Thermoplastic Overmolded with Foamed & Solid LSR at NPE2018
Negri Bossi molds a ping pong bat of PBT, TPU and both foamed and solid LSR.
At NPE 2018 this month, Negri Bossi North America, New Castle, Del., is displaying an example of the Canbio sT servo-hydraulic toggle line (180 to 500 metric tons), recently introduced to North America. These “highly modular” machines have the Tactus controller with 21.5-in. touchscreen and energy-consumption monitor. Particularly notable is the unit on display, a 180-m.t., two-shot model with a third auxiliary injector for molding a ping pong bat with three materials (or four, depending on how you’re counting).
The rigid core of the bat is PBT, molded on the main horizontal injector. The smaller vertical injector molds a TPU soft-touch handle. The mold is directly fed liquid silicone by an “Easy-Balance LSR” unit from Guzzini Engineering. This unit overmolds two different ball-control faces on the bat in two densities—the firmer face in solid LSR and the “spongier” side in microcellular foamed LSR. Parts are handled by a six-axis robot from sister company Sytrama.
Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate.
Most molders work with two parameters for establishing second-stage pressure. But within Scientific Molding there are actually four.
One of the more prominent trends in processing is the need for higher plastic pressures to mold parts.