Hairline Crack In Guitar Soundboard. Repair Or Not?

How to Repair Cracks in Polyethylene

by C.L. Rease

motorcycle image by Aleksander from Fotolia.com

Polyethylene has made its way into many components of cars, motorcycles and boats. Although strong and lightweight, polyethylene is not impervious to cracking. When a polyethylene part cracks, you need to repair the part immediately to reduce the chances of the crack growing and ruining the polyethylene part. Advertised quick epoxy fixes for polyethylene parts will hold temporarily, but they will not create a permanent repair on the part. Welding the crack will permanently repair it, and it will also strengthen the damaged area, eliminating the chances of the crack returning.

Step 1

Set the temperature of the plastic welder to 575 degrees Fahrenheit, turn the welder on and set it aside to allow the plastic welder to reach the correct welding temperature.

Step 2

Wipe the area around the polyethylene crack with a clean rag to clear the crack and the area surrounding the crack of materials that could contaminate the weld joint.

Step 3

Put on your safety glasses.

Step 4

Bevel one side of the crack in the polyethylene part to a depth at least 1/8 inch deep. Make sure that you bevel 1/2 inch past each end of the crack.

Step 5

Align the speed tip of the plastic welder with the beveled end of the crack that is furthest away from you. Slide one end of the polyethylene filler rod into the guide of the plastic welder's speed tip.

Step 6

Apply downward pressure on the length of polyethylene filler rod, as you pull the plastic welder toward you slowly. Watch the area where the polyethylene filler rod meets the surface of the beveled polyethylene crack. If you notice a small bead of melted polyethylene flowing ahead of the filler rod and the polyethylene is not burning, you are pulling the plastic welder at the correct speed.

Step 7

Cut the polyethylene filler rod even with the end of the speed tip guide, when you are 1 inch away from the end of the crack you are repairing. Continue pulling the plastic welder toward you to fuse the remainder of the polyethylene rod to the surface of the polyethylene repair.

Step 8

Allow the polyethylene repair to cool thoroughly before continuing.

Step 9

Attach the 120-grit sandpaper to the palm sander.

Step 10

Sand the polyethylene filler rod smooth with the surface of the polyethylene part to blend the repair into the part.

Repeat the process to repair the backside of the polyethylene crack, to complete the polyethylene crack repair.

References

Things You'll Need

Plastic welder with speed tip
Clean rag
Safety glasses
Die-grinder with a tapered carbide tip
Polyethylene filler rod
Lineman's pliers
120-grit sandpaper
Palm sander