Here is the new technology, UV printer machine for printing on mug cylinder and bottle with gloss Varnish, which is called DTF that is shoter for direct to film. Same, it use uv printer for printing first.
Video1:  UV printer print on the special film first with uv ink as usual
Video2: Get the printed film onto the mug, also for other cylinder bottle and more.
Main difference from printing on mug directly:
1). The printing speed of printing directly on mug is much slower which DTF technology is much faster
2). Pirnting with film can support gloss varnish printing for cylinder mug and bottle