Shocked by a 3D printer

This is based on a Makers Muse  Video .
The problem was  apparently caused by a lack of ground  in the system.
These power supplies have a RF protection capacitor that feed voltage to ground.
Take away the ground and there is voltage on the case , ground yourself and you become part of the circuit. 
This voltage will not likely kill you but will give you quite a tingle.
Such voltages are considered dangerous and are to be avoided,

So prevention, always connect to a properly grounded outlet. I have an old house so  some of the outlets are not grounded. 
Never use a cheater plug you know those things that allow a three pong plug to plug into a two prong extension.
Get an outlet tester and use it. They are like $ 5 us at the local big box home center.
So STAY GROUNDED.

For those of you who have never seen an outlet tester I included a picture.

Safety first .