Bumper repair - plastic welding

[citsncycles]

I have a small amount of damage on the bottom edge of the front bumper on the 4x4. as it's a 2 tone colour coded one I'm considering repairing the bumper instead of trying to find a replacement. I may also be aquiring another BX with a damaged rear bumper - being a Mk1 it'll be difficult finding a replacement, so repair may be my only option.

Has anyone tried these plastic welding kits with the hot air gun and the plastic rods? Alternatively, has anyone got any other ideas on how to repair these bumpers?

[Tim Leech]

Be easier to get another, I think there may be one the right colour on that 19TZS at alan Goodyears? (Where Paul got his spoiler)

[Way2go]

Alternatively, has anyone got any other ideas on how to repair these bumpers?

Perhaps one of these up & coming 3D printers could be adapted for the job?

[Tinkley]

The bumper material is almost certainly Polypropylene. Some manufacturers have got crafty and mould the bumper with the paint already on!. Post BX mind you, they use a paint 'film' on the surface of the mould and then inject. Pretty big tool though and I'd guess around a 1000 or 1500 ton machine depending on weight of bumper. Not many moulders have kit this big. Think whole chairs (including legs) and plastic pallets.
Largest things I've worked on and had moulded were large (110ltr) suitcases and a whole chair. Tooling was in the 300k region 10+ years ago in Portugal and add 40% if done in the UK.... Responsible manufacturers tend to keep these large tools in Europe as quality is much higher and they tend not to explode... and yes that has happened.

We had the suitcases '3D' printed if you like. Stereolithography in these instances but they had to be made from about 3 bits per 'half' ie base and lid because of the limitations of the bath. Even better is the useable bits in nylon and sintered metals that are available.

As for repairing it (bumper) it will weld and there are PP glues. We have used the sticks for repairing Topper dinghies down the Sailing Club with varying degrees of success. Getting a good surface is a bit more difficult and I have yet to investigate the paint procedure ie acid etch? etc

[electrokid]

As for repairing it (bumper) it will weld and there are PP glues.

Would the same apply to old single-skin domestic heating oil tanks ? I have such an animal that I want to clean out and use for rainwater and the best way to get at it to make sure it's fully cleaned would be to cut it open along the seam around its waist.

[Defender110]

Alternatively, has anyone got any other ideas on how to repair these bumpers?

Perhaps one of these up & coming 3D printers could be adapted for the job?

I very successfully repaired a LR Discovery ll front bumper with one of these cheap soldering guns fitted with the flat blade, just melted it back together.

http://www.ebay.co.uk/bhp/electric-soldering-iron-kit" onclick="window.open(this.href);return false;

[Tinkley]

The oil tank maybe PP but it might also be PE. The former is Polypropylene and the latter Polythene or as some prefer Polyethylene. Glues are available for thr former but not as far as I am aware the latter. It can probably still be welded though, but you might want to research this. Sometimes the correct heat from a soldering flat iron is enough or controlled local heating with a paint stripper gun.

Both materials have very good chemical resistance so you should find the material designation on the product somewhere.

If its been outside for years though you may have material degradation which will hinder a good join. Mostly old tanks and similar are turned into regrind for more new tanks etc but there is always a percentage of virgin material to preserve mechanical and chemical properties. Materials like these are limited to 5 cycles of regrind before being binned with progressively less stress being asked of the object being manufactured.

I have seen 'freeze' lines cause cracks in rain water bins, and as these are down to poor mould processing there is not a lot you can do. The 'freeze' lines are the front edges of the material as it flows in the mould. If it gets too cold it (the material) does not melt into a uniform material and although it can come out looking OK retains a hidden hairline 'fault' which can split on minor impact.

Usually large tanks are roto moulded and both PP and PE are used for this.