The wide use of CNC manufacturing and machining equipment promote the development of cutting technology. With the occur of super heat-resistant alloy, composite materials, etc., the quality requirements for cutting tools are more stringent. The performance and cutting tool wear become the key thing. Let’s figure out the types and reasons for tool wear, find out the solutions.
What is tool wear? Tool wear is the gradual failure of cutting tools because of regular operation. There are varying factors causes fast wear of cutting tool.
1) Mechanical wear
Machining hard or difficult materials is easy to cause rapid cutting tool wear. Most of materials that difficult to machine have the characteristics of low thermal conductivity, which results in the bonding strength of the binder in the tool material decrease at high temperature, and accelerate the tool wear.
2) Cutting heat
When cutting materials with high hardness and toughness, the temperature of the cutting edge is very high, and the tool wear is similar to that when cutting intractable materials. Especially when processing the workpiece material that produce short chips, there will be crater wear near the cutting edge, and tool damage in a short time.
3) Chemical wear
The components in the difficult-to-machine material and some components in the tool material react under the high temperature condition when cutting, and the components precipitate, fall off, or generate other compounds, which will accelerate the tool wear such as edge collapse.
Here are some common tool wear patterns in CNC cutting.
1) Flank wear: the part contact with finished workpiece erodes.
2) Crater wear: the rake face will erode when touching chips, typically occurs where the tool temperature is highest.
3) Notch wear: happens on both the insert rake and flank face of cutting tool along the depth of cut line.
4) Built-up edge: the material to be processed is stacked on the cutting edge, most frequently occurs on soft metals with a lower melting point.
5) Glazing: often occurs when the exposed abrasive becomes dulled.
6) Edge wear: outer edge of a drill bit around the cutting face caused by excessive cutting speed.
7) Edge Rounding: radius increase of cutting tool edge due to the material removal
How to reduce or avoid cutting tool wear in CNC machining? Other than tool itself, cutting condition is also an aspect can be considered.
1) Choose right tool material
Alloy steel has high hardness and low price, it is often used to make low-speed tools with complex shapes, such as reamers, taps and dies. High speed steel has higher hardness and wear resistance than alloy steel, and widely used in the manufacture of turning tools, milling cutters, drills, broaches and other machine tools. Cemented carbide blade usually are secured on the cutter body and become one of the main cutter materials now.
2) Use specific cutting fluid
The special cutting fluid with sulfurized EP anti-wear additive can effectively protect the cutting tool and improve the process accuracy. The cutting fluid has passed strict tests in viscosity, pour point, thermal conductivity and other aspects can meet various cutting process requirements. Choose cutting fluid with good environmental protection performance has good stability and will not harm the equipment, human body and environment.
3) Consider the performance of cutting tool
The performance requirements of cutting tool often involve wear resistance, impact resistance, service life and more. The coating materials with good heat resistance, high hardness and multi-layer coating technology allow the coated cemented carbide tools have large working range and long lifespan. In addition, high-speed cutting tool should have high thermal hardness and chemical stability.