METHOD FOR REPLACING MATERIAL IN BLOW MOLDING

摘要

PURPOSE:To efficiently replace a material by detecting the pressure of the resin in a nozzle when a new material different from an old material is supplied to push out a plunger to control the slit interval of the nozzle or the push-out speed of the plunger. CONSTITUTION:When the material subjected to extrusion this time is supplied in an interval Z to push out a plunger 7, the resin pressure signal from a resin pressure detector 10 is shaped in its signal waveform by a filter 12 to be inputted to a comparative operation part 13. The position of the plunger is detected by a plunger position detector 11 and the resin pressure set value to the present position of the plunger is inputted to the comparative operation part 13 and the difference between said positions is sent to a cylinder driving apparatus 14 as a command signal. The cylinder driving apparatus 14 changes the speed of a plunger cylinder 6 on the basis of said command signal to control the pressure of the resin to a set value and an impactive load change can be applied to the resin to effectively replace the material.