– B??c five: Cho máy in s?n xu?t tem nhãn v?i s? l??ng l?n theo m?u ?ã duy?t c?a khách hàngThese pumps are useful for pumping down the column. After the column reaches the necessary vacuum degree, the backing or roughing pump is generally turned off to reduce mechanical vibrations and may mechanically bring about each couple of several hours