I am currently studying a possibility of making a sleeve molding for 5mm led.
Currently I use a lathe part and then after soldering the LED on the cable we cap a small tube of diam 7 by 19mm long. but I would like to replace this with a plastic or resin molding operation, which will still remain a bit artisanal due to the low production of the product (40 per month)
I thought of drawing a mold (2 shells with 10 to 15 slots) and then we could inject resin.... but how does the injection work, what do you have to respect to have a clean finished part...
temperature, pressure, avoid air bubbles, and that the cavity that remains free is completely filled by the molding material, so the choice of the material to be injected is important
Make sure that the minimum number of parts is necessary (2 pieces minimum) to open or close the mold Thermal shock often allows the material to be removed from the molds
Be careful because low pressure also means a reduced flow length. You have to be as close as possible to the footprint and have a large channel diameter.
We use this system for the injection of contact insulators.
As for the mold, I advise you to use a steel with a small regulation so as not to heat the tooling and to be able to demold over time. Small staubli fittings plus water at 20° would be impeccable.
To be sure to unmold I advise you to use 3° drafts on the surface perpendicular to the plane of the joints because they are very adherent materials.
If necessary, I can send you the study of a mold for this type of process and in production for example.
So you should know that you can choose 2 types of injection:
The first one, thermoplastic injection, doesn't seem to suit your project. The temperature of the injected material is about 250°C. Pressures from 300 bars to more than 1000 bars reduce the interest of this solution to nothing for a production rate of 40 parts per month.
The second would be to make a casting of thermosetting resin (transparent I guess). This process is simpler and easier to access. You make a mold and then you use this mold to make epoxy or polyurethane parts by overmolding your LED.
If you want to do it yourself:
In short:
-Make machined parts or parts in rapid prototyping if you have a 3D of your part (stereolytography).
-Make a silicone mold with one or more machined parts. Remember to make a power supply to pour your material and to plan to keep your led in the mold.
If you want perfect parts, I advise you to equip yourself with a vacuum pump (with a waterproof case or a vacuum bell) in order to unbulge your resin while you make the silicone mold and each time you pour the resin for your parts.
If you want professional quality:
Get closer to a rapid prototyping company. She will be able to make you a silicone mold of your parts and even make the castings of your parts with excellent quality and this for a reasonable investment.