How can we solve the problem of low-frequency vibration in inclined bed CNC lathes?

How can we solve the problem of low-frequency vibration in inclined bed CNC lathes?During the machining process, the CNC lathe with an inclined bed sometimes experiences low-frequency vibration, which can easily cause chattering on the surface of the workpiece, resulting in high rework and scrap rates. At this time, it is important to identify the specific cause and take corresponding elimination measures to ensure normal operation.

1. In low-frequency vibration, the main reason is that the vibration in the Y direction causes changes in cutting force, causing F to approach F and generate vibration.

Measure: Tool main deviation angle( μ The larger the r angle, the smaller the Fy force, and the less likely it is to vibrate. Therefore, appropriately increasing the main deviation angle of the tool, eliminating or reducing vibration, and appropriately increasing the front angle of the tool can reduce Fy force, thereby weakening vibration. If the back angle of the tool is too large or the blade is too sharp, the tool is prone to biting into the workpiece and causing vibration. When the tool is properly passivated, the back face of the tool has the effect of preventing the tool from “biting” into the workpiece, which can reduce or eliminate vibration.

2. When wide and thin chips are generated during the turning process, the vibration in the Y direction causes changes in cutting force.

When the cnc micromachining section is wide and thin, the vibration in the Y direction will cause drastic changes in the cutting cross-sectional area and cutting force. Therefore, CNC lathes are prone to vibration in this situation. For example, when turning with a longitudinal cutting tool, the deeper the cutting depth, the greater the feed rate, and the smaller the main deviation angle, the wider and thinner the cutting section, and the easier it is to generate vibration.

Therefore, when selecting the turning speed, it is necessary to avoid the medium speed zone where the cutting force decreases with the speed (when cutting carbon steel, the speed range is 30-50m/min). At the same time, reducing the back cutting force of the car, appropriately increasing the feed rate, and reducing the cutting depth can also help suppress vibration.

3. The insufficient stiffness of the workpiece system and tool holder system is the main cause of low-frequency vibration.

The following measures can be taken to eliminate or reduce vibration: when clamping the workpiece with three or four claws, the coaxiality error between the workpiece rotation center and the spindle rotation center should be minimized as much as possible, to avoid vibration caused by intermittent cutting or uneven cutting caused by tilted or uneven cutting of the CNC lathe workpiece.