Parison programmers

How many points can be programmed rising the parison programmer ... 

The parison weight has always been a problem even with parison programmers. You should always produce a parison with the parison programmer and check the parison to determine if you are achieving the thickness in the heated parison at the desired location within the parison. If you use regrind, this will have a major effect on your parisons repeatedly, also color additives and lubricants. 

Many blow-molding extruders are equipped with parison programmers, which vary the orifice diameter as the parison is being extruded, minimizing variations in wall thickness in the blown product. The parisons may be ovalized to reduce variations in wall thickness in objects of noncircular cross section. 

Fig. 4-4. Schematic of an accumulator head with programmable process controller controls melt characteristics (interrelates with extruder performance), rate of melt flow to form parison, and profiling thickness of parison as it extrudes from die.

Programmable circumferential wall thickness change possible, independent of parison length... 

Sequential blow molding is used for producing bent three-dimensional shapes, for example, a convoluted heat exchange tubular panel and filler pipes in automobiles. The parison is deformed and then manipulated with programmable 3-D manipulators or six-axis robots before being placed directly into a mold cavity. 

The annular die can be designed to incorporate a hydraulic mechanism to vary or programme the annular gap size in both extrusion- and plunger-type blow moulding. With extrusion blow moulding, a specific wall thickness distribntion or controlled weight of the parison can be programmed. 

Fixed, unequal circumferential wall thickness change possible affects entire parison length Settable, unequal circumferential wall thickness change possible rapid optimization Programmable circumferential wall thickness change possible, independent of parison length... 

With extrusion, technology provided improved temperature controls, die controls and takeoff equipment, and cooling techniques. Programmable logic controllers allowed the development of control systems for parison profiling as well as screw speed control based on melt pressure measured at the die. All of these developments have contributed to the development of thinner sheet and very small diameter, multilumen, and multimaterial medical tubing. 

---