In the laser cutting process, a lot of factors affect relative position between focus and processed metal, the workpiece surface is uneven, workpiece clamping method, machine tool geometric errors and the machine deformation under load force, the workpiece processing of thermal deformation can cause the laser focus and the ideal location for a given position (programmed position) deviations occur. 
Some errors (such as machine tool geometric errors) regularity, can be compensated by the compensation method for the quantitative, but some error is a random error, can only be removed by line detection and control, these errors are: 

1. Geometry error 
Laser cutting sheet or cover part, due to various reasons, the object has a bumpy surface, and due to thermal characteristics in the cutting process will produce a surface deformation of the sheet metal parts, for the one-dimensional laser processing, cover press-forming process will produce an uneven surface, the position and the ideal location for all of these, will have a laser focus with the surface of the object to be processed random changes occur. 

2. The error generated by the workpiece clamping device 
Laser cutting is on the needle workpiece table, due to manufacturing errors, time and wear and laser burns between the workpieces, needle beds will be uneven, this injustice will produce steel sheet and the focus of the laser random error between the positions. 

3. Programming error
In the one-dimensional laser cutting process, machining path on complex surfaces by lines, arcs, and another fitting, curve fitting and these actual curve there are some errors, these errors so that the actual focal point and the relative position of the object surface and programmed position over a certain error. While others teach programming system will introduce some bias.