Below is the basic idea of what I'm trying to accomplish. I have a small rubber vacuum tip from a cheap tool I bought on-line pushed onto the end of an angled dispensing tip. The dispensing tip has a luer taper connection that needs to connect to a pen like hand held tool.
|Manual vacuum pick-up tool tip|
The reason I chose this design is that I can easily change tips depending on the size of the part I need to handle. With the rubber suction tip in the image above, I can easily pick up a PCB 0.5 x 0.75 inches. By changing the tip to something smaller like in the image below, I've been able to pick up 0603 resistors easily. This method makes the tool reasonably flexible.
|Smaller dispensing tip|
As I'm unsure of what size tips I'll need, I bought a kit that has a selection of them. Yeah, it's more expensive than buying them off a place like eBay, but once I know what sizes I'll need, I can then buy cheaper batches, but in theory I wont need too many of them.
|Range of dispensing tips|
Seems easy right. Wrong. Adapters for luer lock connections aren't that easy to come by. You don't just go to the local hardware and buy one. I figured the easiest way to get one was buy it from the same supplier that sold me the dispensing tips. I choose the black fitting you can see in the image above. It's a 1/4 inch NPT thread to a male luer lock connector. I however didn't understand that an 1/4 inch NPT thread is actually about 1/2 an inch across. This means that once a pipe had a thread cut in it and attached, the outside diameter of the pipe would be around 20mm in diameter, which is a little too big. "Easy I'll just glue a plastic pipe inside the fitting" i thought. Wrong, the fitting is polypropylene, which is super-glue resistant, which meant I had to track down a heptane primer for the plastic before applying super-glue. Finding a suitable piece of plastic pipe wasn't easy but in a pinch you make do.
|Plastic pipe from a pen case|
Luckily I decided to tackle the fitting on the other end before attaching the pipe to the fitting. All I needed was a 1/4 inch barb fitting to attach to the pipe that I'd bought. I thought I'd go the same route as the other end and get a 1/4 inch NPT fitting and glue the pipe to the inside of it.
|Fittings and altered pipe|
The pipe wasn't quite the right size. To enlarge the ends I softened them with a hot air gun and then pushed them into the fitting. The plastic walls of the pipe pushed out to created a tight fit, kind of like blow moulding. All that was left to do was glue it all together. That's when I found out that the barbed fitting I bought wasn't actually plastic, it was black anodised aluminium. You might think I'm an idiot for not being able to tell the difference, but the thing was so well machined and anodised that it looked like a hard shiny plastic. The perils of on-line shopping.
It was at this point I decided to call a halt to proceedings. I'd made too many compromises and the design had moved too far away from my initial idea. Getting the wrong adapter in the first place caused a chain reaction of forced choices that created a product I didn't like. I decided to go back to the start and find an adapter I can work with. This time around I'm getting a metal adapter that I can hopefully braze a pipe onto. If I can get the parts I'm trying to, the thing should look pretty good when I'm done.