In CNC turning and milling, cutting inserts are consumables. Especially in mass production, frequent wear, chipping, thermal cracking, or sudden breakage of cutting inserts not only increases tooling costs but can also lead to downtime for tool changes, workpiece scrap, and decreased machining efficiency. When faced with the problem of excessively rapid cutting insert consumption, many companies first consider replacing them with cheaper or harder inserts. However, in reality, excessive cutting insert consumption is often not solely caused by the quality of the cutting inserts, but is closely related to the selection of the cutting inserts, cutting parameters, machining stability, and cooling methods.
First, the appropriate insert grade and groove type should be selected based on the workpiece material and specific machining conditions. Different materials experience different cutting temperatures, friction, impacts, and wear mechanisms during machining. For example, inserts designed for stable finishing may not be suitable for intermittent heavy cutting, while inserts with high wear resistance but insufficient toughness may chip rapidly under conditions of significant vibration or impact. Therefore, when selecting inserts, one should not only focus on hardness or price, but also comprehensively consider the workpiece material, whether the cutting is continuous or intermittent, whether it is roughing or finishing, and the actual cutting load. Only by reasonably balancing the wear resistance and toughness of the inserts can the insert tool life be truly improved.
Secondly, optimizing cutting parameters is crucial for reducing insert wear. Excessive cutting speed leads to a rapid increase in cutting zone temperature, accelerating flank wear, crater wear, and even plastic deformation. However, lower speeds are not always better, as excessively low cutting temperatures can negatively impact cutting performance when machining materials prone to built-up edge formation, such as low-carbon steel and stainless steel. Feed rate and depth of cut also need to be matched to the insert groove shape and actual working conditions. If the depth of cut is too small, the cutting edge may be more in a frictional state than an effective cutting state, concentrating wear in a small area. Therefore, a more reasonable approach is to use the cutting parameters recommended by the tool manufacturer as a base and then gradually adjust them based on actual wear conditions, rather than changing the speed, feed, and depth of cut all at once.
Machining stability also directly affects insert life. Vibration and chatter subject the cutting edge to repeated impacts, easily causing chipping and edge breakage. Excessive tool extension, insecure workpiece clamping, insufficient tool holder rigidity, or poor tool holder stability can all contribute to abnormal insert wear. When conditions permit, the tool overhang length should be shortened as much as possible, and the clamping rigidity of the workpiece and tool should be improved. Sometimes, simply improving clamping and reducing vibration can significantly extend the life of the cutting inserts without needing to replace them with more expensive ones. If vibration cannot be completely eliminated, the cutting load can be appropriately reduced, and the use of cutting inserts with higher toughness or stronger cutting edges can be considered.
Cooling methods are also crucial. Insufficient coolant flow or improper spray direction can prevent the heat generated in the cutting zone from being dissipated in time, making the cutting inserts more prone to high-temperature wear and plastic deformation. In some machining processes, increasing cooling pressure can also improve heat dissipation and chip removal. However, for intermittent cutting, intermittent or unstable coolant supply during machining can cause repeated thermal shocks, increasing the risk of thermal cracking. Therefore, more cooling is not necessarily better; a stable and appropriate cooling strategy should be developed based on the specific machining method. Studies also show that improving lubrication and cooling in the tool-chip contact area can reduce friction and cutting forces, thereby slowing down tool wear.
Finally, companies should establish clear standards for monitoring cutting insert wear, rather than waiting until the inserts completely break before replacing them. Different wear patterns of cutting inserts usually reflect different machining problems. For example, rapid flank wear may be related to excessive cutting speed or insufficient wear resistance of the cutting inserts; crater wear is usually related to high cutting temperatures and pressures; chipping may indicate excessive cutting load or insufficient machining stability. By recording the main wear types of the cutting inserts, the root cause of the problem can be identified more accurately. Therefore, observing tool wear should not only be used to determine "whether the tool needs to be replaced", but should also serve as an important basis for optimizing CNC machining processes.
In summary, reducing tool wear in CNC machining cannot rely solely on lowering tool purchase prices. A more effective approach involves addressing the entire machining system, including correctly selecting tool grades and groove types, optimizing cutting parameters, improving equipment and clamping stability, employing appropriate cooling methods, and establishing a regular tool wear monitoring mechanism. When these factors are comprehensively controlled, not only can the actual service life of the tools be extended, but tool change frequency can also be reduced, downtime minimized, and the stability and production efficiency of the machining process improved.
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FAQ
Q1: Why is the use time of my knife grain so short?
Common causes include excessive cutting speeds, mismatched tool grade or geometry, insufficient cooling, excessive cutting loads, and vibration during machining.
Q2: Will reducing the cutting speed definitely extend the tool grain life?
uncertain. Lowering the speed can usually reduce high-temperature wear, but the speed still needs to match the workpiece material and tool grade, otherwise problems such as built-up edge may occur.
Q3: How to reduce blade chipping?
The clamping stability of the workpiece and tool should be checked to reduce vibration and excessive cutting load, and tool grains with higher toughness or stronger cutting edges should be selected according to actual working conditions.