Plastic Welding?

[busastars]

Could pop down Maplins but chatting to the wife ( she knows ) the local cheap shop has big boxes of lego for around £5 and also maybe able to get my hands on it free I'm sure I have Acetone here but if not that's cheap enough.

I'm always one to try a new way of doing things as a few of you know so hopefully in the next month I will have a bash and post up my findings.

Only other problem would be paint work, either learn to spray myself or find someone local who does it as a hobby,,,,, That is a hint mind for anyone local who has there own little setup

 

[GeorgiePorgie]

There ya go....

http://www.youtube.com/watch?v=7g42q1Vm_yY
http://www.youtube.com/watch?v=D8rTwWRYb0c

 

[the snooper]

doubt lego would be any good as its not a flexible plastic you need something that will be a very close if not exact match for it to bond together properly some broken panels of a bike maybe

 

[Shox Dr]

I take it no one bothered to read post #7 then

 

[busastars]

I take it no one bothered to read post #7 then

I did Shox, having spare panels would be the main problem and also costly.

For me my Thunderace has a cracked side panel BUT also the nose cone has damage in two places. Thunderace nose cones are rare as hens teeth unless you buy a patten one and there expensive.

Since starting this thread and the lego tip came up I been doing a few hours of reading and lots of people seem to have had good success with it. Also cheap as chips which is me all over

 

[Shox Dr]

You only need to get hold of "plastics" from a Yamaha. Cut it into strips and use that

 

[busastars]

Thats why I ask stupid question Shox as I always miss something Can ask around a few people local for a broken panel.

Staying on subject: Acetone,,,, I thought I had some but was mistaken. Looking on Boots website they do Nail Varnish Remover, would this be pure Acetone as they also advertise stuff Acetone free ( I may go in the store and just ask for the free Acetone )

So I am guessing this one is Acetone:

http://www.boots.com/en/Boots-Essentials-Nail-Polish-Remover-250ml_1115013/

 

[BeeJay99]

Thats why I ask stupid question Shox as I always miss something Can ask around a few people local for a broken panel.

Staying on subject: Acetone,,,, I thought I had some but was mistaken. Looking on Boots website they do Nail Varnish Remover, would this be pure Acetone as they also advertise stuff Acetone free ( I may go in the store and just ask for the free Acetone )

So I am guessing this one is Acetone:

http://www.boots.com/en/Boots-Essentials-Nail-Polish-Remover-250ml_1115013/

Fibreglass suppliers sell acetone as brush cleaners - might be worth a look.

 

[jordan1]

As has been said, get some damaged Yam panels, cut 6mm strips and clean of all the paint. make sure you also clean off paint around the panel damage or it will compromise the weld. If you use a decent soldering iron of sufficient heat and penetrate through, ideally from both sides you should get the required result. If, when you sand it back, you can see a join you have a weak 'cold weld'.
There are so many types of plastic which are not compatable.

 

[Ducati]

Thats why I ask stupid question Shox as I always miss something Can ask around a few people local for a broken panel.

Staying on subject: Acetone,,,, I thought I had some but was mistaken. Looking on Boots website they do Nail Varnish Remover, would this be pure Acetone as they also advertise stuff Acetone free ( I may go in the store and just ask for the free Acetone )

So I am guessing this one is Acetone:

http://www.boots.com/en/Boots-Essentials-Nail-Polish-Remover-250ml_1115013/

Best not to use nail varnish remover unless you are 100% it is only acetone.

Some of it has oils and nail conditioner in which I'm sure won't help with the bonding

As mentioned anyone who supplies fiberglass and resins should have some.

You could always decant some out of an acetylene bottle

Nooooooooo don't I'm only kidding

 

[busastars]

Got some spare funds in paypal so ordered online 1L pure Acetone £6.78 delivered to my door. Asked around and no spare panels so going to try the lego, have been reading loads about using it so should be easy enough.

 

[jordan1]

Got some spare funds in paypal so ordered online 1L pure Acetone £6.78 delivered to my door. Asked around and no spare panels so going to try the lego, have been reading loads about using it so should be easy enough.

Have you tried local motorcycle dealers, they usually have some damaged panels kicking around.

