GlossaryKind of term: Manufacturing term3-axis milling
What is 3-axis milling?
In 3-axis milling the tool moves along three linear axes, X, Y and Z, while the tool axis keeps one direction relative to the workpiece.
That direction stays fixed for the whole setup, usually perpendicular to the table. Whatever is reachable along that axis is made in one setup: faces, pockets, contours, holes and threads from above, and side walls with the flank of the cutter. Both 2.5D work, where Z steps down level by level, and 3D work with a ball-nose cutter, where all three axes move together, count as 3-axis milling.
What decides what you can make on three axes?
What can be done in one setup depends on the direction of each feature, the length and stiffness of the tool, workholding that covers the sides, and the machine envelope. Features whose axis does not run parallel to the spindle, such as a hole in a side face or an angled hole, need another setup, angled workholding, an angle head or a fourth axis. An angled face can still be 3D-milled with a ball-nose or bull-nose cutter, which takes time and leaves scallops between passes. Some undercuts can be cut with a T-slot or lollipop cutter; deep pockets are limited by tool length and chatter.
How does 3-axis milling work in practice?
A 3-axis machine often has a lower hourly rate and simpler programs than a 5-axis. A part with features in several directions can need more setups on such a machine, with setup time and a possible position error between features from different setups. The choice between 3-axis and 5-axis turns on the number of setups, the quantity, hourly rates, programming time and the workholding available.
What is 3-axis milling often confused with?
3-axis milling is not 3+2 machining: in 3+2 the rotary axes lock the part or the spindle head at a fixed angle, after which the machine mills with three linear axes, without a reclamp. It is not the same as 2.5D either: 2.5D is one form of 3-axis milling in which Z moves in steps, whereas 3D milling moves all three axes at once.
How do you see 3-axis milling in Blake?
In Blake you record each machine with its envelope, axis count and your own hourly rate. The first check per machine shows whether the part fits the envelope and axes, and which limit decides; it is a first check, not a manufacturability verdict. Milling from 3-axis to 5-axis is estimated with setup, machining and programming as separate lines. More on milling.
Frequently asked questions
Is 3-axis milling cheaper than 5-axis?
Per machine hour it often is; per part, not automatically. A part with features in many directions needs more setups on a 3-axis machine. Whether the setup time saved on a 5-axis outweighs its higher rate and extra programming depends on quantity and route.
Which features cannot be reached with three axes?
Not in one setup: features whose axis is not parallel to the spindle, such as an angled or side hole, and the clamped face. An angle head or a fourth axis gets you further in the same setup, angled workholding in an extra one.