There are different variations for 4-axis machining, but we will talk about vertical 4-axis milling. 4-axis machining has the same 3 axes (XYZ) as 3-axis, plus an additional axis for rotation. With a DATRON machine, it's the A-axis. The A-axis has the workpiece rotate around the X-axis. The rotation allows 4 sides to be machined while the part stays in the fixture and needs only one setup.

There are 2 types of 4th axis milling: indexing and simultaneous (this is also the case for 5th axis milling). Indexing in 4-axis milling, known as 3 + 1, has the workpiece rotate into a position where 3-axis milling strategies are then used. For simultaneous machining, the part rotates, and the machine cuts it at the same time

More complex geometries, like arcs and helixes, can be achieved more efficiently with 4th and 5th axis machining. You're also able to cut angled features more easily. However, because the piece is secured in a single setup for 4th axis, the angled features need to be on the same axis. Otherwise, with different angled features, you adjust the setup (and possibly change the fixture) for each angle.

4th axis machining is often used when cut-outs and holes are on the side of a part or made on a cylinder. By using 4-axis instead of 3-axis, you typically save more time because you're eliminating the need for additional setups. It's also easier to hold tight tolerances on all 4 sides of a part since it stays in a single setup. DATRON .