Views: 150 Author: SEPPE Garnet Team Publish Time: 2026-08-03 Origin: SGA Waterjet
Two waterjets can buy garnet at the same price and still report very different abrasive costs. The difference becomes clear only when abrasive use is compared with acceptable cutting output. A low flow setting saves nothing if the machine must slow down or parts need to be cut again.
Generic consumption figures provide little guidance because cutting heads and jobs vary. For purchasing and production control, the useful number is the cost of garnet per accepted metre or finished part on the actual machine.
Begin with the abrasive range approved for the cutting system. Use the machine manufacturer’s calibration procedure, or measure the change in a known abrasive supply during a timed production run. Keep the material, program and target edge quality unchanged while collecting the data.
The following calculations turn the measurement into figures that purchasing and production teams can compare:
| Result | Calculation |
|---|---|
| Garnet use per hour | Garnet used ÷ cutting minutes × 60 |
| Garnet cost per hour | Garnet use per hour × price per kilogram |
| Garnet cost per metre | Garnet cost during the run ÷ accepted cut length |
Illustrative Flow, Output and Cost Comparison
Assumptions: USD 0.35/kg garnet and the same hypothetical machine, material and accepted edge target. The output values are constructed to explain the calculation; they are not calibrated machine data.
| Scenario | Abrasive flow | Accepted output | Garnet cost per metre |
|---|---|---|---|
| Lower-flow example | 0.30 kg/min | 3 m/h | USD 2.10/m |
| Middle-flow example | 0.50 kg/min | 6 m/h | USD 1.75/m |
| Higher-flow example | 0.70 kg/min | 7 m/h | USD 2.10/m |
What the example shows: In this calculation, raising flow from 0.50 to 0.70 kg/min adds little accepted output, so garnet cost per metre rises again. A real operating optimum must be established by a controlled trial.
Abrasive flow has a useful operating range. Too little garnet may require a slower traverse speed or leave an incomplete cut. Adding more can improve cutting action, but the benefit does not continue indefinitely. Beyond the useful range, consumption rises without the same improvement in output.
The required edge also changes the calculation. A fast separation cut and a smoother production edge do not use the same traverse setting. The practical Q1–Q5 convention describes this speed–quality trade-off; it does not prescribe one abrasive rate for every machine. See Q1–Q5 Waterjet Cut Quality and Cutting Speed for that distinction.
Material and thickness affect how long the jet must act on the cut. The orifice, mixing tube and water pressure determine how energy is delivered. Change one condition at a time during a trial so its effect is visible in both cut quality and garnet use.
An increase in cost per metre does not automatically indicate a poor abrasive batch. Moisture or a restriction in the feed path can interrupt delivery. Wear in the orifice or mixing tube can also reduce cutting performance even when the abrasive setting has not changed.
Inspect the feed path and cutting head before changing several settings at once. If the flow remains unstable, compare the current lot with an approved sample under the same program. A fuller troubleshooting sequence is provided in How Garnet Quality Affects Waterjet Feeding and Wear.
Compare Cost per Accepted Output
When comparing garnet grades or suppliers, run each sample on the same machine with the same material and program. Record the abrasive used and the accepted cut length. Note any feed interruptions or rejected cuts because they affect the result even when the purchase price is lower.
Price per tonne remains part of the calculation, but it is not the conclusion. Cost per accepted metre shows whether the abrasive and machine settings are working together efficiently. Keeping this record by job also gives the next batch a reliable production benchmark.
