I have a rapman 3.1. I have had it for 1.5 years and I have been able to run one part. I can not get the z-axis to work. Replaced the control board, motor. Same problem. It turns free by hand. When power is applied it will try to move then it goes back and forth. Any ideas! I have a 2000.00 boat anchor.by gandyo001 - Reprappers