Bending parts. Best technique?

[Chris1992]

Hi guys! I know there is a topic similar to this, but I thought I would start a new one to get some fresh opinions. 

Basically, I've been working on my Tamiya Supra kit, and have noticed that the hood doesn't quite have as much curvature as it should, causing it to sit slightly higher than the bumper when closed. To cure this I can simply bend the hood slightly so the leading edge comes down slightly lower to improve the fitment,  I hope this makes some sort of sense!! 

So has anyone had a go at doing this? I assume heat is the answer, but dose anyone have any tricks or tips regarding what to use as a heat source? The last thing I want to do is melt it as I don't have another! 

Thanks

Chris 

[58 Impala]

Try very hot water, bending a little at a time. Ive done it on a few warped roofs and been successful.

[Ace-Garageguy]

Polystyrene, the plastic kits are made of these days (and like most plastics) has a 'memory'. When you bend it, it wants to spring back to the pre-bent shape.

You CAN bend it cold, but often it's risky (depending on how far you need to bend it). To bend cold, you will need to bend the part well past where you want it to end up, as it will spring back (due to memory). Sometimes it will 'whiten', which means it's on the verge of cracking.

 The nominal T_g  , or "glass transition temperature" of model kit styrene is in the 100C or 212F range. That means that just boiling water will allow your part to permanently deflect.

The problem lies in the fact that different "styrene" formulations can have differing T_g , and without knowing exactly what your part is, that can be risky too.

58 Impala has the right idea. Very hot water will get your part close to its transition temp., but won't make it shrivel up.

I've had excellent results bending cold, bending in very hot water, and also by fixturing the part in question in exactly the shape I want it to be, and dipping it in boiling water for a few seconds.

 

Edited June 12, 2017 by Ace-Garageguy

[Chris1992]

Polystyrene, the plastic kits are made of these days (and like most plastics) has a 'memory'. When you bend it, it wants to spring back to the pre-bent shape.

You CAN bend it cold, but often it's risky (depending on how far you need to bend it). To bend cold, you will need to bend the part well past where you want it to end up, as it will spring back (due to memory). Sometimes it will 'whiten', which means it's on the verge of cracking.

 The nominal T_g  , or "glass transition temperatuyre" of model kit styrene is in the 100C or 212F range. That means that just boiling water will allow your part to permanently deflect.

The problem lies in the fact that different "styrene" formulations can have differing T_g , and without knowing exactly what your part is, that can be risky too.

58 Impala has the right idea. Very hot water will get your part close to its transition temp., but won't make it shrivel up.

I've had excellent results bending cold, bending in very hot water, and also by fixturing the part in question in exactly the shape I want it to be, and dipping it in boiling water for a few seconds.

 

Try very hot water, bending a little at a time. Ive done it on a few warped roofs and been successful.

Great advice guys, thanks a lot!! I think I'll give the boiling water a go first  

[peteski]

I have also heard that after the part is re-shaped in hot water to quickly put it in cold water to permanently set the new shape.

[unclescott58]

Nothing new I can add. The advice above is the way to go. 

Scott

[Chris1992]

awesome, thanks again guys! I'm going to give it a go today, so I'll report back on progress.