Why does the machine need to be stress relieved?
There has always been a saying within the machine tool industry that machine tools need to be stress relieved, and the more sophisticated the machine the more attention needs to be paid to stress relief. So, why do we need to relieve stress? If so, how long should it be released? How to release the stress is good?
What is stress?
When an object is deformed due to external factors (force, humidity, temperature field changes, etc.), internal forces interact between the parts within the object to resist the action of such external factors and attempt to restore the object from its deformed position to its pre-deformed position.
The full name of the stress required to be released by the machine tool is mechanical stress, which is generated by the bed and other components in the thermoforming process. Since machine tools need to be machined to micron or even nanometer accuracy for high precision machining, the deformation error caused by this internal stress generated in the casting is unacceptable, so the machine needs to be stress relieved. Simply put, the machine tool related components in the thermal processing will produce stress, this stress will lead to a certain deformation of the components, and this deformation will affect the accuracy of the machine tool, so the more high-precision machine tools need to release the stress, in order to ensure the accuracy and stability of the machine tool.
How long does it take for the machine tool to be stress relieved?
Machine tools generally use the method of static stress relief, which I believe we all know. I heard that before, some machine tool manufacturers in order to fully release the stress will be castings sunk into the sea or buried in the ground. This statement is not testable, for your reference only. Then the machine tool stress to release how long it?
When searching for information on the Internet, a wide variety of answers to see a dazzling, small to a few months, large to seven or eight years, a variety of answers are available. After reviewing some professional papers, the answer is that stress relief takes several months to several years depending on the metal component and taking into account the volume and shape.
It should be noted that the environment for stress relief should be considered according to the specifics of the member. It is not the case that the best results can be achieved outdoors or in some extreme environments. Of course, with the advancement of technology, there are more and more methods of stress relief nowadays and the time is getting shorter.
How to release the stress?
As mentioned above, resting is one of the methods to release stress, but this method is now used less and less. For no other reason, the time required for static stress relief is too long and the cost is too high for the machine tool manufacturer. As technology advances, there are more and more ways to relieve stress on machine tools, and the time required is becoming shorter. Before talking about the specific method of stress relief to emphasize that stress relief is generally completed before assembly, after the assembly of the whole machine is generally in the machine after the rest of about 10 to 20 days, according to the specific instructions of different manufacturers to do so.
Generally speaking, high precision machine tools will use marble and other materials that are not easy to produce stress to do the bed. And the use of metal materials machine tools will now also use shot blasting, vibration, rolling and other methods to remove stress. Among them, shot blasting is the use of pellets to bombard the surface of the workpiece and implant residual compressive stress; vibration is the use of vibrators and the workpiece to form resonance to eliminate stress; rolling is through some rolling tools to the surface of the workpiece to apply pressure to achieve the purpose of stress relief. In addition, stress can also be relieved by thermal aging, explosion method, thermal shock aging method, acoustic aging method and other methods.