Quality grades Q1 to Q5
The five-grade scale is an industry convention, not a standardised classification. It describes how far the energy available for cutting reaches through the workpiece thickness: at high traverse speed, the jet exits the material with a lag and produces the characteristic striation in the lower region.
| Grade | Rel. Traverse Speed | Edge Appearance | Typical Use |
|---|---|---|---|
| Q1 – separation cut | 100% | Pronounced striation in the lower third, visible lag | Scrap cutting, blanking before further processing |
| Q2 – rough cut | 60–70% | Striation in the lower quarter | Non-critical part edges, hidden surfaces |
| Q3 – standard cut | 40–50% | Striation only at the lower edge | Standard case for job-shop cutting |
| Q4 – quality cut | 28–35% | Largely free of striation | Visible edges, fits with moderate requirements |
| Q5 – precision cut | 20–25% | Smooth edge through the full thickness | Mating surfaces, joining edges with no rework |
Relative traverse-speed figures referenced to the separation cut of the same configuration. Actual values come from the specific controller's cutting database.
Moving from Q3 to Q5 roughly halves traverse speed, and therefore roughly doubles machine time and abrasive consumption per part. A blanket specification of "best quality" across every contour is therefore rarely economical. The common approach is per-contour assignment: functional edges at Q4 or Q5, outer contour and non-critical areas at Q2 or Q3.
Taper and its compensation
The jet loses energy through the workpiece thickness and widens or narrows depending on material and traverse speed. Without compensation, edge inclination typically falls in the range of about 0.5° to 1.5°, and higher at high traverse speed and greater thickness. Cutting heads with controlled tilt compensate for this effect by angling the kerf in the opposite direction.
| Parameter | Guidance Range | Note |
|---|---|---|
| Kerf width | 0.8–1.5 mm | Roughly corresponds to focusing-tube diameter plus widening |
| Taper without compensation | 0.5–1.5° | Increases with traverse speed and workpiece thickness |
| Taper with tilt compensation | < 0.1° | Requires a suitable cutting head and controller |
| Minimum internal radius | ≈ half the kerf width | Geometric lower limit, independent of the controller |
| Heat-affected zone | none in the metallurgical sense | Key distinguishing feature versus thermal processes |
Guidance values for abrasive cuts in the usual thickness range. The cutting data of the controller in use governs.
Influencing factors in order of effect
| Parameter | Edge Quality | Traverse Speed | Cost per Part |
|---|---|---|---|
| Traverse speed | |||
| Condition of water orifice and focusing tube | |||
| Abrasive mass flow | |||
| Operating pressure | |||
| Grit size | |||
| Stand-off distance | |||
| Workpiece fixturing |
Five points denotes the strongest influence. The order serves as a troubleshooting guide: start at the top, not with grit size.
Frequently asked questions about cut quality
Why is the edge clean at the top and striated at the bottom?
This is the fundamental pattern of the process. The jet gives up energy through the thickness and lags; striation begins where the remaining energy is no longer enough for a straight cut. If the effect is stronger than expected, check traverse speed, abrasive mass flow, or the condition of the focusing tube.
Is there a standard for waterjet cut edges?
No specific quality standard equivalent to ISO 9013 for thermally cut edges. In process terms, waterjet cutting is classified under DIN 8580 as a separating process in the material-removal group. In practice, requirements are therefore agreed via roughness figures, dimensional tolerances, and reference samples. The Q1 to Q5 grades are an industry convention, not a normative reference.
What tolerances are realistic?
They are jointly determined by machine accuracy, workpiece thickness, fixturing, and quality grade. For the quotation stage: tolerance figures without thickness, material, and quality grade stated are not verifiable. For tight fits, it should be clarified whether the system has tilt compensation.