As far as brands of machines are concerned, there are no major functional differences between waterjet cutting systems. At the same pressure, orifice & nozzle combination, their ability to cut any specific material is not significantly different. Generally speaking, what one machine can do, any other machine that is similarly equipped can do. Outside of the control and motion systems, any difference in waterjet cutting systems of one pressure range, are generally just minor efficiency differences of the water and abrasive mixing system, which is contained in the mixing chamber.
One of the major differences between waterjet cutting systems is that one machine may be much more difficult to program to do a certain job than another. So, the controls and software are where the biggest difference lies in waterjet cutting machines, in a given operating pressure range. Generally speaking the machines that operate in the High Pressure range are generally easier to program a tool path on, than the Ultra High Pressure Waterjet Cutting machines. The Ultra High Pressure Waterjet Cutting Systems tend to be of a more sophisticated makeup and thus are more complex in nature as far as software and programming goes.
High Pressure Waterjet Cutting Systems
High Pressure Waterjet Cutting Systems (HP) are commonly considered to be anything up to and including 60,000 PSI (60 KPSI) which takes in the vast majority of waterjet cutting systems today. To my knowledge every waterjet cutting machine manufacturer in business today builds machines in this range, which has been the normal operating range for the past 20+ years. These machines are entirely suitable for most jobs and work very well for most materials.
Another of the differences between waterjet cutting systems is the water volume that the pumps put out. A 50 horsepower electric motor will drive a pump that will put out enough water at 60 KPSI for a .014 Ø orifice to create a stream of water that is .014″ Ø. That stream will utilize about 1 lb of abrasive per minute if being pushed through a nozzle with an opening of .030″ Ø. As an established baseline that combination would normally cut 1″ mild steel plate at about 3.34 IPM (inches per minute). You could also use up to a .042″ Ø nozzle which would handle about 1.4 lbs of abrasive and cut the same material at about 3.94 IPM.
A common practice is to add extra horsepower with an example of either 2-50 or 1-100 horsepower pumps. With this system you would be able to move up to a stream size of .020″ Ø and utilize a .042″ Ø nozzle. With this combination you could use 1.8 lbs of abrasive per minute to attain a cutting speed of 4.56 IPM. This does give a big advantage in cutting speed however there are several additional costs associated with it. They would include twice as much, pump maintenance costs, electricity, water, and abrasive costs. There is also other considerations involved which would be, among other things, that the cutting kerf will be wider (at least .042″ wide), the minimum radius that can be cut will be larger (.021 min) and the tank will fill up with spent abrasive much quicker.
Ultra High Pressure Waterjet Cutting Systems
The last of the differences between waterjet cutting systems is the pressure variable. Ultra High Pressure Waterjet Cutting Systems (UHP) are commonly considered to be anything above the 60 KPSI operating range. At the time of this post that range is up to and including 90 KPSI sytems.
A 90 KPSI, UHP waterjet cutting system can use a minimum of a 60 horsepower electric motor. This motor drives a pump that will put out enough water at 90 KPSI for a .011 Ø orifice to generate a .011″ Ø water stream. That stream can utilize 1.4 lb per min of abrasive through a .033″ Ø nozzle and will cut 1″ steel at 4.81 IPM.
The reason this works out is that a waterjet has an optimal amount of abrasive it will cut fastest at. If you don’t have enough or too much abrasive it will cut slower. Every nozzle orifice size combination has a “sweet spot” as far as abrasive flow is concerned for optimal cutting speed. However that same combination will be different at different pressures. If you are pushing water through a .010 Ø orifice at 60 KPSI, it exits that orifice at a given speed in the (Mach 1.5 Range). Physics dictates that if you increase the pressure by 50% then the speed the water exits will proportionally increase.
The way that a waterjet works is by the abrasive eroding the material to cut it. Just like a saw blade running at a faster speed there will be more teeth per minute will contact the material thus cutting faster. So the higher the pressure the faster the stream moves thus cutting the material away faster. If the stream is moving faster then it will utilize more lbs per minute of abrasive to reach that sweet spot that gives optimal cutting speed. But because the orifice and stream size is smaller with the UHP system then the overall abrasive use will be lower even with the higher stream speed.
Some advantages to this system is it will cut down to a .0165″ minimum radius. It will only remove a kerf width of .033″ wide. Since it uses less abrasive per minute and cuts faster through the same material it will also not fill up the tank with spent abrasive as quickly.
So, while there may not be any major difference in basic function the major differences between waterjet cutting systems lie in the amount of pressure they use and the type of control that they use to drive them.
An added bonus is that at Accurate Waterjet our UHP waterjet cutting system utilizes a water recycling system that only has to have additional water added when water evaporates from the tank. It also dumps no water into the sewer system. To the best of my knowledge it is the only closed loop system in use in the state of Arizona, in a waterjet job shop.
While there are systems being tested up to 120 KPSI, they have been in testing for several years and to my knowledge there are no systems being sold as commercially available to shops. I am sure there are a lot of issues to overcome in making a system that will stand up under that tremendous pressure, although I am sure they will eventually, but have no information indicating how long it may be.