Filters, screens, screen inserts, and methods of making same

A method of making a filter or screen, comprising:

• producing a first opening in a hard material by directing a high pressure cutting jet against the material at one or more first positions where the first opening is to be formed, the high pressure cutting jet comprising a continuous high pressure fluid and an abrasive;
• after producing the first opening, replacing the abrasive with a liquid or gaseous interference medium in such a way that reduces an energy density of the cutting jet from an energy density sufficient to remove or cut the material to an energy density insufficient to remove or cut the material;
• while the cutting jet possesses the energy density insufficient to remove or cut the material, the cutting jet moving to a second position on the material where at least a portion of a second opening is to be formed;
• replacing the liquid or gaseous interference medium with the abrasive in such a way that increases the energy density of the cutting jet from an energy density insufficient to remove the material to an energy density sufficient to remove the material, thereby producing at least a portion of a second opening in the material;
• wherein supply of the abrasive and of the liquid or gaseous interference medium are synchronized and dependent on each other, such that supplying the liquid or gaseous interference medium to the cutting jet causes the abrasive to be interrupted and interrupting the liquid or gaseous interference medium causes the abrasive to be supplied to the cutting jet;
• and
• wherein cuts made at least at the one or more first positions are tapering through openings, and wherein edges along the through openings are characterized by sharp edges.