ABRASIVE JET MACHINING
What is abrasive jet machining ?
It is the material removal process where the material is removed by high velocity stream of air/gas or water and abrasive mixture .
An abrasive is small, hard particle having sharp edges and an irregular shape .
High velocity jet is aimed at a surface under controller condition .
components of abrasive jet
machining
Abrasive delivery system Control system Pump Nozzle Mixing tube Motion system
1. abrasive delivery system
Auto abrasive delivery system has the capability of storing abrasive & delivery the abrasive to the bucket . It’s works auto programming system by help of once measuring record & no adjustment or fine tuning system . High sensitive sensor gives extremely reliable & repeatable .
2.Control system
The control algorithm that computes exactly how the feed rate should vary for a given geometry in a given material to make a precise part .
The algorithm actually determines desired variation in the feed rate & the tool path to provide an extremely smooth feed rate .
3.pump
Crankshaft & intensifier pump are mainly use in the abrasive jet machine .
The intensifier pump was the only pump capable of reliably creating pressures high .Crankshaft pumps are more efficient than intensifier pumps because they do not require a power
robbing hydraulic system ultra high pressure
& more stroke per minute .
4.nozzle
All abrasive jet systems use the same basic two stage nozzle . First , water passes through a small diameter jewel orifice to form a narrow jet .
The abrasive particles are accelerated by the moving stream of water & they pass into a long hollow cylindrical
ceramic mixing tube.Generally two type of nozzle use , right angle head & straight head .
Fig. Of nozzle
5. Mixing tube
The mixing tube is where the abrasive mixes with the high pressure water .
The mixing tube should be replaced when tolerances drop below acceptable levels .For maximum accuracy , replace the mixing tube more frequently .
6.Motion system
In order to make precision parts , an abrasive
jet system must have a precision x-y table and
motion control system .Tables fall into three general
categories .Floor-mounted gantry systems Integrated table/gantry systemsFloor-mounted cantilever
systems
working process
High pressure water starts at the pump , and is delivered through special high pressure plumbing to the nozzle .
At the nozzle , abrasive is introduced & as the abrasive/water mixture exits , cutting is performed .
Once the jet has exited the nozzle , the energy is dissipated into the catch tank , which is usually full of water & debris from previous cut .
fig . schematic diagram of ajm
ajm features
There are main features of AJM
Obtainable tolerancesMaterial to machineMaterial thicknessAccuracy of tableStability of tableControl abrasive jet
Machine aspects
Around curves Inside cornerFeed rateAcceleration Nozzle focus Speed cuttingPump pressureHardness & thicknessSoftware controlling the motionPower at the nozzle
Types of abrasive materials
Different types of abrasive are used in abrasive jet machining like garnet , aluminum oxide , olivine , silica sand , silicon carbide ,etc .
Virtually any material can be cut by using abrasive jet machining method , i.e harder
materials like titanium to steel.
Abrasive particles must be hard ,high toughness,
irregular in shape & edges should be sharp .
Advantages Extremely fast setup &
programming No start hole requiredThere is only one toolLow capital costLess vibrationNo heat generated in work
pieceEnvironmentally friendly
Disadvantages Low metal removal rateDue to stay cutting accuracy is
affectedAbrasive powder cannot be
reusedTapper is also a problem
conclusion
The better performance , and the applications represented above statements confirm that
ABRASIVE JET MACHINING is continue to expand .
The new software’s used to minimize time and investments , there by making it possible for more manufacturers of precision parts to install AJM centers .
