The precision with which a waterjet can cut a part is known as tolerance. Waterjets can make objects with tolerances as small as .025 mm, although .05mm is probably a more realistic figure for most machines.
A number of factors – some of which are easier to control than others – can affect tolerance.
Harder materials typically show less taper, gradual narrowing that you sometimes see at the ends of what you cut. You can compensate for taper by adjusting the cutting speed or tilting the cutting head opposite of the taper direction.
Thicker materials make it more difficult to control the behavior of the jet as it exits out the bottom. This can potentially cause splintering on the corners, and more taper around curves. Material thickness also affects both the amount and the type of taper. Materials thinner than 3 mm tend to exhibit V-shaped taper while very thick material can show barrel taper.
Some of the factors that can cause blemishes in a part include vibrations between the motion system and the material, poor velocity control and other sudden variances in cutting conditions. Also, if the cutting head vibrates relative to the part you’re cutting, then your part will more than likely be uneven.
The more precisely you can position the jet, the more precisely you can cut the part. So a precise table is very important and an important component of a waterjet system.
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Rhys Rawson says
Thanks for the information on tolerances of water cutters. It is good to know that “thicker materials make it more difficult to control the behavior of the jet as it exits out the bottom.” I’ll have to consider that when planning my projects. I definitely don’t want splintered corners!