Plastic repair GURUS since 1981
Repairing and Retexturing a Freightliner Bumper End Piece
Many heavy trucks have thermoplastic bumpers and side panels which can be repaired with Polyvance's plastic repair and refinishing products. Here we have the end piece of a Freightliner bumper, which is polypropylene and has an unpainted textured finish. The bumper is torn along a body line. This will be an easy repair with one of Polyvance's nitrogen plastic welders. We will retexture the bumper with our Flextex VT texturing material.
View our Flextex VT Standard Operating Procedure here.
Always wear proper safety gear while working!
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Many heavy trucks have thermoplastic bumpers and side panels which can be repaired with Polyvance's plastic repair and refinishing products. Here, we have the end piece of a Freightliner bumper, which is polypropylene and has an unpainted textured finish. The bumper is torn along a body line. This will be an easy repair with Polyvance's nitrogen plastic welder and refinishing products.
The first step of the repair will be to clean the plastic. Next, we'll line up the crack with a hot staple. Here, we are using the 6213 inside corner staple. Sink the staple into the plastic about halfway through to hold the crack together as we make our weld. Next, clip off the staple ends with a pair of diagonal cutters. To make sure the crack stays together, apply aluminum tape to the outer surface. Prepare the backside for welding by grinding a v-groove with a carbide cutting burr. Grind the plastic slightly flush with the die grinder along the length of the crack. Since this Freightliner bumper is slightly thicker than an average car bumper, we'll crank up the nitrogen flow to about 15 liters per minute. Having flow control is important for speed on thick plastics like this.
Weld the inside corner along the crack with the R02-08 corner welding rod. After allowing the weld to cool a bit, to add extra strength, we will cap the weld with the R02-04 polypropylene ribbon. To increase the strength at the edge of the weld, we will "tee" the edge with two passes of the R02-04 welding ribbon. Teeing the edge is always desirable when the damage extends to the edge of the bumper. As with any nitrogen plastic weld, make sure you melt both plastics at the same time... the bottom surface of the rod and the top surface of the bumper, using the downward pressure on the rod to fuse the two melted plastics together.
When the weld on the backside is completely cool, peel off the aluminum tape on the front side. V-groove with the 6125 carbide cutting burr. Because the plastic is thick, this will be a deep v-groove. V-groove until you are at least halfway through the plastic, or until you start to see the white welding rod from the other side. Remove the grinding slag with a putty knife. To keep the repair area as tight as possible, we are welding with the R02-01 eighth-inch round welding rod on the front side. Focus the hot nitrogen gas at the point where the rod and bumper meet, melting both plastics at the same time, fusing them together with the downward pressure on the welding rod. Since this v-groove is deep, we'll come back immediately with a second pass of the welding rod. Apply as many passes as needed to completely fill the v-groove. Because the bumper is thick, we don't need to worry about overheating the plastic, but be careful not to overheat thinner plastics. You don't want the plastic to become too soft and lose its structure. When the weld is finished, smooth with the airless plastic welder.
Once the plastic cools completely, sand the weld with 80 grit, then 180 grit in a DA sander. Feather the texture back with the 180 grit. Next, we'll apply the high-build primer surfacer. Before you apply any coating to a raw polypropylene plastic, use Plastic Magic adhesion promoter first. After allowing it to flash for a few minutes, spray a coat of the 3043 Black Jack primer to smooth the area out, then sand with 320 grit when dry.
Use your texture reference cards to decide on the proper let-down ratio for the Flextex texture spray. As you can see here, the original texture seems to be somewhere between a medium and coarse, so for the 3803 Flextex, we'll use two parts paint and one part thinner. Again, apply 1050 Plastic Magic adhesion promoter first. Next, spray three light coats of Flextex. You want to "spackle" the paint on; don't let the paint flow out. Spray from about 18" away and keep the gun moving fast. Let the paint flash, then apply the second and third coats. For this spot repair, we'll blend with the original texture.
When you're satisfied with the appearance of the texture and how it blends with the original, color coat the entire part with Bumper & Cladding Coat. Bumper & Cladding Coat sticks to polypropylene, so the Plastic Magic is not needed prior to its application. Mixing 60% 3701 black with 40% 3702 white gives a very close match to the original Freightliner color.
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