Tool bounce is a relatively large vibration caused by excessive force on the tool. The harm caused by tool bounce is overcutting of the workpiece and damage to the tool. Tool bounce occurs when the tool diameter is small, the tool bar is too long, or the force is too large. In the process of CNC machining, tool bounce often occurs at the corner, resulting in overcutting.

If we adopt reasonable tools and processing methods, the chance of tool bounce can be greatly reduced. For example, Figure A shows the state of the tool when processing a relatively flat position. When the tool stops at position B and prepares for reverse processing, the tool will deform due to inertia, resulting in overcutting at the relatively straight position of position B.

The relationship between tool deformation and tool deformation is:

From the above formula, we can see that there are three main factors that affect tool deformation:

L - Tool length

D - Tool diameter

P - Force on the tool

L - Tool length

From the formula, the tool deformation is in a cubic relationship with the tool length. For tools of the same diameter, when the tool length is doubled, its deformation will increase by 3 times. During processing, shorten the tool length as much as possible to reduce the possibility of tool bounce.

D - Tool diameterFrom the formula, the tool deformation is in a 4th power relationship with the tool diameter. For tools of the same length, when the tool diameter is halved, its deformation will increase by 4 times. During processing, if conditions permit, choose large-diameter tools or use reinforced tools to reduce the risk of tool bounce.

P - Force on the tool From the formula, the deformation of the tool is proportional to the force it receives during processing. Reducing the force on the tool can reduce the chance of tool bounce. The force on the tool during processing can be reduced by the following methods.

Analysis of reducing force: Cutting is a shear deformation process. Each material has its own strength. To separate the material, the external strength must be greater than the material's own strength. : Material strength = F force / S : Contact area. From the above formula, it can be seen that the force (F) on the tool is proportional to the contact area (S) between the tool and the workpiece. To reduce the force on the tool, it is necessary to reduce the contact area between the tool and the workpiece.

By comprehensively applying the three factors that affect tool deformation (tool length, tool diameter, and cutting force), the probability of tool bounce can be reduced and processing time can be increased to obtain better processing accuracy and surface roughness.

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