ProtoTYPING: Cool Your Jets

The power of water is evident all around us. Dams are built to force water through turbines to create electricity, and fast-moving rivers can sweep cars away, and erode mountains to form deep canyons. What if we could harness that power and control it to create very specific shapes? Well, we can, and the technology is called water jet cutting. The Edison Nation engineering team uses a water jet cutter to help bring prototypes to life every week, and I will explain how the technology works and how we use it our shop.

Water jet cutting uses a pump to force high pressure water through a small nozzle. The nozzle focuses the 45,000 psi beam of water, usually mixed with abrasive, that erodes the material being cut at a very high rate. The nozzle is attached to a CNC motion platform over a water-filled tank so that it can be used to cut shapes and profiles that are drawn in a CAD program. The tank gives a place for the water from the nozzle to go and keeps the material cool to cut down on distortion. Water jet cutting is a very versatile tool. It can cut just about any material that is not water-absorbent, and it can cut thin pieces of sheet, 12-inch thick pieces of steel, and anything in between. It is also great for cutting plastics as there is no residual dust or fumes released from the cutting.

Water jet 1

The OMAX Maxiem 1515 showing the machine, computer and the pump

 

Most water jet cutters, like the OMAX Maxiem 1515 in the Edison Nation lab are for two-dimensional cutting of sheet material. However, some machines can be fitted with a rotary axis for cutting profiles into tubing, and there are a few new machines that are starting to do 3D cutting. There are also water jet cutters that are FDA approved to cut food, which was actually one of the earliest uses of the technology.

 

Water jet 2

Cutting a submerged piece of aluminum in the EN shop

 

The Edison Nation team uses the OMAX 1515. It is a versatile machine and is perfect for cutting the wide variety of materials and shapes that we come across in our prototyping activities. The typical process for making a cut starts with a CAD file. We use SolidWorks to create a two-dimensional file of the shape we want to cut. Then we open the file with the OMAX software, set the quality of the cut finish we want, and the software creates a cut path for the machine to follow.  The software recognizes holes in the part, and cuts those first before doing the outside profile. If the outside was cut first, the part might shift and the holes might end up in the wrong location. Then we take our material and place it in the water jet tank. The material has to be securely located inside the tank and this can be done in a couple of ways. One method is to lay it directly on the slats in the machine and use clamps to secure it against the wall of the tank. The other option is to place it on a piece of honeycomb plastic, we use a brand called Rhino Block, and hot glue the edges of the material to it. Once the material is secure we set the head of the nozzle to .060″ off the top surface of the material. Then we add abrasive to the hopper and start the run. Depending on the thickness and complexity of the geometry, cuts can take from just a few seconds to over an hour. Most end up being 5 minutes or less, so it is quite fast.

 

Water jet 3

OMAX software showing the cut path for a prototype part

water jet 4

A sheet of carbon fiber hot glued down to the Rhino Board in the cutting tank

The trick to getting accurate parts from a water jet cutter is controlling the beam spread of the water. Anyone who has used a spray nozzle on a garden hose knows that the water tends to spread out when it exits the nozzle. This same phenomena happens with water jet cutters, and it results in a tapered edge of the part. The taper is only a couple of degrees, and if the material is thin enough, it is not noticeable. However, for thicker parts, the water jet can be run at low speed, and this virtually eliminates the tapering. The OMAX is particularly good at compensating for the taper with their software tools and the design of their nozzle. Even when we need a precise diameter machined hole, we still use the water jet to cut the holes undersized and chase them with the right sized drill.

 

Water jet 5

Sample parts cut from a water jet

 

The Edison Nation team has been using the OMAX water jet almost daily since it was installed. We use it for nearly all of our metal cutting as it is so fast and can accurately cut complex curves. We have used it to make the spines of a watch product, as well as the steel parts needed to build a test rig for a lock punching device for emergency services. It was also used during the construction of the Stem light that I first chronicled here. We have also used it to cut some composite materials and even circuit boards.

 

Water jet 6

Stainless steel spine for a watch product that was cut on the water jet

 

While the base price for a water jet cutter is in the tens of thousands and out of the reach for many individual inventors to have in their shop, it can still be an important tool in their product development journey. There are machine shops in all parts of the country that have this technology, and since they are so fast and easy to setup, it is relatively inexpensive to get pieces of prototypes built this way. If your product idea needs parts of any thickness and they are two-dimensional, it will probably be cheaper to get the parts made on a water jet as opposed to CNC machining, or using a 3D printing service. So it would be a good resource to have to find a shop in your area with this capability.

Since water is readily available out of a tap nearly everywhere you go, it is easy to overlook how powerful it really is. Water jet technology harnesses the power that water has to hyper erode material in a controllable way to make parts from nearly any material. It is cheap and fast to do, and great for doing iterative prototyping work. It is also a good technique for the individual inventor to know about so they can make great prototypes on the cheap.