Tearing in machining refers to a phenomenon where the tool, unable to maintain a consistent cutting ability due to wear or the configuration of the cutting edge during the machining process, does not cut but rather tears the material being machined.
When tearing occurs, the machined surface exhibits splits, leading to degraded machining accuracy. This article explains the impact, causes, and effective countermeasures for tearing that occurs during cutting.
Tearing, which leads to various problems such as decreased machining accuracy and cutting performance, must be reliably prevented. Tearing is likely to occur in the following situations:
As tool wear progresses, the tool can no longer exhibit its inherent cutting ability, leading to decreased cutting performance. This decrease in cutting ability can result in the tool tearing the workpiece material instead of cutting it properly.
Similar to when tool wear progresses, minor chipping on the tool also leads to decreased cutting performance. In such cases, the tool fails to cut the workpiece properly, resulting in tearing.
The formation of a built-up edge, where chips adhere to the cutting edge and form a new edge, can cause fluctuations in the cutting surface, leading to tearing.
Tearing can also occur if the chips generated during cutting are not properly evacuated, causing the chips to interfere between the workpiece's cutting surface and the tool.
Tearing can cause issues such as deterioration of surface finish, decreased cutting ability, and worsening dimensional accuracy.
Tearing can deteriorate the surface finish of the cut, such as causing splits on the cutting surface. Although this can be eliminated during finishing operations in rough machining, tearing during finishing operations can lead to a poor surface finish, rendering the workpiece defective.
The conditions that lead to tearing could indicate that the cutting tool is suffering from wear, chipping, or the effects of a built-up edge. In such cases, the cutting ability is decreased, and it is not advisable to continue machining.
Tearing may remove more material than intended, potentially worsening dimensional accuracy. This can lead to reworking before acceptance in subsequent processes or issues with assembly in later stages.
Countermeasures include tool selection, adjustment of machining conditions, and process monitoring.
Specific measures for tool selection include choosing coated tools or tools suitable for the application.
Coating cutting tools can improve wear resistance, preventing a decrease in cutting ability and the occurrence of tearing during cutting.
Choosing tools suitable for the purpose and application of cutting can also be effective. For example, using tools with high rigidity for rough machining and tools with good sharpness and precision for finishing can reduce the likelihood of tearing.
Measures include setting paths considering chip evacuation and adjusting cutting conditions.
Setting paths that consider chip evacuation can prevent tearing caused by chips. Especially when machining deep holes or grooves, setting a cutting path that allows for chip evacuation or chip breaking is advisable.
Reducing cutting conditions to decrease the cutting load can prevent tool wear, chipping, and minor breakage that cause tearing. Lowering the cutting speed may reduce production efficiency but can ultimately decrease the occurrence of defects and improve overall production efficiency. In cases where tearing is caused by a built-up edge, increasing cutting conditions to maintain higher machining temperatures may be an effective countermeasure.
Although it may require a dedicated system, monitoring the machining process during cutting is also an effective countermeasure.
Monitoring the process allows for checking the load on the tool during cutting. Depending on the system, the data used for input, such as current values or sound waves, can vary. However, using these data to calculate the load on the tool can help prevent tearing. Measures can be taken, such as stopping the machine when reaching a certain level or detecting abnormal values.
Identifying the cause of tearing is not easy, as it can be due to various factors. Monitoring the machining process allows for determining whether tearing is caused by tool wear or sudden events. Identifying the cause enables the implementation of appropriate countermeasures, preventing unnecessary shortening of tool life.
This article has explained the overview, causes, and effective countermeasures for tearing that occurs during machining. Tearing leads to issues such as worsened workpiece accuracy, requiring countermeasures tailored to the cause. However, identifying the cause can be challenging due to multiple potential factors. Monitoring the machining process and effectively analyzing and addressing the causes is crucial.
