The six places to check
| Order | Place to check |
|---|---|
| 1 | Leaks in the piping |
| 2 | Nozzle size |
| 3 | Gas-on time while not cutting |
| 4 | Pressure set higher than needed |
| 5 | Nesting and cut strategy |
| 6 | The right gas for the job |
1. Leaks in the piping. This is almost always the biggest item and the least often checked. The test: close the valve at the head, leave the system pressurised, shut down and record the gauge reading. Read it again the next morning. Pressure lost = a leak. Check joints with soapy water.
2. Nozzle size. Gas flow rises with the square of the orifice diameter. Running a larger nozzle than the thickness needs is the fastest way to burn money that nobody sees. Standardise a thickness-to-orifice table and make a nozzle change mandatory with a thickness change.
3. Gas-on time while not cutting. Many programs keep gas flowing throughout the traverse between cuts. On a sheet with many small holes, traverse time can equal or exceed cutting time. Check whether the controller shuts gas off during traverse.
4. Pressure set higher than needed. The common habit is to set it high "to be safe." Try reducing in 0.5 bar steps with a test cut each time until quality starts to fall, then go back one step. The number you find is usually well below the one in use.
5. Nesting and cut strategy. Many small parts on an unoptimised path produce a great many pierces and a great deal of traverse. Common-line cutting and re-ordering the cut sequence save both gas and time, at no cost beyond programming effort.
6. The right gas for the job. High-purity nitrogen gives a bright, unoxidised edge — needed on visible stainless. But if the part will be painted or welded closed, a lightly oxidised edge makes no difference. Many shops run high-pressure nitrogen on parts that never needed it.
The most commonly misjudged point
The gauge on the bottle does not tell you the pressure at the cutting head.
Between the two sit a regulator, piping, filters and fittings — each one dropping pressure. A shop setting 16 bar at the bottle may have 12 bar at the nozzle, conclude "this machine needs high pressure," and raise the bottle further, making the leaks worse.
Measure at the head. If the difference is large, the problem is the piping, not the machine — and fixing the piping costs far less than burning extra gas every day for years.
Safety
High-pressure gas is a mechanical hazard. Never use assist gas to blow dust off yourself or your clothing. Bottles must be secured upright. Nitrogen is an asphyxiant in enclosed spaces — odourless, colourless, and with no warning sensation before loss of consciousness. Bottle storage areas must be ventilated.