Design of an automated electro-mechanical shredder-grid-door positioner for online setting adjustments

The design of an automated electro-mechanical shredder-grid-door positioner and its components, programming, installation and commissioning are presented in this paper. The positioner can be used to vary the shredder grid setting and so preparation to assist processing soft cane varieties through the milling train. A second purpose is to work with shredder drives (such as steam turbines) of limited power, in order to avoid stalling the drive, which can result in factory stops. The driver for this design has been concerns in recent years that some cane varieties in the development pipeline have a fibre quality classified as soft, with some soft enough to cause processing problems in the factory. The main issues have been feeding of the cane through the milling train and high bagasse moistures causing subsequent combustion issues and low steam pressure at the boiler station. These cane varieties are usually designated as ‘soft canes’, and their presence had been noted as far back as 60 years ago. Trials were carried out at Isis Central Mill to understand and improve the processing of existing soft cane varieties. The automated shredder-grid-door positioner was installed during October of the 2021 crushing season so that full factory trials could be carried out, including automated grid positioning. The positioner was made up of a master/slave configuration with two 5 t power jacks driven by servo gear motors controlled by two inverters.