I am toying with some things with my resin printer. I am wanting to render 15/32-32 thread fitting for big gun usage. I'm trying to use the thread tool rather than the coil. The coils aren't coming out straight and have a slight cone. I've seen a method of making a custom thread tool by modifying a thread file. I've attempted to make a custom thread file but I think the numbers I input are off or something as it doesn't seem to come out right. Any help is greatly appreciated.
I played around with 15/32-32 threads for a long time, both manufactured and 3d-printed. See my printer test piece here: https://a360.co/3PWQJsQ The basic idea is I created a cylinder, then used a triangular coil function to cut threads into the cylinder. I set the pitch correctly (0.79375mm), then made a test piece with a variety of major and minor thread diameters to get a model that would print correctly-sized 15/32-32 on my printer. The 15/32-32 thread was very difficult to print reliably, quite sensitive to settings and environmental factors. I was able to get some good threads, but was never truly satisfied. Also clippard parts are very expensive and the 3d-printed threads are extremely weak. This was true for both FDM-printed threads and resin SLA-printed parts. My final solution for the cannons I'm using in my predreadnought, and all future Big Gun ships, is to manufacture my own actuator using aluminum tube, o-rings, and 3d-printed piston. It's stronger, it's cheaper, it's more compact, and it gives me more control over the specifics of the design. I printed all of the valve parts in resin. Most body parts were done in a mix of 90% ABS-like, 10% Siraya Tech-blu. Seals were a mix of U-shaped o-rings from Mcmaster-Carr and specialized shapes using rubber-like resin. For best results, I did a lot of calibration prints to ensure precisely correct exposure times for each material.
Are you referring to the negative pressure cannon design? My shipmates in MABG made one. Not sure I'd its the same design or not though. I'm getting to the conclusion that the ball valve for the Indiana style cannons as difficult particularly the 15/32 fitting. I've done the coil idea but I can't seem to get the coil the stay parallel on both sides.. I've got a design for the manifold and mag that I created and can print I was just hoping to be able to print the ball valve on my resin printer
An alternative to making plastic threads is to buy a bulkhead connector from Clippard with the 15/32-32 threads. https://www.clippard.com/part/15027-PKG I machined a smaller thread on one end and used that to attach it to my accumulator. That requires a lathe and is obviously not for most people. You can also just use provided 10-32 internal threads and a M-M 10-32 connector (https://www.clippard.com/part/15453-PKG) to connect. You are limited to a 3/32 rod through the fitting in this set up. Example in lower left of picture. You could also drill out the inside of the bulkhead connector and tap it to a larger thread like 1/4-20. A little more work, but the taps are cheap and it can all be done with hand tools. If you do start modifying the bulkhead connector you will need some way to hold it without messing up the threads. I sacrificed a MPA-3 actuator, cutting a slit in the side so that I could clamp it down on the bulkhead threads. I used a 1/2" ID collar to provide the clamping force. The MPA-3 with a slit is also a good way to clean up threads if your printer can get close to the desired threads.
