We have been making some soda recently, and I found myself bruising my finger to open the valves on the Cornelius keg fittings while I was cleaning the lines. I decided to re-design my ball lock fitting dummy, and I made a few improvements to it.
First, the fit is a lot looser now. This really helps to get it seated easily, and it’s not like it was going to hold pressure anyway.
Second, it has a channel for an o-ring. I had an old damaged o-ring from a corny keg, so I used that on the dummy.
Third, the pipe through the part is improved. It has much more cross-sectional area, the walls transition smoothly, there aren’t a lot of places for fluid to get trapped or cause bubbles to form, and the pipe is shaped a bit like a funnel, so you can use it to very slowly and gently pour stuff into a siphon line if necessary.
I made the design changes in FreeCAD, and the file is available here (fair warning, FreeCAD does not do fillets well so the model technically has holes in it):
And here is the STL file:
This model has made me rethink using FreeCAD for modeling many times. I would say 90% of my problems with FreeCAD come down to fillets and chamfer issues, and these issues seem to be treated as a fact of life rather than something that is likely to be fixed soon.
All I want is the functionality of Creo Parametric, Solidworks, Inventor, Fusion 360, or Onshape on my Linux desktop, and I’m willing to pay a lot of money as long as I don’t need to use Windows.
I tried using lots of options, and they all fell far short of my goal:
- FreeCAD (AstoCAD fork): fillets and chamfers can’t overlap seams and can’t be on an edge that tapers tangentially to a surface
- Plasticity: not a parametric modeling tool in the way I need
- BricsCAD: feels a lot like AutoCAD, in a good way, but not in a parametric solid modeling solver way. It would be a horizontal step if I was using AutoCAD, but it’s a big step down from Onshape in my workflow.
I really like Onshape. I might splurge on the $1.5k/year standard tier, but it’s hard for me to spend that much money on something that is fully on someone else’s computer in the cloud. Unfortunately, it might be the only real option for complicated designs like this for the time being.