Shawn Collins, 3M Senior Technical Services Engineer, shows tips and tricks for weld bonding.
Step 1: Remove seam sealer (01:09)
Clean off the area to see the welds. Remove all the seam sealer in the area that will remain on the vehicle. For the rest, remove just enough to see the welds. I like the Scotch-Brite™ belt — it highlights the welds so you can see exactly where they are.
Step 2: Tape the section (03:37)
I’ve removed the welds except the ones in the area I’m going to section. Mark the sectioning area with tape. If you’re sectioning to a manufacture’s procedure, follow their directions. Then identify the marks in the same area on the replacement panel.
Pro tip (04:38): Add some markings to help you keep track of what’s replacing what. For example, I write “scrap” on the areas being replaced and “save” on the areas I’m keeping.
Step 3: Cut as far as you can with cutoff wheel (05:14)
You can only cut so far before you start cutting the bottom flange — and the key to this repair is to not damage the bottom flange on the host panel. So cut as far as you can, and then we’ve developed a technique using the file belt tool called a plunge cut.
Step 4: Finish with a plunge cut (06:30)
You’ll cut from two different angles and grind the material down to finish the cut started by the cutting wheel.
Pro tips (09:35): Slip a metal plate underneath so you don’t grind the bottom plate (the host panel). Also, cut just a hair larger and little bit longer, then grind it back when you make your final fit for the sectioning joint.
Step 5: Clean it up to prep for adhesive (11:53)
Remove all the seam sealer and the weld nuggets for a nice flat surface. And cut the replacement panel so it’s ready to go. Finally, touch up the sectioning line for a good fit.
Step 6: Prep for welding (15:06)
Choose which side you’re going to MAG weld on and mark it up. Mark the other side for squeeze-type resistance spot welding. Then clean the surfaces for welding and punch some holes for your plug welds.
Step 7: Double check your cleaning and mark your welds (18:12)
Don’t miss any spots because it will contaminate the welds. If the manufacturer recommends epoxy primer, go ahead. Mark where your welds go. A lot of OEMs have very specific information for squeeze-type welding, so always check them.
Step 8: Apply 3M™ Weld-Thru II coating primer (24:10)
It’s important to agitate the Weld-Thru primer very well before spraying. Apply only to the MAG welding side, not anywhere you’re using adhesive. Apply two coats.
Pro tip (24:29): Store Weld-Thru upside down or on its side so the zinc powder doesn’t settle to the bottom.
Step 9: Clean the plug weld holes (26:10)
The easiest way to do this is to apply the Weld-Thru primer after your holes are punched, then test fit the part. While it’s on for the test fit, mark the holes, then hit those spots with a file belt sander.
Step 10: Prepare replacement side for adhesive (28:00)
Clean the surface with a VOC-compliant cleaner.
Step 11: Apply the adhesive (28:58)
Equalize the cartridge into a paper towel and extrude a couple inches onto a mixing board or back into the paper towel. Make sure you have an adequate mix. Three applications: one on the host part, one on the replacement part, then a third squeeze-out bead.
Step 12: Clamp the parts (32:40)
You can use many different types of clamps, but clamp tightly. It’s virtually impossible to overclamp.
Step 13: Look at OEM procedures (34:14)
Now that you’re clamped up and ready to weld, see if the OEM has any special recommendations.
Step 14: Finish the repair (36:25)
Complete the repair process, finishing up with 3M™ Cavity Wax Plus 08852.
Important note:
There are of course many factors and variables that can affect an individual repair, so the technician and repair facility need to evaluate each specific application and repair process, including relevant vehicle, part and OEM guidelines, and determine what is appropriate for that repair.
Products used in this video:
3M™ File Belt Sanders for Body Repair
~/3M-File-Belt-Sanders-for-Body-Repair/?N=5002385+8709313+8710928+8711413+8743663+3291220166&preselect=8716717&rt=rud
Scotch-Brite™ Durable Flex Belt
~/Scotch-Brite-Durable-Flex-Belt/?N=5002385+3293241214&preselect=3293786499&rt=rud
3M™ Weld-Thru II 05917
~/3M-Weld-Thru-II-Coating/?N=5002385+3293194153&preselect=3293786499&rt=rud
For more advanced tutorials, check out 3M Collision Repair Academy
You’ll find courses that will expand your knowledge, deliver practical procedures that you can use right away, and, in many cases, earn you I-CAR credits.