 

[6PTsocket]

I have the Urethane Supply #6 kit. There is a "soldering gun" with a feed through tip for the plastic rod and another, larger tip for smoothing larger areas. The upgrade kits come with a better iron. There is a heat controller with a knob and a scale calibrated for different plastics. It comes with a whole bunch of rods and coils of different plastics. The principal is just like metal welding, soften the base material and add filler at the joint. There are suggestions to help you figure out which plastic you are dealing with. Basically, if it melts instead of burns, you can weld it. You have to get the temperature right; too low and it doesn't fuse, too high and the whole thing runs. There is an additional plastic in the kit called Fiberflex that does not fuse but bonds to many plastics when melted on to them. It is used with a stainless mesh that is embedded in the Fiberflex. They claim that it is often stronger than a true weld. I have always been able to match the plastic so I have not tried it. Many plastics can be cemented with the right stuff but Polyethylene and Polypropylene are really troublesome. Most plastic glues specify that they do not work with them. With some very expensive primer and industrial grade cyanoacrylate (crazy glue) they can sort of be repaired. On the other hand, they are thermoplastics so they are no worse to weld than other plastics. The over all results with the kit are often not pretty but I have gotten many functional repairs. I have always wondered if I should have gone with hot air instead of airless.

 

[DanielW]

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

The idea is to drill two small holes at the ends of the crack to stop it going further,then brace the crack at the back with pieces of plastic and expoxy glue, two over the holes so you can fill those holes with a filler,you won't see those braced pieces when the fairings go back on.

 

[Screwdriver]

I do quite a bit of fairing repairs and a heat gun weld is generally the best, strongest solution. Soldering irons can work if you embed a wire mesh into the join but they tend to burn ABS which makes the repair brittle. The key issues are:

Crack preparation, needs to be grooved out, with a stop hole at the end of the crack
Needs to be super clean
As has been said, you need the same type and grade of plastic welding rod as a filler. Other plastics might look like they work but most cable ties are nylon, not ABS and they will not weld.
Temperature is critical. Too cold it won't weld, too hot and the panel will burn, distort and the weld will be brittle. Tables are available and the Leicester heat guns are accurately marked. It took me quite some time to learn how to do it, even with all the right kit. TBH, I'm not even that good at it now!

Acetone does not work as a welding method. It breaks down the plastic which does not reform when the solvent evaporates. You can grind up your own ABS particles for example (doesn't affect the long chain polymers) and use <another solvent> which sort of works (aka Plastex kits) but I have had mixed result with those too. I tend not to disclose the precise solvent openly, it cost me a lot of time and effort to discover!

I might be able to dig out some pictures of my previous efforts if interested.

 

[Rocketman]

Doesn't matter what you do when you re-melt the plastic it will never be as strong as the original moulding.

 

[Screwdriver]

Doesn't matter what you do when you re-melt the plastic it will never be as strong as the original moulding.

What makes you say that? In the original process, plastic pellets (typically) are heated and formed under pressure into a mould. So far as I understand, if the plastic is heated to a specific temperature it doesn't change the molecular structure or polymer. Pressure is used merely to ensure the molten plastic fills the mould. I don't think pressure changes the strength of the final form.

Plastics can degrade, the long chain molecules break up and don't join up or become entangled properly. This can happen with age, UV exposure or through the action of certain solvents. That's why the solvent welds are never as good.

Like I say, this is just my understanding and if that's wrong, I really don't mind being put right.

S.

 

[Rocketman]

Every time polymer is re-melted it looses some mechanical properties. So to put this in prospective when moulding you may be allowed to use so much regrind or in some cases regrind isn't allowed at all depending on the moulding. I doubt regrind would be used in these types of mouldings originally.

Now moving on from that you are pointing to the fact if you have the correct heat it will be fine. Hardly possible in the first case you will never be able to control the correct temperature to anything remotely approaching a injection mould machine. Then take into consideration how the plastic flows over the mould, how all the polymer is melted, holding pressures while the plastic is cooling, etc etc.

Basically it isn't never going to happen.

You may do a adequate repair but it's far from the original moulding.

 

[Screwdriver]

Well, according to your own logic, the weld might even be stronger since you are introducing a new solid rod into the crack which hasn't been through the additional hot melt.

Do you know or are you sort of guessing?

 

[Rocketman]

I know

My logic doesn't not suggest for a second introducing a new solid rod into the crack will make it stronger. You are remelting the existing polymer.

Apart from anything I said you will not be able to control the heat to anywhere near the accuracy of a machine.

To highlight the regrind problem. When you use regrind one of the problems is properly mixing it so it is fully blended in the barrel screw before injection through the nozzle.

Not withstanding this anyway ABS has rubber in which makes the main difference between it and styrene. The level of this is not set you can have it at any level depending on the properties you require from the particular moulding. So this in itself is another reason you will get problems.