how to make replica plastic lenses?

[hairymel]

are there any shiters with experience of mould making / plastic casting?

 

i think at some point i am going to need to fabricate some indicator lenses - (chrysler) sunbeam items are mega expensive now and i only have a few faded/cracked ones.

 

google is all well and good ,but much of it is in american and tbh i am finding it difficult to understand what i need and how to go about it.

 

anyone want to do my thinking for me 

[Tamworthbay]

I have made moulds using liquid latex with great success, but never used clear plastic. Making mounds with it couldn't be easier, just paint on layers and wait till it goes off, add pieces of wood or carboard if you need structure and cast in a pot of sand to support the mould. If you need two part moulds then use a wood support and put pegs in to locate the two halves.

[castros_bro]

3d printing?

[Vantman]

This chap made some for his old Saab--

 

 

http://www.saabisti.fi/saab-96-1964/polyester-resin-casting-light-lens-saab/#.Vye9ObxwbIU

[purplebargeken]

Wow, excellent outcome. 

[Rovorsche]

I have seen a couple of people make headlight covers from lexan/plexiglass by heating plastic sheet over a mould.

 

With some jiggery pokery I suppose you could do this and paint the inside with bulb paint or even leave it clear for the "Lexus Lites Innit Bruv" look.

 

As a complete wild card, is this something you could do with access to a 3D printer ?

[Barry Cade]

There was an article in Practical Sportsbikes a while ago, telling you how to do it and the kit you need- results were spot on. I'll see if I can find it.

[dollywobbler]

This is great stuff. Just wondering how you could make lenses with different colours - ie combined rear lamps. 

[garethj]

You can get dyes for the resin so it should be possible to tint them different colours too.  I get my stuff from Alec Tiranti, they have a shop in London and do mail order too.

 

I've done dozens of slot car bodyshells like this, the only thing it doesn't say on that Saab page is how to get rid of air bubbles in the mould and the castings.  You can either cast (the mould and the casting) under vacuum or under pressure.  As I couldn't stretch to a vacuum pump I cast my stuff under pressure, about 35psi.  That's plenty to squeeze the air bubbles so small that they can't be seen.

 

Have a look on this page for one of my bodyshells, I make the inner mould without pressure and you can see a few bumps and bubbles, the outer mould is done under pressure and it's completely smooth.

 

One last tip, you can make the mould box out of Lego, then when the silicone has set it's easier to break the box apart around it.

[garethj]

But the translucent resin from an SLA isn't strong enough to cope with being mounted to the outside of a car, is it?

 

It would crack as soon as you did the screws up or tried to squeeze down the rubber seal.

[SiC]

You can get dyes for the resin so it should be possible to tint them different colours too.  I get my stuff from Alec Tiranti, they have a shop in London and do mail order too.

 

I've done dozens of slot car bodyshells like this, the only thing it doesn't say on that Saab page is how to get rid of air bubbles in the mould and the castings.  You can either cast (the mould and the casting) under vacuum or under pressure.  As I couldn't stretch to a vacuum pump I cast my stuff under pressure, about 35psi.  That's plenty to squeeze the air bubbles so small that they can't be seen.

 

Have a look on this page for one of my bodyshells, I make the inner mould without pressure and you can see a few bumps and bubbles, the outer mould is done under pressure and it's completely smooth.

 

One last tip, you can make the mould box out of Lego, then when the silicone has set it's easier to break the box apart around it.

What about using an old fridge/freezer compressor? They have been used quite a lot for vac bagging GRP model aircraft parts like wings.

[hairymel]

great response guys 

 

the saab thing is sort of what i am looking for i think - although the lenses i need to replicate have a more complicated shape.

 

don't think a 3d printer is ideal as i would like to mould in amber and don't like the idea of sanding and polishing 

 

just got paid so will have a look at whats available material wise - polyurethane is top of the list i think and mould research needs doing!

 

sounds like i also need to raid my daughters toybox - pirate lego should be ok i hope

[vulgalour]

Mel + car + Lego... this is inevitable really.

 

[hairymel]

 lets hope not

 

1kg addition cure silicon ordered from ebay and hopefully on its way from lithuania 

 

i will await mould results before spunking loads more on polyurethane resin and dye!