How to deal with the phenomenon of tool vibration in the process of CNC lathe machining?

                        Tag: tungsten carbide inserts,milling inserts,end mills

   

Have you ever had the following conditions when machining with a CNC lathe?

The vibration of the tool, the workpiece and the lathe is large, and the harsh noise is transmitted. This situation not only causes the clamping of the tool or the workpiece to become loose, but also causes a bad physical and mental impact on the operator due to its noisy noise, and the machining accuracy cannot meet the requirements of the customer. This is the problem of the vibration of insert cutter. Every tool manufacturer regards how to deal with the problem of vibrating inserts as a great challenge.

tungsten carbide inserts

How to deal with the phenomenon of tool vibration in the process of CNC lathe machining? Let’s share some our experience to you. Because we are professional tungsten carbide inserts supplier, and learned a lot when we help our customers deal various problems. It is also constantly processing the site for customers of different tool manufacturers around the world to solve various problems encountered in processing and provide high-efficiency solutions for metal processing.

When the lathe machine is working, the following situations of "vibration of insert cutter" will occur:
1. Forming turning with forming inserts,
2. Outer circle turning of slender round bar,
3. External turning of thin round bar,
4. Turning of box parts (such as sheet metal welded structural parts),
5. Super hard material cutting,
6. The bearing has been damaged and is still cutting.

CNC lathe tool processing

1. Basic Methods
(I) Forced Vibration
This is the forced vibration caused by intermittent cutting or the vibration caused by the defect of rotating parts. The common phenomena such as abnormal sound caused by the damage of bearings or poor engagement of gears, poor clamping of workpiece and excessive swing of main shaft are all of this kind.
In this kind of problems, intermittent turning belongs to the processing technology, and the defects of parts are mostly from the assembly technology of machine tool and the quality control of its key parts, and also related to the design concept of machine tool structure. The characteristics of its vibration are directly related to the number of revolutions.
(II) Self-excited Vibration
This is due to the periodic working unevenness in the cutting process, which causes a little staggering of the periodic phase and the effect of repeated overlapping regeneration. It can also be called "resonance", which is mainly caused by the excitation of the natural frequency from the machine structure or the low self frequency of the workpiece clamping system.
Since the natural frequency of the structure changes only with the change of clamping or fixing mode, changing the cutting conditions (such as changing the rotation speed) can often improve the cutting vibration when the vibrating knife occurs. However, in some occasions where the cutting speed cannot be changed (such as attacking) tooth or cutting of certain materials, it is often only possible to solve such problems by changing the clamping method or even changing the tool or tool fixing method.

CNC tungsten carbide inserts processing

2. The countermeasures to suppress the vibrating inserts
According to the vibration knife principle obtained from the research, there are some more specific and practical methods applied to the processing site:
(1) Try to choose all the conditions with small cutting impedance, that is also the most appropriate tool feed rate and cutting speed (or spindle speed).
(2) Adjust the cutting speed to avoid resonance.
(3) Reducing the working weight of the part causing the vibration, the smaller the inertia, the better.
(4) Fix or clamp the place with the largest vibration, such as the center frame, work holder, etc.
(5) Improve the rigidity of the processing system, for example, using a tool holder with a high modulus of elasticity or using a special shock resistance added to the dynamic damper to absorb the impact energy.
(6) Working hard from the direction of the blade and the work rotation (the work will lower the tool while also increasing the stability of the tool).
(7) Change the shape and advance angle of the tool. For example, the smaller the nose radius, the better, to reduce the cutting resistance. The roll angle must be positive so that the cutting direction is closer to vertical. The back rake angle is preferably positive, but the chip removal ability is relatively poor. Therefore, a groove cutter is generally used to make the inclination angle negative, but still maintains a positive cutting effect.
(8) The smaller the lead angle, the better, of coarse preferably zero.

As a manufacturer specializing in the metal processing industry, UKO not only provides high quality tool products, such as carbide CNC turning inserts, milling inserts, thread inserts, parting and grooving inserts, drills, end mills and other quality products. We also could provide professional solutions for metal working. Is there anything or any problems in CNC machining confused you? Contact Ashley. 

Edited by: Ashley Chan