# REPAIRING PLASTIC, THE RIGHT WAY



## armyadarkness (Dec 7, 2020)

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.









For reference, here's my soldering station









Heres a missing hinge









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


































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...










Here you can see it just needs to be shaped and redrilled

















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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## michaelfind (Dec 14, 2018)

I wish I had your skills and experience! That is a great tutorial. Thank you.


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## armyadarkness (Dec 7, 2020)

You don't need my skills and experience, you just need some Russian porn stars and alcohol to trade for them.


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## Joes1966GTO (Apr 27, 2020)

@armyadarkness - Amazing work, as always, Jimmy!! I'm just glad that the case took the hit and not your cranium. Stay safe, brother!


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## armyadarkness (Dec 7, 2020)

Thanks. I wouldve preferred to have extensive "BEFORE" pictures, as well as pictures of it when all finished, but as I said, I had no helper and only a small window of time, so hopefully just the information is enough to help someone out of a jam.


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## armyadarkness (Dec 7, 2020)

Not bad for 50 cents and 20 minutes with a soldering iron. Will save me $1000


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## 67lemans (Oct 30, 2009)

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?


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## 1969GPSJ (Feb 26, 2020)

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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## AZTempest (Jun 11, 2019)

Awe, how's Bambi? 

Kidding aside, nice write up. I've tried a little plastic welding but not enough to say I'm even close to say I know what I'm doing.


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## 67lemans (Oct 30, 2009)

1969GPSJ said:


> 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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## 1969GPSJ (Feb 26, 2020)

I have also used Folgers coffee plastic lids for a template or possible repair


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## armyadarkness (Dec 7, 2020)

67lemans said:


> 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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## armyadarkness (Dec 7, 2020)

67lemans said:


> 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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## armyadarkness (Dec 7, 2020)

BTW...



Amazon.com : Plastic Welding Rods


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## 67lemans (Oct 30, 2009)

If it is ABS plastic, do you use a different welding rod material? I have to repair my lemans grills in a couple small spots as well.


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## armyadarkness (Dec 7, 2020)

Yes, the kit comes with ABS rods!!!

My cases used Polyethelene


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## lust4speed (Jul 5, 2019)

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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## armyadarkness (Dec 7, 2020)

lust4speed said:


> 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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## CDub67 (Jun 20, 2019)

Thanks Army. I love learning new things. My plastic repairs have consisted of baking soda sprinkled on super glue. Works great but is hard to make look good as it hardens like cement.


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## armyadarkness (Dec 7, 2020)

Baking soda and crazy glue is awesome! Just not strong enough. Been using it 40 years, but it didn't get popular until the YouTube age. It started out as micro balloons, which are glass, and we mixed it in with fiberglass resin so that it could be molded and sanded!


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## 4rd4fun (Oct 24, 2019)

armyadarkness said:


> 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!
> 
> ...


Very cool and hope you are ok- hitting a deer can have dire consequences.


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## armyadarkness (Dec 7, 2020)




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## armyadarkness (Dec 7, 2020)

4rd4fun said:


> Very cool and hope you are ok- hitting a deer can have dire consequences.


Thanks! Yeah, was a bad year for accidents. Somone backed into the GTO, I hit a deer on the bike, and a fence hit my Silverado. Knowing how to fix stuff should never be confused with wanting to. But... I have no complaints.


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## armyadarkness (Dec 7, 2020)

Here's the extremely popular Polyvance kit that everyone raves about... you can see, it's just a soldering iron.


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## Colorado67GTO (Sep 11, 2014)

Is there an easy way to tell what plastic is what?


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## armyadarkness (Dec 7, 2020)

Colorado67GTO said:


> Is there an easy way to tell what plastic is what?


Glad you brought that up!

No!

lol... Ive been messing with it long enough to guess, pretty close... but most tests involve melting the base material, and who's going to do that with a 65 GTO grill surround?

Most of the rigid stuff is abs, the pliable rubbermaid stuff is poly or nylon, but if you use the wrong rod, usually it wont blend, so it's obvious. Some day Id like to find a quicker way to tell.


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