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Waterjet Cutting |
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| Quality Criteria’s |
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The sources of errors that will affect the quality of cut by an AWJ includes the random side-to-side deflection of the jet (striation marks), backward deflection of the jet (jet lag), energy dissipation along the thickness coordinate, dispersing of the jet, particle size and particle embedding, etc. |
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| On a typical AWJ cut surface at its maximum speed, regardless of the material and thickness, the surface shows a similar pattern, starting out to be smooth, sand-blasted-like at the top, then gradually showing some feather-like striation marks and growing worse and worse towards the bottom. These striation marks are the results of random deflection of the jet by the top portion of the work piece. |
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| The magnitude of these striation marks is much larger than that of the surface roughness caused by abrasion of individual particles. A quality level index (q) stands for the quality of the upper 1/q section of a separation cut surface. For convenience, descriptions are given for the following five quality levels: |
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A typical Abrasive Water Jet machine is composed of a high-pressure pump, motion equipment and control, nozzle and abrasive system, a working table, and a waste collecting unit. A typical layout is shown: |
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| » Quality Levels Descriptions |
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• q = 1 Criteria for separation cuts. Usually, q < 1.5 should be avoided. |
• q = 2 Rough surface finishes with striation marks at the lower half surface. |
• q = 3 Smooth/rough transition criteria. Slight striation marks may exist. |
• q = 4 Striation free for most cases. |
• q = 5 Best surface finish. |
• Replacement glass for antique autos |
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| COMPARE WATERJET MACHINING TO OTHER PROCESSES: |
| Process |
Part Cost * |
Part
Precision * |
Part Turnaround * |
Material Type Restrictions |
Material Distortions
or Stresses |
Cut Quality |
| Jet Machining |
-- |
0.005" |
-- |
no |
no |
smooth |
| Laser |
higher |
higher under 0.5" thick |
faster on thin materials |
yes |
yes |
rough |
| Wire EDM |
higher |
higher |
75% slower |
yes |
yes |
smooth |
| Plasma Cutting |
lower |
lower |
faster |
yes |
yes |
rough |
| Flame Cutting |
lower |
lower |
faster |
yes |
yes |
rough |
| Punch Press |
higher on short runs |
similar |
slower |
yes |
yes |
burred edges |
| * compared to Waterjet machining. |
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| » Quality Evaluation |
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