Technician reached into machine to unjam a part. Machine cycled when part was moved and technician’s hand was caught between upper tooling and core. Resulted in cuts to top and palm of right hand requiring a total of 9 stiches to close cuts.Machine cycled because interlock was bypassed by another technician. Door was closed and injured technician had no indication that interlock was bypassed. Due to many chokoteis, other technician bypassed the interlock to study the operation. However he did not place the interlock bypass tag on the door as he had left the tag at the workbench. Thinking that he was working alone, he had gone to get the tag without re-enabling the interlock switch and had not yet returned when the injured technician entered the machine.