Thermoplastic case repair

[Woodland]

In addition to running a small shop out of my home, I also do repair work for a family-owned band/orchestra store. They have a growing collection damaged (yet repairable) black thermoplastic violin cases. I'm looking for the ideal adhesive/filler to repair cracked bodies. A common place for the cracks is on the edge where the metal feet rests against the floor or other surface. Some of the feet are pushed in, pulled out or missing altogether. I need to have a case repair week sometime soon, as I'm running out of solid cases for rentals.

[ThePublic]

I have used Bondo to repair sax, clarinet and cello cases to good results. It is easy to use and holds up the best in my experience allowing me to get 4 + years more out of a case I would have had to replace.

Hope it helps!

[Bill Yacey]

First you need to identify the type of plastic to choose the best adhesives and repair method. Who is the manufacturer?

[edi malinaric]

Hi Woodland - don't raise a sweat looking for an adhesive. They store adhesives in plastic tubes don't they?

My tools of choice for these repairs (was repairing the front bumper my neighbours Mercedes yesterday afternoon) are a hot air gun, a soldering iron and thrown away cable ties (those lovely ratchety things that the police use as temporary handcuffs during mass demonstrations).

The hot air gun to soften the plastic so that one can return it to where it was originally and the soldering iron and cable ties to weld the break together.

Been doing it successfully for 50 + years - no - a correction there - my first attempt failed. It was a inflatable buoy that had been cut with a knife by the diver who wanted to sink something. I tried to weld the cut closed. Seemed to work - it held 30 psi. Then I wondered if it would stand up to 50 psi and turned up the regulator on the air compressor. My repair failed at 45 psi. (A pox on Second Thoughts. They should be strangled at birth)

To misquote friend Robson "and so we learn!"

Oh - another two indispensible tools - a couple of ~4mm thick pieces of flat steel. I use these to push and hold the softened plastic into its original position until it cools down to rigidity.

Good Luck.

Cheers edi

[~ Ben Conover]

I always wondered what the word 'Thermo' meant in the GEWA catalogue, now I know.

Thanks.

It seems that even the top line of cases are being made of thermoplastic stuff these days.

I prefer the old ply wood cases.

Good luck with the repairs.

[Addie]

My soldering “gun" came with a plastic welding tip. Polypropylene is what is commonly used to weld with. That’s anything with a recycle number 5.

For big cracks that will flex, I think I would pop-rivet a backing on as well.

[fiddlemark]

Be carfull not to spend more time on the repair than the case can justify. new thermoplastic cases wholesale for 20-30 dollars. So if you spend more than 1/2hr on the repair then you lost money. It is almost inpossable to do a professional looking repair without excceding the wholesale cost, but it is a good skill to "have in your pocket"

a good source for case parts is Ohio Travel Bag. I use a lot of there yakees zipper pulls on costomers cases.

[Darren Molnar]

this is used in the autobody repair industry to repair plastic parts, a huge selection, you'll only need one or two of these to repair your cases. It's very strong and durable stuff, stronger than what you're repairing in most cases.

http://www.autobodys...tegory-s/79.htm