Mixing tubes are made of extremely hard materials such as sintered boride or more commonly composite tungsten carbide. However, the nozzles are subject to wear and their cost must be taken into consideration for job costing. The orifice of a mixing tube will typically increase in diameter by about 0.0001" per hour of cutting because of the erosion of the abrasive flowing through the nozzle. If this wear occurs in an even fashion, up to 120 hours of cutting can be realized with a nozzle. The biggest factor affecting nozzle wear is the material from which they are made. Controls allow for compensating for this wear by allowing the operator to change the tool offset.

<img class="alignnone size-full wp-image-6967" src="http://www.wardjet.com/wp-content/uploads/2022/03/new-mixing-tube.jpg" alt="new mixing tube" width="280" /> <img class="alignnone size-full wp-image-6966" src="http://www.wardjet.com/wp-content/uploads/2022/03/used-mixing-tube.jpg" alt="" width="280" />

<span style="color: #808080;"><em>Figure 11 - New and used mixing tubes. Note orifice on right is off-center.</em></span>

If the wear of the nozzle is not symmetrical, the waterjet stream will also not be round. This will result in wider tolerances when cutting in a certain direction.

The tolerance requirements of a job will dictate the actual number of hours a user can expect from a nozzle. The nozzle can, of course, be set aside and used later for looser tolerance jobs. Control software should allow the ability to track hours on individual components to make consumable management easier. See Figure 12 below for an example of orifice and mixing tube tracking.