Ask Dr. Hashish - Archived Questions
Can the length of the waterjet stream be controlled?
Waterjet is the right tool for many cutting applications, but the depth of the stream cannot be controlled. The water and abrasive must be stopped by something and usually that is a tank of water. Without something to stop or slow the force of the stream it will cut and erode anything in its path.
Does the nozzle ever wear out? What material is it made of to withstand such pressure and erosion?
Yes, the nozzle on the machine does wear out. The mixing tube is where the abrasive and ultra-high pressure water mix together then exit to perform their cutting duties.
These tubes are made of Carbide and can last up to 2.5 weeks, depending on actual use, type of abrasive, etc.
Many variables come into play when calculating the life of mixing tubes. As the mixing tube wears, it becomes larger, allowing the water to fan out more, causing a less accurate cut.
In some cases this is not a problem, but in high precision work it is necessary to routinely check the mixing tube for wear. Most waterjet users do not discard their worn mixing tubes, they use them for rough cutting or low precision work.
Is Dyanmic Waterjet Technology available in entry level machines (Mach 2 Models)?
Dynamic Waterjet with active tolerance control allows for more accurate parts at significantly higher cutting speeds versus conventional abrasive waterjets.
Dynamic Waterjet is standard on our Mach 3 Series and is not available on our Mach 2 series.
What is the 3d software being used and where can I get professional training on a Flow Jet?
We have developed our own software suite for 3d cutting called FlowXpert. Flow partnered with SolidWorks to develop the most advanced, yet easy to use waterjet software for 2d and 3d waterjet cutting.
Flow offers waterjet training for operation and maintenance. Our training facilities are located in Jeffersonville, Indiana and Kent, Washington. Contact: techtraining@flowcorp.com to inquire more or call 812.285.4322.
Will it cut 1/2" stainless steel plate?
Abrasive waterjets can cut nearly any material, including stainless, from 1/16" to 8" thick. Typical part tolerances range from 0.003"-0.005", and up to 0.001" in some applications.
Cutting ½" stainless can be done at 7-30 inches per minute depending on the waterjets operating pressure and the desired edge quality.
What kind of abrasive are you using?
Garnet is by far the most commonly used abrasive material. Users have found garnet to be the best for them in terms of cost, cut speed, mixing tube life, and health hazards.
Other abrasives include olivine sand, aluminum oxide, and some man-made materials.
What is the difference between a 60 hp pump verse a 120 hp pump?
A 120 Horsepower pump will have a higher maximum flow rate of water versus the 60 HP, which may let you cut faster.
Keep in mind that any increased cutting speed is a result of pumping more water & abrasive through your orifice, which increases your operating cost and wears out your orifice faster. If you're looking for more cutting speed with lower operating costs, higher PSI is more effective than increasing HP.
Flow's 94,000 PSI pumps achieve higher cutting speed with less water & abrasive than our 60,000 PSI pumps. Pressure = Productivity.
How thick of material can be cut
How thick of material can be cut without using any abrasive? Also, what is the hardness range that can be cut without abrasive?
Generally speaking a pure waterjet can cut nearly any soft material. The rule is, if it can be cut with a pair of scissors it can be cut with only water. We have many customers who use our waterjets to cut gaskets, paper, foam, and food with great success.
How thick can we cut? Nearly any thickness. My question to you is how hard and what edge quality is required? That information will give us cut speeds and cost information. Of course the thicker and harder the material, the lower the edge quality and slower the speed.
Can abrasive waterjet cutting be applied in a Robotic system?
We have partnered with Kuka Robotics to create 6 Axis Abrasive Waterjet Robot Workcells. These units are an economical solutions for multi-axis machining. They feature high accuracy combined with increased flexibility.
For more information on our robotic machining solutions >>
Before cutting on a waterjet, do you have to pre-drill holes?
Typically, no. In most materials, no special requirements are necessary. The waterjet can pierce the starting hole itself. In some composites and brittle materials, lowering the pump pressure and/or using a UltraPierce Vacuum Assist piercing attachment is required. For more information on Flow's UltraPierce Vacuum Assist >>
At what pressure do you cut?
