screw things in place

roman_herweg

Hi there,

Is there anybody who can give an Instruktion how to design screws that fit in place.

Like if you have a cube of two parts und you want two screw them together. And all sides should fit together after screwed together.

Thanks for your help and regards.

robert_scott_jr_

Hello Roman. I interpreted your description as having the sides of the cubes aligned flush when screwed together. Perhaps the document via the link below is a method you could use. However, when actually screwing two such actual parts together, the flush surfaces cannot be guaranteed due the material of the parts stretching when torque is applied when screwing them together. - Scotty

https://cad.onshape.com/documents/c1a7f7d9a75486b68188feda/w/1d2e7e9f62a68a03990db10d/e/07a701881de5c5ab484b5d50

roman_herweg

Hi, that's exactly what I was asking for. But if I would print it like that, I think this will not fit. Because you cannot fit printed screws together if not modified before ? Correct? So I used the threads plugin. Which I modifiy normally. But then I cannot use the method you scetched correct?

Thanks and regards Roman

nick_papageorge073

That does not seem a realistic and repeatable design. Tightening it more or less would cause the sides to not be flush. Why don't you use a separate metal screw instead?

If you really want the screw as part of the cube, then perhaps print a few samples, and offset the face of the cube slightly until the sides become perfectly flush with the tightening torque desired.

Or better yet, change the design to a cylinder instead of a cube.

eric_pesty

You would have to add a "stop" feature in there somewhere, and move the faces on one half to introduce some "preload" in the thread if you want the sides of the cube to align

roman_herweg

Hi Eric,

I didn't quite get that. Maybe because I'm not a native speaker.

But speaking in general shouldn't there be an option to simulate this in onshape via assembly?

Thanks and regards Roman

eric_pesty

@roman_herweg
It's not so anything specific to Onshape. Just that physical objects will need some clearance to fit together and materials will stretch so it will be difficult to make sure the two cubes line up when screwed together. It's hard to tell why you want to do it this way but it will be hard to make it work well compared to using a separate screw to attach the two parts together (or some other fastening method).

If I really needed to do this, here's how I would do it:
https://cad.onshape.com/documents/03b907808cba0ea7d03c4409/w/bc349104f523dec3214447f2/e/79776eb34da790741a774b47?renderMode=0&uiState=64a5d6ccc675a17779b84d44

- Add clearance to the boolean that creates the female thread so they fit properly after printing (would to have to experiment to see how much you need)
- Move the bottom the face to create a "preload" in the thread (so things are nice and tight)
- Add a "stop" so the rotation ends with the sides of the cube aligned, although it would likely always be off a bit...




Maybe something like this might be a better way to get the sides of the cube to naturally stay aligned:

https://cad.onshape.com/documents/03b907808cba0ea7d03c4409/w/bc349104f523dec3214447f2/e/a02ec7324aacc823a9b8e1d4?renderMode=0&uiState=64a5d717c675a17779b84dfc

nick_papageorge073

roman_herweg said:

Hi Eric,

I didn't quite get that. Maybe because I'm not a native speaker.

But speaking in general shouldn't there be an option to simulate this in onshape via assembly?

Thanks and regards Roman

It's a bad design. Don't make it like this. There is no product in the real world made like this.

If you want two blocks to assemble together in a twisting fashion, and maintain their orientation, a screw built into one part won't work. Instead, you can use a bayonet mount (how a lens attaches to a camera), or something similar.

Example: