There has always been a saying in the machine tool industry that machine tools need to release stress, and the more high-precision machine tools, the more attention must be paid to stress relief.
So why release stress?
How long does it take to release? How to release the stress?
Do not worry about a series of questions about the stress of the machine tool, all you need is to slowly read the article.
What is stress?
When an object is deformed due to external factors (force, humidity, temperature field changes, etc.), internal forces that interact between various parts of the object are generated to resist the effects of the external factor, and try to restore the object from the deformed position to the position before the deformation.
The stresses that need to be released from the machine are called mechanical stresses, which are generated during the thermoforming process of the bed and other components.
Since the high precision of the machine requires micron or even nanometer accuracy, the deformation error caused by this internal stress in the casting is unacceptable, so the machine needs to release the stress.
In simple terms, stresses are generated in the relevant components of the machine during thermal machining, which can lead to certain deformations in the components, which can affect the accuracy of the machine.
Therefore, the higher the precision of the machine, the greater the need for stress relief to ensure the accuracy and stability of the machine.
How long does it take for a machine to be released from stress?
As we all know, the machine is generally used to relieve stress by stationary means.
I have heard that before, some machine tool manufacturers would sink or bury the castings to the bottom of the sea to fully release the stress.
This statement is not quantifiable and is for your reference only.
So how long does it take to release machine stress?
When searching for information online, there are a dizzying variety of answers, ranging from as small as a few months to as large as seven or eight years.
After consulting some professional papers, my answer is that the stress relief depends on the metal components, and then takes into account the volume, shape and other factors, it may take several months to several years.
It should be noted that the stress relief environment should be considered according to the specific conditions of the component.
The best results are not achieved outdoors or in extreme environments.
Of course, with the advancement of technology, there are more and more methods of stress relief, and the time is shorter and shorter.
How to release stress?
It was mentioned above that immobilization is one of the methods of stress release, but this method is now used less and less.
There are no other reasons, the time required for static stress release is too long and too costly for the machine tool manufacturers.
With the development of technology, there are more and more ways to release stress, and the time is shorter and shorter.
Before going into specific methods of stress release, it should be emphasized that stress release is generally done before assembly.
After assembly, the whole machine is generally left standing for about 10 to 20 days after assembly, which can be done according to the instructions of different manufacturers.
In general, high-precision machine tools are made of materials such as marble, which are not stress-prone.
Machines using metal materials now also use shot blasting, vibration, rolling methods to remove stress.
Wherein the shot blast is used to blast the surface of the workpiece with pellets and to implant the residual compressive stress.
Vibration is to eliminate stress by resonance between vibrator and workpiece.
Rolling is the removal of stress by applying pressure to the surface of the workpiece with a number of rolling tools.
In addition to this, stress can be eliminated by thermal aging, explosion, thermal shock aging, acoustic aging, and some other methods.
Compared to the above-mentioned aging methods, vibration aging is more suitable for stress relief in machine tools.
Vibration aging is the use of mechanical resonance methods to eliminate or equalize the residual stresses generated by the metal structure after casting, forging, welding and cutting and other mechanical processing.
It transfers energy to the workpiece by exerting an excitation force of a certain size and frequency on the workpiece, causing the workpiece to undergo micro or macro plastic strain to homogenize and eliminate the residual stress.