Case repair?

[Axtman]

How do you repair those molded plastic cases? Is there a glue that will repair the cracks? I think that they are made from Hight Density Polyethylene and I can't find anything that will repair them. I don't expect an invisible repair just a repair. Thanks.

[Wayne8]

Go ask at the hardware store. There's glue that comes in two parts and when mixed together makes a bond that's stronger than what you've glued together. I forget what it's called and I think there's more than one brand but they can tell you what's best.

[unbridled]

J B Weld is the kind of epoxy I think Wayne is talking about and works good in most applications. However, I've found it darn near impossible to stay on top of all the cracks in those types of cases once they start cracking. Other resin based epoxies do OK too but I usually use some kind of fiberglass backing material like you find in automotive applications. You have to be careful with anything you use because some adhesives can melt the hard plastic and also melt the styrofoam inside the case.

[ByF]

To stop a crack from continuing to propagate, drill a small hole at each end of the crack. I've never done it to a bass case, but I have done it in metal castings and other things. The end of a crack is a "stress riser" meaning a lot of stresses are concentrated there. Drilling a hole spreads out the stress, so the material won't continue to crack.

Ed

[Pilgrim]

Originally Posted by ByF

To stop a crack from continuing to propagate, drill a small hole at each end of the crack. Drilling a hole spreads out the stress, so the material won't continue to crack.

Ed

EXACTLY! It's called "stop-drilling", as it generally stops the crack from extending. Do it immediately.

I don't think JB Weld will work in that application. I would probably try a very good product I ran into some years ago called Devcon Plastic Welder, but I'm not sure if it comes in any color but cream. It does NOT flex, which is going to be a problem with any epoxy-based material.

It might be the best idea to contact the case manufacturer and see what they recommend. Problem is that the case will flex, and most epoxies and similar materials that will adhere to the plastic (and there aren't many of them) won't flex.

If the cracks aren't bad and you AFTER you stop-drill them, as a last resort you might get some black silicone sealer and run a generous bead over every crack, then gently smooth it with a moistened finger - just good caulking technique. But once you put silicone on there nothing else will stick, so do not do that unless you have no other options. At least it WILL flex and will probably hold the case material together. I would not do this unless you are unable to find any other material for the repair.

In brief: check with the manufacturer first.

[Bardley]

I repaired a case with plastic weld once after the airline ripped the corner off in the Virgin Islands. It was an SKB case.

I filled the gap under the corner piece that was hanging off with that spray in expandable foam you use for sealing gaps and such. I let it dry, shaved it down, placed the plastic piece back on the corner, mixed up the plastic weld, and sealed her up. It wasn't pretty, but it held together just fine for years.

[T-Bird]

Hi.

On the few ABS Gator cases I've repaired, I've just welded them.

With nothing fancier than a soldering iron either.

Regards
Sam

[Axtman]

Sam,

Please explain the welding process. Thanks!

[T-Bird]

Hi Axtman.

Nothing really to it. Just melt the plastic with the iron and with a swirling motion mix the melted ends together.

It takes some practice not to melt holes if the plastic is thin, and in some instances You have to apply some filler material (strips of same plastic) to make up for the losses.

If the case in question is really polethylene (which I doubt a bit), You can practise on almost any cup or container having the PE identification stamp you find in your household. Scrap pieces of said items will also serve as a filler if needed.

Obviously the joint needs to be gapless, so some sort of clamping is advisable.

Not all plastics are weldable but ABS is, and so is polyethylene.


When I get back from work, I'll take some pics of the said Gator case.

Regards
Sam