Abrasive jet machining (AJM) – a detail overview
Abrasive jet machining (AJM) utilizes a high velocity jet of abrasives to remove material from work surface by impact erosion. Get an overview of AJM process, mechanism, parameters, equipment, MRR, accuracy, capability, pros and cons, applications, etc. Read detail…
What is the basic mechanism of material removal in AJM?
Mechanism of material removal in abrasive jet machining is impact erosion, sometime assisted by brittle fracture. So material is removed in solid form due to micro-cutting action caused by the impact of hard abrasive grits. Read detail…
Explain working principle of abrasive jet machining with sketch
In AJM, material is removed by controlled micro-cutting action caused by the impact of a concentrated high-velocity (100 – 300m/s) jet of abrasive grits accelerated by dehumidified pressurized carrier gas (10 – 15bar). Read detail…
Desired properties of abrasives used in abrasive jet machining
Abrasive grits should have sharp edges, irregular shapes, less size variation, high hardness, good flow characteristics, and must not contain moisture or metal particles. Read detail…
Compare various types of abrasives used in AJM process
Brief comparison among various types of abrasives used in AJM from application point of view is discussed here. A hardness comparison among various abrasives and common engineering materials is also provided here. Read detail …
Why abrasive particles cannot be reused?
Reuse of abrasive particles is not recommended as abrasives get contaminated by wear debris and also they lose sharpness after first impact. If used, it may result in lower MRR, reduced nozzle life and poor surface finish. Read detail…
Functions of carrier gas in abrasive jet machining
It accelerates tiny abrasive particles, helps forming abrasive jet and blows away eroded metal particles and used grits from machining zone to protect fresh jet from collision. Read detail…
Can pure oxygen be used as a carrier gas in AJM?
Pure oxygen gas is not used in AJM because it can quickly oxidize the work surface and form a hard oxide shielding layer. Also it is inflammable and costlier. Read detail…
Functions of nozzle in abrasive jet machining
In abrasive jet machining, nozzle serves basic three functions—it delivers high velocity jet, controls abrasive jet diameter and regulates impingement angle. Read detail…
Can you choose a nozzle with arbitrary inner diameter?
No, as it can result in inaccurate kerf width, tapered or parabolic hole, lower MRR, insufficient depth of penetration, choking within nozzle, etc. Nozzle diameter usually varies between 0.15 – 1.5mm. Read detail…
Various components of AJM set-up and their functions
AJM set-up comprises air compressor fitted with drier and cleaner, abrasive feeder and vibratory mixing chamber, nozzle, well ventilated machining chamber and various gauges for detecting pressure, flow rate, etc. Functions of the components are also discussed here. Read detail…
List of factors that affect abrasive jet machining performance
Factors related to abrasive, carrier gas, abrasive jet, nozzle, work material, and process parameters and their influences are briefly discussed here. Read detail…
Effects of abrasive on abrasive jet machining performance
Effects of abrasive flow rate, abrasive size and also abrasive type on abrasive jet machining performance are discussed here. List of abrasives in AJM and desired properties are also given. Read detail…
Why different abrasives produce different MRR?
Different MRR for different abrasives is attributed to the hardness of abrasive particles (when process parameters and geometrical features are same). Harder abrasives produce higher MRR. Read detail…
Effects of carrier gas on abrasive jet machining performance
Influences and effects of carrier gas on abrasive jet machining (AJM) performance are discussed here. Increased gas pressure can enhance MRR but it is limited by set-up capabilities. Higher gas flow rate can degrade MRR of mixing ratio is not maintained. Read detail…
What is mixing ratio in abrasive jet machining?
