How to judge the wear of the cutting tools and what improvement methods are there?
In the metal cutting process, the surface load at the tool/ workpiece interface, the energy, and friction generated by the high-speed sliding of chips along the rake face are converted into heat, and usually 80% of this heat is carried away by chips (the change of this proportion mainly depends on the cutting speed), while the remaining 20% is transferred into the tool. Heat and temperature are the basis of wear and tear of the tool.
ONE: The Judgment of Wear and Tear of Tool
- The Tool Life Table ( based on the number of the machined workpieces) is used by some high-end equipment manufacturing enterprises or single-product batch production enterprises to guide production. This method is suitable for aerospace, steam turbine, automobile key components such as engines, which are very expensive.
- If there are intermittent and irregular sparks in the processing process, it turns out that the tool is worn out and should be changed in time according to the average life.
- Color of the chips. If the color changes, it shows that the temperature has been changed when processing, which may be caused by tool wear.
- The shape of the chips The serrations appear on both sides of the chips, curl abnormally. The chips become more fine and small. These phenomena are the judgment basis for tool wear.
- The surface of the workpiece. there are bright marks, but no obvious change of roughness and size, which show that the tool has been worn.
- The Sound. When vibration intensifies on processing, or when the tool is not sharp, there will be abnormal sound.
- A load of machine equipment. If there are obvious incremental changes, the tool is worn.
In addition, some obvious phenomena such as serious burrs, roughness reduction, change of size, are also the criteria for judging tool wear.
TWO: Types of Tool Wear and Common Methods to Prevent from Damage
- Worn cutting edge.
Improvement measures: Properly reduce cutting speed; use more wear-resistant material; use coated tools.
- Broken teeth.
Improvement measures: use material with better toughness; use tools with strengthened cutting edge; check the rigidity of process system.
- Chip accumulation and breakage.
Improvement measures: use chucks with overload protection; make the chip groove on the drill bit and improve the groove of machine tap; make the cutting edge sharper.
- Insufficient precision.
Improvement measures: Improve the runout of cutting edge about drill bit. Control all runouts of machine taps. If the requirement is high, choose a tool with high precision as much as possible and do not grind repeatedly during use.
The continuous development of best tool matrix, coating and cutting edge technology is crucial to limit tool wear and high-temperature resistance when cutting. These factors, together with the chip groove and the radius of the corner arc radius used on the indexable insert, determine the applicability of each tool to different workpieces and cutting processes. The best combination of all these elements can prolong the service life of cutting tools and make cutting more reliable and economical.