3D Full Feature
In another definition, a 3 axis CNC machine commonly has a full feature of 3D while 2.5D machine is a kind of machine that uses 2D drawing for 3D material. In 2.5D, you just simply put the information about thickness in the software so that the machine can cut the material in 3D manner. So to say, with 2.5 axis CNC machine you are only capable of viewing the angles from two points while with 3 axis machine, one more angle can be accessed.Concurrent Process 3 axis CNC machine
Designing and cutting happen simultaneously in a 3 axis CNC machine as it works on X, Y, and Z axes. The tip of the cutter will follow the path of 3D curves which have been determined in the program. This enables the machine to make a fine cut of a complicated pattern on a piece of material.On the other hand, a 2.5 D machine can produce similar items but in much different way, like a v-carving method. This method allows the machine to create a 3D result yet the designing is supposed to be done in 2.5D. The best news is 2.5D designs have relatively lower price than 3Ds. Therefore, this type of machine can be chosen in case of you are on a budget.
Choosing which type of CNC machine suits you depends on the urgency and the budget available. If you think that you can manage with 2D drawing and v-carving method, your plan to buy a 3 axis CNC machine can be postponed.