Wrap your head around this: One rotating block + two indexing platens = molding and assembling two parts in one mold

August 09, 2010

Inmold operations such as labeling, decorating, painting, clear-coating, and even assembly are becoming more common as the technology catches on and catches the attention of OEMs eager to save time and cost-to-manufacture. Zahoransky Formenbau GmbH (Freiburg, Germany) is becoming known for its creative and unique developments with respect to rotationally performing assembly operations. Its newest development is a new option for molding and assembling two different parts in a single cycle within the framework of the mold system.

Called the Turn-Stack system, Zahoransky's newest system, which will be shown at K 2010 in Düsseldorf, includes two shouldered index platen molds, resulting in a multidaylight mold system. Two sets of different components can be assembled using a central rotary indexing assembly block located outside the molds between the two indexing mold platens.

"This configuration allows for molded parts to be made in both daylights during the same cycle, and finished components from the previous cycle to be assembled at the rotary assembly bloc, which is located outside the mold," explains Frank Kigyos Jr. of Zahoransky USA Inc. (Sugar Grove, IL). "Assemblies can either be further processed on the assembly block with up to two additional components or ejected and transferred downstream."

For example, the first part is a one-component part molded in the first daylight (moving platen). This product is carried by an index platen that rotates 180° per cycle between two stations. At the first station the platen rotates inside the mold for injection. At the second station the platen rotates outside the mold for transferring parts to the rotary assembly block.

The second part consists of two components molded in the second daylight (fixed side of the platen), which is also carried by an indexing platen; however, in this case, it rotates 120° per cycle between three stations. The first two stations are located inside the mold and are for injection and the first and second shots, respectively. The third station is located outside the mold for transferring parts to the rotary assembly block. 

Since both parts are assembled outside the molds during injection, cycle time is not sacrificed, which is one of the huge advantages to the Turn-Stack system, notes Kigyos. Assembled parts are removed from the assembly block by either an integrated ejector system or an outside handling unit.


Walking Beam system cuts mold size and clamping force
The Turn-Stack is the second new development that Zahoransky Formenbau has introduced in the past year. In August 2009, the moldmaker introduced what it called a "new and unique" concept for a four-component mold. The Servo Cavity Positioning System (SCPS), also called the Walking Beam injection mold system, uses conventional injection molding presses. However, the process sequence of the multicomponent mold differs substantially from previous designs using rotary tables, index platens, or stack turning technology. The SCPS was shown at Fakuma 2009, and will again be shown at K 2010.

All the movements in the mold are servodriven with positioning accuracy independent from the machine hydraulics. Compared with an existing 16-cavity, three-component mold with index platen, the SCPS mold halves the platen size and thus the clamping force of the machine. The control sequence of the mold, including the drives for all other injection units, and the hot runner control are handled by the mold's own newly developed control system, says Zahoransky.

Another advantage is that the SCPS mold is only slightly larger than a standard mold and requires none of the usual platen enlargement or guide pillar extensions typically required for similar types of molds. "We're automating the mold without modifying the standard machine," says Michael Schmidt, sales director for Zahoransky Formenbau. "This also applies to the use of the mold on any other injection molding machine."

The process sequence begins as the mold opens after the pre-injection molded parts are injected in Station One. These parts are then taken to the second injection station via a spindle drive, where the parts are finished and carried by a spindle drive to the removal station after the mold has opened. A handling unit removes the finished parts during the next injection phase without requiring any additional cycle time.

The empty mold halves are handed over the nozzle side and carried via a second spindle drive during the mold opening stage from the removal station to the primary injection station (Station 1). The mold closes, the cycle is complete, and begins again. During each cycle, the pre-injection molded parts and the finished parts are injected simultaneously and the finished parts are taken off the removal station. Just 3 seconds are needed for opening, carrying the mold inserts to the next station, and the mold closing.

For a first-hand look at the Turn-Stack and the Walking Beam injection mold systems, visit Arburg's Stand (Hall 13/A13-2) for the SCPS or Walking Beam or Zahoransky's Stand (Hall 02/A02) for the Turn-Stack system. Clare Goldsberry


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