Don't be afraid of welding plastic

[beededea]

The various ABS plastic components of my Rover 75 have held up well being solid and well specified/designed. However some of the more flimsy components have weakened over time and cracks/breaks develop. Solution buy better unbroken replacements or - weld the old.

So, I have realised that you can repair the broken pieces reasonably well to store integrity if not always cosmetic looks. I have repaired a few broken and cracked pieces on my Rover 75 and MGZT-T and the result has been an improvement.

Taking a soldering iron to a crack and running the tool up and down the crack from both sides will cause the two cracked pieces of plastic to melt and bond. The plastic will move and you can move the hot tool to push the displaced plastic back into any holes you make. Don't be afraid to make a hole with the tool straight through the plastic, you can fill the hole with plastic pushed in from the wleds nearby. If the remaining plastic area has raised plastic then rub it down. If it has any dents or remaining holes fill with plastic padding or milliput.

It the plastic has broken then be a little more extreme, join the pieces and push the hot tool straight through the join mating the pieces at the melt. Do that a couple of times at different places then work along the crack melting and joining. Try to do it on both sides. The end result may not be particularly pretty but it will be a join and it should be strong.

Once again, sanding and filling with black milliput will cover a multitude of sins, painting afterward with omnicote will restore the sheen on ABS plastic and the paint will stick... It is good stuff.

I have repaired the scuttle panel that sits at the base of the windscreen, broken at several points, the fuse box bracket as well as several other areas where cracks were starting.

I learnt this technique from repairing fridge shelves that always crack prematurely at the corners. Welding restores strength and a little filling restores them cosmetically.

I'll post a picture or two soon.

Omnicote is available here: http://www.newventureproducts.co.uk/omnicote.html Ask for Steve and say Dean sent you (he is a very good mate of mine)

[clf]

The various ABS plastic components of my Rover 75 have held up well being solid and well specified/designed. However some of the more flimsy components have weakened over time and cracks/breaks develop. Solution buy better unbroken replacements or - weld the old.

So, I have realised that you can repair the broken pieces reasonably well to store integrity if not always cosmetic looks. I have repaired a few broken and cracked pieces on my Rover 75 and MGZT-T and the result has been an improvement.

Taking a soldering iron to a crack and running the tool up and down the crack from both sides will cause the two cracked pieces of plastic to melt and bond. The plastic will move and you can move the hot tool to push the displaced plastic back into any holes you make. Don't be afraid to make a hole with the tool straight through the plastic, you can fill the hole with plastic pushed in from the wleds nearby. If the remaining plastic area has raised plastic then rub it down. If it has any dents or remaining holes fill with plastic padding or milliput.

It the plastic has broken then be a little more extreme, join the pieces and push the hot tool straight through the join mating the pieces at the melt. Do that a couple of times at different places then work along the crack melting and joining. Try to do it on both sides. The end result may not be particularly pretty but it will be a join and it should be strong.

Once again, sanding and filling with black milliput will cover a multitude of sins, painting afterward with omnicote will restore the sheen on ABS plastic and the paint will stick... It is good stuff.

I have repaired the scuttle panel that sits at the base of the windscreen, broken at several points, the fuse box bracket as well as several other areas where cracks were starting.

I learnt this technique from repairing fridge shelves that always crack prematurely at the corners. Welding restores strength and a little filling restores them cosmetically.

I'll post a picture or two soon.

Omnicote is available here: http://www.newventureproducts.co.uk/omnicote.html Ask for Steve and say Dean sent you (he is a very good mate of mine)

I dont know if it would be applicable to a bumper, but have seen youtube videos of this. They also used plastic cable ties as a kind of solder/welding rod. I am not sure what type of plastic cable ties are madde from, but using a similar type will allow you to let in plastic or fill holes or dimples etc.

[Jim Jamieson]

I got to try out realtime plastic welding a few years back.
I was doing some contract work with a company who were installing a chemical scrubber which was made entirely from plastic.

The welding was done by a special heat gun with a special attachment on the nozzle through which you passed a length of plastic wire. You simply layered the plastic weld to build up to sufficient thickness and strength.

[Mike Trident]

I have "welded" plastics on my old bike's many times with a soldering iron.

You can use plastic from a lot of things as a filler rod. Old plastic bucket, cable ties, plastic jug, and bendy kind of plastic will do.

Here's another tip, if you are repairing a crack or a joint that needs strength. Melt a hot paper clip or similar across the joint. If you place it (or a few if needed) across the joint the put the soldering on it until it melts into the plastic it will make for a really strong joint.

[Dallas]

Plastic welding can give some good results.

More and more people will need to be skilled at this type of work, the amount of plastic being used on new cars is ridiculous. :eek:

https://the75andztclub.co.uk/forum/attachment.php?attachmentid=68011&stc=1&d=1498386165

[roverbarmy]

Just remember to do it in a well ventilated area. Plastic can give off very toxic fumes when melted. ;)

[beededea]

The picture above speaks volumes, nicely done too. Looks like stitching.

The idea about reinforcing with a paper clip is something I have done on a fridge shelf, albeit inserting a long thin screw, it was tough to make the whole shaft heat enough to sink into the plastic. I imagine that a paper clip will be much easier to heat. A good suggestion.

I used some offcuts of ABS plastic to melt fill in the holes, one of the suggestions here to try cable ties as a source of meltable plastic, this method seems to work too.

The imortant thing here is to get the plastic to bond with the older plastic, welding plastic requires both surfaces to melt and mate.

http://i.imgur.com/gFMLApZ.jpg


This is the scuttle panel prior to cosmetic rubbing down, the joint is now strong but it had previously snapped completely.

The problem is that the melted plastic does not shape easily using a heat gun on the surface normally results in a blob of malformed plastic or it catching fire. The soldering iron's heat is enough to melt but the tip is too small to shape nicely. The cosmetic work after is essential if the part is exposed. If it is just a bracket then I suppose it matters less.

http://i.imgur.com/pMbJCQE.jpg

The bracket on the relay/fuse box that attached to a metal bar extension had cracked completely and was only held together by the bolt. It looks a little rough but it is under the bonnet and no-one will see it. The weld is now strong.S ave
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[beededea]

Showing the bracket, cleaned, derusted, the plastic welded.

http://i.imgur.com/3tWE4Jq.jpg

It'll do.

This chap used the same solder gun that I used.

https://www.youtube.com/watch?v=S_0ge01X5jI
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[beededea]

I was experimenting on exterior bodywork to see whether I had any skill in welding the visible areas made in ABS plastic. I welded the large crack in my rear bumper using a Weller soldering iron and cable ties as the welding rod.

http://i.imgur.com/0wMlcr6.jpg

It appears to have done the job of mending the crack, you can see the result after welding and a rough rubbing down.

http://i.imgur.com/HxyiXCw.jpg

I will have to use some body filler next to achieve the smooth surface I require but the repair is largely done.

[roverbarmy]

I will have to use some body filler next to achieve the smooth surface I require but the repair is largely done.
Make sure that you use flexible filler. ;)

[beededea]

Absolutely correct - good reminder - I may have forgotten! I wouldn't admit to it though.

[murphyv310]

Weller soldering guns used to come with assorted tips and accessories, there was a flat ended one for "plastic" repairs, being flat you got really neat results once you filled splits and cracks.
TV engineers have been doing these repairs on plastics for years, many items have been saved like this and often on parts that are impossible to source.