7.2.2.3 transmission error
When machining some surfaces such as helical surface, gear, worm wheel, the constant motional relationship between the cutting tool and the workpiece is ensured by the transmission system of the machine tool. Transmission error refers to the relative motional error of the elements at the two ends of the transmission chain.
6.2.3 deformation of the machining system
themachiningsystemwilldeformunderthecuttingforce,clampingforce,transmissionforce,weightandinertialforce，whichwilldamagethecorrectpositionbetweenthecuttingtoolandtheworkpieceandcausemachiningerror.ThisphenomenacanbeexplainedbyFig.6.12(a),(b09c)
Fig 6.12 error caused by deformation of the machining system
（a）slim shaft deformation movie
（b）short and big diameter workpiece deformation movieThe stiffness of the machining system refers to the the ratio between the resultant normal cutting forces on the machining FyYsystemsurface and the deformation value in the normal direction ：
Ksystem?FYYsystemwhere
Ksystem——thestiffnessoftheprocesssystemN／mm；
FY——normalcuttingforceN；
——normaldeformationmm。Ysystem
