction and velocity of abrasive particles striking the work surface. The first phase is essentially a two-phase (solid-gas suspension) flow problem and is beyond the scope of present work. The discussion will, therefore, be confined to mechanism of material removal or erosion rate. The erosion of materials by surface impact of hard particles is a complex phenomenon, consisting of several simultaneous and interacting, typically involving mechanical, chemical and material parameters as well as complex mechanism

WORKING PARAMETERS IN ABRASIVE JET MACHINE Variables in that influence the rate of metal removal and accuracy of machining in abrasive jet machining process are:   Carrier gas. Types of abrasives. Size of abrasive grains. Velocity of abrasive jet. Mean number of abrasive particles per writ volume of carrier gas. Work material. Stand of distance Nozzle design. Shape of cut.

FACTORS EFFETING PROCESS ARE   Material removal rate (MRR). Geometry of cut. Roughness of surface hardness. The rate of nozzle wear.

ADVANTAGES : Abrasive jet machining has following advantages: There is no mechanical contact between the tool and work piece. It can cut hole of intricate shapes in hard and brittle materials. Surface finish obtained is high. Depth of surface damage is low. Power consumption is low. Capital cost is low. Accuracy up to 0.05 mm can be obtained.

LIMITATION Abrasive jet machining has following limitation: Metal removal rate is low. Nozzle wear is high. In machining soft metals, abrasive get embedded into the metals as a result an additional cleaning operation is required. Stray cutting and tapering are unavoidable, thus, machining accuracy is poor. Process tends to pollute the environment, so, dust collecting system is required.

APPLICATION Abrasive jet machining (AJM) process has been used in many engineering operation.  Removal of flash mid parting lines from the injection moulded parts. It’s widest used is in cutting, drilling, deburring and cleaning of hard and brittle materials. The process is also used to machine thin section and intricate shapes in hard and brittle materials. Deburring and cleaning of Plastic, Teflon, Nylon components is another application of this process. It is used in producing high quality surfaces Production of high quality surface. Removal of glue & paint from painting and leather objects. Frosting of the interior surface of the glass tubes. Etching of markings on glass cylinders. Cleaning of metallic mould cavities which otherwise may be inaccessible. For cleaning of the spark plug and casting.

CONCLUSION Abrasive jet machining can be used for polishing, deburring and other finishing operation where the rate of material removal is important, while in operation such as micro-drilling and cutting it is the erosion depth which is more relevant