Maintaining your waterjet

Modern equipment is easier to maintain than even just a few years ago, and also requires much less maintenance than in years past. Much progress has been made in this area, but no machine is maintenance free yet. The factors that affect how often maintenance is required include:

high frame bridge style cutting machine

high frame bridge style cutting machine

  1. How the equipment is run
    The harder the equipment is run, the more frequently things break. Running at higher pressures will also require more frequent maintenance.
  2. How much care is taken during maintenance
    If you rebuild in a clean-room, your equipment will last much longer than if you rebuild in a dirty environment. There are a lot of high precision components in a waterjet that microscopic bits of grit can easily damage. A tiny speck of dust underneath the jewel in the nozzle will cause the jet to shoot to the side, and cause accelerated wear of the mixing tube. Take the parts to a clean area of your shop, preferably with a sink where you can wash the parts before reassembly.

When you first get your machine, you will probably be overwhelmed during the few days of training that you get. Once training is complete, you will feel pretty confident that you know how to operate the machine, and you may have a general idea of how to maintain it. It will, however, be a few weeks before you perform your first maintenance, and even longer before it’s time to rebuild the pump. Once these items do come up, you probably will have forgotten everything you have been taught. Therefore, consider having someone from the factory or a distributor use your first pump rebuild as an opportunity to provide you with advanced training on the machine operation, and refresher training on how to do maintenance.
Frequency of maintenance
Waterjets certainly require maintenance. Expect to change nozzle parts frequently (daily). Expect to change pump parts less frequently, but regularly enough that you wish you didn’t have to. You should also keep some critical spares at hand, so that you don’t have to stop machining while waiting for a spare part to be shipped.
Generally speaking, the higher the pressure at which you run, and the more on and off cycles the equipment sees, the more frequently it will need maintaining.
Also, if you have dirty or hard water, you will either need to maintain everything more often, or purchase a good water softener and filtration system.

Ease of maintenance
For the most part, anyone who can change brake pads on a car can keep an abrasive jet going with a day’s training and a good manual, and the occasional phone call to tech support. Mixing tubes wear out and are easy to replace (often similar to replacing a drill bit). Pumps will need periodic seal changes. Depending on pump design, seals can be anywhere form relatively easy and quick to quite awkward and time consuming to replace.

Reducing maintenance
However easy it is to maintain your waterjet, it’s even better to reduce the need for maintenance.

Start with clean water
If your water has particles in it, or dissolved minerals, these will bang into or accumulate on high pressure components and accelerate wear. Dissolved minerals can accumulate as a deposit on the top of the jewel, and cause the jet to cut less efficiently, and worse yet, deflect it sideways so it’s cutting the side of your mixing tube. Tiny invisible-to-the-naked-eye sized particles underneath the jewel can cause it to miss align, and eat your mixing tube quickly. Dirt in the high pressure plumbing can become bullets that crack the jewel.

Water quality has a large impact on frequency of maintenance. Better water means less frequent maintenance and more time cutting and making money with your waterjet.

Be clean
Tiny bits of dirt can have devastating effects on component life, especially the nozzle components. Waterjets typically operate in a harsh environment, one that’s filled with abrasives and often other machining tools. You need to be extra vigilant to keep everything as clean as possible to avoid unnecessary maintenance.

  1. Always rebuild high pressure or nozzle components in the cleanest possible conditions.
    Do not store high pressure or nozzle components where dust (or worse yet microscopic abrasive particles) can settle on them.
  2. Rinse all dirt from components prior to disassembly, and go to another room to do maintenance.
  3. Get an ultrasonic cleaner for cleaning nozzle components
  4. When rebuilding something up-stream of the nozzle, remove the nozzle, and flush the lines with low pressure prior to putting the nozzle back on. This prevents dirt in the lines from damaging the nozzle.
  5. Remember, anything you do upstream has only one way to exit: through the nozzle.
  6. Plungers and seals inside of the pump are also sensitive to particles.

Avoid pressure cycles on high pressure components
Each time high pressure is applied to the plumbing, the metal expands. When the pressure is removed, it contracts. This causes fatigue that can cause the components to eventually crack. Operating at lower pressures is one way to solve this. Pressure fluctuations typically either come from the pump itself, or from turning the nozzle on and off. There are also methods employed in most equipment for maintaining relatively consistent pressure in the high pressure tubing even though the nozzle is being turned on and off. Understand, though, that all of the high pressure plumbing is considered “wear parts” and does need to be periodically replaced.

Rotate your mixing tube every morning
In the event that the jewel is slightly misaligned, it will hit one side of the mixing tube harder than another side. This causes uneven wear. By rotating the mixing tube once in a while, this is minimized.

Understand the basic principals of how ultra-high pressure tube fittings work
Ultra-high pressure tubing is different than standard household plumbing. For example, in high-pressure tubing the thread is not what makes the seal. Instead the screw threads force the parts together to make a metal-to-metal seal. The threads are only used to hold the pieces in place. Once in place, the cone of the tubing fits inside a negative cone in the mating piece.

  1. There is no need to over-tighten the components. You do have to make it tight enough to allow it to have a basic metal to metal seal, but you don’t have to use a lot of force to do it.
    A small piece of dirt between the cones can scratch it, or otherwise prevent the seal from occurring. Again, cleanliness reduces maintenance.
  2. If you find that you do need to put a lot of torque on the fittings to make a seal, then something is wrong, such as a scratch, bend, or piece of dirt interfering with the seal.
  3. Another possibility is that the cones are not properly touching due to improper assembly of the high pressure seal.
  4. If you have a leak, fix it soon. Otherwise, the leak will erode the components that make the seal, and you will have to replace it.

waterjet http://waterjetapw.com

http://waterjetapw.com

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