K Show Report: Auto glazing reaches critical point in commercialization

As reported in an earlier Pre-K Show report, Battenfeld together with partners Summerer Technologies and Exatec, demonstrated the production of large car windows made from polycarbonate in a work cell based on Battenfeld’s IMPmore (In-Mould Pressing) injection compression process. A first-hand look at the work cell in action at the show revealed the specific technological strides that have been made in auto glazing in the last few years, as well as where the technology is headed.
The 1 sq. m non-production windshield was molded on a Battenfeld HM 20000/19000 injection molding machine featuring a "hinged" core. The hinged core is the key to the injection-compression process and its ability to produce a stress-free part. The melt is injected under low pressure; as the mold begins to fill, the hinged core slowly straightens from the hinged position to close the mold. In-mold pressure across the 4 mm-thick windshield is kept below 200 bar, and the cycle time is 70 sec.
According to Thomas Betts, Battenfeld of America Midwest regional manager, one of the key benefits afforded by the injection-compression process is the lowering of required press tonnage. "The size of this part would normally require a 4000-ton machine. We’re able to mold it on a 2000-ton machine, and even then we’re only using about 1,500 tons of clamping force in the actual process."
Betts said a two-component machine will be used to mold a 1.5 sq. m sunroof for a 2005 production vehicle. The machine, which in the final stages of testing, has two injection units mounted opposed to one another. The first injection unit shoots polycarbonate into the window mold using the injection-compression method. The mold rotates 180 degrees on a rotary table and the second unit injects a black polycarbonate "casing" around the perimeter of the window.