feature：
* anti-obstruction structure to prevent colorant in nozzle from drying.
* five kinds of colorants can be filled into five canisters simultaneously, thus dispensing time is
　shortened greatly.
* formula can be downloaded to the machine by usb flash disk; it can be easily amended and updated.
* distance between can and nozzle is adjusted automatically, this can prevent colorant from
　spilling.
* each kind of colorant can be mixed dividually. speed of mixing can be adjusted; it is in favor of
　dissolving the deposited colorant, meanwhile colorant can be prevented from spilling, mass air
　bubbles can be prevented from coming into being. thus accuracy of colorant dispensing is guaranteed.
* each module can be dismantled and replaced dividually; it is convenient for after-sale services.