Cutting tool chipping or breakage is an serious problem in CNC manufacturing, it may lead to the failure of whole process. To ensure the CNC turning and machining goes in normal efficiency, follow us to explore the reasons and types of cutting tool failure, and how to prevent or avoid tool breakage.  

Types of Cutting Tool Failure and Reasons in CNC Turning

During the CNC machining and CNC turning services, which forms of failure and breakage the cutting tool will appear?

1) Slight cutting edge chipping

When the structure, hardness, and the rest part of the workpiece are not uniform, the rake angle is too large, which causes the strength of cutting edge is too low, system rigidity is poor to cause vibration, or intermittent cutting, and cutting tool quality is not very good, then the cutting edge is easy to get chipping, refers to slightly fall, notch, or spalling on the turning cutting tool edge. If continuous cutting, it may lead to greater cutting tool breakage and failure.

2)Cutting edge or tip crumble 

This kind of cutter breakage is the development of slight chipping, often occurs under the worse cutting conditions, the size and range of crumble is larger than that of chipping, leading to the cutting tool lose the cutting ability completely, and the turning work need to be stopped.

3)Cutting tool or blade break off

When the cutting amount is too large, there is impact load, slight crack has existed in tool or blade material, then if there is residual stress in the blade due to welding and grinding, the turning cutting tool may be broken off, which directly causes tool scrapped.

4)Cutter surface or coating peeling

For cutting tool materials with high brittleness, such as cemented carbide, ceramics, and PCBN with high TiC content, if there are defects or potential cracks in the surface, or residual stress  due to welding and edge grinding, it is easy to cause surface peeling off when the cutting process is not stable or the tool surface bears alternating contact stress. Peeling may occur on the rake and rear. The coated tool is more likely to peel off. After the blade is slightly peeled off, it can still work, and it will lose the cutting ability if it is seriously peeled off.

5)Plastic deformation

Because of the low strength and hardness of high speed steel, plastic deformation may occur in the cutting part. The cemented carbide tool may also appear plastic deformation in certain condition, while PCD and PCBN are basically free of plastic deformation.

6)Hot-tearing 

When the CNC turning cutting tool bears alternating mechanical load and thermal load, the surface of cutting part will crack due to inevitable alternating thermal stress and repeated expansion and contraction. Although some tools do not have obvious alternating load and stress, because of the temperature difference between the surface and the inner, adding the inevitable defects in the cutting tool material, cutters also may appear hot-tearing.

How to Prevent the Cutting Tool Breakage and Chipping

1)Select right and appropriate tool material based on the characteristics of the part to be machined. Ensure the hardness, wear resistance and toughness required.

2)Set up the geometry parameters correctly, adjust rake angle, rear angle, lead angle, cutting edge inclination angle, etc. Ensure the cutting edge and tip have good strength, grinding negative chamfer on the cutting edge is an effective measure to prevent chipping.

3)Ensure the quality of welding and grinding, check out whether there is crack on the cutting tool.

4) Select proper cutting amount, avoid excessive cutting force and high cutting temperature, in order to prevent tool damage

5) Ensure the processing system has good rigidity to reduce vibration

6) Perform correct operations, try to make the tool bear no or less sudden load