Needle valve (standard design):

Closing action displaces an additional amount of adhesive (can be minimised with stroke limitation).

Only two positions: “Open” and “Closed”

Snuff-back valve:

Closing action creates a slight vacuum in the outlet needle → clean cut-off when dosing is ended.

Only two positions: “Open” and “Closed”

Proportional valve:

Control of the volume flow by varying the stroke (water cock principle).