How to avoid vibration when turning thin walled long rollers

Regardless of any machine tool, if vibration occurs when machining a workpiece, there is nothing more than one reason, the only reason: there is [pair] vibration. (To be clear:

This pair, in the field of mechanical design industry, it means the contact part, if it is point contact, it is called high pair, and if it is surface contact, it is called low pair. )

Well, let's not go so far, now that we know the cause of the vibration, I will tell you how to effectively prevent and eliminate the vibration.

1.The workpiece is large and thin, which is equivalent to the chuck can not clamp the workpiece very tightly, at this time, if it does not affect the processing, you can use the tailstock to install a special thimble, or use the thimble to hold up a wooden board or iron plate, and the workpiece is resisted on the shaft end face of the workpiece, which can prevent the workpiece from being dislocated by force, and can increase the vibration resistance when vibrating, and reduce the fluctuation frequency of vibration.

2.Try to keep the amount of cutter on one side less than or equal to about that, and use 45 ° positive deviation cutter from the tailstock direction to the chuck direction turning, see the difference in the outer diameter size and length of the workpiece, should use different spindle speed and pass speed, generally speaking, if the outer diameter of the workpiece is greater than 200mm, I suggest that your spindle speed is controlled at 63 rpm. Due to eating less, the passing speed can be larger than normal, but not too large, because if you eat less, the cutting edge is bearing all the cutting resistance, and it is easy to damage the cutting tip.

3.Why is it not recommended that you use a 90° knife, the reason is very simple, because the inclination angle of the cutting edge of the 90° knife is too small, and the tip of the knife is easy to produce a large friction contact range with the surface of the workpiece after wearing, and the workpiece vibrates violently!

You can add my QQ

There are many reasons for the tremor of the lathe, such as the geometric angle and strength of the tool. rigidity of workpieces and machine tools; Selection of cutting amount; Workpiece material. In general, vibration can be reduced by reducing the depth of cut and increasing the feed.

How to reduce and prevent deformation of the workpiece when turning thin-walled workpieces?

1. The clamping force is appropriate.

2. Increase the contact area during clamping.

3. Axial clamping device is adopted.

4. Add auxiliary supports and linings, such as center rest and inner hole lining devices.

Forced vibration prevention measures in the process of grooving and cutting The forced vibration is caused by external interference force, so the vibration system should be tested to find out the vibration source so that appropriate measures can be taken to control. On the machine side, the vibration source can be isolated from the lathe. The vibration isolation device can absorb most of the vibration generated by the vibration source, and reduce the interference of the vibration source on the turning process.

Dig anti-vibration ditch and place lathe on anti-vibration foundation, set spring or rubber pad to dampen vibration; Eliminate the imbalance of the rotary part and reduce the excitation force. Static balance and dynamic balance test are carried out on motor rotor, pulley and chuck, and the bearing assembly accuracy is improved and the manufacturing accuracy of lathe transmission parts is improved; Increase the stiffness and damping of the process system. Increasing the stiffness of the machine, workpiece, tool and fixture can increase the vibration resistance of the system; Adjust the natural frequency of the process system, change the frequency of the excitation force according to the characteristics of the forced vibration, and avoid the natural frequency of the system; In the structural design, the natural frequency of each component of the process system is kept away from the resonance zone to avoid the occurrence of resonance phenomenon.

Shock absorbers and dampers are also available. In terms of workpiece, for the grooving or cutting off of slender part, because workpiece is clamped on chuck, part is equivalent to a stressed cantilever beam in the processing process, therefore in order to reduce bending deformation and cause strong vibration, the length of workpiece stretching out jaw should be as short as possible, and the tangent point position should be as close to chuck as possible (to the tool holder does not collide with the end face of the jaw as limited); Because the excitation force is proportional to the square of the workpiece speed, so appropriately reduce the speed of the machine tool, can greatly reduce the vibration, play a good damping effect; For thin-walled rings, sleeves of workpieces, adopt tension jaws or mandrel clamping, in order to reduce the uneven contact surface caused by deformation and cause vibration; Yes"One clip and one top", "Wedge top"The workpiece clamped in the other way, adopt the elastic top instead of the dead center, avoid the workpiece bending caused by excessive top force or the top force is too small to make the workpiece swing, and pay attention to the tailstock sleeve overhang can not be too long.

