No. 15 - Accumulatorhead Blow Molding

evelopment of the first accumulator-head extrusion blow molder by Germany’s Kautex (later Krupp Kautex and then SIG Kautex) in 1963 enabled production of large industrial parts and storage containers with improved wall consistency, strength, and surface finish. Molten material is stored in a shot pot and a parison is preformed within the head itself. A low-pressure ram forces the material through the die at high speed. This technology was a major improvement over the existing ram-accumulator technology, a two-stage system that had limited capabilities due to the high shear stress placed on parison formation.

In the early 1970s, California blow molder Advanced Chemical Technology (ACT) was the first U.S. company to purchase a Kautex accumulator-head unit. ACT used it to manufacture HMW-HDPE 55-gal drums.

John Hsu of Barr Polymer Systems (later acquired by Uniloy Milacron) was the first to develop an accumulator-head extrusion blow machine in the U.S. in 1972. Barr Polymer sold its first two machines (with single 20-lb and dual 10-lb heads) to Harley Corp., Spartanburg, S.C., for production of 15- to 20-gal HMW-HDPE tanks. Other early makers of accumulator-head machines were Hartig, starting in 1976, and Sterling Extruder Corp. (1979).

Accumulator-head technology filled the need for increased plasticating capacity to produce large parts and faster production through quicker parison drop. Today, the technology has found success in large ducts, panels, drums, and toys.

A threat to the technology was the long, costly downtimes for material and color changeovers. A key development came in 1991, when Win Industrial developed the first spiral-diverter accumulator-head with the ability to lift up the internal parts of the diverter and plunger. This allowed for quicker cleanout of the head’s internal flow paths.

Over the years, head sizes continued to get larger and larger due to intensified focus on very large parts. For, example, at K 2004 in Dusseldorf, Rikutec of Germany introduced the largest coextrusion blow machine in the world with a shot weight of 770 lb for production of septic tanks.

Accumulator-head technology has also resulted in the use of larger tooling (up to 36-in. diam.) for parts such as sheds and tabletops. It also facilitated the use of engineering resins such as PC and ABS, which were difficult to run on other machine styles.