Waterjet Cutting Glass is a little bit different process in many ways than cutting other materials. However, generally speaking you can cut any type of glass except for “Tempered Glass”.
Over the past 19 years in waterjet cutting we have been involved in cutting many different types of glass for many different types of projects. I have cut everything from windows for cars, to stained glass panels. I have cut ballistic glass for box offices and bank teller windows (back before the developed plastics for that purpose). I even cut the glass awards that were given out for the Vogue Fashion Awards show that was televised in October 2000 on VH1. I have cut outlet cutouts in large bathroom mirrors for some very high end house construction projects.
I have cut many thousands of pieces of glass over the years and waterjet cutting glass presents some specific challenges. A couple of which are that you must be very careful if you are to cut a hole out of the center of the glass as piercing glass is rather touchy business. If the cutting stream doesn’t have sufficient abrasive flow when you fire on the jet it will just shatter the glass or blow a big star chip out of it.
Low Pressure Piercing
One way to get around that is to lower the pressure of the water enough so that it will not break the glass from just the stream hitting it without the abrasive. That may sound like an easy solution but since the abrasive is actually pulled into the cutting head by a vacuum that is created in the cutting head by a “venture effect” from the water passing through the mixing chamber the lower the water pressure the slower the stream is moving. That in turn lowers the amount of vacuum generated in the chamber raising the risk that there will not be enough abrasive to make the pierce work.
There is a very fine line between having the pressure low enough to not break the glass and still being able to create enough vacuum to pull the abrasive into the head to make it cut. Then once you get through the glass with the stream you need to have enough pressure to cut the glass at a decent cutting speed. The best solution is that most modern waterjet cutting systems have the ability to pierce at low pressure that you preset to whatever pressure that is needed for the specific type of glass you are cutting then ramps up to a higher pressure for the actual cutting of the shape. There are still some risks but this has helped out a great deal with the whole process from what it was 20 years ago.
Then of course there are a new set of problems that were addressed in a previous blog post here Waterjet Cutting Laminated Materials.
The second problem with waterjet cutting glass is that glass will break when it flexes too much and waterjet cutting will put a certain amount of down pressure on the glass during the cutting process. This pressure increases the faster you try to cut. So the faster that you try to cut the higher the risk of cracks developing in the material as you are cutting it. There is an added risk of the glass flexing down and then back up as you go if it is not completely supported by a perfectly flat surface. This is especially bad in thinner glass as it flexes easier. Due to this issue it is more of a problem in larger pieces than smaller ones. That can be a difficult thing to accomplish when you are cutting on top of slats that constantly get chopped up from the cutting stream passing over them so they are often not a nice flat surface to support the glass.
That is why we normally use waterjet brick to support our glass as we cut. Waterjet brick is a product that has a planed surface that is perfectly flat to support the glass. It adds cost to the process certainly but will greatly lower the risk of breakage during cutting so is often offset by the higher yield of parts you get. It also allows you to cut much smaller parts without losing them into the cutting tank. You can cut parts down to as small as 1″ or even smaller sometimes with this system.
So it is better to go slow and safe when waterjet cutting glass.