After reading it for a long time, I don't quite understand what the straightness and parallelism of the machine tool guide rail specifically mean. Who can tell me about it?

The guide rail of the machine tool is pressed up and down by the installed bolts. Generally, as long as the flatness of the installation surface meets the requirements, this direction does not need to be considered. Generally speaking, the straightness of the linear guide rail refers to the straightness of the running direction, and the parallelism refers to the fact that the interval between the two guide rails is the same (that is, if the two guide rails are parallel), because one of the functions of the guide rail is to guide the movement direction of the workbench. If the straightness and parallelism are not good, stress will occur during operation.