Repairing plastic parts is common in almost any collision repair shop. But if the repaired bumper or plastic part has damaged or missing tabs and can’t be reattached to the vehicle, you can still end up paying to replace it. 3M provides these simple, step-by-step standard operating procedures (SOPs) for repairing plastic tabs commonly used to attach these plastic parts to vehicles. Here you will find the best practices for plastic tab repair, including sanding, tab preparation, use and shaping of flexible plastic repair material, and final inspection.
Keeping the repair area clean – both the tab area and the area of the vehicle where the tab will be reinstalled – is crucial to the strength, integrity and adhesion of the tab, and to an effective overall plastic tab repair.
3M recommends cleaning the entire part with soap and water, followed by a VOC compliant surface cleaner to eliminate any additional contaminants. Cleaning the entire part can also help you identify any hidden damage. Use a dedicated microfiber detail cloth for each cleaning agent.
Grinding and sanding the area immediately around the broken tab creates a surface that best accepts the flexible adhesive material used in plastic tab rebuilding and repair.
Grind the broken tab area using a 3-inch 60 grit 3M™ Roloc™ disc. Take care to create a tapered edge, as this will make the following tab preparation steps smoother and more effective. Next, using a dual action sanding tool, sand the tab repair area with a 3-inch 80 grade abrasive disc to remove any melted or shiny plastic. It’s best to DA sand until all shiny plastic is removed, and the surface is “fuzzy” for best adhesion.
Drill 1/8-inch pinning holes in the damaged area. Drill the holes about ¼ inch within the tapered area and ¼ inch apart. Pinning allows the adhesive to flow through holes and bond with itself for added strength. It’s almost like creating extra rivets or bolts securing the replacement tab or the repaired tab to the part.
Next, apply aerosol adhesion promoter to the sanded repair area. This is a critical step to ensure the new or repaired tab will remain functional long after repair. Allow the adhesion promoter to cure for 5 to 10 minutes.
In the next two steps, you will rebuild or recreate the plastic tab using contour film and a fast-curing plastic tab adhesive repair material such as 3M™ Super-Fast Repair Material. For longer worktimes or if working in hot environments, 3M advises substituting 3M™ Semi-Rigid Repair Material.
Roll out contour film sheet and cut it 3 times the length of tab. Fold the sheet over the tab repair area and verify that you are using enough to recreate the entire tab. For best results, use a marker to draw a rough version of the finished tab on the sheet. Mix the plastic adhesive material and apply it to the contour sheet. Fold the sheet and the adhesive over the damaged tab. Shape the adhesive material between the folded sheet, making sure that you’ve applied enough adhesive to form a complete tab. Also, be sure the adhesive flows through the pinning holes. Allow the adhesive to cure 5 to 10 minutes. Remove the contour sheet.
The properly cured tab repair adhesive material can now be cut and shaped just as if you were working with the original plastic tab. Rough shape the entire repaired tab area with a 3-inch 60 grit 3M™ Roloc™ disc. Remove as much adhesive material as you can to achieve your desired tab shape.
Next, using a dual action sander, sand the repair area with a 3-inch 80 grade abrasive disc. DA sand the tab as close to your desired shape as possible. Redrill any original mounting holes as necessary.
This step is necessary to achieve a professional final finish for the tab, and to help ensure a lasting plastic part and bumper repair. Using a DA sander and a 3-inch 180 grade abrasive disc, finish sand the tab repair area.
Blow off the tab repair area using clean, dry compressed air and inspect for quality. If painting is required, follow paint manufacturer’s guidelines for plastic parts refinishing. Once all plastic tabs are properly repaired and refinished, you should be able to reinstall the bumper or other plastic part as you would if it was new.