You want to cut at the highest pressure available to you so you can maximize your cutting speed and minimize the cost per part. The higher the pressure, the less need for abrasives and thus lower overall cost of operation, in spite of the slight increase in the pump maintenance cost.
94,000 psi is the maximum commercial intensifier rated pressure today for highly reliable operation at 87,000 psi.
I realize RO water may be too aggressive. What makes Nanofiltriation water too aggressive for the Intensifier?
We recommend against de-ionized (DI) water as it is too aggressive. We do have customers that use reverse osmosis (RO), but in most situations RO is an unnecessary precaution for waterjet cutting.
I have spoken to several associates and there is little experience in nano-filtration. I do not believe that nano-filtration is too aggressive, but it too might be an unnecessary precaution, but we would need more data to completely understand the process.
At our Demo Lab in Kent, Washington we run a double filter system of 1 micron and 0.5 micron filters from local tap-water. At times Flow recommends water softeners for customers who have hard water. This prevents deposits building on the orifice.
If there are concerns about your local water quality I would recommend performing a water quality test. This is done for all Flow customers before they purchase our equipment. If you would like more information on this please feel free to contact me.
What type and how much material can you stack on each other to get a good finish size?
(Dynamic head 30 hp hyplex)
Stack cutting with a Flow waterjet can save you time and money if the application is right.
The best range of stacking is .400 to .600 inches. The higher the stack the slower the cutting. Stacking is best for thin material - say a .125 piece can be cut in 3 minutes but stacking 4 high .5 inches it will cut in 8 minutes taking the cut time down to 2 minutes per piece. If I stack 8 high it will now take 32 minutes to cut or 4 minutes per piece.
The edge quality will still stay the same as if your cutting .500 inch or 2 inch since 20% speeds will change based on thickness. At higher speeds, 60 to 80 % the bottom pieces will be rougher then the top pieces.
Although, it is certainly possible to stack 2" or even more, the effect of worse edge finish and striations become more apparent as the stack gets thicker. The only remedy to this would be to slow down the machine to help ensure that the bottom pieces of the stack have an acceptable edge finish.
As a result, the overall cycle time may increase to the point where it's not worth stacking in the first place.
As mentioned before, the most effective total stack thickness would be around 0.400 – 0.600 inches. Up to this thickness, there is still significant energy available in the cut stream as the jet exits the bottom of the material, maintaining a reasonable edge finish for the whole stack.
Beyond this thickness, it takes exponentially more time to maintain a consistent edge finish.
What is kerf?
Kerf is defined as the width of the cut, or a groove or slit caused by cutting. In Waterjet cutting the width of the Kerf is directly affected by the mixing tube diameter. The kerf is about 10% larger than the mixing tube diameter.
So, for a 0.030" mixing tube, the kerf will be 0.033" Of course, the kerf will increase as the mixing tube grows. Tube growth is about 0.001" per 8 hours of jet-on time.
What kind of abrasive are you using?
Garnet is by far the most commonly used abrasive material. Users have found garnet to be the best for them in terms of cost, cut speed, mixing tube life, and minimizing health hazards. Other abrasives include olivine sand, aluminum oxide, and some man-made materials.
What stops the waterjet from cutting through the tank to the floor?
In most waterjet systems 36 inches of water in the catchers dissipates the energy of the jet.
At what pressure do you cut?
You want to cut at the highest pressure available to you so you can maximize your cutting speed and minimize the cost per part. The higher the pressure, the less need for abrasives and thus lower overall cost of operation, in spite of the slight increase in the pump maintenance cost.
94,000 psi is the maximum commercial intensifier rated pressure today for highly reliable operation at 87,000 psi.
What happens if I stick my finger in there?
It will get cut. However, the industry is very aware of and proactive in the safety of its equipment. Consequently, abrasivejet users actually have a better safety record than most machine tool users.