In order to avoid the status that the changing of actual cutting feed speed debases the CNC machining quality of roller gear indexing cam

starting with the physical meaning of the programming feed speed F command

the relationships between actual cutting feed speed and programming feed speed under the situation

which the roller gear indexing cam was machined in a general CNC machine tool

were analyzed.The results show that the difference between actual cutting feed speed and programming feed speed is caused by the difference between actual distance and equivalent distance of two sequential tool center positions

because the general CNC machining of roller gear cam requires 4 or 5 coordinate axes simultaneous movement including 2 rotate movement.According to the relationships between actual cutting feed speed and programming feed speed

every CNC program block is arranged a various programming feed speed

so the actual cutting feed speed of CNC machining of roller gear cam can be keep a constant value and the machining quality of cam is improved obviously.The research results are worth applying to engineering.