2.5D (machining)

In machining, 2.5D refers to a surface which is a projection of a plane into 3rd dimension – although the object is 3-dimensional, there are no overhanging elements possible. Objects of this type are often represented as a contour map that gives the height (i.e., thickness or depth) of the object at each point.[1]

2.5D objects are often greatly preferred for machining, as it is easy to generate G-code for them in an efficient, often close to optimal fashion, while optimal cutting tool paths for true 3-dimensional objects can be NP-complete (nondeterministic polynomial time complete), although many algorithms exist.

2.5D objects can be machined on a 3-axis milling machine, and do not require any of the features of a higher-axis machine to produce.

A 2.5D machine, also called a two-and-a-half-axis mill, possesses the capability to translate in all three axes but can perform the cutting operation only in two of the three axes at a time due to hardware or software limitations, or a machine that has a solenoid instead of a true, linear Z axis. A typical example involves an XY table that positions for each hole center, where the spindle (Z-axis) then completes a fixed cycle for drilling by plunging and retracting axially. The code for a 2.5D machining is significantly less than 3D contour machining, and the software and hardware requirements are (traditionally) less expensive. Drilling and tapping centers are inexpensive, limited-duty machining centers that began as a 2.5-axis market category, although many late-model ones are 3-axis because the software and hardware costs have dropped with advancing technology.

A 2.5D image is a simplified three-dimensional (x, y, z) surface representation that contains at most one depth (z) value for every point in the (x, y) plane.


  1. 2.5D and 3D Machining, archived from the original on March 1, 2012, retrieved 2009-11-11.
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