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Pendulum Wig-Wag Stacker

The VMI Pendulum Wig-Wag (PWW) Stacker was developed as the most simple but sturdy stacking system for stacking endless slabs of rubber-compound up to 900 mm wide.

The stacker is to be mounted on top and at the end of a Tunnel type Batch-Off.

The slabs are taken out of the cooling installation fully automatically by a gripper. The slab is subsequently positioned on a take-out conveyor that transports it toward the pendulum of the PWW Stacker. This stacker is designed to stack onto a flat pallet, a pallet with side walls or into a box.

Product highlights

  • Automatic slab take-out
  • Stacking with lots of ‘air’ in between
  • Simple, economic and reliable design
  • Robust design shows very little wear over the years


When a cooled and dried rubber slab reaches the end of the cooling rack, it is automatically taken out by the automatic rotary type gripper and released onto the take out conveyor. The two gripper arms of this unit make a rotating movement after the slab is clenched. This construction ensures that the leading end of the slab is positioned at a safe distance beyond the beginning of the take out conveyor.

The take out conveyor takes up the slab and transports it upwards to the pendulum type stacker mechanism. For securing the slab or strips on the belt, a pressure roller with top conveyor is mounted on top of the take out conveyor. A micro switch is mounted on this roller, so that it serves as a rubber detector.

The oncoming leading end of the slab of compound runs off the end of the take out conveyor and is caught in a stacker pendulum. The discharge opening between the rollers, formed by the two sides of the V-shaped stacker pendulum can be adjusted in width in order to optimize the stacking result for various compounds.

A photocell between the stack of rubber compound and the stacker pendulum protects the latter from hitting the stack of compound in case it is being stacked too high. Stacking is interrupted automatically when the stack of rubber compound almost reaches the level of the stacker pendulum.

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