WEB EXCLUSIVE: When a national truck fleet approached Maxi-Seal Harness Systems of Grandview, Mo., to design a new modular wiring harness for the underside of long-haul semi-trailer trucks, Maxi-Seal saw an opportunity to deliver a new level of reliability. So when Maxi-Seal launched its “Defender” wiring harness system, it carried an unprecedented 10-yr warranty against leakage and corrosion.
Wiring harnesses are exposed to grimy exhaust and road particulates, as well as water spray, caustic de-icing solutions, and other chemicals. A water-tight seal and chemical and corrosion resistance were thus essential design requirements. But the initial prototypes failed due to moisture penetration. At the heart of the device is the connection point between a rigid housing and an overmolded TPE elastomer, which requires a water-tight seal. Maxi-Seal tried several material combinations without success. “We called several plastic suppliers and explained our challenge,” said Eric Doerflinger, manufacturing engineer. “They would look at their catalog and say, ‘Try our product number such-and-such.’ We did, and when it didn’t work they would say, ‘Sorry, that’s all we have.’ That happened time and time again.”
But after discussions with Maxi-Seal, custom compounder RTP Co., Winona, Minn., decided to develop two custom materials for this application. “We tried them and found that RTP pretty much provided the right solution on the first try,” said Doerflinger. RTP developed an RTP 1000-series glass-reinforced PBT compound for the rigid housing and an RTP 1500 Series copolyester TPE with 30 Shore D hardness for the flexible overmold. RTP modified the PBT substrate to enhance bonding to the TPE. It also modified the TPE to minimize shrinkage so it wouldn’t pull away from the PBT and break the water-tight seal. The new harness has survived field tests on 20 trucks driven a total of 1.6 million miles. The new harness design has become the standard for an entire national truck fleet, a very large piece of business for Maxi-Seal.
(800) 433-4787 • rtpcompany.com
580 E. Front St. Winona, MN 55987
Phone (507) 454-6900 Fax (507) 454-2041