×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Aperture true position

Aperture true position

Aperture true position

(OP)
Hi all - I wanted to get your take on how you may go about GD&T of an optic/aperture. Let's assume I have a square optic/lens that is 1" x 1". It is too difficult to achieve a clear aperture over the entire 1x1 face so let's assume that the clear aperture must be centrally located in the 1 x 1 square. The clear aperture will need to be .8 x .8.

So my question is...is it even possible to control the location of the clear aperture via GD&T? Keep in mind the clear aperture is just a surface within the 1 x 1 square, it is not a feature of size.

Curious if anyone has any thoughts.

Thanks

RE: Aperture true position

I suppose you could reference datum feature definitions from a D&T standard like Dimensioning & Tolerancing ASME Y14.5-xxxx, where any of a number of versions that will likely cover the subject. The latest is 2018, but 2009, and 1994 are also possibilities. The ISO has similar standards. After you describe the frame of reference for making the measurement it's going to be up to you to define how the aperture is to be measured/verified.

RE: Aperture true position

This is outside my field, but to my understanding, you don't control the location of the clear aperture,  you just set it, and it is where the properties you want to control apply. Limited Area Indication per ASME Y14.5 comes to mind.

RE: Aperture true position

(OP)
Thank you both. I was leaning towards the limited area indication that Burunduk shows from section 1 of Y14.5-2009. I guess my follow up question is..do I show the limited area with basic dimensions in size and location (from the edges of the optic)?

RE: Aperture true position

Yes, the limited area should be fully defined by basic dimensions.

RE: Aperture true position

dthom0425,

A clear aperture, round or square, is a feature of size, and can be controlled by a positional tolerance. What is wrong with a profile tolerance? Read up on unilateral profile tolerances. You can precisely define your aperture keep-out

--
JHG

RE: Aperture true position

(OP)
The optic in my example is square. Yes I agree the optic size dimensions, 1 x 1, are a feature of size. However, the clear aperture is just a zone within the 1 x1 square…much like that “mask from plate” example about from the standard. Guess I’m not sure how a positional tolerance can apply considering this.

RE: Aperture true position

RE: Aperture true position

Quote (dthom0425)

However, the clear aperture is just a zone within the 1 x1 square…much like that “mask from plate” example about from the standard. Guess I’m not sure how a positional tolerance can apply considering this

I think you are correct about it. And neither limits of size nor position can apply. Not only that it's not a Feature of Size, it's not a "Feature" at all in the ASME Y14.5 sense. Correct me if I'm wrong, but it doesn't have distinguishable geometrical limits. It only has the limits that you prescribe so that certain evaluations need to be done in the area that is inside these limits.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close