Causes, characteristics, and control measures of debris accumulation tumors

1. Causes of formation

In the part near the cutting edge, in the tool chip contact area, due to the high downward pressure, the underlying metal of the chip is embedded in the micro uneven peaks and valleys on the front cutting surface, forming a true metal to metal contact without gaps and producing bonding phenomenon. 

This part of the tool chip contact area is called the bonding area. In the bonding zone, a thin layer of metal material will accumulate on the front cutting surface at the bottom layer of the chips, and the metal material of this part of the chips has undergone severe deformation and strengthening at an appropriate cutting temperature. 

As the chips continue to flow out, under the pushing force of the subsequent cutting flow, this layer of stagnant material slides away from the upper layer of the chips, becoming the foundation of chip accumulation. 

Subsequently, a second layer of hysteresis cutting material will be formed on top of it, which continuously accumulates and forms debris accumulation nodules.

2. Characteristics and impact on cutting processing

1) The hardness is 1.5-2.0 times higher than that of the workpiece material, and it can replace the front cutting surface for cutting. It has the effect of protecting the cutting edge and reducing the wear of the front cutting surface. However, when debris falls off and flows through the tool workpiece contact area, it can cause wear on the back cutting surface of the tool.

2) After the formation of chip accumulation, the working rake angle of the tool significantly increases, which plays a positive role in reducing chip deformation and cutting force.

3) Due to the accumulation of chips protruding from the cutting edge, the actual cutting depth increases, affecting the dimensional accuracy of the workpiece.

4) Chip accumulation can cause a "furrow" phenomenon on the surface of the workpiece, affecting its surface roughness.

5) The fragments of accumulated debris can bond or embed into the surface of the workpiece, causing hard spots that affect the quality of the machined surface of the workpiece.

From the above analysis, it can be seen that chip accumulation is unfavorable for cutting, especially for precision machining.

3. Control measures

The following measures can be taken to prevent the formation of chip buildup by avoiding bonding or deformation strengthening between the chip substrate material and the front blade surface.

1) Reduce the roughness of the front blade surface.

2) Increase the rake angle of the tool.

3) Reduce the cutting thickness.

4) Use low-speed or high-speed cutting to avoid cutting speeds that are prone to chip buildup.

5) Properly heat treat the workpiece material to increase its hardness and reduce plasticity.

6) Use cutting fluids with good adhesion and hair resistance (such as extreme pressure cutting fluids containing sulfur and chlorine).