pps proceeding - Abstract Preview
pps proceeding
Symposium: S02 - (General Session 2) Extrusion
Oral Presentation
 
 

New head design opens up improved processing possibilities in pipe extrusion and in extrusion blow molding

Gross Heinz Guenter (1)*

(1) Gross Kunststof-Verfahrenstechnik - Rossdorf - Germany

Short flow length and residence times are an important aspect when building extrusion diss. This is still best achieved when designing simple spider-type annular dies. If only the disadvantage of the spider lines could be overcome. New processing techniques give rise to even convert this flaw into an advantage. Generating production techniques allow for the production of complex mixing structures. Integrating such a mixing element into the inlet channel of the die melt inhomogeneities can be reduced. Such inhomogeneities do result normally from the melting in the extruder and from the transporting of the melt to the die. In the same time the individual mixing bars can be used to fix the pin in the middle of the die. So using a generating production method the housing, the mixing bars and the pin becomes an extremely stiff homogeneous entity. Spider lines will no longer be generated and a melt with improved homogeneity will be purged out of the die. New processing possibilities will be generated when additionally integrating a simple three functional device into the head construction. The special three functional metal part first seals the dividing area between the head and the die and it additionally allows for a shifting and a tilting of the die in regard to the pin. So in pipe extrusion a closed-loop control for eccentric thickness variations can be easily established. Furthermore the flow channel gap at the exit of the die can be modified when using a conical pin. By this means pipes having a different wall thickness can be produced while maintaining the optimum stretching ratio between the die and the calibrator. In extrusion blow molding a dynamic radial wall thickness programming of the parison can be realized for the first time. This can be done for every possible die diameter when simply using a solid cylindrical die and a solid pin. To achieve this the pin has to be especially shaped according to the stretching situation during the blowing process.