newby200x
12-01-2017, 09:38 AM
I've been experimenting around w/ plastic welding for some time now, probably not long after I got into the hobby many years ago. My first attempts started w/ a soldering iron and small strips of cut up fenders, which seemed to work, but failed to leave a favorable finish. From there, I upgraded to a Harbor Freight Hot Air Plastic Welder. I've played around w/ this tool now for several months and think I have a process, for the most part, calculated out. I thought I'd share my procedure w/ everyone.
Tools:
Hot Air Plastic Welder
Specialty Convex Finishing Tool
Dremel
248046248050
My first real attempt at a desirable fixed part is a 85 250R Headlight Shroud. These pics show a crack along the top and extending outward.
248048248049
1) First, I used my trusty soldering iron to position the plastic to the original shape it used to be by tacking several spots on the back side. Once in position, I went through and finished melting the crack back together.
248051
2) Next, it was time to move onto the main area. I used a small carbide bit from my Dremel set and slowly routed a V-Groove into the affected areas. After the groove has been machine, make sure it is thoroughly clean and I also use a scuff pad to remove any stray plastic burrs.
248052248053248054
3) For my filler strips, I used a piece of an old 85 Big Red rear fender that had been cracked and sun toasted. I used a utility blade to scrape this clean and remove any impurities. Then I used the Dremel and cut off wheel to cut thin strips.
248056
4) I found the heat setting of 5 to work the best, it seems to heat up quickly, but not scorch or burn the plastic at the same time. To start, I heated the tip of the filler rod until it became soft and also heated the start of the cracked area. I continued going back and forth between these areas until you can notice the plastic just slowing starting to melt on the very outside tips/crack. Once it is hot enough, place the tip of the filler rod into the crack and let it cool such that you have a solid filler rod at the beginning of the crack.
248055248047248057248058
5) With the filler rod tacked in place, use the plastic welder to heat the crack and rod simultaneously, sort of in a back and forth motion. If heating correctly, the crack will soften just enough to adhere to the rod, and if the rod is cut thin enough, it will almost fall directly into the groove. I try to keep the filler rod almost in a vertial position at all times, just slightly pointing back the opposite way from the plastic welder and pushing into the groove. This step is hard to explain and I don't have enough hands to capture a pic and weld at the same time.
248061248060248062
6) When the weld has been completed, I use my "special" spoon and go back and heat up the welded area and "roughly" smooth out the area w/ a spoon. This helps fill in any cracks or crevices.
248063248064
7) Now that the welding and filling is done, the hard part begins. Sanding and finishing. I use a 120 grit drum sander for my Dremel and attempt to remove the high areas. This can be difficult to do w/o going to deep or gougin the material. I got a little too agressive on a few areas on this. I'm hoping most the of the imperfections will come out in the wet sanding steps.
248065
8) I also picked up some fine sanding wheels for my Dremel. I belive I received a 180 and 220 grit wheel? Shown is the coarser of the 2. After the drum sander, I use this wheel to fine tune the area a little. It will still look rough after this is done, but it should start to come back to life after a 180 grit wet hand sand.
248066248067248068248069
9) After these steps, its onto a wet hand sand and buff process. This is as far as I have made it on this area. I have a few pics of an area I already performed. In my opinion, it turned out well. It's hard to see where the filler material was added, but up close you can see it. It's also extremely hard to finish these small contoured areas. If it were on a big rear fender and not curved so much, it would be easier to sand and make it look even better.
248070248071
I hope to add more pics in the next few weeks of more finished results. I wouldn't claim this is a process for a showroom restore, but it's better than stitching or a soldering iron. I think it will just fine shined up and from 10 feet away.
Tools:
Hot Air Plastic Welder
Specialty Convex Finishing Tool
Dremel
248046248050
My first real attempt at a desirable fixed part is a 85 250R Headlight Shroud. These pics show a crack along the top and extending outward.
248048248049
1) First, I used my trusty soldering iron to position the plastic to the original shape it used to be by tacking several spots on the back side. Once in position, I went through and finished melting the crack back together.
248051
2) Next, it was time to move onto the main area. I used a small carbide bit from my Dremel set and slowly routed a V-Groove into the affected areas. After the groove has been machine, make sure it is thoroughly clean and I also use a scuff pad to remove any stray plastic burrs.
248052248053248054
3) For my filler strips, I used a piece of an old 85 Big Red rear fender that had been cracked and sun toasted. I used a utility blade to scrape this clean and remove any impurities. Then I used the Dremel and cut off wheel to cut thin strips.
248056
4) I found the heat setting of 5 to work the best, it seems to heat up quickly, but not scorch or burn the plastic at the same time. To start, I heated the tip of the filler rod until it became soft and also heated the start of the cracked area. I continued going back and forth between these areas until you can notice the plastic just slowing starting to melt on the very outside tips/crack. Once it is hot enough, place the tip of the filler rod into the crack and let it cool such that you have a solid filler rod at the beginning of the crack.
248055248047248057248058
5) With the filler rod tacked in place, use the plastic welder to heat the crack and rod simultaneously, sort of in a back and forth motion. If heating correctly, the crack will soften just enough to adhere to the rod, and if the rod is cut thin enough, it will almost fall directly into the groove. I try to keep the filler rod almost in a vertial position at all times, just slightly pointing back the opposite way from the plastic welder and pushing into the groove. This step is hard to explain and I don't have enough hands to capture a pic and weld at the same time.
248061248060248062
6) When the weld has been completed, I use my "special" spoon and go back and heat up the welded area and "roughly" smooth out the area w/ a spoon. This helps fill in any cracks or crevices.
248063248064
7) Now that the welding and filling is done, the hard part begins. Sanding and finishing. I use a 120 grit drum sander for my Dremel and attempt to remove the high areas. This can be difficult to do w/o going to deep or gougin the material. I got a little too agressive on a few areas on this. I'm hoping most the of the imperfections will come out in the wet sanding steps.
248065
8) I also picked up some fine sanding wheels for my Dremel. I belive I received a 180 and 220 grit wheel? Shown is the coarser of the 2. After the drum sander, I use this wheel to fine tune the area a little. It will still look rough after this is done, but it should start to come back to life after a 180 grit wet hand sand.
248066248067248068248069
9) After these steps, its onto a wet hand sand and buff process. This is as far as I have made it on this area. I have a few pics of an area I already performed. In my opinion, it turned out well. It's hard to see where the filler material was added, but up close you can see it. It's also extremely hard to finish these small contoured areas. If it were on a big rear fender and not curved so much, it would be easier to sand and make it look even better.
248070248071
I hope to add more pics in the next few weeks of more finished results. I wouldn't claim this is a process for a showroom restore, but it's better than stitching or a soldering iron. I think it will just fine shined up and from 10 feet away.