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Making an inspection light lens

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The inspection light is is NLA or very hard to find at the least, so I decided to try and make the lens. I had a light in good condition, but the lens was brittle and badly faded.

Since I had all the equipment for making a set of tail light lenses for my 280Z it was not too much work to try make the inspection light lens.

The Equipment I used:

1. Vacuum chamber and vacuum pump. This is needed to remove air from the silicone resin used for the mould and the clear resin used to make the lens. You can do it without using vacuum to de-gas, but the results are not as good.

2. Pressure chamber and compressor. The pressure chamber is used to pressurize the silicone mould when its curing and to pressurize the resin when you mould the lens.

If you don't do this you run the risk of getting a champagne bubble effect. This effect is caused by small air bubbles captured in the resin during stirring.

The silicone mould suffers a different problem. Uncompressed air bubbles in the mould will compress during the pressurizing phase of the lens making. When the bubbles are compressed the mould is then distorted and you get a strange looking lens. Trust me, I know from experience.:stupid:

3. Scale that can measure 1 gram for measuring resin, dye and hardener ratios. Very important for reproduction later.

Note: If you are using dye, I suggest mixing the dye in the resin before adding dye. Mix enough for your total production and keep it stored. Mix the quantity needed with the hardener. This way you maintain the colour through out the production run.

4. Injection needle or device to evenly inject the resin without trapping bubbles in the mould. This is probably the hardest part of making the lens.

I prefer to inject the resin instead of pouring it into the mould. I have found it easier to prevent bubbles this way. I fit a plastic tube to the seringe (plastic tube used for fish tank pumps) and make sure you use enough tube to hold the resin.

5. Releasing agent. Spray pack. This helps prevent the resin sticking to everything you can think of. Makes cleaning easy.

Pressurize the mould. Once the mould is poured it needs to be pressurized to remove any small bubbles. I use 2Barg for 8 hours and warm the chamber to 60°C. This helps cure the lens and helps give it a shiny finish.

Remove the mould, dismantle it and trim the excess of the lens.

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My experience up till now is without vacuum you get a lot of large bubbles is the mixture. Its very hard keeping it bubble free and still mix it thoroughly.

You can compress the bubbles during the curing period to make them small, but if its exposed to heat the bubbles will expand to the point of cracking the lens or making it all lumpy.

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