Inside Manufacturing: Thermoplastic Composites Lighten Transit Bus
Low-pressure forming processes and low-density, long fiber-reinforced thermoplastic come together to cut weight of aluminum transit bus roof air conditioning door by 40 percent.
By Dale Brosius, Contributing Writer | February 2008
Source: Univ. of Alabama – Birmingham
Step 1: Detailed aluminum forming tool for the lofted glass-reinforced polypropylene structural inner panel. Cooling lines are cast into the mold to remove heat from the preheated sheet.
Source: Univ. of Alabama – Birmingham
Step 2: Preheated, lofted sheet is placed between the aluminum upper forming tool and the mating lower tool. The mold is closed under low pressure and the sheet is cooled.
Source: Univ. of Alabama – Birmingham
Step 3: After cooling, the formed composite inner panel is removed from the clamping frame. The part will be trimmed prior to bonding to the outer skin.
Source: Univ. of Alabama – Birmingham
Step 4: The aluminum vacuum forming mold for the Class A thermoplastic olefin (TPO) outer skin. As with the inner panel, cooling lines are cast into the mold to remove heat from the preheated sheet.
Source: Univ. of Alabama – Birmingham
Step 5: The formed outer TPO skin has been indexed to the removal station and is ready to be unloaded from the clamping frame and trimmed.
Source: Univ. of Alabama – Birmingham
Step 6: A technician applies adhesion-promoting liquid primer to the bonding surfaces of the composite inner panel. The primer also is applied to the inside of the outer skin panel.
Source: Univ. of Alabama – Birmingham
Step 7: Foam tape adhesive is applied to the bonding surfaces of the inner panel. The outer and inner panel are mated at low pressure to insure full contact.
Source: Univ. of Alabama – Birmingham
Step 8: Two finished doors, after robotic trimming (the one at left is viewed form the inside, the one at right, shows the outside surface.
