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Cameo Ivory 1967
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Discussion Starter · #1 · (Edited)
Repairing cracked plastic comes up a lot in here. Many of us have tried and trusted methods that we've been using for decades... Polyvance, JB Weld, 5 Min Epoxy.

I've been plastic welding for about 30 years, and in many instances, it's the only way to fly! My "go-to" for cracked endura/ urethane covers and body panels, has always been layered fiberglass repair tape and 5 minute clear epoxy. It's easy, flexible, and strong!

But when it comes to hard plastics, like grill surrounds and console stuff, or aesthetic things... plastic welding is better.

Anywho... I hit a deer on my motorcycle the other night... and one of my cases imploded. The main case was in four separate pieces and the lid was in two. The hinges were completely gone and the elaborate lock was destroyed. Of course, thanks to our bend-over economy, replacements either arent available or they want $1000... so, out came the plastic welder.

This job was definitely too-far gone, but I had no choice. I also had no videographer, so you'll have to use a little imagination.

For the record, a plastic welder is just a soldering iron, torch, or heat gun. I have a great unit, which is called a soldering iron/ rework station, because I do a ton of wiring. It has both an iron and heat gone, with a ton of attachments.

First thing you'll need is a set of plastic repair rods from Amazon. It'll include rods for all the common types of plastic. As I said, you can use a torch and heated screwdriver if you like... anyway to melt the base materials.
Product Rectangle Wood Publication Font


For reference, here's my soldering station
Pliers Tool Hood Wood Garden hose


Heres a missing hinge
Hood Gadget Eyewear Communication Device Automotive design


Here's me lying the rod on the missing part and working it with the soldering iron

Hood Automotive tire Automotive lighting Bumper Vehicle door

Hood Bumper Automotive lighting Tool Wood

Hood Microphone Audio equipment Automotive lighting Fender

Automotive tire Automotive lighting Hood Vehicle Bumper


Here's all of the cracks after being fused back together. First I tack the joint, then groove it, then fill it. FOR THE RECORD! I couldve made this MUCH prettier than I did, but since its a side case on an adventure bike, I was going for strength, not appearance. Still, when I sand it, you'll never see it.

Sorry I have no "BEFORE" pictures, but I only had a few hours to complete the job, so...

Automotive tire Bumper Gas Gadget Audio equipment


Here you can see it just needs to be shaped and redrilled
Tire Bicycle tire Bicycle frame Crankset Motor vehicle

Automotive tire Motor vehicle Tire Automotive exterior Bumper


So... Yes, it's ugly because I didn't sand and finish it yet, but as I said two hinges were completely missing and the mechanism was destroyed, and now it's fixed. The main case (in the last picture) was literally in four separate peices. It'll sand easily and then I can paint it if I choose. It's also stronger than it was in the first place.

So, next you're missing a tab from a grill or interior trim part, just figure out what the base material is, grab a rod and a soldering iron, and get to work!

Once you build up the part, you can tool it with the soldering iron to any shape needed. It's not visible here, but there were some very intricate parts in the lock mechanism that I had to repair, and it was a breeze!

In fact, you can even make missing pieces, using a 3D printer, and then weld them in with a soldering iron. I wish I couldve made a video, but between the cigar, the wiskey, the tequila, and the beer, I could barely hold the soldering iron, no less a camera.
 

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Nice work Jim
If you have a large hole ,I have used old plastic wheel liners from a u pick it yard, the plastic is stiff enough and has some "built in " contour for corners, you can also mold it with a heat gun if needed but wear leather welding gloves , I use a utility knife to cut the needed plactic then use the method Jim outlined for the repair
 

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Nice work Jim
If you have a large hole ,I have used old plastic wheel liners from a u pick it yard, the plastic is stiff enough and has some "built in " contour for corners, you can also mold it with a heat gun if needed but wear leather welding gloves , I use a utility knife to cut the needed plactic then use the method Jim outlined for the repair
Sounds good, Thanks,
 

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Cameo Ivory 1967
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Discussion Starter · #12 ·
Nice Army!

I need to make some repairs to the large AC under dash black plastic unit (67 lemans). I used some all purpose ABS/PVC adhesive that worked pretty well, but is there something better?
Adhesive will work "ok", but theres no substitute for welding. Same as gluing a quarter panel on a car, vs welding... Although, modern NASCAR trends have led manufacturers to start bonding panels with high tech adhesives, vs welding, thats a "lap-joint" and not a butt-joint.

When repairing a crack or replacing a missing tab, a soldering iron with some filler would definitely be the best. Once sanded and polished, youll never see any repair in plastic, that's not so with the glues and adhesives.

In my example above, the repair is butt-ugly, but it's a side case on a woods-basher, adventure bike, so not much point in making it too pretty... that being said, I will sand 80% of that mess away.
 

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Cameo Ivory 1967
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4,302 Posts
Discussion Starter · #13 ·
Nice Army!

I need to make some repairs to the large AC under dash black plastic unit (67 lemans). I used some all purpose ABS/PVC adhesive that worked pretty well, but is there something better?
BTW... that sounds like it would be ABS plastic, which is what the GTO grill surrounds are, I think.
 

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Curious if the parts made on the 3-D printer are as strong as original or even as strong as your repair? I don't have a clue but wondering if the print layering process creates failure seams? I can see where the melted material you put down wouldn't really have a consistent fault line and might be stronger than the printed material?
 

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Cameo Ivory 1967
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Discussion Starter · #18 ·
Curious if the parts made on the 3-D printer are as strong as original or even as strong as your repair? I don't have a clue but wondering if the print layering process creates failure seams? I can see where the melted material you put down wouldn't really have a consistent fault line and might be stronger than the printed material?
We think alike. But this is exactly why you want to plastic weld vs. JB Weld/ Glue? etc.

I wish I had more time (at the time) to invest in this thread... Before and after pics with a video wouldve been so much better, but in lieu of them, I was hoping to at least enlighten a few members about the concept and practice.

This summer I repaired a 400 gallon Rubermaid stock tank (which I connected an electric hot water heater to and made a hot tub) and it holds water effortlessly, because when welded, it doesnt even know that it was repaired. that's not so with the adhesive route.

When I repaired these cases, I used (as you can see) a chisel tip soldering iron to open the area (same as you would with metal welding) and then went back over it adding filler. Since the plastic is in a liquid state when you're repairing it, adding filler rod, which is also in liquid state, will become a permanent part of the base material.

3D printers use the same concept; when done correctly, new fluid plastic is added to the model before the previously applied thread has dried, so it's all-as-one when done. Of course, not all printers are created equal, either. Just like all parts and tools, the better stuff will yield better results.

Ive also started working with carbon fibers and modern composites, and with that stuff, you could make indestructible parts.

However, while I do maintain that a 3D printer is fully capable of making anything, bullet proof... I do think that the application rarely justifies the cost of the high-end stuff... So in my opinion, where the cheap/ hobbiest 3d printers really shine for me is:

Make my part, test it, modify it, perfect it, then send my file to a machine shop and have it milled out of aluminum (or whatever). At the end of the day, the most expensive part of the manufacturing process is the design and programming. I can now eliminate that.

That's how I made my shifter plate for the TKX conversion.

This video isnt the best, but it's enlightening
 
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