Gluing in the broke out piece

Raider L

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@SirRobyn0,

So what prompted your shop needing you to learn plastic welding instead of just gluing the parts together with some of that stuff I showed? The two part epoxy.
 

Raider L

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@SirRobyn0, @Corvette Ed,

Okay, I just watched a YouTube video on repairing a crack in a plastic car fender with a repair kit that has the soldering iron with a temp. control box attached to the iron to make settings in heat for the different types of plastic. The guy used, in this case a "PP" Polypropylene filler rod, and the "fiberflex" reinforcement rod on the back of the crack and a little bit on the front of the crack. Now he put a screen, he called "mesh", on the back and washed plastic from the fender onto the screen. He didn't identify the screen but it appeared to me to be stainless steel screen, which I have, to lay over the crack before he put the fiberflex over it. And then he back grooved the crack on the front, which I can see doing just like back gouging a weld on one side of a seam in order to groove the seam into the weld from the back before welding the seam on the front for final welding. Then he filled the crack with the polypropylene filler rod and laid the fiberflex over that and smoothed it all out with a power sander and then put a little bit of flexable body filler over that and sanded for the last time and then, what I wasn't aware of, a "flexible primer" onto the repaired area.

Sound about how it's done? I get what you were saying about using a soldering iron now. It's a special soldering iron just for plastic welding. I had not been aware of that type of soldering iron before. I had seen plastic welding with a hot air tool. But I can see where for cracks and things like that being welded with the soldering iron. I think using the hot air blower would be for, what this tool was being shown doing was for making welds where a fillet weld is being done along side two thick pieces of plastic, like steel plates. And where fillet welds would be needed just like building up a weld similar to making a weld on steel or Aluminum.
 

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@SirRobyn0,

So what prompted your shop needing you to learn plastic welding instead of just gluing the parts together with some of that stuff I showed? The two part epoxy.
So I have $600 soldering station at work. It's one of those all in one soldering units, with adjustable temp for the iron, and a built in heat gun for shrink wrap. Well we had guy working for us for a little while that already knew how to weld plastic, and one day he showed me how to do it. Also for example I plastic welded the strap on my face shield back together after it broke. It's just a thin band of plastic and it came back apart after using super glue. 1 1/2 later the welded band is still going strong. It's not I plastic weld every bit of broken plastic, but there is some structural parts that it works really well at.

I gotta go do some work on the farm, when I get back to night I'll reply your comment on the video, because I do it a little differently than he does.
 

SirRobyn0

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@Raider L About the Youtube video you watched. I have never used filler rod that has been made for plastic welding. To use my face shield as an example, what I did for filler was to cut a bit of the strap from beyond the hinge point and used that for filler. You need to use filler material that is the same type of material as the plastic your welding. I've never used mesh screen in the welding process either, but then I've never tried to put a fender back together either.
 

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@Raider L I've used super glue and keep a tube just about everywhere. I've never used quick grip but will keep it in mind. I remember at one time we use to have a two part super glue type product at the shop. It wasn't really an epoxy I don't think, it acted much more like a super version of super glue and would pretty much stick anything together for life. I no longer remember the products name and it doesn't really matter because it's been unavailable for years now.

A couple years ago a guy I use to work with taught me how to weld plastic with a soldering iron. It's really kind of an art form almost, you have to have some plastic just like the stuff your welding and , like welding metal, you have to melt in deep enough to get good penetration, hot enough to melt, but not so hot you burn the plastic, and fill with the correct plastic filler, or donor piece from the parts your welding together. Done right the welded part of the plastic will be stronger than the rest of the plastic. So these days I do a lot of plastic repair like that.
I feel like the plastic weld thing if its old plastic or just a certain kind in general would lead to spot thats strong yes, but the surrounding stuff could potentially split from it like that process may create a stress point dpeending on what it is or what its doing. Im sure you use it wisely and where needed tho, but at least epoxy exists where there would be any doubt. I used jb weld just yesterday on smooth plastic to a piece of scrap wood and the weak point now is probably the face of the wood LOL (like to try and pull them apart)
 

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I feel like the plastic weld thing if its old plastic or just a certain kind in general would lead to spot thats strong yes, but the surrounding stuff could potentially split from it like that process may create a stress point dpeending on what it is or what its doing. Im sure you use it wisely and where needed tho, but at least epoxy exists where there would be any doubt. I used jb weld just yesterday on smooth plastic to a piece of scrap wood and the weak point now is probably the face of the wood LOL (like to try and pull them apart)
I don't disagree though I can't think of a plastic weld that I've had come apart, at least not since I was learning it. We keep JB weld on hand at the shop. I do find welding plastic tedious and time consuming if I have to do very much of it. But for another example you break a plastic clip off an interior piece and there is no room to JB weld the clip back on and super glue won't hold it. Plastic weld it. It doesn't have to (nor should it) replace other methods it's just another tool to put plastic back together with.
 