1. In terms of machine tools, the vibration source can be isolated from the lathe. The vibration isolation device can absorb most of the vibration generated by the vibration source, and reduce the interference of the vibration source on the turning process.

2. Reduce the excitation force. Static balance and dynamic balance test are carried out on motor rotor, pulley and chuck, and the bearing assembly accuracy is improved and the manufacturing accuracy of lathe transmission parts is improved;

3. Improving the stiffness of machine tools, workpieces, tools and fixtures can increase the vibration resistance of the system.

You can consider: 1. Choose a suitable clamping method. Axial clamping is used as much as possible to avoid deformation caused by radial clamping. 2. Select the appropriate knife attempt and feed to reduce the deformation. 3. If it is convenient, a certain auxiliary support can be added. FYI.

(1) Due to the thin wall of the workpiece, it is easy to deform under the action of tension, which affects the dimensional accuracy and shape accuracy of the workpiece.

2) Because the workpiece is thin, turning is easy to cause thermal deformation, and the size of the workpiece is not easy to control.

3) Under the action of cutting force (especially radial cutting force), it is easy to produce vibration and deformation, which affects the dimensional accuracy, shape and position accuracy of the workpiece and the rough grass poison on the surface.

In the process of CNC lathe, the processing of some thin-walled parts is often encountered. When turning thin-walled workpieces, due to the poor rigidity of the workpiece, in the turning process, the processing deformation of thin-walled workpieces of CNC lathes is generally the following phenomena.

1.Due to the thin wall of the workpiece, it is easy to deform under the action of clamping pressure. This affects the dimensional accuracy and shape accuracy of the workpiece.

When the three-jaw chuck as shown in Figure 1 is used to clamp the workpiece to process the inner hole, under the action of clamping force, it will slightly become triangular, but what is obtained after the hole is turned is a cylindrical hole. When the jaws are released and the workpiece is removed, the outer circle reverts to a cylindrical shape due to elastic recovery, while the inner hole becomes an arc-shaped triangle as shown in Figure 2. If measured with an inner micrometer, the diameter d in all directions is equal.

2.Under the action of cutting force (especially radial cutting force), it is easy to produce vibration and deformation, which affects the dimensional accuracy, shape, position accuracy and surface roughness of the workpiece.

3.Due to the thin workpiece, the cutting heat can cause thermal deformation of the workpiece, making it difficult to control the size of the workpiece. For thin-walled metal workpieces with large linear expansion coefficients, if semi-finishing and finishing turning are completed continuously in one installation, the thermal deformation of the workpiece caused by cutting heat will have a great impact on its dimensional accuracy, and sometimes even make the workpiece stuck on the fixture.

We know how the thin-walled workpiece of the CNC lathe is deformed, so what should we do about the deformation of the thin-walled workpiece of the CNC lathe? Several solutions are described below.

1. The workpiece is rough, and when the finishing stage is rough, due to the large cutting allowance, the clamping force is slightly larger, and the deformation is correspondingly larger; On the one hand, the clamping deformation is small, and on the other hand, the deformation caused by excessive cutting force can also be eliminated during rough turning.

2. Reasonable selection of geometric parameters of the tool When finishing turning thin-walled workpieces, the stiffness of the tool holder is required to be high, and the wiring edge of the turning tool is not easy to be too long (generally taken, the cutting edge should be sharp.

3. Increase the clamping contact surface as shown in Figure 3, using a seam sleeve or some special soft jaws. The contact surface is enlarged, so that the clamping force is evenly distributed on the workpiece, so that the workpiece is not easy to deform when clamping.

4. Fully pouring cutting fluid By fully pouring cutting fluid, the cutting temperature is reduced and the thermal deformation of the workpiece is reduced.

5. Increase the process rib Some thin-walled workpieces are specially made with several process ribs at their clamping parts to enhance the rigidity here, so that the clamping force acts on the process ribs to reduce the deformation of the workpiece, and then remove the process ribs after processing.

6. When the axial clamping fixture is used to turn the thin-walled workpiece, radial clamping should not be used as much as possible, and the axial clamping method as shown in Figure 4 should be preferred. The workpiece realizes axial clamping by the end face of the axial clamping sleeve (threaded sleeve), and because the clamping force f is distributed along the axial direction of the workpiece, and the axial stiffness of the workpiece is large, it is not easy to produce clamping deformation.