The rigidity of a CNC machine tool refers to the oscillation that occurs when the machine tool is processed. The rigidity is high and the oscillation is small, and the rigidity is small and the oscillation is large. The bed and transmission system of the machine tool can directly affect the rigidity of the entire machine. Different rigid machine tools have a great influence on the selection and loss of the tool when processing the product, and directly affect the final production efficiency and production cost.

The rigidity of the machine tool is manifested in two aspects: static rigidity and dynamic rigidity.

1. Static rigidity indicates the size of the deformation of the machine tool caused by the machine tool during the cutting process.

For a detailed performance, for example:

The cutting force is 1000N in the X direction, 500N in the Y direction, and 200N in the Z direction. The rigidity of the XYZ direction screw system K=100, 100, 80. The deformation of each of the three axes during cutting: δx=1000/100=10μm=0.01mm, δy=0.005mm, δz=0.0025mm.

For example, the K value described in the figure is a value that measures the rigidity of the machine tool. The K value of the general machine screw system is between 50 and 200.

In addition to this, there are deformations of the guide rails, deformation of the bed, and the like. Static stiffness is composed of many elements, but the most important part is the static rigidity of the three-axis screw system (the two-axis lathe).

Second, dynamic rigidity is the most important indicator to measure the rigidity of a machine tool.

In a nutshell, the dynamic rigidity of a machine tool refers to the ability of a machine tool to resist forced oscillations. The term is called the size of the natural frequency.

The tool rotates at high speed during cutting, and the rotating cutting and internal data are not uniform, and the impurities may cause oscillation. The cutting location is the source of oscillation for the entire device. The screw system and the guide rail system of the equipment will be forced to oscillate under the influence of the oscillation source. If the vibration of the various parts of the machine tool is large, it will have a very strong impact on the machining, which will affect the roughness of the cutting and the life of the tool, which will have a fatal effect on high-precision machining.

Dynamic stiffness is affected by many aspects, the most important of which is the dynamic rigidity of the screw guide system and the anti-oscillation frequency of the cast iron of the bed. Of course, the rigidity of the spindle is the most fundamental and most important.

According to experience:

1. The larger the diameter of the screw, the larger the weight of the bed, the larger the inner diameter of the front end bearing of the spindle, the better the dynamic rigidity;

2, the general roller bearing or roller linear guide is better than the ball type dynamic rigidity, but the speed is affected (roller bearings are generally only used for lathes);

3. The general sliding guide rail has better dynamic rigidity than the rolling guide rail, but the sliding speed is affected (the sliding guide rail speed is generally <30m/min, the rolling guide rail can reach 180m/min). In addition, the setting of the machine debugging parameters has a very large dynamic stiffness function. Impact. The mechanical function is the foundation, and the fit of the electrical commissioning and the mechanical function is the key condition for the mechanical function. Assume that the mechanical function score is 80 points, but the electrical debugging number can only play 50%, which is 60 points lower than the mechanical function, and the electrical debugging is 90% of the situation. (Unreasonable electrical parameters can cause feedback tremors in the servo motor).

Dynamic stiffness has no detailed inspection indicators, but the prototype can be used to roughly see the dynamic rigidity of the machine. It is mainly detected by three aspects: large cutting test, precision sample test, and dome spherical test.

In summary, the dynamic rigidity is affected by all aspects of machine tool production, such as mechanical design, mechanical manufacturing, and electrical debugging. It is the performance of a comprehensive function of a numerical control device. In general, dynamic stiffness is directly proportional to static stiffness.

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