12 Tips for Cutting Glass with your OMAX Waterjet

Cutting glass with an abrasive waterjet can be a tricky job without the right set-up and some experience, but it can be well worth the effort as new applications are becoming available regularly. OMAX recently provided some tips for users to help reduce the amount of trial and error required to get you to the best possible results.

Here are 12 tips to get you started:

1. Fixturing, fixturing, fixturing – this is always tip number 1 for any application but is especially crucial when cutting glass. If your material is moving during the cutting process you’ll never end up with a usable part. Fixturing is especially important with glass cutting. Given the fragile nature of the material it’s critical that the material be fully supported during the cut. Waterjet brick is the ideal option. This corrugated plastic material fully supports the glass but is soft enough to keep the jet from kicking back and frosting the bottom of the material. It’s recommended to use new pieces of jet brick for glass cutting to ensure that they are perfectly flat and level.

2. Use fine mesh abrasive – good quality abrasive always improves your finish however with glass cutting you’ll see a particular difference by going to smaller abrasive such as a 100, 120 or 150 mesh size. You’ll also want to reduce your flow rate to around 0.4 lbs/min.

3. Pierce using vacuum assist – this option ensures that abrasive is flowing before the water reaches full pressure and prevents the scenario where the initial blast from the pierce actually doesn’t have any abrasive in the jet stream. It essentially primes the line with abrasive before the water travels through which is a requirement for successfully cutting brittle materials.

4. Pierce at low pressure – to avoid cracking the glass it’s recommended to pierce using the lowest pressure your pump can operate at while still creating the vacuum necessary to pull abrasive in to the line. Generally speaking this would be around 10,000-15,000 psi.

5. Mirrors – mirrors have a few special requirements within the glass arena. It’s recommended to cut them with the reflective paint side down, this means you should be able to see yourself in the mirror when the material is loaded. It’s also encouraged to use the finest abrasive you can get to minimize the chance of chipping the reflective paint.

6. Eliminate Sagging in Abrasive Line – the consistency of the abrasive flow during cutting is particularly important when cutting glass so it’s strongly recommended that you check the abrasive line and make sure there’s no sagging. Sagging will interfere with the flow of the abrasive and increase the chance of cracking your material during piercing. If needed shorten the length of the abrasive line to eliminate sagging.

7. Ramp Pump Pressure Slowly – As part of further efforts to pierce at the lowest pressure possible it’s recommended that the pressure be slowly ramped up from the pump. Start at zero pressure so that only the lowest pressure water hits the material as the abrasive begins to flow.

8. Make all pierces before cutting – by completing all of the pierces first it will ensure that the pressure in the plumbing stays consistent throughout the cutting and reduces the risk of shattering the glass. After the pierces are complete the cutting can be done at high pressure. You’ll want to make sure when you do your programming that the path starts with the cutting beginning inside the pierced holes.

9. Use brittle cutting mode – take advantage of the full power of the OMAX software by making sure the “very brittle material” box is checked in Make prior to cutting glass. The software development team has spent countless hours making this a useful feature to automate many of the steps that improve the outcome of brittle material cutting.

10. Plug MaxJet 5 nozzle vent hole – when using the Maxjet 5 nozzle it’s recommended that the vent hole be plugged to create additional vacuum pressure at lower pump pressures. Because this will reduce the life of the jewel slightly it’s recommended that you only plug the hole when necessary.

11. Avoid big temperature changes – watch out for dramatic temperature changes between the water in your catch tank and the air and water used after cutting. For example don’t pull your material out of hot cutting tank water and then immediately hose it down with cold tap water.

12. Use long lead-ins – if at all possible use longer lead-ins when cutting glass so that if a crack does appear at the pierce point it’s less likely to make its way all of the way to the edge of your part. These lead-ins are automatically lengthened in the software if you check the “very brittle mode” box.
Even with these tips it is not recommended that you attempt to cut tempered glass as it will still shatter.