You should return the machine for a refund as it should not be tripping the RCD. The fact that it does not blow a fuse is neither here nor there - they are completely different things. A fuse is to protect the the wiring (from fire) whereas an RCD is there to protect life - yours in this case.
ON NO ACCOUNT USE THE MACHJINE ON AN UNPROTECTED CIRCUIT. It is tripping the RCD for a reason.
If you are in the UK and have any problems with the place that you bought it threaten them with Trading Standards as the machine is potentially dangerous. In other countries you need to use whatever consumer law protects the public from unsafe equipment.
t
August 2008