We have all encountered the problem of workpiece surface chatter during CNC turning. The light chatter requires rework, and the heavy chatter means scrapping. No matter how it is handled, it is a loss. How to eliminate the chatter on the operating surface of CNC turning?
In order to eliminate chatter of operating surface in CNC turning, we need to know the cause of chatter.
1. Machine problems
There are two possible causes for the machine tool.
(1) When the workpiece is jacked with the top cover, the jacking extension is too long, resulting in insufficient rigidity.
(2) The machine itself has been used for a long time, the maintenance is not timely, and the internal bearings and other parts are seriously worn.
There are four possible reasons for the machine tool.
(1) The tool rest extends too long during turning, resulting in insufficient rigidity.
(2) The blade is worn and not sharp.
(3) The selection of machine tool parameters during turning is unreasonable.
(4) The tip arc of the blade is too large.
3. Problems of Workpieces
There are three possible causes for artifacts.
(1) The material of turning workpiece is too hard, which affects turning.
(2) The turning workpiece is too long, and the workpiece is not rigid enough during turning.
(3) Thin wall workpieces are not rigid enough when turning excircles.
First, check whether there is a problem with the workpiece.
(1) If the workpiece material to be turned is too hard, can you change the process to reduce the hardness of the workpiece, and then improve it in other ways later.
(2) If the workpiece to be turned is too long, follow the tool holder to improve the stability of the workpiece.
(3) If the workpiece is thin-walled, tooling can be designed to improve the rigidity when turning the excircle.
Next, let’s see if it is a tool problem.
(1) If the tool rest extends for a long time, check whether the position of the lower tool rest can be adjusted. If not, replace the tool rest with a higher steel. If necessary, use an anti vibration tool rest.
(2) If the blade is worn, replace the blade.
(3) If the reason is that the selected machine parameters are unreasonable, change the program and select reasonable parameters.
(4) The tool tip arc is too large, and the blade needs to be replaced.
3. Machine tool
Finally, judge whether there is a problem with the machine tool and whether the improper tool tip is used
(1) If the improper top is used, the top with good performance needs to be replaced.
(2) If the machine tool itself is used for too long and the maintenance is not timely, it is necessary to contact the machine tool maintenance personnel to repair the machine tool.
If we don’t find any problems based on the above points, what else can we do? It can be based on the research on the vibration principle of tool setting. At present, there are some specific and practical methods applied to the processing site:
(1) Reduce the working weight of the parts that cause vibration, and the smaller the inertia, the better.
(2) For eccentric workpiece, make corresponding tooling.
(3) Fix or clamp the parts with the greatest vibration, such as center frame, working cage, etc.
(4) Increase the rigidity of the processing system, for example, use a tool holder with high elastic coefficient or use a special anti vibration force combined with a dynamic damper to absorb impact energy.
(5) From the point of view of blade and workpiece rotation direction.
(6) Change the tool shape and feed angle, the smaller the tool tip radius is, the better, and reduce the cutting resistance. The lateral inclination angle must be positive to make the cutting direction closer to vertical. The caster angle is better to be positive, but even if the chip removal ability is poor, it can generally be used to make the caster angle negative, but still retain the positive value of the cutting effect.