Repair Method C: FiberFlex
Repairing with Uni-Weld FiberFlex Universal Rod
Uni-Weld FiberFlex is a unique repair material in that it sticks to any plastic substrate. It is not a true welding rod, but rather a thermoplastic or hot-melt adhesive. When you do a repair with the FiberFlex, you will actually be using the heat of the welder to apply an adhesive. FiberFlex has a very strong bond and is reinforced with carbon and glass fibers for outstanding strength.
FiberFlex is the best way to repair TPOs (aka TEO, PP/EPDM, TSOP), the most common automotive bumper material. The reason is that there are no two TPOs that are exactly alike. As a result, our 5003R5 TPO welding rod will not match any TPO exactly. The FiberFlex, with its fiber reinforcement, actually makes a stronger repair than the true welding rod. Therefore, you’ll find the FiberFlex to be the easiest and best way to repair TPOs.
The FiberFlex can also be used to repair virtually any plastic. It will stick to urethanes and Xenoy also. When you are not sure what type of plastic you are repairing, try the FiberFlex.
V-Groove Damaged Area
Line up the outer surface of the tear with 6481 Aluminum Body Tape or with clamps. You may also tack the tear together with 2200 Insta-Weld 1 thin adhe- sive, however, instant adhesives don’t stick well to TPO.
Remove plastic in the shape of a broad V-groove halfway through the backside of the part using a die grinder with either the 6122 or 6122NF Heavy Duty Round Burr or the 6134-R Round Cutter Bit. You’ll want the v-groove to be about 1-1/2 inches wide when you get done.
It is very important to put some “tooth” in the plastic by grinding the v-groove with 50 grit or coarser sandpaper. Use a low speed grinder. Grinding at high speed will tend to melt many thermoplastics.
Using 80 grit in a DA sander, remove the paint in the area around the v-groove and radius smoothly into the v-groove. This will give you a better featheredge when you get ready to sand the FiberFlex.
Melt on the FiberFlex
With the airless welder set to the highest temperature setting, use the 6028RT Round Tip to melt the 5003R10 FiberFlex welding rod onto the surface. Best adhesion is achieved by premelting one side of the end of the rod, then flipping the rod over so that the melted portion sticks to the plastic. Cut the melted part of the ribbon off using the edge of the welder tip and spread the FiberFlex into the v-groove. Do not attempt to melt the base material together with the FiberFlex. Repairing with Fiber-Flex is similar to a brazing process.
You may also apply the 5003R11 FiberFlex Round Rod with the 6030 Speed Welding Tip for faster application.
V-Groove and Weld Opposite Side
After the FiberFlex on the backside cools (you may force cool with water), repeat the v-grooving and welding process on the opposite side. Build the Fiber- Flex slightly higher than the surface. FiberFlex is also a sandable filler.
After allowing the FiberFlex to cool completely, sand with 80 grit paper in a DA sander at low speed. Progress to finer grits, ending with 320 grit.
Fill any low spots with more FiberFlex or with a skim coat of 2000 Flex Filler 2 or 2020 SMC Hardset epoxy filler.