What is 3+2 Machining? | 3+2 vs 5-Axis CNC Machining, Which Process to Choose? – CNCLATHING

Other than the common 3/4/5-axis CNC machining, 3+2 machining is also an optimal manufacturing technology for some applications, what is 3+2 machining and how does it work? CNClathing.com will get into the difference between 3+2 and 5-axis CNC maching, as well as their pros and cons for reference in determine which one to choose.

What is 3+2 Machining?

3+2 machining is a manufacturing method through which a 3-axis milling program is executed, 2 rotating axes of the 5-axis machine are used to fix the cutting tool in an tilted position, the fourth axis and fifth axis are used to determine the direction of the cutters, different from the continuous or simultaneous 5-axis machining. 3+2 operation is applicable for moldmaking and curves or angled tubular shapes processing.

How Does 3+2 Machining Work?

Actually, the principle of 3 + 2 positioning CNC machining is to realize 3-axis machining at a specific angle. Simply speaking, when the CNC machine tool turns to certain angle, it still processes as the ordinary 3-axis machine.

Difference Between 3+2 and 5-Axis CNC Machining

The main difference between 3+2 and 5-axis machining is the applicable industry and products. 5-axis CNC machining is suitable for complex contour surface machining, while 3+2 machining mainly works for plane processing. The biggest benefits of 5-axis machining is it can achieve various types of CNC machining parts and geometries fabrication, suitable for aerospace, military and more demanding industry, while not all parts require full 5-axis, sometime 3+2 CNC machining is more efficiently. Which process to choose? You need to familiar with their advantages and disadvantages respectively.

Advantages/Pros of 3 + 2 machining:
1) Shorter, more rigid cutting tools can be used, enables undercuts in cavities and steep walls.
2) The cutter can form a certain angle with the surface, and the spindle head can extend to lower position and closer to the workpiece.
3) The tool moving distance is shorter and the program code is less.

Disadvantages/Cons of 3 + 2 machining:
3 + 2 machining is usually considered to set a constant angle to the spindle. Complex CNC parts may require many tilted views to cover the entire workpiece, but it will cause tool paths to overlap, thus increasing machining time.

Advantages/Pros of 5-axis machining:
1) No special fixture is needed, which reduces the cost of fixture, avoids multiple clamping and improves the machining accuracy.
2) Reduce the number of clamps used.
3) Reduce special cutting tools and cost.
4) It can increase the effective cutting edge length, reduce the cutting force, improve the service life of the tool.

Disadvantages/Cons of 5-axis machining:
1) Compared with 3 + 2, the spindle rigidity is worse.
2) In some cases, it is not suitable to adopt the 5-axis, for example, when the cutter is too short or the handle is too large, the vibration cannot be avoided under any condition of tilted angle.
3) Compared with 3-axis, the machining accuracy error is larger.

In general, for tighter tolerances and more complex shapes, 5-axis machining is better, 3+2 allows cutting tool angled toward the workpiece, it is suitable for positioning the part for faster feeds and speeds.