Cap for vacuum pump - almost parametric

thingiverse

This is a top for cylindrical vacuum pumps. I have a lot of different sized cylinders with varying o-ring sizes as well. This allows me to plug in the ID and OD (inner and outer diameter) for the tube and the size of the o-ring. Its my first attempt to use parameters in F360. It's messy - especially the distances between the holes. There are a lot of ways the parameters can break - I didn't see a way to constrain inputs or use conditionals so this is the best I can do for now. It has grooves for O-rings and holes for connectors. The STLs here have holes sized for predrill for 1/4" NPT. That can be swapped for a 1/8th NPT via parameters or just enter in whatever diam you'd like. I think G/PT and NPT have the same predrill sizes, just different threads and tapers. The holes are not tapered, but they've tapped well for me. The space between the holes is based on the size of the holes. I have two holes so I am able to add an emergency vent that has been needed often during testing. You can create a single hole just by setting the numHoles to 1 in the parameters panel. You can also get rid of the hole for a hook by setting the HookHoleSize to 0. There's a groove on the underside of the cap for the tube to slide into. This can make it difficult to remove, which might be a solution or a problem depending what you need. You can get rid of the groove by setting the depth to 0. For thicker o-rings, I use the metric R-26 size on a cylinder with an ID of 57mm from this kit: https://www.amazon.com/gp/product/B07GSKKHQM/ I also use : Silicone O-Ring, 53mm OD, 49mm ID, 2mm Width - https://smile.amazon.com/dp/B07CVJJ5TH and Fluorine Rubber O-Rings, 54mm OD 49.2mm ID 2.4mm Width https://smile.amazon.com/dp/B07YJVJS2C I just pick the size close to what I want that's cheap. The silicone ones above are $5 for ten, but 1mm OD larger doubles the price. I wouldn't recommend going with an o-ring under 2mm wide. Silicone rings stretch a lot more than others, but might not last as long. As far as making it airtight - the majority of the leakage is from the holes. Adding 100% infill modifiers around them helps dramatically if the entire cap isn't printed with 100% infill. Leakage is not a big concern in my configuration. Its all DIY - the cheap $20 pump used combines with some pressure sensors can hold indefinitely with the pump coming on for 2-3 seconds at 5-10% power every few minutes. If leakage is a major concern, print at 100% infill and coat with polyurethane after tapping / drilling any holes. I have used an epoxy coating from Smooth-On (XTC-3d),which does help with the air and it also makes parts incredibly strong. It can add some thickness if you're undersized slightly. It requires very thin coats - usually 3 to 5. The product goes a LONG way - 0.15g will more than coat one cap. I like an overhang for my caps on one side. It makes it easier to hold and also provide space to add a little OLED to display the pressure, timers, program number etc. Print it top side on the bed for no supports.