|I was in a Hangout talking to Josh and he asked about designing some Switch Lamps for his Fastrack switches. With the Switch Stand removed he had a small pad with a .090″ hole. I told him I could see what I could do and this is the result.|
I had previously found a bi-color … Red/Green SMD Pre-Wired 0603 LED on eBay. I thought these might work (emphasis on might). The link is good at the time I am typing this .. 10PCS 0603 1615 Pre-soldered Bi-Color Red Green Light Pre Wired SMD LED Diodes – 10 pcs for $10.99 with free shiipping is a pretty good deal IMO.
These are SMD LEDs so the viewing angle is 120° unlike the more common ‘mushroom’ shape so that might affect how well they work. Donno.
|>What caught my attention was 1) they are bi-colored – and that is what some model railroaders wanted for signals and 2) they were SMD .. so small(ish) in size. The smallest I found were these 0603 LEDs. If you look at the diagram to the left (click to enlarge) you will see that it shows as 1.5 mm across the soldering pads. That is fine for the Anode connections but if you look at the photo above you see that the Cathode (black wire) runs down the side of the LED package. I *guesstamate* that adds another .50 mm so it will need approximately a 2 mm hole.|
|The Lamp Design|
When working on something small like this to be 3D printed we have to take into account the material used to print the model and the capabilities of the printer itself. I used FD (Frosted Detail) plastic for this – it being the one that provides the best detail from Shapeways and passes light. The biggest constraint is what Shapeways calls ‘Wall thickness” which is 0.3 mm .. which I never use. Every time I have tried to use that suggested minium I get the models kicked back for thin walls. I have found that using a 0.4 mm minimum works fine so that is what I go with. The Switch Lamp itself is nothing more than a cylinder with other shapes that resemble the top of full-size lamps and four projections that resemble lenses. I use the term ‘resemble’ here because the model is so small we have to get ‘close’ while keeping within the constraints for the material and printer.
A lot of searching for dimensions came up blank so I found a photo that showed a man next to a switch lamp and I *guesstamated* (love that word) that around 12″ across the width of the lenses would not be that far off. The Lionel Fastrack switch that Josh has with the switch stand removed has a .090″ hole that can be used to mount the lamp and pass through wiring. With that I went to work.
I can pretty much guarantee that there will be wax left inside the models. During processing of FUD/FXD it involves a series of steps (this is taken from a video .. think I have the steps right . or nearly so):
With all of that you will still get parts with wax in hollow spaces. I can almost *guarantee* this will be so with the lamps. That requires additional cleaning – more so in this case as we would like the lamps as clean as possible inside so the LED has a chance to shine through the plastic ‘lens’.
This is some information I have gathered on cleaning Frosted Detail plastics .. some of which I have used. Note that using Simple Green has risen to the top of my list. I also have an Ultra Sonic cleaner .. and am thinking of trying to combine the two and use the Simple Green as the agent in the Ultra Sonic bath and see how that works.