Custom pneumatic switches

[Technic tango]

There are a couple sources to get modified parts but 20$ although sensible for the time required to mod, isnt really justifiable for me, and whenever i try it myself it never works out. Ive been toying with the idea of making 3d printed pneumatics that already have lower friction requirements to move, and have wider ports. What im struggling to overcome though is what to do about the nature of 3d prints. The surface finish may look smooth, but it definitely has substantial friction to it when rubbing other parts and if i smooth it with sandpaper then i lose my tolerances. I have not found anyone else trying to do this or anyone else selling ready made lpe valves that are injection molded, likely because so few people want them.  Any insights to making something like this would be appreciated because im stumped on how to make a valve design like lego's work in the same or similiar form factor.

[2GodBDGlory]

Hmm, that sounds like a challenging, though interesting, project!

If modified valves are too expensive for you, have you thought about modifying them (even starting off of clone ones) yourself? That could save you a lot of money, and still probably be less effort than 3D printing.

[Technic tango]

1 hour ago, 2GodBDGlory said:

Hmm, that sounds like a challenging, though interesting, project!

If modified valves are too expensive for you, have you thought about modifying them (even starting off of clone ones) yourself? That could save you a lot of money, and still probably be less effort than 3D printing.

Ive tried a few times and it never really worked for me. I was also thinking that since im printing i can use fasteners that are inset into the corners to generate the pressure instead of glue to make things easier

 

[deehtha]

Most 3d prints are not airtight and very leaky, how do you plan to account for this? 

[Moz]

Would you be better off 3D printing a jig or guide so you can drill the necessary holes more accurately?

Edited May 11, 2023 by Moz

[allanp]

Certainly FDM printing would be very difficult even if you allowed enough extra material to drill/finish smooth because of the tiny gaps between layers. Resin printing however might work better? But I wouldn't limit yourself to just thinking of 3D printing. I love 3D printing but I do get the feeling that now it's more available people are slowly forgetting about more traditional means of making things. Back to your need for an LPE valve, there is something I have wanted to try but haven't gotten round to. Most pneumatic valves in industry are nothing like Legos valves (Lego valves need to fit the "system") but are actually spool valves which are physically much closer to a pneumatic piston. My idea is to take a small 1x Lego pneumatic piston (which slides nice and freely) and figure out a way to glue/drill extra ports on the side in such a way as to turn it into a free sliding spool valve. It's easy to add a port in the centre to direct air to one side or the other, the tricky part is the exhaust, as you need to let air exhaust from the other side of the attached piston.

Edited May 11, 2023 by allanp

[dr_spock]

3D prints could be sealed with a sealant.  It can be trickly to make them air or water tight.  If you print in ABS, you could try an acetone vapour bath to smooth out and fuse the layer lines.

Milling them out of a block of material like plastic or aluminum could be another option.

 

 

[Moz]

12 hours ago, allanp said:

take a small 1x Lego pneumatic piston

Wall thickness will be the issue I think. You will need to glue/weld stuff to the sides anyway which quickly leads to "I wouldn't start from there".

I've made values for Lego before but out of brass tube using solder. But the circularity of the tubing wasn't great, so I ended up machining them from solid and paying a bit of attention to rotational symmetry in order to get better circularity. It was still a PITA and I never got the solenoid part working very well (think 9V/1A to switch). These days I know way more about machining but I still think you'd want to ream your main hole to get it as round as possible, then use a lathe to get similar roundness out of your spool. And the even better news is that you can buy cheap desktop sized machine tools off AliExpress that work way better than anything I had access to in the 1990's. I am resisting the temptation to look at them :)