Mixing ratio is the ratio between mass flow rate of abrasive grits and mass flow rate of carrier gas. Although, many proponents define mixing ratio using volume flow rates (instead of mass flow rates). Read detail…
Effects of mixing ratio on abrasive jet machining performance
MRR initially increases with mixing ratio and after reaching maximum, it starts descending. However, MRR can be improved by proportionally increasing both abrasive flow rate and gas flow rate maintaining mixing ratio constant. Read detail…
What is stand-off distance (SOD)? Explain its effect on AJM performance
Distance from work surface to tip of the nozzle in abrasive jet machining set-up is called Stand-Off Distance, abbreviated as SOD. It is also called Nozzle Tip Distance (NTD). Its effects on abrasive jet machining performance are also discussed here. Read detail…
How stand-off-distance affects machining accuracy in AJM process?
Longer SOD degrades erosion capability of jet because of spreading. Thus result will be very low penetration but a wider machined area; whereas a smaller SOD can cut narrow and deep shots. Read detail…
Effects of impingement angle on AJM performance
With increase in impingement angle, initially material removal rate (MRR) increases as strength of perpendicular component enhances. Maximum MRR is noticed in between 70º – 80º. Read more…
Assumptions considered for modeling MRR in AJM
Assumptions considered for modeling material removal rate in abrasive jet machining include participation of all grits equally, spherical shape of grits, same diameter, 90º inclination angle, no loss of energy, etc. Read detail…
Formulas for MRR in abrasive jet machining (AJM)
$$∴{MRR_{brittle}} = 1.04{{{M_g}.{U^{3/2}}} \over {{\rho _g}^{1/4}.{H^{3/4}}}}$$
$$∴{MRR_{ductile}} = 0.5{{{M_g}{U^2}} \over H}$$
Meaning of notations is also provided here. Read detail…
Modeling for material removal rate in AJM
Detail step by step modeling of MRR for abrasive jet machining is given here. It describes how to estimate material removal rate in AJM for ductile and brittle materials from process parameters and material properties. Read detail…
Condition for equal MRR in ductile and brittle materials in AJM
Under which condition material removal rate for ductile material will be equal to brittle material in abrasive jet machining? Condition along with mathematical calculation is provided here. Variation of MRR with jet velocity is also depicted here. Read detail…
How material removal rate can be increased in AJM?
Enhancing material removal rate (MRR) in abrasive jet machining (AJM) is one challenging task because of its dependency on many controllable and uncontrollable factors. Possible ways are: enhancing abrasive flow rate, using high gas pressure, reducing SOD, and using proper impingement angle. Read detail…
Advantages and disadvantages of AJM
Pros are: wide ranges of surface finish, independent of electrical properties, no thermal damage, suitable for nonconductive brittle materials, low capital investment, etc. Cons are limited nozzle life, not suitable for ductile materials, abrasives are not reusable. Read detail…
Applications of abrasive jet machining
Applications include surface cleaning, coating removing, deflashing, trimming, engraving, deburring, drilling, parting, ceramic abrading and glass frosting, etc. Read detail…
How to determine taper angle of abrasive jet machined slot or hole?
Determination of taper angle is necessary to get an idea about the level of accuracy and tolerance achievable by the process. Steps with diagram and mathematical calculations for determination of taper angle of a slot or hole are given here with example. Read detail…
Why kerf width is larger than jet diameter in abrasive jet machining?
In AJM, Kerf width is usually larger than diameter of jet as abrasive jet spreads while travelling through stand-off distance and also due to side cutting caused by coming out abrasives. Read detail…
Why abrasive jet machining is not recommended for ductile materials?
While machining ductile materials by AJM, hard abrasives remain embedded on soft machined surface. This hampers cut quality and properties and appearance of machined surface. Thus AJM is not recommended for ductile materials; however, preferred for non-conductive brittle and hard materials. Read detail…
Write reasons for inaccuracies in abrasive jet machining
Stand-off distance is dominating parameter that affects dimensional accuracy of machined profile. Thus, any anomaly in SOD can lead to dimensional error of the abrasive jet machined features. Read detail…
What precautions you must take while utilizing AJM process?
List of safety precautions required to consider while employing abrasive jet machining in industrial applications are: use of mask, protective clothing, face and eye protector, proper ventilation, proper abrasive disposal facility that has minimum impact on environment. Read detail…