What is the difference other than communications between a powerflex 70 and powerflex 40. They both seem to offer vector control. I have an application that has solids milling equipment and screw conveyors driven by a VFD. The last unit that we upgraded used powerflex 70 drives (the powerflex 40 was not available at that time). However I really do not see any reason not to use the powerflex 40 for this application (5-10HP).