How to eliminate chatter lines on the surface during turning?

We have encountered the problem of chatter on the surface of the workpiece during the turning process. The lighter chatter needs to be reworked, and the heavier chatter needs to be scrapped. No matter how it is handled, it is a loss.

How do we eliminate chatter?

To eliminate chatter, we need to know the cause of chatter.

1. Problems with machine tools

There may be two reasons for the machine tool:

(1) When the top is used to push the workpiece, the top extends too long, resulting in insufficient rigidity;

(2) The machine tool itself has been used for too long, maintenance is not timely, and internal bearings and other parts are seriously worn.

2. The problem with the tool

There may be four reasons for the machine tool:

(1) When turning, the tool bar extends too long, resulting in insufficient rigidity;

(2) The blade of the blade is worn and not sharp;

(3) The machine parameters used in turning are unreasonable;

(4) The tip arc of the blade is too large.

3. The problem with the artifact

There may be three reasons for the artifact:

(1) The material of the workpiece to be turned is too hard, which affects the turning;

(2) The workpiece to be turned is too long, and the rigidity of the workpiece is insufficient during turning;

(3) Insufficient rigidity when turning the outer circle of thin-walled workpieces.

If chatter lines appear during the turning process, how to eliminate the problem?

1. Workpiece

First, see if it is a problem with artifacts:

(1) If the material of the workpiece to be turned is too hard, can the process be changed to reduce the hardness of the workpiece, and use other methods to increase the hardness later;

(2) If the workpiece to be turned is too long, the tool holder can be used to improve the stability of the workpiece;

(3) If it is a thin-walled workpiece, tooling can be designed to improve rigidity when turning the outer circle.

2. Tool

Second, take a look at whether it is a tool problem:

(1) If it is the reason that the knife bar extends too long, see if the position of the knife bar can be adjusted. If it cannot be adjusted, it is necessary to replace the knife bar with higher rigidity, and if necessary, use the anti-vibration tool bar;

(2) If it is the cause of blade wear, the blade needs to be replaced;

(3) If the selected machine tool parameters are unreasonable, change the program and select reasonable parameters;

(4) If the blade tip arc is too large, the blade needs to be replaced.

3. Machine tools

Finally determine if there is a problem with the machine tool:

(1) If the top is used improperly, you need to replace the top with better performance;

(2) If the machine tool itself has been used for a long time and the maintenance is not timely, you need to contact the person who repairs the machine tool to check and repair the machine tool.

If the problem is not found?

If we do not find any problems according to the above points, what else can we do? According to the principle of vibration knife obtained from the research, there are some more specific and practical methods that are currently applied in the processing site:

(1) Reduce the working weight of the part that causes vibration, the smaller the inertia, the better;

(2) For eccentric workpieces, make corresponding tooling;

(3) Fix or clamp the places with the greatest vibration, such as center frame, work holder, etc.;

(4) Improve the rigidity of the processing system, such as using a tool holder with a higher elastic coefficient or using a special anti-vibration force with dynamic shock absorbers to absorb impact energy;

(5) Consider from the angle of blade and working rotation direction;

(6) Change the shape and timing of the tool, the smaller the nose radius of the tool, the better, in order to reduce the cutting resistance. The roll angle must be positive to make the cutting direction more vertical. The back rake angle is preferably a positive value, but the chip removal and cutting ability is relatively poor, so generally you can choose a grooved knife to make the rake angle a negative value, but still maintain a positive cutting effect.