Threading and rapid prototyping

[calico]

First and foremost, I consider myself a beginner in
SolidWorks and I am brand new to this forum, so please
bear with me if I posted this in the wrong place, used
the wrong terminology, etc.

I am planning to model a threaded hole according to the C
mount standard: http://en.wikipedia.org/wiki/C_mount. The
assembly I am modeling is to be manufactured in metal
(aluminum probably, but I am not the one deciding) at
some point, and possibly have a plastic rapid prototype
done first.

I have done some research online and found that:

1. Although there seem to be some screw thread standards
3D models floating out there, C mount is not one of them.

2. Rapid prototyping real threads in plastic seems to be
a terrible idea, as 3D printers may not have the
precision for them.

So my question is...are my two conclusions true? I'm
guessing at least #1 is, as much as I would like a
magical database out there with a C-mount 3D model ready
for public use. I've found a model of a C mount adapter,
but no threading.

I am not experienced with rapid prototyping however, and
would very much like input on that department. So far, my
idea is to make cosmetics threads for presentation
purposes, and for manufacturing purposes, just let the
machinist know the specs. If I can get it done cheaply
enough, I have the option of modeling the C-mount
threading in some random block and get a rapid prototype
done of it. If that would be a complete waste of time and
money, let me know.
Edited by: calico

 

[jimshaw]

Calico,


0. Welcome to the forum


1. Even if there were a library out there, I'd still do it myself to ensure accuracy. Sweep the profile through a helical curve, and you should be good to go, plus it's great practice.


2. C mount is 1-32 UN 2A, so the pitch is .031". Many RP processes are now good to a few thousandths, but it all comes down to cost and capability of the prototype house you go to. If you want the threads, then they will probabably just make the part at the major dia, and turn down the threads manually on a lathe. Bottom line is yes, it can be done, but you need to get a couple quotes and determine if it's worth it or not. Everybody on this forum has done a prototype cost analysis, and each designhas it's own unique requirements. It's up to you to decide if it's worth it or not.


If this is for testing an actual lens, then I would certainly do the threads, because then you can actually see how it mounts, as that is very important in optics.


My two cents.

Jim Shaw
http://www.linkedin.com/in/shawengineering

 

[calico]

Thank you very much for your reply. I particularly appreciate the bit about RP being able to do the threads. The only RP experience I've had was with the machine in my engineering department back in college, and it did not seem like it was capable of very minute features.

I did try the helix method and it worked great, though I'll need a little more practice to get it closer to my reference C-mount adapter. Thanks again!

 

[michael3130]

We've had a number of threaded parts rapid prototypes using SLAs and they have been very successful. It requires discussion with the supplier though as to exactly what you're trying to achieve. I did find though that with the resin SLA parts, when you thread them together they feel kind of 'sticky' as the surfaces rub together. Sorry, best way I can describe it, but they did work and worked well.


Using the printing types you talk about in colleges won't get you a good enough finish

 

[bcooper]

We do threads on parts as a matter of routine, we make rapid prototypes to check form, fit and function of our new designs. I agree you may have to clean them up a bit, run a die over them or run a tap through them but I have found the accuracy will largly depend on you output file. After you create you output file open it with Efiles or some 3d viewing package and you can make a visual check of what you are going to get.