Material Preparation
A central material conveying system is a closed-loop conveying system that automatically feeds all the injection molding machines in a plant from dryers and silos through a single vacuum source, pipeline and distribution table. It eliminates manual handling and the contamination and moisture pick-up caused by open hoppers; it manages centrally which material goes to which machine.
The system consists of five components: the vacuum source (pump and filter unit), machine-mounted loaders, the pipe and hose line, a distribution table or automatic coupling station, and suction lances and metal protection. A weakness in any link affects the whole line.
The issues most often overlooked in design are wear in the pipe elbows, choosing the line diameter to suit consumption, and granulate conveyed at high speed creating "angel hair" through friction. On long lines the speed is reduced, the number of elbows is cut down and wear resistant elbows are used.
The general rule is five or six machines and above; but even two or three machines working with hygroscopic material can justify a central setup, because they need to be fed from the dryer through a closed line.