Plastic Welding?

[busastars]

I have a few bike panels with cracks in them, I have tried before at Plastic Welding but with little success.

What I have done in the past is use a soldering iron and melt the to parts together, never have felt strong, always brittle and tend to break after.

Is it just the technique I was using, I have been google'ing and would a Heat Gun and ABS rods be any different and work?

Cheers

 

[Robotstar5]

Have you tried melting a paper clip (using a decent soldering iron) into the plastic across the break to give a "mechanical" connection?

 

[busastars]

Only ever tried with a cheap old soldering iron or a gas torch heating the end of a screwdriver.

Always brittle afterwards. On my Thunderace the mirror section is broken off, I used a soldering Iron to re'join but it was brittle and broke again. Thunderace fairings are like rocking horse poo unless you pay £££

So it got me thinking about trying a different way, use my heat gun, put a cowl on the end so I can direct the heat and buy some Plastic Welding Rods of ebay.

Am I aiming in the wrong direction?

 

[shenion]

A lot depends on the type of plastic.

I have had two plastic welders. One was hot air, the other used what is similar to a soldering iron. The hot air one was hard to use as it was way too hot.

One hard part is finding the plastic type and using the right filler. Things like ABS are easy, some others are more difficult.

I did the fairings on my '86 ZX600A. Worked well. Here is one fairing:

Hard to see but there is a white line across the raised area that curves down to the bottom right. That is the filler. Really had to press hard with the iron to get the filler to fuse. Was also done from the back.

Here it is after sanding/priming:

Just a bit of spot putty to fill a pinhole in the weld. No body filler used.

The iron has a temperature control and takes a while to get the temp exact. Too hot and it is brittle, too cold and it won't fuse. I have used a regular sodering iron on a light dimmer.

 

[busastars]

Cheers shenion,

Also seen on ebay plastic repair kits, obviously some kind of epoxy and like a mesh pad. Has anyone used these or know how good they are?

 

[shenion]

I might add that that firing was repaired with epoxy and fiberglass tape.

I just peeled it off as the epoxy did not stick to the plastic. Must have been regular epoxy, not something for plastics.

 

[Shox Dr]

I been told to use strips of fairing from the same manufacturer as filler, to ensure the right type.

 

[Engineer]

A proper plastic welding set up consists of a variable output heat gun, as well as a wide selection of filler rods. These work very well, but cost quite a lot of money. Best way to repair ABS bike parts is to use a kit designed for repaired car bumpers. Epoxy or GRP repairs are not a good idea, as adhesion to ABS will be poor, and both are inflexible.

 

[Delgado]

As said, we used to use a heat gun for PVC tube (it was more like the shape of a die grinder than a gun), with variable temp control and a tube type attachment on the end to give a thin stream of hot air. It wa a bit fiddly at first but after a couple of goes (and someone showing you how) it was pretty easy to pick up how to add the heat and melt the filler rods in properly. For PU tube (I think it was PU anyway?) we just used a hot plate on a stand, melt each end of the tube on either side, then pull them away, and simply stick them together.

 

[the snooper]

this is the model i have with adjustable heat output they are around £300 i had mine given and have not done a lot with it i do know that you need the correct filler and the correct temperature info

 

[GeorgiePorgie]

Also seen on ebay plastic repair kits, obviously some kind of epoxy and like a mesh pad. Has anyone used these or know how good they are?

Have a look on You tube,many pros showing how to repair plastics ie type plastic repair.

Its obvious that a bridge repair is a lot stronger than a weld repair but sometimes a bridge repair cannot be done.

 

[Ian D]

Intresting thread as i offered a while have ago on a bumper of an astra, but have not as yet done it.

 

[busastars]

I also asked on another forum I use and someone dropped this link:

http://www.urethanesupply.com/pdf/thebook.pdf

Only had a quick look for now but seems really informative

 

[pedrobedro]

You can melt broken up Lego bricks in acetone to make a paste which can be used to repair fairings, it's an ABS plastic. I read about someone moulding new bits from it to attach to a broken fairing. Here's a link.

 

[jugs]

And then there's ultrasonic welding,
SEE THIS & THIS

I've got a system that we used to use for a process yrs ago, still comes in handy somtimes , for plastic it works like magic.

 

[busastars]

You can melt broken up Lego bricks in acetone to make a paste which can be used to repair fairings, it's an ABS plastic. I read about someone moulding new bits from it to attach to a broken fairing. Here's a link.

The link in the link don't work but that's some nice information. I may try this, wonder if I can use something other than lego, just so happens I never kept any of my lego from childhood. Maybe cable ties, old bottle tops etc.

 

[GeorgiePorgie]

The thing with plastic you have to weld the same material with the same material otherwise this will compromise its strength or its ridgidness or at worse won't bond very well.

Bit like painting a surface with household paint and then going over it with a cellulose paint ie it cause a crackle effect because the two paints are opposing eachother in chemical reaction.

 

[busastars]

More google'ing and it seems lego for ABS fairing repair is quite well know and popular, how did I not no this ( answers on a postcard )

Not got any lego but ebay should come up trumps for a job lot of used blocks for peanuts.

 

[GeorgiePorgie]

Go to Maplins and buy a cheap ABS plastic box,be far cheaper than messing with Lego blocks.

An ABS box from Maplins for as little as £1.99,eck you'd pay that in postage on ebay

 

[jugs]

The link in the link don't work but that's some nice information. I may try this, wonder if I can use something other than lego, just so happens I never kept any of my lego from childhood. Maybe cable ties, old bottle tops etc.

cable ties are usually nylon bottle tops can be anything from PET to Polypropylene.

Would you TIG a manifold with something out of the scrap bin ??

GeorgiePorgie
The thing with plastic you have to weld the same material with the same material otherwise this will compromise its strength or its ridgidness or at worse won't bond very well.

Bit like painting a surface with household paint and then going over it with a cellulose paint ie it cause a crackle effect because the two paints are opposing eachother in chemical reaction.