CNC Knowledge: Why should machine tools relieve stress?

There has always been a saying in the machine tool industry that machine tools should relieve stress, and the more high-precision the machine tool, the more attention should be paid to stress relief. So why relieve stress? If he is released, how long will it take to release him? How to relieve stress and a series of questions about machine tool stress, don’t be worried and read it slowly with the article.

▌ What is stress? When an object deforms due to external factors (force, humidity, temperature field changes, etc.), an interactive internal force is generated between different parts of the object to resist the action of these external factors and attempt to restore the object to its distorted state. position before deformation.

The full name for the stress that must be released by machine tools is mechanical stress, generated by components such as the bed during the thermoforming process. Since the high-precision machining precision of machine tools needs to reach the micron or even nanometer level, the deformation error caused by the internal stress generated during molding is unacceptable, so the machine tool must relieve constraint. To put it simply, components related to the machine tool will generate stress during heat treatment. This stress will cause some deformation of the component, and this deformation will therefore affect the precision of the machine tool. precision of the machine tool, the more it must be released under stress. This ensures the precision and stability of the machine tool.

▌ How long does it take for the machine tool stress to be released? Machine tools generally use the static method to release stress, I think everyone knows it. I have heard that in the past, some machine tool manufacturers would sink the castings into the seabed or bury them underground in order to completely relieve the stress. This statement cannot be tested and is for your reference only. So, how long does it take for the machine tool stress to be released?

When searching for information on the Internet, the variety of answers is dazzling, ranging from a few months to seven or eight years. After looking at a few professional articles, my answer is that stress relief takes anywhere from several months to several years depending on the different metal components and taking into account factors such as volume and shape.

It should be noted that the stress release environment must be considered based on the specific conditions of the component. The best results are not obtained outdoors or in certain extreme environments. Of course, with the advancement of technology, there are now more and more ways to relieve stress and the time is getting shorter and shorter.

▌How to relieve stress? As mentioned above, rest is one of the methods of relieving stress, but this method is used less and less today. The reason is that it takes too long to rest to release the stress and the cost is too high for machine tool manufacturers. With the advancement of technology, machine tools have more and more ways to reduce stress, and time becomes shorter and shorter. Before talking about specific stress relief methods, it is worth pointing out that stress relief is usually completed before assembly, the complete machine is usually left to sit for about 10 to 20 days after it is dropped. manufacturers.

Generally speaking, high-precision machine tools use marble and other non-stress-prone materials as the bed. Machine tools using metallic materials now also use shot peening, vibration, rolling and other methods to remove stress. Among them, shot peening uses pellets to bombard the surface of the part and implements residual compressive stress; vibration uses a vibrator to resonate with the workpiece to eliminate stress, rolling uses rolling tools to apply pressure to the surface of the workpiece to eliminate stress; . In addition, stresses can also be eliminated through thermal aging, explosion method, thermal shock aging method, sonic aging method and other methods.