Why Do machine Tools Release Stress?
March 12, 2020
There has been a saying in the machine tool industry that machine tools need to release stress, and the more sophisticated the machine tool is, the more attention should be paid to stress release.
What is stress?
When the object deforms due to external factors (such as stress, humidity, temperature field changes, etc.), interacting internal forces were caused by each part of the object to resist the effect of such external factors and try to restore the object from the position after deformation to the position before deformation.
The stress of the machine tool that needs to release is mechanical stress, which is caused by the machine tool bed and other components in the thermoform mold process. Because the high precision machining precision of machine tools need to reach the micron or even nanometer level, the deformation error caused by the internal stress generated in the casting is unacceptable, so the machine tools need to release the stress. In short, the machine tool related components will produce stress in hot processing, this stress will lead to a certain deformation of components, and this deformation will affect the accuracy of the machine tool. In order to ensure the accuracy and stability of the machine tool, the higher the precision of the machine tool is, the more stress needs to be released.
How long will it be to release stress?
As we all know machine stress relief generally used the static methods. It has been heard that in order to complete to release stress, some machine tool factories sink the casting into the sea or into the ground. This saying cannot be tested, only for your reference. Then how long will it be to release stress? When we search the internet, we will find that there are so many dazzling and various answers, the time they said ranges from a few months to seven or eight years. After consulting some professional papers, my answer is that according to the different metal components, and taking into account the volume, shape and other factors, the stress release time 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 components. The best results are not obtained outdoors or in extreme environments. Of course, with the advancement of technology, there are more and more methods of stress release and the time is getting shorter and shorter.
How to release stress?
As mentioned above, static resting is one of the ways to release stress, but this method is now used less and less because it takes too much time and too many costs for machine tool factories. With the progress of technology, There are more and more ways for the machine to release stress, and the time is shorter and shorter. Before talking about the specific method of stress release, it should be emphasized that the stress release is generally completed before assembly, and the whole machine after assembly is generally left to stand for about 10 to 20 days after being dropped, and it can be done according to the instructions of different manufacturers.
Generally, high-precision machine tools will use marble and other materials that are not prone to stress as its bed. Machine tools made of metal materials now also use shot blasting, vibration, rolling and other ways to remove stress. Among them, shot blasting uses pellets to bombard the surface of the workpiece and implant residual compressive stress; vibration uses a vibrator to resonate with the workpiece to eliminate stress; rolling is to apply pressure to the surface of the workpiece through some rolling tools to achieve stress relief. In addition, stress can be eliminated by thermal aging, explosion method, thermal shock aging method, sonic aging method, and other methods.