Trying to design a reversing screw mechanism. Please Help.

[superart]

I'm working on a project right now that involves a reversing screw mechanism. I am trying to design and model it in SolidWorks, but am having trouble getting the profile of the threads right. My problem is that the follower seems to be getting stuck at the end of the threads where it is supposed to change direction.

I tried searching online for more information about this type of screw, but have not been able to find anything that will help me design the threads and follower to my needs. I even looked through some older engineering books, and couldn't find what I need.

Here is an example of what I am trying to make:

http://www.youtube.com/watch?v=zv7cXR1UkWQ

I have also attached a SolidWorks model that I am working on.

Thanks in advance for any help you guys could provide me.

Thanks.

 

[desertfox]

Hi superart

Any chance you can supply a pdf format? because I can't open your solidworks file, we need to see what might be causing the follower to stick.

desertfox

 

[superart]

Here you go. Hope this works better.

Thanks.

 

[hydtools]

It would help to have a picture of the follower, also.

Ted

 

[superart]

Oh yea, I probably should have uploaded both of those.

 

[btrueblood]

Your follower appears to take up too much of an arc. Needs to be shorter in width, probably also narrower, and tapered near the ends where it needs to engage the "frogs" (areas where alternate threads intersect).

Might help to see the assembled pair.

 

[superart]

That's kind of the other problem that I am having. I am having a hard time getting the follower to mate up with the shaft in the SolidWorks assembly.

 

[btrueblood]

Always a bit of a pain. When doing these types of mechanisms, I usually start with a hand sketch, and define some datum surfaces/planes/origins, then base all my model sketches on those. Subsequently, I mate/constrain at the assembly level using the origin and origin axes/planes.

 

[superart]

I changed the follower a bit making it shorter and thinner. I looked at these images:

http://www.abssac.co.uk/s/Self+reversing+screws/1/8/

and it seems that the follower wants to be about half the thickness of the grooves. I made that change, and also made it a bit more shallower by putting fillets on the ends.

I also managed to get it to mate to the shaft along the axial direction, but I still cant get it to mate to the actual grooves.

I'm attaching a zip with the actual assembly and the follower. I appreciate you guys taking the time with this problem.

Thanks.

 

[desertfox]

I can't open solid edge files

 

[superart]

those are solidworks-2011

 

[desertfox]

solidworks or solidedge makes no difference if you can't open it.

 

[vpl]

superart

There are two SolidWorks forums: forum559 and forum1183. I also don't use SolidWorks, so I don't know which is more appropriate. However, lurking on those forums you will find people who can open your files and probably tell you exactly how to fix the problem you're having. I've even heard that one of the SolidWorks designers has been known to show up there.

If you do decide to post over there, do everyone here a favor by posting a reply and stating that you've started a post in the SolidWorks forum and give the thread number. You can find the thread number at the top of the screen directly under the title. (For example, this is thread 404-305502.) If you take out the space between the word thread and the first number "thread404" it will "magically" activate a link to the new thread.

Patricia Lougheed

******

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.