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Hey so theres a product we have been prototyping. We cant do FDM. The item has a ball valve. and the ball ~ 1.6-1.9mm I cant seem to prototype it. I have tried SLS, SLA, Polyjet. Anybody knows what could be wrong, or what should be the dimension i should be using? I thought I would post this at engineering section, but since I have to prototype I thought its best if its in 3D Printing section

Edit:

Ball is 2mm in dia. clearance of 0.1mm is used

Update:

Figure explains the direction of air

So heres a figure showing the direction of air flow.

Update: Thanks both answers are helpful. though not a precise answer. Then again, there is no correct answer. Thanks a bunch. Lets see how the coming months are. :p

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  • $\begingroup$ It would be helpful if you would provide what aspect of each of the methods was unacceptable. For example, is the problem with FDM that the part is out of dimension? I think that's unlikely, more likely that supports would be needed that FDM does not do well. If you've tried SLA, which provides "automatic" support, was there a problem with residual powder? What went wrong or is expected to be wrong with the various methods? $\endgroup$
    – fred_dot_u
    May 1, 2016 at 11:27
  • $\begingroup$ The precision required in the ball for a ball valve to properly seal is greater than can be achieved with 3D printing. Do you need it to seal properly, or do you just want to verify the fit or something? $\endgroup$
    – Tom van der Zanden
    May 1, 2016 at 13:23
  • $\begingroup$ It would be great if i could have it with the proto. Or else I will have to keep a finger all the time i press a container. its basically a one way valve for air. If i press the valve closes, and when i leave air is allowed to let in. We have not really designed a valve like that before, so the bigger concern would be that we get the design right for manufacturing. $\endgroup$
    – albseb
    May 1, 2016 at 14:00
  • $\begingroup$ Why can't you seem to prototype it? You're asking us what could be wrong, but there's no description of the problem anywhere. How are we supposed to know what's wrong without even seeing the model file, or one of the resulting prints (and why that print is "bad"). $\endgroup$
    – Tom van der Zanden
    May 2, 2016 at 6:08
  • $\begingroup$ Hey, so its a 2mm ball. and its supposed to act like a check/one way valve. in theory it works, FDM parts are too small or fragile. I tried SLA, but the ridges did not come in SLA. Polyjet the support material is a problem. My question is what should be the appropriate dimensions to get a ball valve working for such a setting(image shared above) $\endgroup$
    – albseb
    May 2, 2016 at 7:52

2 Answers 2

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Hey why to make it soooo sophisticated and poor? Air valve cannot be designed with 2 stiff elements - it will never work.

Make the air your friend but not the enemy. Use old good rubber (silicone) "flake" instead. Especially when you have such small design.

Take a look on the picture.

enter image description here

Here you have black element which is rubber or silicone. It's sticked on one side. When air goes from the pipe (goes up) then rubber is slack so the air can flow. When you suck then rubber seals the pipe.

[edit]

You can find such solution in for example bike pumps, inflatable matterss pumps also gas masks and so on. It's pretty fine for low pressure.

Of course ball valves are also widely use but then such device has to have "rubber" ball nest so ball lies on the rubber ring to seal it. There has to be a spring to tight the ball to the ring. Without such spring turning the device upside down would cause the valve would not work at all. Ball solutions are intended to higher pressure.

Please note the spring which tights a ball creates kinda threshold on the pressure level which means that pressure has to exceed a spring force to reduce a pressure. This doesn't occure in rubber valve.

I don't know what device you are trying to prototype but I'm pretty sure a rubber valve will be just fine.

Please also note that sealing surface is very low in ball valve solution but in rubber valve it can be almost unlimited so it can seal quite well even when the surface is not perfect.

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  • $\begingroup$ The air passage would be opposite for me. So i am guessing the silicone pad will be on the bottom. It does seem like a nice workaround. Any products which uses these? $\endgroup$
    – albseb
    May 3, 2016 at 12:06
  • $\begingroup$ Pretty sure water "floaties" use this design. $\endgroup$
    – tbm0115
    May 3, 2016 at 12:47
  • $\begingroup$ @albseb see edit in my answer $\endgroup$
    – darth pixel
    May 3, 2016 at 14:47
  • $\begingroup$ @tbm0115 I would say that ball or cone is more often used with water devices than flap valve as the water is denser and it's easier to seal it with such valves. A pressure of water column is also higher helping to seal the valve. $\endgroup$
    – darth pixel
    May 3, 2016 at 14:54
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As mentioned above in the comments, this really isn't a good application of 3D Printing. At least, not with expectation that it functions. I'd suggest using 3D printing to verify other dimensions and having the part machined traditionally. That ball and "seal" needs to be precision ground or honed to fit in order to stop air flow.

My company has manufactured parts similar to this and the way to go was to produce a concave "cup" for the ball to settle into and hone the edges with a diamond slush using a ball end mill. That way, the ball settles into the cup and the pressure creates the seal.

Omitted due to update in OP's imageUpdate Excuse the poor SketchUp drawing, but this might help explain a potential design change: Deprecated image

Please see DarthPixel's answer for a good design choice.

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  • $\begingroup$ Oh thanks. Good to know its not possible, so i dont need to spend more time looking for. Any suggestions on the design. Yea i know it has to be a cup. Its supposed to be made in Injection molding. How would it be assembled in production? $\endgroup$
    – albseb
    May 2, 2016 at 19:50
  • $\begingroup$ I wouldn't say it's not possible, but more not plausible with the current technology. As far as suggestions, you might consider creating a removable cover on the backside where the precision ball is and add a rubber washer to ensure an air-tight seal when you screw the cover on. This allows you to insert/replace the precision ball. However this may add some undesired complexity to the assembly of the part. It all depends on how you balance the complexity of manufacturing vs intended use. $\endgroup$
    – tbm0115
    May 2, 2016 at 19:55
  • $\begingroup$ so you see the rectangle thing on the part. I was thinking of producing that separately and after pushing the ball in from the top i could close it with the rectangular slab. However where I see the problem is I wont be able to put a cup shape design. $\endgroup$
    – albseb
    May 2, 2016 at 19:58
  • $\begingroup$ Please see my updated answer for what I had in mind. Keep in mind that there are many different ways to go about doing this, and it depends a lot on the purpose of the part and intent on manufacturing process. $\endgroup$
    – tbm0115
    May 2, 2016 at 20:10
  • $\begingroup$ This makes sense, except i wont be able to use any of the screws os seals. Its okay if it leaks a bit, as long as reduced air flow. I have updated an image showing the direction of airflow. $\endgroup$
    – albseb
    May 3, 2016 at 6:05

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