Modern high-performance drawframes are fitted with automatic can changers. These reduce the burden on personnel, enable more machines to be allocated to one person, reduce the necessity for the operative‘s attendance at the machine, and (the chief effect) also increase efficiency. They can be classified into:
- single-step changers (flying change);
- multiple-step changers (interrupted change).
Single-step changers result in higher machine efficiency since full cans are replaced by empty ones at full speed, i.e. without stopping the machine. Multiple-step changers result in lower machine efficiency since the machine must be brought to a stop during the change. To permit long periods of operation without personnel intervention, modern drawframes are equipped with magazines for up to 8 empty cans. The full cans are ejected onto the floor or onto a can trolley.
If feeding is performed with circular cans (the normal procedure) at the subsequent processing stages quite a lot of empty space remains between the cans. Especially on rotor spinning machines this necessitates using small diameter cans with correspondingly low feeding capacity. It is far better to use rectangular cans, which can be placed side by side in front of the machine without wasting space. That is why Rieter introduced this new type of cans as an option.