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I don't disagree though I can't think of a plastic weld that I've had come apart, at least not since I was learning it. We keep JB weld on hand at the shop. I do find welding plastic tedious and time consuming if I have to do very much of it. But for another example you break a plastic clip off an interior piece and there is no room to JB weld the clip back on and super glue won't hold it. Plastic weld it. It doesn't have to (nor should it) replace other methods it's just another tool to put plastic back together with.
JB weld does make a "plastic weld" too lol!
You must be registered for see images attach

thats a picture of the accidental 4 ply(or was it 2 ply?) tire I put on and now it rides like a jackhammer

Buttttt, the point was I used "plastic weld" to piece together the hood that was in about 7 pieces and I wasnt going for a perfect look just serviceable and It did okayu, even sitting above a radiator and 26hp engine. But there is one spot I insufficiently covered and Need to over-correct so I can ignore it for more years :)

The jackhammering probably wasnt helping lol
 

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JB weld does make a "plastic weld" too lol!
You must be registered for see images attach

thats a picture of the accidental 4 ply(or was it 2 ply?) tire I put on and now it rides like a jackhammer

Buttttt, the point was I used "plastic weld" to piece together the hood that was in about 7 pieces and I wasnt going for a perfect look just serviceable and It did okayu, even sitting above a radiator and 26hp engine. But there is one spot I insufficiently covered and Need to over-correct so I can ignore it for more years :)

The jackhammering probably wasnt helping lol
I wouldn't want to plastic weld a hood back together, it would just be so time consuming IMO. For me at least it's small parts only. I've never used JB plastic weld that I can remember. The regular JB quick, we get in big tubes at the shop I think 10oz and it seems to do very well with plastic, but of course it looks gray.
 

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I wouldn't want to plastic weld a hood back together, it would just be so time consuming IMO. For me at least it's small parts only. I've never used JB plastic weld that I can remember. The regular JB quick, we get in big tubes at the shop I think 10oz and it seems to do very well with plastic, but of course it looks gray.
yeah the plastic weld is clear with a hint of opaque maybe hint of yellow so its not an eye sore but I went over the thing with flat hvac duct metal tape, tad a glue to hold it best, then went over with build up primer, then john deere green. the upper hood piece is only the top part the lower hood was okay but i had to manuever with it attached to do the final parts to gether. Was a lot of clamps weights things etc. I Only had one little triangle piece evidently missing but I Just used the scrap chips off another couple and made it work.

Doesnt even look badd
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you can see the foreground the tape

the tape was to provide a small amount of "Fishplate" type of support, its not a fishplate in the sense its not bolted or welded, so there is probably another word, but that I figured was surface area where the tape has tensile strength and kinda can hold some of the force off the worst/heaviest/more issue prone area and also to improve the looks because it looked god awful lol. I could have probably went across it another direction and made it better looking yet but I was good with it. the primer did a lot too. then i ran out so we switched to painting
 

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yeah the plastic weld is clear with a hint of opaque maybe hint of yellow so its not an eye sore but I went over the thing with flat hvac duct metal tape, tad a glue to hold it best, then went over with build up primer, then john deere green. the upper hood piece is only the top part the lower hood was okay but i had to manuever with it attached to do the final parts to gether. Was a lot of clamps weights things etc. I Only had one little triangle piece evidently missing but I Just used the scrap chips off another couple and made it work.

Doesnt even look badd
You must be registered for see images attach

you can see the foreground the tape

the tape was to provide a small amount of "Fishplate" type of support, its not a fishplate in the sense its not bolted or welded, so there is probably another word, but that I figured was surface area where the tape has tensile strength and kinda can hold some of the force off the worst/heaviest/more issue prone area and also to improve the looks because it looked god awful lol. I could have probably went across it another direction and made it better looking yet but I was good with it. the primer did a lot too. then i ran out so we switched to painting
A little bondo and some actual JD paint and be as good as new.
What You did do there looks good as is.
 

Raider L

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@AuroraGirlI figure in the hood, I think it being flexible as it is plastic welding, if you had the time would be the best way to go if you wanted to experiment with that method. But yeah, JB weld would be the quickest for sure.

@SirRobyn0,
I wonder what shops use the actual "plastic welding", like the video I watched, method to do repairs? And what would be the charge for the tech doing it, hours? Would they explain to the customer what they did? Or just tell them, "Here you go, it's fixed."?
 

SirRobyn0

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@SirRobyn0,
I wonder what shops use the actual "plastic welding", like the video I watched, method to do repairs? And what would be the charge for the tech doing it, hours? Would they explain to the customer what they did? Or just tell them, "Here you go, it's fixed."?
I don't know the answer to that, I've never worked in autobody. With plastic body panels around here all I hear about is body shops replacing them. I would think in many cases the cost in labor to weld a plastic panel would exceed cost of replacement.
 

Raider L

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Yep, you're right about that. That's all these shops do around here is replace. The days of working a fender or some other body panel are dead and gone. They don't care about learning craftsmanship anymore where a man would hammer out dents. They just rip the thing off and bolt another one in it's place then charge you as if they did something real technical. The proverbial monkey could do what they did. But you get charged new body part costs when they got the part off a wrecked car out of the wrecking yard. You ought to be charged for a used body part, and the shop should give the customer the choice of used or new part, but you're charged new body part costs as if they bought it from the manufacturer. And the dealer is where they do that the most. They don't have the time to order a new fender from some warehouse and wait for it to come. They want that car done and out of the shop that day. They make their money off volume. That's so it'll make room for another car they might be able to make even more money off of.

My wife bought a new Toyota Camry many years ago. Every single time she took it in for something, not that a whole lot was ever wrong with it, it cost her over $350+ no matter what. Now, what the hell? Yeah, yeah, I know you're paying for a "technician" and his training, skill, and all that, plus the best parts, blau, blau, blau. So why is my 50+ year old truck still running and nothing ever goes wrong with it and it runs just as good, even better since I rebuilt it, and not that it needed it, only because I wanted to, than the day it was new??
 

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