In abrasive jet machining, as the distance between the nozzle

In abrasive jet machining, as the distance between the nozzle tip and the work surface increases, the material removal rate

1. increases continuously
2. decreases continuously
3. decreases, becomes stable and then increases
4. increases, becomes stable and then decreases

In abrasive jet machining the variation is as shown

MRR – Metal removal rate
NTD – Nozzle tip distance.