Introduction: A Functioning 3D Printed Electric Switch
This is an electric momentary switch for small, low voltage, low amp projects. It still needs to be fully tested, but I've already successfully made printed projects that incorporate non-plastic materials embedded within 3D printed items and fully functioning, mechanical objects for quite some time, including my wife's favorite potato chip bag clip and my most recent hinged project.
This is less about hinging, but he key to adding non-plastic materials to prints is allowing a deep enough opening for the added part so it is completely beneath the following layers of the print. Knowing exactly when to add items to the print is the critical step.
I've been using the following method to embed all sorts of materials from cloth bag cords to spring steel clips with a nearly perfect rate of success. Any errors I've made have been related to the aforementioned "critical step".
The following process should result in a perfect print, with brass connectors that makes a simple momentary electric switch. Conceivably, this process can be used to create custom switches or contact sensors for virtually any electronic project.
Step 1: The Parts
THE METAL PARTS:
Before you print the switch, you'll need to make two brass contacts. The first image shows the steps:
1. The contacts are made with .030 1/4" wide brass strips, available at most hobby shops in 6" lengths.
2. You'll only need to use 2", so cut two, 1" pieces.
3. If you stack the pieces, or cut a single piece 3" long and bend it in half, the job will go quicker. Drill holes for the leads and file for the notches. Make the notches slightly oversize to fit.
4. Round off the edges. If you used a single 3" piece, now's the time to cut it into two 1" long parts. Finish the cut ends.
5. Using a 1/4" chisel or screw driver, raise a .010" ridge by tapping the back side. This job can be made easier by grinding a small slot into a scrap piece of metal and using that as a mould. Make sure the protrusion doesn't exceed .010". It will be much better to err on the small side here.
I've added a file to be used as a "go-no go" gauge. If your brass contacts fit in the gauge, they'll also fit the part when it's time to place them onto the print.
THE PRINTED PARTS:
These parts are designed to be printed at .27mm. And here's how we'll know when to pause the print and add the brass contacts. As the print is progressing, watch the small squares next to the housing. When you first see the number "1" being printed, pause the machine and set the first contact into the slot in the housing. Don't try to use the squares as supports for the ends of your contacts. Your extruder head may crash. Be sure your contacts are no longer than 1".
Un-pause the print and watch the other square. When the number "2" is printed, pause the machine again and set the second contact in place. Un-pause the machine once more and let the print finish.
The final part you'll be adding is the push button. It will have to be snapped into place once the print is completed. This may need to be fine-tuned. Once I've printed this myself, I'll fine-tune it and up date this instructible.
Step 2: MAKING THE SWITCH WORK
Here's the caveat. I've printed moving parts and have added secondary components to prints before, but never at the same time (I'm not counting the potato chip clip as a "moving part" since the printed part isn't what moves).
Theoretically, this concept is valid, but there'll be a bit of difficulty getting the button into place. The plastic will most likely be too ridged to fit. LIGHTLY tapping the button with a phenolic hammer might shock the button enough to knock it in, but not very hard though... You wouldn't want to permanently bend the upper contact and short the connection. I think this could use a little re-design.
The operational movement of the button is very small (.010 designed). There's more movement of the button available (upward) and space beneath it in the print to allow the second contact to be added. There'll be a bit of loose, low density material between the button and upper contact that might allow the button to move further and help with the break.
You might also want to reduce the thickness of the brass. .030 is pretty hefty and it will take some pressure to make contact. As I said, this is proof-of-concept.
As previously stated, I'm already confident about the ability to produce each of these unique additions, but not at the same time. If you attempt this, I hope it works. As soon as my plate is empty of the important stuff, I'll be trying this. When I do, I'll update this instructable with my results.