One-Sided Repair on a Molding Strip Insert

One-Sided Repair on a Molding Strip Insert


The molding strip insert on this Kia
Optima bumper is torn.
In most cases, when a bumper is damaged, a repair on both the frontside and the backside is recommended.
However, this plastic will be v-grooved thin enough that the front will fuse when the backside is welded.
This allows us to do a quality repair on the backside alone,
which saves us time by eliminating any refinishing and paintwork on the front.
This video will show you how to make a quality one-sided repair on a molding strip insert.
First, clean the bumper to remove any grease or grime.
Then, heat the bumper to release any tension around the damage.
This will help you properly align the crack.
Here, we used Polyvance’s Hot Spot Stapler to keep the crack aligned
so we could accurately apply aluminum tape to the frontside.
Apply the aluminum tape and use a body spreader to crease the tape into the groove.
The aluminum tape holds the crack together while also creating a backing for the welding rod.
Now that the aluminum tape is securely holding the crack together, we can remove the staples.
Next, make a deep v-groove down the center of the crack.
You want to v-groove almost all the way through to the tape.
Etch the plastic on both sides of the v-groove.
Because the plastic has been v-grooved very thin,
you need to make sure the nitrogen flow on the welder is set between 10 to 12 liters per minute
to prevent blowing through the plastic.
Now that the welder has been adjusted, you can begin the welding process.
Use Polyvance’s round R02-02 welding rod to make your first pass.
As you go along, make sure the welding rod melts through to the tape.
Melting the welding rod all the way through to the tape
allows the front to be fused at the same time as the backside.
After you complete this first pass, do any necessary shaping.
Use Polyvance’s R02-08 corner welding rod to cap the weld.
Use the airless plastic welder to shape and smooth the weld.
When welding a long tear, it is best to weld a few inches at a time and then smooth immediately.
After the weld is cool, you can safely remove the aluminum tape.
Use a utility knife to cut away any welding rod that would prevent the molding strip from snapping into place.
As you can see, this one-sided repair is extremely strong.
Thanks for watching!
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Let us know in the comments what you thought of this repair,
and check out our other videos for more plastic repair tutorials.

5 Replies to “One-Sided Repair on a Molding Strip Insert”

  1. Do you see the repaired fog light mounting bosses on this bumper? Do you want to know how to do that kind of repair? Check out our other video: https://goo.gl/71dfRZ

  2. Do you have some company branch, workshop or similar facility in Australia that performs similar work to your vintage car bumper repairs? An american car in australia is never easy to fix!

  3. View this video on our website for more information about the products used for this repair and for some helpful tips: https://www.polyvance.com/video/nitrogen-hot-air-welding/one-sided-repair-on-a-molding-strip-insert

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