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Author Topic: Building trick?  (Read 1031 times)

Tim_M

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Building trick?
« on: October 05, 2014, 04:42:31 PM »

I have been following a lot of the builds on here. It's a painful process as my jaw keeps hitting the table when I see the standard that 'real' modellers achieve. Keeps me inspired though.

I was impressed with the DIY vacuum forming machine in the Huntsman refurbish. Here's something that may be of use to other modellers. Some of you will already know all this!

PET drinks bottles start life as an injection moulding, called a parison, about the size of a large test tube and quite thick. (Google it) This is then heated and inflated into a mould. It stretches a lot. The bottle is cooled and keeps its shape. However, the bottle has a lot of frozen-in stress and if you warm it again, it will try to shrink back to its original form. You can use this property to make simple shapes around a plug. I used it to make a replacement cockpit for my Bluebird. I had the original one (several, actually) formed on a real vac forming machine when I was on a training course at a university. The first picture shows the last one with the plug. It is paper thin. I will need a new canopy for my next model and no longer have access to the real machine (finished studying many years ago  :}) so I had a go with 'shrink forming'.

It won't work for everything and takes a bit of trial and error. Make sure the plug is a snug fit in the bottle with packers before you start. I use a paint stripping gun as the heat source. Take it steady and 'pull' the plastic into shape. If the plastic goes white, you have melted it and there will be no stress left to pull the material in. Start again! I'd be interested to see what others can make using this technique (perhaps dished windows??).

By the way, if you don't need clear plastic (perhaps you are going to paint the item) I can assure you that this technique works far better with empty beer bottles. Doesn't work at all on mineral water bottles, in my experience.

There's a very short video - http://youtu.be/jY0jpbOtfDQ, but it's not exactly enthralling!)

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Tim_M

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Re: Building trick?
« Reply #1 on: October 05, 2014, 05:22:40 PM »

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