Analysis of Forms and Causes of Turning Tool Wear in CNC Lathes

During the cutting process of a CNC lathe, the tool wears to a certain degree, the cutting edge is chipped or broken, and the cutting edge is rolled (plastic deformation), the tool loses its cutting ability or cannot guarantee the processing quality, which is called tool failure. The main forms, causes and countermeasures of tool breakage are as follows:

Wear on NC Face of CNC Lathe

Flank wear is frictional wear that occurs on the flank due to mechanical stress. Because the tool material is too soft, the rake angle of the tool is too small, the cutting speed is too high during the machining process, and the feed is too small, which causes excessive wear on the flank surface, which reduces the dimensional accuracy of the machining surface and increases the friction force. High abrasive tool materials, at the same time reduce the cutting speed, increase the feed, increase the rake angle of the tool, so as to avoid reducing the occurrence of flank wear.

CNC lathe tool edge wear

Boundary wear on the main cutting edge is common at the contact surface with the workpiece. The main reason is the friction caused by surface hardening and sawtooth cutting, which affects the flow of cutting and causes chipping. Only by reducing the cutting speed and feed speed, while selecting wear-resistant tool materials and increasing the rake angle, can the cutting edge be sharper.

Wear of NC Face of CNC Vertical Lathe

The wear caused by friction and diffusion on the rake face is higher than that of the rake face. The rake surface wear is mainly caused by the contact between the cutting and the workpiece material and the diffusion to the heating area. In addition, the tool material is too soft, the cutting speed is too high during the machining process, and the feed is too large, which is also the cause of rake face wear. Wear on the rake face will cause tool deformation, interfere with chip removal, and reduce cutting edge strength. Decreasing cutting speed and feed speed, while choosing coated hard alloy materials, can reduce the wear of the rake face.

Plastic deformation of CNC lathe tools

Plastic deformation is the deformation of the cutting edge under high temperature or high stress. Cutting speed and feed speed are too high, the role of hard points in the workpiece material, too soft tool material and cutting edge temperature and high are the main reasons for plastic deformation. It affects the quality of chip formation, and can sometimes cause chipping. Measures can be taken to reduce the cutting speed and feed speed, and select tool materials with high wear resistance and high thermal conductivity to reduce the occurrence of plastic deformation.

CNC lathe cutting edge

There are some small notches and uneven wear on the cutting edge, that is, the edge flaking, which is mainly caused by intermittent cutting and chip removal. Decrease the feed rate at the beginning of processing, and choose a material with good toughness and a cutting edge with high strength to avoid cutting edge spalling.

CNC Lathe

CNC lathe cutter collapse

The chipping will damage the tool and the workpiece. The main reasons are the transitional wear of the cutting edge and the higher stress, which may also be caused by the tool material being too hard, the cutting edge strength insufficient, and the feed rate too large. The alloy material with good toughness should be selected, the feed and cutting depth should be reduced during processing, and the inserts with high strength or large rounded corners should be selected.

CNC lathe tool thermal cracking

Thermal cracks are cracks that are perpendicular to the cutting edge due to temperature changes during intermittent cutting. Thermal cracking can reduce the surface quality of the workpiece and cause edge spalling. The alloy material with good toughness should be selected, while reducing the feed amount and cutting depth, and dry cooling or sufficient cutting fluid during wet cutting.

Summarizing the above points of CNC lathe tool materials, geometric angles, coatings, cutting edge strengthening conditions and horizontal lathe processing conditions, play different roles in the tool life, indispensable and complementary. A good tool should have a smooth chip flute, a long service life, and can save machining costs.