DIY Plastic Welding - ABS Plastic Front lip/bumper - how?

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  #1  
Old 09-12-12, 06:50 PM
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DIY Plastic Welding - ABS Plastic Front lip/bumper - how?

Hi all!

Welcome to my first post I come from the land downunder so a big G'day to you all!

Yours truly had a bit of a incident last night coming around a very slippery corner in the rain and managed to damage his bottom lip on his bumper.

The lip is ABS plastic and removable however it's sustained some cracks and splits, and will most likely need to be repaired via plastic welding. I've gotten a quote around $300AU to fix it, so if I can do it at home for cheaper then I am willing too. It doesn't seem too hard (famous last words?).

It's incredibly hard to buy this for my car (almost obsolete) so I would prefer to repair it.

Here's some pictures:
http://imghost.me/images/2012/09/12/0QYxo.jpg
http://imghost.me/images/2012/09/12/segXp.jpg
http://i479.photobucket.com/albums/r...mporary-30.jpg

I've seen a video on youtube on plastic welding, and I'm confident enough to give it a shot myself, if it is possible at all. The video I was watching was for TPO plastic not ABS plastic, which is what my bumper is made out of.

Here's the video I was looking at:
http://www.youtube.com/watch?v=qVLBD-uHRgE
So do I need to do anything different to the above video since I have ABS platic? Also is there any problems with getting a Hot Air welder from ebay?

Appreciate any and every help!

Thanks,
DIY_FTW
 
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  #2  
Old 09-12-12, 07:30 PM
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well, firstly, if you cleaned plastic, do not wipe anything off it with bare hands thereafter.

I make braces as my vocation. We had much better quality welders than what you see here. They simply do not last, as in - welds. Maybe if it's in a very stable zone, otherwise - cracks always came back, no matter how well or how much we welded them.

What you can also do on the inside, is to roughen plastic, lay spray thin layer of Super78 glue, glue fiberglass cloth over, and spread luiquid resin with tongue depressor. When it hardens, it makes very strong backing to your project. PAint it over if you wish.
 
  #3  
Old 09-12-12, 07:46 PM
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Thanks for the response mate!

Appreciate the input!

I've had this lip professionally plastic welded before - it is actually made of two parts as I found two lips that were broken on opposite sides. Until last night's accident, it held up fine. It did even cop a bit of a hit when I went down a very steep driveway.

How long do you find that the welds have lasted before they cracked again?

I will look into finding a Super78 equivalent here in Australia. I've been told that fibreglass doesn't stick to ABS plastic hence why I didn't look going down that route. Should I plastic weld and then fibreglass over the crack? My only concern is that fibreglass is very brittle has no flexibility. The lip doesn't really need to be super flexible but some flexibility is good to have especially when it's close to the ground.

Thanks for the help mate!
 
  #4  
Old 09-13-12, 07:48 PM
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resin sticks to anything rough and degreased. I use some resins that will stick to anything and will be stronger than metal they bond. But a decent polyester resin will work for you.
Super78 is simply spray on glue. What you do not want to do, is several things:
- have glue in clumps, so spray just enough for tack
- touch it anywhere with hands, so wear gloves.
If you can, remove that spoiler, roughen it well, clean well, spray some glue, tack fiberglass sheet on, and spread it well and with no wrinkles with say plastic spatula, like you use on Bondo. Pour resin on in a puddle, and spread around with tongue depressor.

Siegelhartz is a very good resin for such projects. That will be very strong lip thereafter.

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You'll need benzoil peroxide hardener in paste also. But that's same hardener they sell for Bondo. Working time is about 10 minutes.

Any plastic weld cracks very fast under load or torsion. But that's on braces. For your application - till you bump it again. ABS is crappy plastic. But with fiberglass backing, it may last long time.
 
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