1. A method of part flow for a programmable logic controller logical verification system, said method comprising the steps of: constructing a simulation model of a manufacturing line using a computer; playing the simulation model by a PLC logical verification system on the computer and viewing a flow of a part through the manufacturing line by a user, wherein the PLC logical verification system dynamically interacts through input and output with the simulation model to verify a PLC code of the manufacturing line; determining if the part flow represented in the simulation model is correct to the user; generating the PLC code if the part flow represented in the simulation model is correct; and using the generated PLC code and implementing the manufacturing line according to the part flow simulation model.